"So, naturalists observe, a flea has smaller fleas that on him prey; and these have smaller still to bite ’em; and so proceed ad infinitum."
- Jonathan Swift

August 31, 2010

August 31 - Placobdelloides jaegerskioeldi

Yesterday, you met Oculotrema hippopotami, a parasite of hippos that lives under their eyelids. Now, today, meet a parasite from the other end. The leech, Placobdelloides jaegerskioeldi, lives in the last 10 centimeters of the rectum of hippopotamuses and feeds on blood through that delicate tissue. A few years ago, I did some pretty exciting fieldwork in South Africa collecting these critters with Mark Siddall. But, don't worry - it was not necessary for anyone to reach up into the backside of any hippos (nor distract them on the other end). We were able to obtain some specimens when a nuisance hippo had to be culled by the Park Service there and the rangers very kindly removed some tissue with leeches attached for us (click on photo for a better view of the adult plus several of its offspring). However, we still spent a very harrowing morning poking around a river, looking for more samples, with hippos just 30 feet away or so. These leeches were collected as part of a larger project that we were conducting on the endosymbiotic bacteria that they have.

August 30, 2010

August 30 - Oculotrema hippopotami

The hippopotamus is notorious for being one of (if not the most) dangerous large animals of Africa, as they are extremely aggressive and unpredictable, and are responsible for killing more people than some of the iconic predators of Africa such as lions and crocodile. However, even this fierce giant is ailed by a tiny irritant - Oculotrema hippopotami - a species from a group of ectoparasitic flatworms known as the monogeneans.

Most monogeneans live on the skin or gills of fish, however there is an unusual family of monogeneans called the polystomatids that live mostly in the bladder of frogs and turtles. O. hippopotami can be considered even more of an oddball out of a family of oddballs. Not only has it colonised a mammal, it also lives in a peculiar part of its host. As its name implies, it lives in proximity of the hippo's eye, more specifically, under the eyelids. So for all its brazen brawn and strength, the mighty hippo is not immune from being parasitised!

Photo is from this site.

Contributed by Tommy Leung.

August 29, 2010

August 29 - Linguatula taenioides

Linguatula taenioides is a species of pentastomid worm that alternates between an herbivorous mammal (e.g. sheep) and a carnivorous mammal (e.g. wolf). The adults, which can be quite large - we're talking females that can be 4 inches or so! - live in the nasal passages. The eggs are sneezed out where they get eaten by grazing or browsing animals. Once into the gut of this intermediate host, the larvae, armed with two short claw-like arms, bore through the tissue of this host until they find a place to reside such as the liver or the lungs. There they encyst and wait for the host to be eaten, when they will repeat this process until they get to the lungs or nasal passages of the carnivore and mature into sexually reproducing adults.

August 28, 2010

August 28 - Cyttaria espinosae

Here's another parasite that people eat on purpose. Cyttaria espinosae is a fungus that is a parasite of beech trees (Nothophagus) and is native to Chile, where locals call it Digüeñe, Lihueñe or Quideñe. The fungus produces fruiting bodies that look remarkably like golf balls - and for a similar reason. The little divots in the fruiting body seem to promote air flow around them - which helps the fungal spores disperse in the wind. Locals like to serve them in salads and it supposedly has a gelatinous texture.

August 27, 2010

August 27 - Crataerina pallida

Crataerina pallida or the swift lousefly, is a hippoboscid fly that feeds off the blood of swifts that are found in Europe and Asia. The life cycle of the parasite is synchronized with the life cycle of the birds. In the late summer, the flies produce larvae (not just eggs), that will pupate and basically hang out like that over the winter in the birds' nests. The next spring, when the birds lay a new batch of eggs and the hatchlings are present, the flies will finish their development, feed off the baby birds and their parents, and begin the cycle all over again.

August 26, 2010

August 26 - Plasmodium malariae

Plasmodium malariae is another of the five species of Plasmodium that cause the disease malaria in humans, but this is the one you need to worry about least. It's not because it's only found in a tiny area - to the contrary, it has an almost worldwide distribution. But, the symptoms that it produces are fairly mild and it's rarely fatal. The fevers induced from infection with P. malariae occur every three days, thus it was known as "quarten" malaria in the ancient world (the Romans did not use zero). A species originally isolated from New World monkeys known as Plasmodium brasilianum was recently found to be genetically indistinguishable from P. malariae and probably represents a shared parasite, though the order of the move is still somewhat uncertain, i.e. whether human infections in the New World have recently spilled over into monkeys or whether this is a recent zoonosis acquired by humans.

August 25, 2010

August 25 - Ixodes holocyclus

This tick, the most commonly found tick along the east coast of Australia, is sometimes called the "Paralysis Tick" due to the unusual symptoms that it can produce in some people. Ixodes holocyclus lives in the wet forests, primarily, and would prefer to feed on Australia's charismatic marsupials (koala, kangaroos, etc), but will readily take its blood meal from humans if it encounters one instead. Toxins in the tick's saliva seem to disrupt neurotransmitters and can produce paralysis in humans, dogs, or other hosts and this can even be fatal if not treated because the paralysis can include muscles for pretty important things like breathing, swallowing and circulation. That said, paralysis from these tick bites is fairly rare, as it is necessary for the tick to remain attached for many days before the toxins will have these kinds of effects, so careful inspection of yourself or pets if in the area can literally be a life-saver. The good news is that there is an antiserum that can be administered if paralysis does set on. The image is a nice example, too, of how drastically different in size a tick will be before and after their blood meals.

August 24, 2010

August 24 - Thyca crystallina

Thyca crystallina is a tiny little limpet mollusc that lives on and sucks the "blood" - the hemolymph - out of blue sea stars (Linckia laevigata). The females of this species can become permanently attached to the exoskeleton of the echinoderms and just live their happily, feeding - oh and mating - with a tiny little male, one-tenth their size, that just lives in their shells and fertilizes her eggs. One might say that they are sort of a "tick of the sea" (oh, this really ought to confuse Jessica Simpson).

The image comes from this site.

August 23, 2010

August 23 - Lobatostoma manteri

Lobatostoma manteri is a species belong to a group of parasitic worm call the Aspidogastrea. The aspidogastreans are a very ancient group of parasitic flukes and are the sister group to the far more numerous and diverse digenean trematodes. In contrast to the digeneans which have a 3-host life-cycle (or variations on such), aspidogastreans only have 2 hosts in their life-cycle with the larval stage living in a mollusc and the adult living inside the gut of fishes. Unlike their digenean cousins, aspidogastreans do not asexually multiply within the mollusc host.

Lobatostoma manteri itself can be found on many tropical islands on the Great Barrier Reef of Australia. The definitive host for Lobatostoma is the Snubnosed Dart, Trachinotus blochi, from which the parasite's eggs are shed into the surrounding water. Marine snails become infected when they ingest the eggs and the larvae hatch from the eggs then develop into juvenile stages within the snail, which are in turn eaten by the Snubnosed Dart. L. manteri is very host-specific to this fish host because only that particular species of Dart has the well-developed pharyngeal plates (special teeth found in the throat of some species of fish) necessary to crack the hard shells of snails.

While it is a popular (and misguided) belief that the evolution of parasitism results in a lost of morphological complexity, this is a misconception, as the lost of certain sensory organs (such as eyes) which not necessary for navigating within the body of the host are replaced by the evolution of other sensory systems which are more appropriate for such an environment. Lobatostoma manteri has a complex and extensive nervous system, and the surface of the larval stage is dotted with over 8000 sensory receptors, with the adult (which grows to 4 mm in length) estimated to be covered in 20000-40000 receptors!

Contributed by Tommy Leung.

August 22, 2010

August 22 - Cuculus fugax

We have met other cuckoos before, birds that are known as brood parasites that usurp other birds' nests and trick them into raising their chicks instead of their own. Cuculus fugax, commonly known as Hodgson's Hawk-cuckoo, is a native of Southeast Asia that proves in a way that birds are pretty hard-wired and easy to fool. The parasitic bird lays one egg in the nest of another bird and when it hatches, it kicks any resident chicks out of the nest. And then it begs its new parents to feed it. But, the little chick is tricky - because it now only has one mouth gaping open for the parents to see, it also flashes the undersides of its wings, which have patches that look like two other chick mouths. The parents then go out and forage for three hungry chicks, bringing back enough food to feed the hungry cuckoo.

August 21, 2010

August 21 - Lucilia silvarum

Lucilia silvarum is a species of blowfly that has been found across much of the northern hemisphere. Females need to lay their eggs in a moist, nutrient-rich place and while this sometimes is a pile of animal feces, they also seem to have a fondness for the backs of frogs and toads. The eggs hatch and the larvae bury into the skin of the frogs and consume tissue. This is very often fatal for the frogs, though some species seem to have evolved an ability to survive these nasty infections. But, frogs and feces are not the only spots a female L. silvarum will lay her eggs -they will also use corpses and, because their development timing is so well known, can be helpful for forensic investigations.

August 20, 2010

August 20 - Ophryocystis elektroscirrha

Ophryocystis elektroscirrha is a protozoan parasite that infects monarch and queen butterflies. Spores of this parasite are ingested by the caterpillars and will migrate through their bodies to the hypoderm. When the caterpillar pupates, the parasites reproduce sexually and produce lots of daughter spores. These spores will cover the scales and abdomen of the adult butterflies when they emerge, where they will be ready to be rubbed off onto the host milkweed plants and available for the next generation of monarchs to ingest them and begin the cycle all over again. The fitness effects of this parasite on the butterflies is varied and includes lower survival, smaller size, and lowered flight performance.

Image is from The Monach Lab at the University of Minnesota.

August 19, 2010

August 19 - Leishmania tropica

"Baghdad Boil"..."Jericho buttons"..."Oriental sore" - these are the common names for a rather nasty infection called cutaneous leishmaniasis by one of several species of Leishmania, including Leishmania tropica. These parasites are single-celled eukaryotes called kinetoplasts, related to trypanosomes such as Tryanosoma brucei and Trypanosoma evansi. L. tropica and its kin are vectored by sandflies and are transmitted when these insects take bloodmeals from humans and other mammals. These nasty little buggers are not afraid of the vertebrate immune system, either - oh no - they go right for the macrophages themselves and invade these cells. The infection causes really disgusting sores on the skin that will not heal and which can become sites for secondary infections. Treating these parasites is itself a very risky venture, as the most commonly used drugs are those containing antimony, which is a heavy metal; new drugs are being developed, however. If you've got a strong stomach, do an image search for "cutaneous leishmaniasis"...but don't say I didn't warn you.

August 18, 2010

August 18 - Profilicollis altmani

Parasites that have complex life cycles involving marine creatures really baffle me - the odds of them completing their life cycle just seems so unlikely - and yet they do. Profilicollis altmani is a species of acanthocephalan (thorny-headed worm) that uses mole crabs (Emerita spp.) as its intermediate hosts and then infects shore birds like Herring Gulls as the definitive host. The adult parasite attaches to the intestines of the bird and then will release eggs into its feces where they somehow make their way to new foraging crabs. This parasite is also of recent interest because it appears to have jumped hosts into sea otters, where it can cause fatality. The otters are not normally hosts of these parasites, but perhaps are becoming infected as a result of eating prey that they normally do not.

Photo by Tricia Goulding, Romberg Tiburon Center for Environmental Studies, San Francisco State University.

August 17, 2010

August 17 - Acanthoparyphium sp. B

The purpose of this blog is to celebrate parasite biodiversity, but what some people might not realise is that much of parasite biodiversity might simply be hidden from sight, in more ways than one. It isn't just that parasites are hidden within the body of their free-living host, sometimes, previously unrecognised species could be right under your nose and you wouldn't know it even if you see it.

For example, take today's parasite. For quite a few years, it was thought that the Acanthoparyphium found at Otago Harbour, South Island, New Zealand consisted of a single species. It infects the marine snail Zeacumantus subcarinatus as the first host, within which it undergoes asexual replication to produce free-living larvae call cercariae which then infect the New Zealand cockle Austrovenus stutchburyi (which also happens to be the second host for another trematode, Curtuteria australis - featured on January 15). However, during some routine investigation with molecular markers, it was serendipitously discovered that what was initially thought to be a single species of trematode actually turned out to be composed of at least four different species that are morphologically indistinguishable from each other (or at least very similar), but genetically distinct. At the moment, they are provisionally known as Acanthoparyphium species A, B, C, and D. While they all utilise the same species of snail as the first host in their life-cycles, since the initial discovery, it has been found that they differ in term of the next host they infect. Whereas the encysted stages of species A were commonly found in cockles, those of species B were found to infect ragworms, and the second host of species C and D remains unknown.

Cases like this goes to show that there's more than meets to the eye with most parasites!

For more details see:
Leung, T.L.F., Keeney, D.B. and Poulin, R. 2009. Cryptic species complexes in manipulative echinostomatid trematodes: when two become six. Parasitology 136: 241-252

Photo credit: Haseeb Randhawa and Matthew Downes.
Contributed by Tommy Leung (with B for Birthday - Happy Birthday, Tommy!)

August 16, 2010

August 16 - Lernaea sp.

"Ummm...you have something hanging off your gill..." says one fish to another. Could very well be an anchor worm, which is not a worm, but instead is a parasitic copepod. They begin life as free-living, but after the female mates, she burrows herself into the flesh of a fish and becomes a long worm-like creature (hence the name). These parasites can cause major problem for aquarium and pond fish such as goldfish or koi, both because of the damage they do burrowing in and back out and also because of promoting opportunistic infections.

Photo is by Alaine Knipes. Check out this video of an anchor worm on a minnow that she made, too.

August 15, 2010

August 15 - Spinturnix americanus

Spinturnix americanus is a species of mite that uses several species of vespertillionid bats as its hosts, including little brown bats (Myotis lucifugus), big brown bats (Eptisecus fuscus) and eastern pipstrelles (Pipistrellus subflavus). These mites are specialists on the wings and tail membranes of their flying hosts and have no interest in venturing into the forest of fur on those mammals.

Photo is by Christopher M. Ritzi and comes from this site.

August 14, 2010

August 14 - Fahrenholzia pinnata

Fahrenholzia pinnata is a species of louse that is found sucking blood on kangaroo or jumping mice in the western U.S. The name of this genus is in honor of Heinrich Fahrenholz, who was a German entomologist who studied lice. The pattern that the evolutionary trees of parasites tend to mirror those of their hosts is now called "Fahrenholz's Rule" (though was coined by Eichler, not by Fahrenholz himself). And, lice are almost always the textbook example of this rule. This is because lice spend almost their whole lives on their hosts and become adapted to clinging to their hair to avoid being groomed away. The only time they have an opportunity to transfer from one host to another is via direct contact - which, if you're a rodent, is likely to only occur between members of the same species. This phenomenon is especially true in gophers. See the post from July 16 for more information on gopher lice.

August 13, 2010

August 13 - Phytophthora infestans

Phytophthora infestans is a potato-infecting water mold (oomycete) that travelled with tubers from America to Europe and was the causal agent of the Irish Potato Famine in the 1840s that led to massive emigration to the New World. The potato late blight disease is difficult to control even today, and is usually attempted by repeated spraying of chemicals. Although P. infestans might look like a typical fungus, it isn't one, but rather is related to brown algae, and relies on water for efficient infection. Swimming flagellated zoospores start germinating when they come into contact with host plants like potatoes, tomatoes and a few other nightshade relatives. Quickly a hyphal network grows between the cells of leaves and tubers. Hyphae produce digit-like extensions called haustoria that stick into the cells to acquire nutrients. To suppress the plants immunity, P. infestans delivers dedicated effector proteins into host cells (learn more here). At later infection stages the parasite shifts into killing mode and destroys leaves to finally produce sporangial containers filled with an army of new zoospores to start a new infection cycle. Sequencing of the pathogen’s genome revealed a huge amount of repetitive regions which enable the parasite to exquisitely adapt to new conditions.

Image and post contributed by Sebastian Schornack.

August 12, 2010

August 12 - Tetrameres sp.

Nematodes often exhibit sexual dimorphism, usually with the males being smaller than the females. An extreme example is found in species of the genus Tetrameres, which live in the glands of the proventriculus of birds. The males look like typical nematodes, long and thin, but the females expand as they become distended with eggs to these bright red, pea-sized individuals that barely resemble nematodes at all, dwarfing the males. As they expand, they can cause pressure necrosis in the tissues of the host.

Post and image contributed by Mike Kinsella.

August 11, 2010

August 11 - Protospirura numidica

Protospirura numidica (Seurat 1914) can be found inhabiting the stomach or lower esophagus of the deer mouse, Peromyscus maniculatus as well as other small rodents that are commonly found in the Great Basin Desert in Utah including: Ord’s kangaroo rat, western harvest mouse, Great Basin pocket mouse, and the piñon mouse (Grundmann and Frandsen 1960). P. numidica has a complex lifecycle and requires passage through a beetle (Cook and Grundmann 1964). Interestingly, there is an increase in parasite prevalence in the fall in deer mice, likely due to the increase in insect consumption by the definitive host. A mean of 4 nematodes per host is common, however, I found up to 50 individual nematodes in a single deer mouse stomach. Talk about digestion issues…de-wormer please?

Contributed by Craig Gritzen.

August 10, 2010

August 10 - Dicrocoelium dendriticum

Dicrocoelium dendriticum, better known as the lancet fluke, is a species of fluke that lives in the liver of grazing mammals such as sheep. Like most flukes, it has a 3 host life-cycle, the adult worm living inside the sheep, lay eggs which are shed into the environment with the sheep's faeces. The first intermediate host for this parasite are terrestrial snails which become infected by accidentally ingesting the parasite's eggs. The parasite undergoes clonal replication inside the snail, producing hundreds of infective larvae which are then packaged into slime balls and extruded into the environment. For some reason, these slimeballs are eagerly gobbled up by ants which are the parasite's second intermediate host.

Now sheep are not known for including ants as a significant part of their diet, so how is D. dendriticum supposed to get itself into a sheep through an ant? It does that by taking control and setting its ant host up for a rendezvous every evening. Once infected, the ant begins to behave very oddly indeed. As dusk falls, it would crawl up a blade of grass until it reaches the tip, then firmly clamps itself into that position with its mandible for the entire evening. The infected ant would perform this peculiar routine every night, but as the sun rises, it would resume its usual activities - assuming that it has survived the evening and not been incidentally ingested by a hungry sheep. By inducing this peculiar behavioural pattern in the ant host, D. dendriticum brings itself (through the ant) within the vicinity of a grazing sheep, thus setting up an encounter which otherwise would not have occurred, allowing it to complete its seemingly obtruse life-cycle.

Check out the very funny cartoon version of this life cycle here.

Contributed by Tommy Leung and thanks to Craig Carlough (Lancaster, PA) for sending along the Oatmeal comic.

August 9, 2010

August 9 - Schistocephalus solidus

Schistocephalus solidus is a tapeworm with a three-host life cycle. Free-swimming coracidia are eaten by copepods, the first host. After about 2 weeks of development in copepods, the worm is ready to be transmitted to the second intermediate host, three-spined sticklebacks. In the fish host, the worm grows to gargantuan sizes; in exceptional cases it can even weigh more than the host. Fish are impacted in various ways by infection, showing altered behaviours (risk-taking, flight response, etc.), brain chemistry, and immune responses. These modifications are thought to lead to a higher transmission rate of the parasite to its final host, fish-eating birds. Within 48 hrs of reaching the intestine of the final host, the parasite is reproductively mature and producing eggs. After about a week, the worm has produced all its eggs and dies. This short and explosive reproductive period is presumably the reason why S. solidus is one of the few helminths that can be bred in vitro.

Contributed by Daniel Benesh.

August 8, 2010

August 8 - Nybelinia surmenicola

Nybelinia surmenicola is another tapeworm parasite that infects the salmon shark, Lamna ditropis. The sharks get these parasites when they prey on either fish or squid that are serving as the intermediate hosts for this parasite. Salmon sharks are interesting creatures, themselves, in that they one of the few fishes that exhibit homeothermy, or the ability to regulate their own body temperature. These sharks live in the northern Pacific ocean. At least one case of a human infection of Nybelinia surmenicola has been reported. A Japanese woman complained of severe pain in her mouth after eating uncooked squid. Doctors removed four larval tapeworms from her tongue and pharynx.

August 7, 2010

August 7 - Caligus oculicola

The parasite Ommatokoita elongata probably made a few of you squeamish. If so, then you probably want to just close this page, too. Caligus oculicola is a recently described species of copepod that lives on the surface of the eye of tiger sharks (Galeocerdo cuvier). Although most species of Caligus infect teleost (bony) fish, not sharks, this copepod seems to have found an ideal habitat of the eyes. They have specialized structures that allow them to adhere, suction-cup style, to the eye and then they proceed to feed on the host's tissue through a scraping and swallowing kind of fashion.

Drawing of a male Caligus oculicola, modified from the original paper.

Thanks to Laurence Frabotta and Colleen Ingram for nominating this parasite.

August 6, 2010

August 6 - Paronatrema sp.

On the whole, digenean trematodes aren’t very common in sharks. Parasitologists learn early that tapeworms rule the sharks, and trematodes rule the fishes. There are a few exceptions, like the giant flat gorgoderids that live in the body cavities of sting rays, and today’s parasite, Paronatrema, which is a member of a very poorly known group called the syncoeliids. Paronatrema and the only syncoeliid that infects sharks – Otiotrema – are unusual in another way: they are ectoparasites. Nearly ALL trematodes are endoparasites; even the ones that live on the skin (e.g. Transversotrematids) are technically endoparasites because they are under the first layer of skin. Not syncoeliids; these are bold enough to choose a totally different host group and to live free and open on the surfaces of the gills and branchial cavity of sharks. How do they do this? No one really knows, because they have hardly been studied at all. Given that you have to put your hand in a tiger shark’s mouth to get one, perhaps its no surprise…

Contributed by Al Dove.

August 5, 2010

August 5 - Dinemoleus indeprensus

Dinemoleus indeprensus is a parasitic copepod which is in the same family as Pandarus rhincodonicus (the whale shark ectoparasite), however there is something that sets this little guy apart from the rest. For obvious reasons, parasite fauna are usually described only after their host species are recognised - but not this one. D. indeprensus is an ectoparasite of the Megamouth Shark (Megachasma pelagios), and it is notable for being probably the only parasite to have been formally described before its host. Due to some unusual reasons, while D. indeprensus was already described in 1978, the Megamouth itself was not officially described until five years later in 1983!

The description for D. indeprensus is here:
Cressey, R., Boyle, H. (1978) A new genus and species of parasitic copepod (Pandaridae) from a unique new shark. Pacific Science 32:25-30, which is also where the picture came from - check out the intro of that paper!

Contributed by Tommy Leung.

August 4, 2010

August 4 - Pandarus rhincodonicus

The host for today's parasite is the mighty whale shark (Rhincodon typus). Pandarus rhincodonicus is parasitic copepod which lives on the skin of the whale shark and are frequently found on the leading edge of the shark's lips and fins. As you can imagine, this is not an easy place to make a living, as the whale shark swim at a speed of about half a metre (almost 2 feet) per second, the drag forces on P. rhincodonicus is substantial. However, the copepod's streamlined shape minimises drag forces, while a series of adhesion pads and hooks allow it to cling tightly to the whale shark's skin. The edge of the carapace is also fringed, which may also help generate a vacuum which press the copepod firmly down upon the skin, acting like a living suction pad.

The photo is a dorsal and ventral view of a female copepod and it came from this paper:

Norman, B.M., Newbound, D.R., Knott, B. (2000) A new species of Pandaridae (Copepoda), from the whale shark Rhincodon typus (Smith)' Journal of Natural History 34:355-366.

Contributed by Tommy Leung.

August 3, 2010

August 3 -Branchotenthes robinoverstreeti

Guitarfish are really rays, not sharks, but they're closely related and some species are also called sand sharks, so thought this one could slide as a "Shark Week" parasite. Besides, the irony of this parasite is just too much to pass up. Branchotenthes robinoverstreeti is a recently discovered monogenean parasite that infects the gills of guitarfish in the Indian ocean. The haptors of B. robinoverstreeti, which are the posterior structures used to attach to their hosts, look strikingly like the head of a guitar with the six tuning keys. The parasite was named after Dr. Robin Overstreet, an eminent parasitologist of the Gulf Coast Marine Laboratory.

Image is from the original paper.

August 2, 2010

August 2 - Gnathia trimaculata

TThe parasite for today is a parasitic isopod belonging to the family Gnathiidae - the larvae of this particular species feed upon the requiem shark (Carcharinus melanopterus). There are many different species of gnathiids parasitising many different species of fish, and they have an interesting life-cycle which involve "protelian parasitism" where only the juvenile stages (called a praniza) are parasitic, while the adult stages are free-living. They go through several stages of development, alternating between feeding and non-feeding developing stages (when they are engorged with blood) before reaching sexual maturity.

They are almost like a functional equivalent of ticks for fishes - they wait in ambush for a passing host, and when one arrives, it climbs onboard, sucks blood for a few days until full, then drops off to develop into the next stage. And like ticks, they can also act as vectors which can transmit blood parasites between the fishes they feed upon.

The photo shows a pair of third-stage pranizae, scale bar is 1 mm and it came from this paper:

Coetzee, M.L., Smit, N.J., Grutter, A.S., Davies, A.J. (2009) Gnathia trimaculata n. sp. (Crustacea: Isopoda: Gnathiidae), an ectoparasite found parasitising requiem sharks from off Lizard Island, Great Barrier Reef, Australia. Systematic Parasitology 79:97-112

Contributed by Tommy Leung.

August 1, 2010

August 1 - Anthobothrium sp.

Sharks are predators, usually thought of as at the top of the food chain in ocean ecosystems. As such, they can accumulate a lot of poisons or toxins, as we have seen recently in the news with scares of mercury in tuna. But it turns out that some of their parasites can be accumulating the toxins in extremely high concentrations and there is speculation that in doing so, they may be protecting their hosts. A recent study by scientists at the University of Aberdeen, Scotland, and the University of Tehran, Iran, found that tapeworms such as Anthobothrium, had concentrations of cadmium and lead, two heavy metals, that were as much as 455 times that of their hosts. The scientists suggest in their paper that parasites can serve as useful bioindicators - squishy little canaries in coal mines, if you will.

You can read about this in the original paper or on this site.

Image is of the type species of the genus Anthobothrium, A. cornucopia, from its original description in 1850.