I have lost track of who is winning between verts and inverts. I can't help but think that the spineless are kicking backbone butt. Like in the Seattle Aquarium:
Hat Tip to John Wilkins. I think that this means that we are winning the philosophers over to our side.
Friday, May 30, 2008
Risking having it look like snail week... but ...
These little fresh water gastropods are from my son's aquarium. I believe that the snail is a Lymnaea sp., but I'm not a freshwater gastropod expert . It is dextral (aperture is on right with the spire pointed and oriented to see the aperture), with a thin shell that has 5-6 whorls (see below). Adults (in our tanks at least) range from 10 to 25mm while the young, fresh hatches, are about 1-2mm. They are pulmonate with no operculum, lay eggs in a gelatinous mass on the under side of broad leaved aquatic plants. The feed mainly on algae and detritus, but will preferentially go after any rotting plant leaves. The tentacles are triangular with eyes at the base. As a pulmonate this snail regularly rises to the surface to refill it's pallial lung.
Lymnae snails are simultaneous hermaphrodites, and from 2 individuals a water body can quickly be colonized. Which is precisely what happened to our larger tank when some snails or eggs made it into our tank attached to some plants. Egg masses have 20-40 individual eggs each which hatch 10-14 days after being laid.
As an informal experiment we placed one single snail in our smallest tank when it was torn down and rebuilt. All previous snails were removed and the tank torn down to bare glass removing all substrate material. Sterile sand and gravel were used as the base, to which plants were added that were wiped down and inspected for snails and egg masses. Fresh water, shrimp and fish were added to the tank and it was allowed to settle for a month, during which time the tank was inspected daily for snails or snail egg masses. After a solid month with no evidence of any snails, an 18mm adult snail was moved from an adjacent tank. Again the tank was inspected daily for snail egg masses and a snail count made. After 45 days there was still only the one introduced snail in the tank. Now (3 months later) there are 50+ snails in the tank: one 18mm adult and 49+ young snails of 2-4 mm lengths.
Sperm sequestration? Self fertilization? Both are reported in Lymnaea so it is hard for me to tell exactly, but no matter which, it does reveal a key trait that these snails use to for survival and to exploit new territory.
Thursday, May 29, 2008
PhD position - molecular systematics and evolution of freshwater gastropods
A three year PhD position is available at the Museum of Natural History Berlin in a research project on the molecular systematics and evolution of viviparid snails. Funding is provided by the Deutsche Forschungsgemeinschaft (DFG).
Viviparids are a species-rich and phenotypically diverse group of freshwater gastropods with an almost worldwide distribution and a long fossil record. We want to use this group to address issues in evolutionary biology such as the evolution of morphological disparity, biogeography or ancient lake radiations. A major component of the project will be the reconstruction of viviparid phylogeny using both molecular and morphological techniques. The geographic focus will be on Asian taxa.
We are seeking a student with a MSc or equivalent degree (diploma) in biology. The successful candidate should have experience with techniques in molecular and/or morphological systematics and should have a strong interest in biogeography and evolutionary biology. Good communication skills, the ability to work independently and the willingness to conduct fieldwork in South and Southeast Asia are essential.
We offer an intellectually stimulating research environment in one of Europe’s largest natural history museums with well-equipped state-of-the-art lab facilities.
To apply, please send an e-mail application including CV, names and addresses of two referees and a brief letter explaining why you are interested in this PhD position by June 20 to Thomas von Rintelen: firstname.lastname@example.org
This week, as Alex Wild put it, Brian Fisher and Alex Smith "break the PLoS taxonomy barrier". In my last post, I evangelized and pontificated on the benefits of open access publishing in PLoS for taxonomy. That in itself is a ground-breaking accomplishment, but the paper by Fisher and Smith is interesting in own right. They report on ants in the Malagasy region from 2 genera, Anochetus and Odontomachus, and describe 3 species new to science. Additionally they evaluate the efficacy of DNA Barcoding as a "tool to accelerate species identification and description".
Of Ants and Islands
Madagascar is a unique island off the eastern coast of Africa with a highly endemic fauna, meaning that many of the creatures found there are found no where else on this planet. Fisher and Smith also report the first records from the nearby islands of Seychelles and Comoros. Using 500 individuals from 6,000 leaf litter samples, 4,000 pitfall traps, and 8,000 additional hand collecting events over a 14 years period, they were able to group together worker, queen and male castes. The descriptions are fine and document the features and variation in morphology well. One criticism I have is they contain no information that I could see on the etymology of the new species. Etymology is where the author describes what the name means. For the 3 new species described in the genus Anochetus, each is given a specific epithet honoring an individual, a Mr./Ms. Bolton, Goodman and Patterson. Who these people are that should get immortalized in ants we shall never know.
DNA Barcoding and Species Assessment
While the description and discussion on the ants' distributions are important for biodiversity studies, the authors spend a good deal of the paper discussing the efficacy of DNA barcoding in helping to delineate taxa. DNA barcoding is using a standard gene, typically the mitochondrial COI gene, as a marker to identify a species. This is useful when there is a specimen voucher with a known barcoded sequence to match unknown to. There is a good deal of controversy surrounding its use in taxonomy. Many taxonomists agree that describing species based only on a short snippet of DNA is bad practice.
Fisher and Smith use DNA barcoding on their ants for two reasons. The first is group the different castes together. Ants are social insects separated into workers, queens and males. Some ant societies have even more castes, such as sanitary workers and fungal farmers. Because the different ant castes are morphologically different from one another, it is sometimes difficult to tell closely related species apart, especially if they co-occur in a similar location. The authors assert that DNA barcoding was the "principal source of data" that group together different castes, sizes and genders.
The other reason is to rapidly assess species identification. Fisher and Smith analyzed all the collections of a genus. Those showing a high degree of sequence divergence, i.e. the outliers, were "culled" from the analysis for morphological scrutiny. Traditionally, each individual would have to have measurements and notes taken on the morphological characters of interest. This is an extremely time-consuming process, but amplify that to 500 individuals of ants. The barcode method actually allowed them find the interesting individuals right away. This might not work for every taxon, but considering how affordable DNA sequencing has become this practice might take off for large collections. This will be extremely important as many biodiversity inventories are ongoing or coming to a close in the near future.
Another use for DNA barcoding brought up by Fisher and Smith is hypothesis generation. Hopefully most people will agree me (and the study's authors) that species are testable hypotheses. Like any scientific hypothesis, it is subject to refinement with new data. The barcode data helped Fisher and Smith to generate testable hypotheses regarding within-species divergence, several interesting aspects of biogeography (see page 20, last paragraph of first column for list) and female-limited dispersal capabilities in species with wingless queens.
I'll let Fisher and Smith have the final word:
"Nothing can replace the countless hours of careful observation necessary to understand variation and to delimit species boundaries. However, the addition of sequence data provides a means to create short-term results from inventories and at the same time generate data helpful to taxonomists. For taxonomists, sequencing highlights the specimens most deserving of focused study."Disclaimer: Brian Fisher was my Evolution teaching assistant at UC-Davis. Although he is unlikely to remember me anyways, but the contents of this post are not in any way an artifact of this coincidence.
Fisher, B.L. & Smith, M.A. (2008). A Revision of Malagasy Species of Anochetus Mayr and Odontomachus Latreille (Hymenoptera: Formicidae). PLoS ONE, 3(5), e1787. DOI: 10.1371/journal.pone.0001787
Wednesday, May 28, 2008
PLoS ONE has heeded the call of the systematic wild and made open access history with an excellent paper by Fisher and Smith on the ants of Malagasy region with an evaluation of the role of DNA barcoding in species identification and description. What makes this particular article so special? It is the first time a species description has been published in a PLoS journal! I applaud PLoS ONE at taking the initiative and contributing to advancing the science of systematics and biodiversity research. Maybe it was my call to PLoS to publish taxonomy open access or maybe it was just destiny. I will talk about the ant paper in a separate post. First, I would like discuss further the role of open access publishing in taxonomy.
Why should one support open access publishing of taxonomic papers?
Visibility is important to the field of systematics, where the relevance is often lost amidst the taxonomic jargon. By removing the subscription barrier, taxonomists make their work accessible and noticeable to researchers all over the world. Increasingly, the need has never been greater for high quality taxonomy. The treatment of neglected tropical diseases relies on proper identification a the pathogen or parasite. Species form the fundamental unit of much of evolution and ecology. Sound knowledge of species and their attributes is basic to all other fields of biology ranging from the molecular to the metacommunity. While scientists might not agree on what a species is, there is no doubt about their importance and the necessity to identify and describe them.
The time is now for taxonomy and taxonomists to enter the digital age. New web technologies can prove effective at linking papers, potentially increasing readership and bringing disparate fields together. For instance, a paper describing a new species of pathogenic nematode can have hyperlinked keywords that summarize the findings, i.e. "Nematoda" "Genus species sp.nov." "Genus species (of host)" "Pathogenesis" "Endoparasite" "Locality Information", etc. Other articles of interest with hyperlinked keywords can be linked together for researchers to uncover. Species names themselves can be linked to the original paper, so one can find basic information about that species. This will make it easier to ground-truth simple observations about a species that can affect interpretations in other research, such as where it has been described from, variation in characteristics between sexes and sites, behavioral and diet observations and life history traits.
Why should one care if PLoS ONE publishes taxonomy?
PLoS ONE is an innovative publishing model that is part of the PLoS (Public Library of Science) network. PLoS is already established as a leader in online, open access publishing of high quality research in biology and the health sciences. The importance of the papers published in PLoS journals is well-recognized by academics and funding agencies. PLoS ONE, being relatively new, has yet to acquire the same metrics as the other 6 journals. Seeing the diversity and quality of papers being published, there is little doubt the initial metrics will reflect positively on the mission of PLoS. The visibility and reputation that articles published in PLoS journals gain will benefit taxonomy.
PLoS ONE's model allows for post-publication tools such as annotating and commenting on articles. Instead of articles being the final word on an experiment or hypothesis, they become the beginning of a conversation. For taxonomy, one can comment on new observations or developments in that species. You can drop a link on the comments of that paper to a revision you did or another paper investigating that species physiology. In short, the PLoS ONE model lets a paper, or species description, have a permanent home on the web where it be used as a record of its existence and any discussion of that species.
Some barriers exist to publication in a journal like PLoS ONE. Taxonomy is not a rich science despite its unsung significance. In the open access model, the author pays a publication fee to offset the journal making the paper freely available in perpetuity. Its a trade-off and it prevents publishing houses from double dipping into funds by charging institutions for access to content and charging authors page fees. Libraries and institutions worldwide can openly access content irrespective of their financial status, as can members of the public whose tax dollars pay for a good chunk of research. One obvious solution is for more funding to taxonomy and systematic research. Publication fees can be written into new grants or possibly creation of special grants from money saved from journal subscriptions can be used to pay open access fees. PLoS journals also make sure that the ability of authors to pay publication charges is not a consideration in the decision whether to publish. They can provide fee waivers for authors without grants or other financial resources.
This may encourage more papers being published to include a synthesis of many taxa or to be written in monographic style encompassing the fauna of a region per se. Putting more taxa into the paper may increase the bang for the buck. You pay less in fees (per page charges are eliminated in online publishing) and perhaps make the paper more citable. I am not suggesting this works in all cases, more information in a paper certainly doesn't make a better paper. Certainly there are situations where grouping taxa into a single article may make sense, i.e. The Crustacea of Coastal Norway instead of a 2 papers on shrimp and a paper on crabs.
Another barrier deals with requirements by the International Code of Zoological Nomenclature, which promotes "stability and universality in the scientific names of animals and to ensure that the name of each taxon is unique and distinct". One requirement (Chapter 3, Article 8.6) for articles published online is for deposition of the printed article in "at least 5 major publicly accessible libraries which are identified by name in the work itself". PLoS ONE went out of their way to work with leading institutions in 5 countries to ensure the proper cataloging of their first taxonomic paper. This willingness to do what it takes to get quality publications published irrespective of their discipline highlights their commitment to their core principles, in particular those of Breadth, Cooperation, Internationalism, and Science as a Public Resource.
Should taxonomists forego traditional publishing outlets?
The better option would be for those outlets to go online and open access! If there is some success to PLoS ONE in their venture to publish papers of a taxonomic nature, hopefully it will inspire established journals to follow suit. If you believe strongly in the force of the digital age to implement positive change in science, support open access initiatives by publishing your articles there. One may posit that hybrid journals, where authors may elect to pay an additional fee to make their article accessible online for free, is a step forward in the right direction. Noted open access proponent Peter Suber notes one should proceed with caution when electing to publish in a hybrid journal for several reasons. In particular, hybrid journal options do not free up subscription money from libraries. Because it is a risk-free strategy for journals, there is not an incentive to get rid of subscriptions fees all together, since most authors do not elect the free-access option. Many publishers still do not make their publishing model or data on the efficacy of the hybrid option available. This makes it difficult to police whether they are reducing subscription fees in relation to author uptake of the free-access option, where high fees are paid to offset subscription fees.
In conclusion, I applaud PLoS ONE for working hard to pave the way for publications with a taxonomic nature to be published truly open access and online. I would like to see more web tools being utilized in online scientific publishing. The tools exist and the potential is great for weaving together the threads of science. I look forward to submitting my next paper to a PLoS journal!
Another top ten featuring inverts was recently posted by Christopher at the Catalogue of Organisms - his top ten phylogenetically problematic taxa. I guess this is a good list to have a strong showing of inverts in, but then again?
7 out of 10 are inverts including one of my favorites - Pycnogonida.
Gotta check out the complete list including why they are so challenging to taxonomy.
Tuesday, May 27, 2008
It's a bright and squidly day!
DSN reports the catching of a giant squid stalking orange roughy trawlers. Ok, so it wasn't stalking the trawler it was actually caught in a fisherman's net)
Yesterday, Florence from Te Papa was kind enough to let us know that the lectures from the Colossal Squid event earlier this month were available. Due to copyright issues some of the lectures are unavailable, but there are two video lectures and one audio only piece:
The International Institute for Species Exploration (IISE) released their first ever State of Species report on Friday (to be issued annually on May23rd, the birthdate of Linnaeus). Pouring through the journal reports and monographs from 2006, the IISE found 16,969 new species (not counting any new microbes) described in that year. Invertebrates accounted for 13,900 of the 14,912 new animal species. That's 93% of new animal species and 82% of total new species described in 2006. (And, yes, insects accounted for over half the new species by themselves)
The selected inverts in the top ten are:
At #9 there is Megaceras briansaltini, a rhinoceros beetle from Peru described as being a case of nature imitating art, as this beetle bears a "striking resemblance" (save the color) to Dim from Pixar's animated hit "A Bug's Life".
Ratcliffe, B.C. 2007. A remarkable new species of Megaceras from Peru (Scarabaeidae: Dynastinae: Oryctini). The “Dim Effect”: Nature mimicking art. The Coleopterists Bulletin 61(3): 463-467. DOI:10.1649/0010-065X(2007)61[463:ARNSOM]2.0.CO;2
The deadly Malo kingi appears at #8, this Irukandji (a type of Cubozoan jelly) is named after one of its most famous fatal encounter victims, Robert King. So exactly how does one study a tiny, highly lethal, almost transparent marine jelly anyway??? Any cubozoa experts out there?
Gershwin, L.A. 2007. Malo kingi: A new species of Irukandji jellyfish (Cnidaria: Cubozoa: Carybdeida), possibly lethal to humans, from Queensland, Australia. Zootaxa 1659: 55-68.
Crawling in at #3 is Desmoxytes purpurosea (a.k.a. shocking pink dragon millipede), showing Diplopoda's brighter side in a bright coral pink. It doesn't hide it either, resting in the open and on vegetation during the day in its native Thailand.
H. Enghoff, C. Sutcharit & S. Panha. 2007. The shocking pink dragon millipede, Desmoxytes purpurosea, a colourful new species from Thailand (Diplopoda: Polydesmida: Paradoxosomatidae). Zootaxa 1563: 31-36.
Hopefully this annual release will continue. Considering the various Census of Life projects under way, the job of the compilers will not be easy! Of course, the top ten list is highly subjective, as they readily admit. Marine life, in addition to inverts in general, seem woefully under represented with one marine invert (malo kingi) and one marine vertebrate, the electric ray (representing an entirely new genus, named after a vacuum cleaner - Electrolux addisoni).
Maybe we should team up with DSN and pick a top ten new marine species at some point. Kevin?
Sunday, May 25, 2008
While the deep-sea may be the final frontier for marine biologists, caves are one of the least studied environments on land. Some caves can extend dozens of miles below the ground in sinuous networks, all but cut off from the grassy hills and tree-lined horizons above. Its not an easy environment to access and many explorers have perished attempting to map these subterranean labyrinths. Yet, recent investigations have found an astonishing community of invertebrates associated with caves, existing nowhere else. Many of these species are insects and spiders, adapted to the dark conditions, muggy conditions. Nearly every new cave expedition turns up species never before seen.
How do these animals exist down there? What is their source of food? It turns out that nestled in the Blue Mountains of Australia at the 350 million year old Jenolan Caves Karst Conservation Reserve, the base of the invertebrate community consists of decaying leaf litter. Eucalyptus trees, native to the area, historically contributed the most to the leaf litter pool. Over the years, introduced trees have naturalized around the cave opening. Sycamore from Europe was brought in to stabilize steep, rocky slopes and Radiata Pine from North America was provided for the timber industry. Hills and colleagues from the University of Technology Sydney compared leaf litter decomposition rates and invertebrate diversity between the 3 leaf litter pools in "twilight" areas (i.e. near cave openings) and "dark" areas deeper in the cave.
The introduced Sycamore leaves decomposed much faster than the radiata pine needles and native eucalyptus leaves. This suggests that Sycamore leaves release more carbon and nutrients into the cave ecosystem, potentially supporting a more abundant and diverse invertebrate community. Interestingly, there was no difference in leaf mass loss between twilight and dark leaf litter. Proximity to above-ground features like light, rain and wind appear not to affect leaf litter decomposition.
Before I discuss the trends for invertebrates there, I want you to sit back in your chair, take a deep breathe and relax. Close your eyes and envision a cave. Its dark, moist, there is only one opening. All that remains of it is a singularity of daylight. For hundreds or thousands of years this cave has been fed organic matter from the surrounding vegetation. Trees such as Eucalyptus abound in the limestone hills, shedding off their leaves which make their way by the cave opening eventually being blown in by a gust of wind. This occurs daily for millennia. Insects and arachnids feast on the leaves as well as the fungi and bacteria associated with the leaf matter. Over time one might suspect that the animals become adapted to the leaf litter type in some way.
Fast forward to the last 100 years and globalism has introduced new organisms to every corner of the planet at an unprecedented pace, including Sycamore and Radiata Pine to eastern Australia. Are the invertebrate communities more diverse and abundant on the native vegetation that is may have adapted to?
As you can see from the above figures, abundance and species richness are much greater for the introduced european Sycamore than either the pine or Eucalyptus, especially nearer the cave opening. The authors don't really nail the answer with their experiment, but narrow it down to attributes of Sycamore that favor colonization by invertebrates over Pine and Eucalyptus. For instance, Sycamore has a higher specific leaf area (SLA) than both Pine and Eucalyptus. A low SLA is associated with long-lived leaves containing many structural and defensive compounds. These trees invest heavily to guard against plant-eaters whereas the broad-leafed Sycamore does not invest against herbivory, so leaves break down quickly. This faster nutrient release may be part of the reason sycamore leaves have a more abundant and diverse community.
So what would happen if Sycamore were to completely supplant Eucalyptus? It is a higher nutrient leaf and releases carbon faster (i.e. breaks down faster), so it should be better for the spineless society down under, right? One problem is that Sycamore is a deciduous tree. This means nutrient pulses to the caves would occur on a seasonal basis. Since its leaves break down so quickly, this pulse would be short lived compared to the structurally-strengthened Pine and Eucalyptus, both of which keeps their leaves year-round. Being below-ground, caves are protected from the variability of the seasons and are relatively stable environments in terms of climate. The invertebrate community there needs a more constant or stable supply of leaf litter to be sustained. The authors propose
"The short-term influx of energy provided by sycamore litter could be detrimental to subterranean invertebrate diversity in the long term. We would expect to see invertebrate species predisposed to utilizing sycamore derived energy dominating subterranean invertebrate communities and perhaps out-competing other invertebrate species, thereby reducing invertebrate diversity."Interesting food for thought: nutrient pulses reduce diversity over time. On the other hand, if the authors are talking about partial species replacement, I would also expect to see increase in diversity pooled over the whole year. If this is only a seasonal phenomenon, complete species replacement would be unlikely given that established invertebrates that can utilize multiple plant sources over the year will persist over the long-term. It would certainly be an idea worth funding, especially from the angle that caves may be sheltered from the immediate effects of climate change. A nice replicated mesocosm study within the caves and near the entrances. 'X' amount of replicates sampled throughout the year at various time points to gauge the effect of seasonal nutrient pulses. How about adding various mixtures of different quality leaves to test the hypothesis that maximum food quality results in highest species richness.
HILLS, N., HOSE, G.C., CANTLAY, A.J., MURRAY, B.R. (2008). Cave invertebrate assemblages differ between native and exotic leaf litter. Austral Ecology, 33(3), 271-277. DOI: 10.1111/j.1442-9993.2007.01814.x
Saturday, May 24, 2008
I remember the brief discussion in Invert Biology about the 100+ year old mystery of the "y-larvae" crustacean. The jist of the conversation was that there was still much to learn about larval development of many crustaceans and there were some which were known as larvae but not as adults, for instance... "y-larvae" (also known as Facetotectans), a taxa of crustaceans which is described solely on the basis of the naupliar and cyprid larval stages.
Pachenik's Invertebrate Biology, the standard undergraduate textbook for invert biology/zoology, doesn't mention y-larva at all, while Brusca & Brusca's Invertebrates, 2nd Edition, gives them a single image and a one paragraph nod as members of the subclass Thecostraca, infraclass Facetotecta:
Monogeneric (Hansenocaris): The "y-larvae", a half-dozen small (250-620 μm) marine nauplii and cyprids (Figure 16.16I). Although known since Hansen's original description in 1899, the adult stage of these animals has still not been identified (although it has been suggested that they might be the "missing" larval progeny of sexual reproduction in tantulocarids). The prehensile antennules and hooked labrum of the y-cyprids suggest that the adults are parasitic. For details see Høeg and Kolbasov (2002).
Fortunately, The Atlas of Marine Invertebrate Larvae had more information on them, including illustrations of both nauplius and cypris y-larvae.
Kevin recently wrote up a great piece on the related Rhizocephalans at Deep Sea News complete with pictures from his own research. Catalogue of Organisms has a nice quick review of the parasites of subclass Thecostraca with a focus on the y-larvae and a description of the naupliar and cyprid stages. As mentioned in both those articles it is the cyprid larval morphologies that links all the Thecostraca species together.
This week an open access research article in BioMed Central's BMC Biology significantly extends the knowledge of these potentially important crustaceans. In their paper Henrik Glenner, Jens Høeg, Mark Grygier, and Yoshihisa Fujita report both a great diversity of y-larvae and document a new metamorphic stage of development.
In recent years the number of Facetotecta species has increased as new species have been described worldwide. The author's study area, Sesoko Island near Okinawa, Japan, was also the area of intensive sampling for Facetotectans. That sampling revealed 40 new species, and a density that made y-larvae a significant portion of the plankton, suggesting that the adult form may be ecologically important as well.
What I found most interesting in the paper, however, was the inducing and documentation of a previously unobserved juvenile stage of y-larvae. Up to now all y-larvae were observed as one of 5 naupliar instars or the next stage, a non-feeding cyprid. No one has found or been able to raise y-larvae past this cyprid stage.
The authors tried several compounds known to induce metamorphosis in the cyprid stage of related parasitic barnacles. They found that only 20-hydroxyecdysone (20-HE) induced metamorphosis in the y-cyprid. They then used photo and video to document the successful metamorphosis of the cyprids exposed to 20-HE. The cyprids transformed from an articulated, segmented form to a simple, unsegmented, pulsating, slug-like juvenile stage, which the authors have called the ypsigon. The ypsigon is without a gut, but has very visible fat globules throughout its body. The cyprid eyes and muscles are visible but degenerating in the ypsigon as well. The ypsigons underwent a molt 24 hours post metamorphosis as well. The study was terminated by preserving the the juveniles at 48h post metamorphosis.
This same morphological larval devolving has also been recently described in the vermigon stage of Rhizocephala, a connection that is a "stuning example of convergent evolution." This also suggests that the adult form of the y-larvae, when finally found, will be endoparasitic. The authors note that the analogy with Rhizocephalans suggests that the adult form will also have a "highly simplified structure" and that this possibility may explain why the adult form remains so hard to find.
Glenner, H., Hoeg, J., Grygier, M., Yoshihisa, F. (2008). Induced metamorphosis in crustacean y-larvae: Towards a solution to a 100-year-old riddle. BMC Biology, 6(21) DOI:10.1186/1741-7007-6-21.
Aditional pictures are in the PDF of the paper and videos of the metamorphosis are available on the BioMed Central website:
We are calling for a rejuvenation of the scientifically literate populace! Do your duty and reproduce! Now, have at it.
Trumping my story of giant spitting, lily-smelling earthworms from Idaho, those wily Bleimans have an article on giant blue, radioactive earthworms from Australia.
Oh and check Aydin's snail schlong. Its half the snail's coil length.
Help the Brine Queen catch runaway crayfish larvae.
Friday, May 23, 2008
As part of the Life Photo Meme, I am posting this shot I took in Belize almost a year ago of a hermit crab, Coenobita clypeatus. My labmate, Alex (he is the one holding the crab), found him at South Water Caye's Marine Biological Station. The caption, etc. is from when I originally loaded the shot onto my Flickr account some time ago.
Although I refer to it as a male, the hermit crab could easily be a female, as there is no way to tell with them in the shell. The female gonopore is located under the 3rd pair of legs, securely locked away inside the shell. I will continue to refer to this one as "he" for the sake of continuity.
I seriously hope this little guy managed to find a better home shortly after this shot. Like most hermit crab species, C. clypeatus can change shells at the drop of a hat, though they often change back and forth "trying on" new shells a few times before settling in.
These crabs are generally nocturnal, hiding in leaf litter and in burrows during the day, and coming out in the evening to begin scavenging and climbing trees. They primarily eat fruit, dead plants and animals, and even feces. On the island we would find upwards of 20 hermit crabs dining on one cracked open coconut. They chirped and displayed dominance shoving behavior in these large communal dining events.
C. clypeatus can live to be in excess of thirty years old. They start life as fertilized eggs released to the ocean, where they develop as zoea through several molts before their gills are developed enough to extract oxygen from the air. Adult crabs remain on land for the remainder of their lives, but they do use ocean water as a source of salt during ecdysis.
Like many crabs, these hermit crabs have one claw, or cheliped, that is significantly larger than the other. Of the four pairs of walking legs, the rear most two are kept inside the shells to hold the shell, while the forward two pair of legs are used for walking.
The largest C. clypeatus we observed wore shells that were larger than my fist. One had a shell 8 inches from the outer lip of the aperture to the apex. These, however, are nothing compared to the 10 pound coconut crabs (Coenobeitidae birgus latro) from the Pacific, which can rip open a coconut with their large claws.
Here, then, is what the fellow above should look like:
Monday, May 19, 2008
Today is my son's birthday and one of his presents (found through Kevin's comic book posting - Johann says "Thanks Kevin!") is The Marine Biology Coloring Book by Tom Niesen. I hadn't seen this one before, and it is definitely not a run of the mill coloring book!
The illustrations are far more anatomically correct with wonderful details such as the reproductive cycle of sacculinid barnacle. The text that accompanies it is both explanatory and accessible. It is very specific and aimed generally at students or very serious beachcombers. While accessible to advanced middle school, high school, or early college students, some professors use the book as a quick orientation to marine biology for students coming to the marine biology graduate program from other fields.
The book starts with a general overview of oceanographic currents, weather, tides and proceeds into 14 page spreads covering major habitats including zonation concepts, the photic zone and a page spread each covering deep sea and hydrothermal vent habitats. Spreads on biological diversity and reproduction are organized taxonomically. Special topic pages follow on migrations, symbiosis, competition, defense, feeding strategies and oceanographic technology.
The book does a very good job covering the balance of verts to inverts despite the cover focus. After taking out the 17 page spreads on physical oceanography and habitats, there are 4 page spreads on plants and algae. Invertebrates are represented by 54 page spreads while fish, reptiles, birds and mammals by total 37 spreads. Some of those are overlap such as the spread "Symbiosis: Parasitism" which highlights three parasitic relationships: copepods parasitizing fish, fish parasitizing sea cucumbers and barnacles parasitizing crabs.
A Highly recommended book for junior marine biologists, or maybe for all the family members.
(edit 5/22 - added author information (doh!) after noticing I forgot it after three of his former students - including authors of the Brine Queen and Echinoblog - checked in with wonderful comments.)
Friday, May 16, 2008
WTF!!11! OMG11!!!eleven!! WTF!!!!111!!!!11! I DON'T THINK SO!?!?!?!!!??!one!!!!!!111!1!!!
Well, I don't have any offhand evidence for it, but I seriously doubt it. Especially in the ocean where vertebrates IMHO probably aren't the majority in ... oh I don't know... diversitybiomassabundanceandeverythingelse. CNN reports this quote paraphrasing the World Wildlife Fund (WWF) in an article today titled "Humans Blamed for Sharp Drop in Wildlife" (duh!).
The Living Planet Index measured 4,000 populations of 1,477 vertebrate species, which the WWF says is a good indicator of overall biodiversity trends.OK, I understand its hard to get cuddly dollars from donors out of a jelly like you can a polar bear, but I really doubt vert "biodiversity trends", whatever that means, are indicative of the Living Planet. I don't have the time or patience to delve into the literature for this, so lets use a bit of the ole common sense.
Those containing backbones account for roughly 5% of animal diversity (by generous estimates), while those without said characteristic are embodied in THE OTHER 95% (ahem, *clears throat*). Of course the purpose of an indicator taxon in ecology is to be able to characterize and extrapolate the dynamics of a given genus or family to the whole community level. For instance, in agricultural landscapes one might use use carabid beetles to extrapolate to the rest of the insect community. This might be founded on an earlier study saying that carabid beetles made of 87% of the insect community. Therefore one may suppose that it is easier and cheaper to use beetles in the family Carabidae as an indicator for the community. Then you can perform experiments using this taxon to test ecological hypotheses and implement a monitoring program using carabids to make sure a protected parcel of land is be preserved, etc. etc. The key point is that for an indicator taxon to be useful it must be shown it represents the community or excompasses its diversity well enough.
Admittedly, I haven't read all of the WWF report 2010 and Beyond: Rising to the Biodiversity Challenge. But because of their select sampling, all they can say is that vertebrates (or 5% of animal diversity) is severely affected by "human demands on the biosphere". With their study design, you cannot extrapolate to all wildlife, unless by wildlife they mean cuddly little furballs and other relatives of our spined pets.
I do not disagree that human activities are responsible for accelerated biodiversity loss. It is a real phenomena as it has been directly observed and reported in many studies. But that is not what this study addresses and I remain unconvinced that marine vertebrates can indicate for deep sea sediment communities, cold-water corals, rocky intertidal, mudflat or any other ecosystem dominated by invertebrates.
Wednesday, May 14, 2008
The Beagle Project
The latest and greatest edition of The Tangled Bank is at the blog of my favorite marine project, The Beagle Project. Karen James and Peter McGrath collaborate yet again to bring a collection of biology and evolution related posts collected from submissions from the last two weeks. Actually, this version has something I haven't seen for a while, a discussion on abiogenesis, from Larry Moran.
More relevant to The Other 95% is a post at Science Made Cool, on parasitic anemone. The bastards, in their larval stage, steal food from ctenophores. (I would link to the post directly, but I really want our readers to go to The Beagle Project and read the entire Tangled Bank.)
And buy a T-Shirt from them while you are there.
Saturday, May 10, 2008
Friday, May 9, 2008
Dover Publications has the best deal on the net for coloring books! For $3.95 plus S&H you can get 32 pages of underwater reef pleasure! Who says the blue-ringed octopus (below) has to have blue rings? Why not lemon, or dirt brown (to signify where you will be buried should you touch it)? Stocked full with corals, nudibranchs, and oh yeah, those swimming vertebrate things that Mike the traitor likes, this coloring book will be sure to inspire your little ocean diver! Just look at the pretty coral on the cover. Its too bad those blobby orange stripey things are in the way.
Hat tip to Michael Barton, FCD.
Thursday, May 8, 2008
While there is some debate over which creature is the coolest, it is generally understood* that marine molluscs and echinoderms both will face severe stresses coping with increased ocean acidification due to increased CO2 concentrations. The shelled molluscs use calcium carbonate to build their shells and echinoderms use it in creating their exoskeleton. Calcification is strongly related to ocean pH levels and there have been numerous studies looking at the impacts of pH on calcification rates and metabolism in marine inverts.
Much of the published research has been focused on the molluscs and hermatypic (reef building) corals, which has shown that acidification (with levels predicted for the year 2100) will have detrimental effects on calcification and on the metabolic rates of the animals under study.
New research was published yesterday in the Proceedings of the Royal Society B on the effects of ocean acidification on the brittle star Amphiura filiformis and its arm regeneration. The researchers from Plymouth Marine Lab exposed A. filiformis to pH levels of 8.0 (control), 7.7 (IPCC predicted average ocean pH by 2100), 7.3 and 6.8 for a 40 day period. Regeneration effects were tested by detaching one leg from half the subjects and two legs from the rest in each pH group. The team found significant results for the length of regenerated arms, the calcium content and the metabolic rate caused by decreased pH levels.
Some of the results were surprising. Specifically, they found that the amount of calcium - which dissolves in acidic conditions - in regenerated arms was higher in acidified tests than in controls. They also found that non-regenerated arms maintained calcium levels in lower pH and even increased calcium content at a pH of 6.8. The researchers included a test of the calcium content of the separated arms as well. In acidified conditions the dead arms lost calcium as expected.
Brittle stars must increase calcification in the arms just to keep pace with the calcium disolution occuring due to pH. With regenerated arms having an even higher calcium content, this means A. filiformis must significantly increase the calcification under these conditions. The research found that the length of the regenerated arms was longer in acidified test conditions. All of this points to increased energy expenditure under acidified consitions in order to maintain calcium in extant arms and regenerate lost ones. This was confirmed by the oxygen uptake study, which found a significant increase in metabolic activity linked to incresed acidification.
Sounds pretty good then. A. filiformis can increase their metabolism and fuel an increaced calcification to cope with acidification. Except... the researchers also found that muscle wastage occurred and increased with greater acidification. It appears that the muscles are the fuel for the metabolism increase. The muscle wastage happened in regenerated and extant arms subjected to acidification at a rate of up to 20% muscle loss over 40 days. So they can regenerate faster and the calcium levels are higher, but the muscles are weaker and the net effect is a less capable arm. The trade offs to cope with acidification
are killing them.
And why do we care?
These brittle stars are an echinoderm model for what may happen as the ocean becomes more acidic. The fact that they will be increasing their metabolism just to maintain calcium levels in their skeleton means greater stress and muscle loss, which in turn may mean less effective use of the arms which they use to burrow and feed. Keep in mind this was a short term experiment. The wastage seen in 40 days, while not fatal, could explain the mortality seen in experiments involving smaller pH changes over longer periods of time.
Burrowing brittle stars, such as A. filiformis, can be siginifcant ecosystem engineers in soft bottom areas through bioturbation and are a major food source (through nipped off arms) for a number of commercially important fish and crustaceans. Other echinoderms responsd in a similar way to acidification. This is a phylum that is, in many ecosystems, a key linkage in ecosystem dynamics and trophic webs so understanding how they react to environmental changes will be important to predict ecosystem changes.
The study also highlights the fact that acidfication affects different organisms in vastly different ways. The effects need to be examined on an organism level instead of only looking at processes. There is still a lot of research needed here, but right now it doesn't look good for the brittle stars, at least A. filiformis.
Wood, H.L., Spicer, J.I., Widdicombe, S. (2008). Ocean acidification may increase calcification rates, but at a cost. Proceedings of the Royal Society B: Biological Sciences, -1(-1), -1--1. DOI: 10.1098/rspb.2008.0343
Wednesday, May 7, 2008
The 32nd edition of the Circus of the Spineless is up at Deep Sea News! Go there and work your way through the Dichotomous Key to the Fauna of the Blogosphere. Some excellent posts without backbone, like always!
Saturday, May 3, 2008
Oh, man, do I love conch!
When I lived in Honduras, I was fortunate enough to get out to Roatan every few weeks for diving, Garifuna music, good food, and relaxation. One of the best parts for me was the near daily serving of conch. Usually it was as conch salad, but I love them in fritters as well. Unfortunately, Honduras Queen Conch are still being heavily fished, even though their numbers have decline very sharply since tourism increased.
Three conch shells
in the mangroves.
Photo ©Eric Heupel
And Belize... During my recent trip to Belize at South Water Cay and Carrie Bow Cay, there were only a handful of live conch to be seen, but hundreds of empty shells. Most of the live individuals were 2-3 years old. This is very disconcerting for a species which doesn't reach full size until 4-5 years and can live for up to 40 years. The large number of empty shells were often occupied by damselfish (Stegastes spp., especially beaugregories, who use them as shelter and nesting grounds, the little buggers can be quite aggressive about it as well (a study of that aggression was one of the things we studied there.)
Steve Palumbi has a nice Micro-Documentary movie about the
lifecycle of Conch at the Garthwait & Griffin Films MicroDoc website. Just found out that all the microdocs are now available on DVD through them. (They are also at Palumbi Lab at Stanford.)
If you love reefs, seagrass beds, and invertebrates, how can you not love the conch, a giant marine mollusk that helps keep macro algae under control? And they taste good. Oh, wait...except the whole CITES II listing and dangerously decreasing population, conservation...
Well, it looks like there are a few successful, complete life cycle conch ranching operations and Rick reports on the one in Turks & Caicos, Caicos Conch Farm, which appears to be doing a great job of helping wild conch populations, while continuing to provide a sustainable source of conch meat and shells.
guarding its conch shell.
Photo ©Eric Heupel
Friday, May 2, 2008
Pygmy Gobies Outdo James Dean
All right, so they are vertebrates. (Please don't kick me off the blog, Kevin.) I just wanted to write something cool during Coral Week, and I just realized that it's already Friday. So, with a bottle of "Hazed and Infused" beer at my side, I am going to wander into the world of a coral denizen that has no time to spare.
In a sad display of rampant unoriginality, most of the popular articles I found on the pygmy goby were cleverly titled "Live Fast, Die Young..." So, when I was thinking of a title for this post I struggled to resist the urge to use the phrase. It isn't clever any more, so I just had to stop myself before I finished the title.
The little buggers don't last all that long, it's true. The maximum lifespan is 59 days. So, what have you accomplished in the last fifty nine days? Probably not nearly as much as a pygymy gobi who just died today of old age; satisfied and leaving many grandchildren. It was born and lived three weeks as a larvae in the open ocean. Then it found a coral reef and settled in and hid from predators.
Females lay three clutches of eggs during their lives, and the fathers guard the eggs furiously until they hatch to become larvae who float through the ocean until they, in turn find their coral home and repeat the cycle again and again and again.
The cool part of the saga of the pygmy goby is that their short life spans their status as favored foods for predators places heavy selective pressure on them. Yep, back to evolution. (We just can't get away from it, can we?.) The pygmy gobi caught the attention of Astrobiology Magazine in 2005, following the release of a study authored by Martial Depczynski and David Bellwood of James Cook University. Depcsynski and Bellwood determined the lifespan of Eviota sigillata in part by scanning rings in the tiny fishes' otoliths (ear stones.) They lay down a ring a day, every day; and the rings are discrete, much like tree rings.
Okay, so I asked myself why Astrobiology would be interested in E. sigillata. Well, here is why:
In a series of supplemental field studies, the researchers showed that many small reef fish may be under intense pressure from predators. Daily mortality rates of 2%-8% were common, indicating the severe biological time constraints and intense selective pressure that this community experiences.
It has been a grand Coral Week in the blogosphere, and we learned that coral are not important just for themselves but also for the diversity of vertebrates dependent on them.
Until a recent marine discovery, the dwarf goby was also the record holder as the world's smallest vertebrate (animal with a backbone).
These findings on the shortest-living vertebrate, along with recent discoveries on coral reefs of the smallest and earliest-maturing vertebrate species, are helping to broaden our understanding of the range of vertebrate life histories and the potential for reef fish to contribute to this area of research.
Coral-reef ecosystems represent exceptional biodiversity and environmental stability, and this recent research is beginning to unravel the possible reasons for the ability of these ecosystems to support extremes in vertebrate evolution.
Living fast, dying young. It's over-rated, but instructive.
Posted by Mike Haubrich, FCD at 9:53 PM