Nature Blog Network

Wednesday, September 3, 2008

Right Whale Lice

Cyamus ovalis Photo: Vicky Rowntree, University of Utah

In an earlier post, I joked (well half joked) about the need to save the whale lice, even if you don't care about the right whales. I thought today I would expand on the brief comment about the lice and their special relationship with whale and how they can actually tell us about the populations of right whales and their evolution.

Image courtesy of Mariano Sironi, Institute of Whale Conservation, Buenos Aires

In the image above you can see the characteristic white and black rough patches known as callosities on the face of a right wale. The raised dark grey bits are indeed part of the whale. Those are rough ridges that become sharper and harder. They are not really lice, but a caprellid amphipod, in other words a crustacean. Whale lice specifically are in the family Cyamidae consists of 35+ species in seven genera and are collectively known as cyamids.

On each right whale around 5000 Cyamus ovalis coat the callosities and gives them their white color is Cyamus ovalis. In the spaces between the raised callosities live around 500 C. gracilis. On adult whales approximately 2000 C. erraticus live in the genital and mammary slits. C. erraticus is highly mobile though often occupying wounds, and living in large concentrations on the heads of young calves. Of these C. gracilis is the smallest with ~6mm long adults and with the other two species measuring ~12-15mm long as adults.

Closeup of Right Whale callosity with C. ovalis. From Iain Kerr, Ocean Alliance/Whale Conservation Institute

The cyamids were named "whale lice" by early whalers in reference to their own head and body lice. Mmmmm fun! While not actual lice, they behave similarly in a few key ways. Cyamids have no free swimming stage and spend their entire life on one species of whales, transferring from whale to whale through intimate contact, primarily between a mother and it's calf. They were recently used, similarly to their lice namesakes, to track the population structure and evolution of their hosts.

In 2005 a team of scientists published the results of their study of the population structure and evolution of right whales based on DNA studies of the whales' cyamids. The cyamid DNA is in some ways more informative than the whales' own DNA as the cyamids complete many generation per whale generation and the population of the cyamids, especially C. ovalis, is far greater than that of the whales, offering the researchers more mutations to track.

The team collected cyamids from globally distributed right whale strandings and used variation in the mitochondrial COI gene to analyze the population structures of both the cyamids and by inference the right whales they inhabit. The first finding was that there was no obvious population structure within ocean basins. They also found high levels of haplotype diversity but low gene differentiation suggesting a large population with high transfer rate between individual whales.

The North Atlantic and Southern Ocean populations however have apparently been fully isolated for several million years. This supports the view that the North Atlantic, Southern Ocean and North Pacific right whales have been isolated for millions of years and shouldbe considered separate species. In a gene tree for the right whale cyamids the three different nominal species clustered out as seven distinct species. C. avalis, C. gracilis and C. erraticus fall out with separate North Atlantic and Southern Ocean species which diverged approximately 6.3mya. Interestingly the Northern Pacific C. ovalis form a tight clade nested within the tree of the Southern Ocean C. ovalis suggesting that there was more recent contact those two populations than between the Northern Atlantic and Southern Ocean populations.

By studying the cyamid crustaceans Jon Seger and his team were able to provide another line of evidence that each oceanic basin population of right whales is in fact a distinct species. They also found four new species of right whale cyamids and that the number of right whales in each basin was higher than originally estimated for pre-commercial whaling populations.

Classification of the nominal species Cyamus ovalis:








Cyamus ovalis

Kaliszewska et al. (2005). Population histories of right whales (Cetacea: Eubalaena) inferred from mitochondrial sequence diversities and divergences of their whale lice (Amphipoda: Cyamus) Molecular Ecology, 14 (11), 3439-3456 DOI: 10.1111/j.1365-294X.2005.02664.x


  1. Wow, I had no idea the colour of the callosities was actually due to thousands of whale lice. That comes directly under the heading of "seriously cool yet somehow disturbing".

    That do the whale lice actually feed on? I always assumed they were parasites of the whales, but surely that's a pretty heavy parasite load? And why would the whale grow its own special microhabitat for its parasites?

  2. Great post, Eric!
    It just goes to show you how jokes can lead to serious scientific discussions.

    At least that's my defense.

  3. Aren't there also barnacles on whales?

  4. Jives -
    Ya never know where inspiration will strike.

    Chris -
    quite a parasite load, but they mostly feed on dead and dying skin and detritus that lands on or attaches to the skin, so maybe not really parasitic, but commensal, but still a lot of them.

    Re: Callosities - A very good and unanswered question as far as I can tell.

    The whales' use of callosities is not really understood (still so much to study and learn about them, especially behaviorally). Some hypothesize that the callosities are used in male fighting for position near females during mating season. Of course then why do females also have large callosities and why do the callosities begin to form on late stage fetus.

    Aydin -
    Yes there are barnacles which are not uncommon on whales, but they do have a planktonic stage. One I have been meaning to read is on the larval development and host cues for the barnacle Coronula diadema's cyprid stage larvae to recruit from plankton to whales.

    Another paper speaks specifically to the Coronula diadema and other barnacles on right whales, it is a slightly older paper, neither online nor in my library (Arggghh!).

    Scarff J.E. (1986). Occurrence of the barnacles Coronula diadema, C. reginae and Cetopirus complanatus (Cirripedia) on right whales. Sci. Rep. Whales Res. Inst. 37:129–153.

    Nogata et al. (2005). Larval development and settlement of a whale barnacle. Biology Letters vol. 2 (1) pp. 92-93 DOI: 10.1098/rsbl.2005.0409

  5. wow! I'm amazed. I knew a little about whale lice but never thought about their potential in looking at differences in whale populations...

  6. Are the lice only found on the callosities? I know other whales which don't have callosities have whale lice...

    Are the lice themselves different in terms of attachment morphology? I would think it is easier to attach onto a callosity than directly onto the skin.

  7. @Brine Queen: The C. ovalis cyamids coat the callosities, but the other two do not. Well in newborns there is a "bloom" of C. erraticus on the callosities (from nursing?) but then they move to the genital slits, wounds and other smooth skin areas of relatively low flow.

    The callosities are dense, hard callouses, except in babies, so perhaps C. erraticus is less adept at holding to the tougher skin? Or perhaps they simply utilize a mobile strategy to inhabit other areas, avoiding resource competition.

    A problem in determining some of the answers, is that much of the available information, especially recent information, comes from populations of cyamids on beached whales. Early papers and book references are primarily ID keys with gross morphology but little detail of behavior etc.

    @Aydin: If you look at the full shot of the callosities close-up there appears to be at least one barnacle in the callosities area. In the far left edge of the image in the vertical center is what may be a barnacle.

  8. Do these pictures look like anyone you know?


  9. Woa!

    For more than just a second there I though the one on the left was my father! So did Tammy & Johann.
    (Without snow on it, my beard is not white - yet)


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