October 19 - Pseudomyicola spinosus

Pseudomyicola spinosus is a parasitic copepod that is found in more than 50 species of bivalves around the world, ranging from clams to mussels to scallops. It dwells in the mantle cavity of the bivalve, where it grazes on mucus produced by the host. This copepod has a pair of hook-like attachment appendages that allow it to cling to the host tissue and avoid being swept away by the constant water flow that passes through the mantle cavity. In large numbers, they can cause considerable tissue damage to the host - the constant attachment and reattachment of the copepod (which can be highly mobile within the host's body cavity) aggravate host tissue, causing epithelial erosion and induce over-production of mucus. At lower infection levels, the tissue damage caused by the copepod is almost negligible, but it does have a more subtle effect on its host. It has been found that infection with just a few P. spinosus is associated with higher levels of infections by metcercarial cysts of echinostomatid trematodes such as Curtuteria australis and Acanthoparyphium. Once again, this is possibly due to the effects of the copepod's attachment appendages, which damage the epidermis in such a way that facilitates subsequent invasion by trematode cercariae.

References:

Cáceres-Martínez, J. and Vásquez-Yeomans, R. (1997). Presence and histopathological effects of the copepod Pseudomyicola spinosus in Mytilus galloprovincialis and Mytilus californianus. Journal of Invertebrate Pathology 70, 150–155.

Leung, T. L. F. and Poulin, R. (2007). Interactions between parasites of the cockle Austrovenus stutchburyi: Hitch-hikers, resident-cleaners, and habitat-facilitators. Parasitology 134, 247–255.

Post and image by Tommy Leung.

October 14 - Lepeophtheirus pectoralis

Lepeophtheirus pectoralis (Müller, 1776) is a caligid copepod usually found on the body surface of the European flounder, Platichthys flesus (Linnaeus, 1758) (Teleostei: Pleuronectidae). Its relatively large body size makes it easily recognizable to any observer. As any other caligid, the parasite has the ability to move freely over the body surface of its host. Notwithstanding, it is remarkable in presenting a well-defined spatial distribution pattern on the host’s body, with the gravid females accumulating, mainly, in the inner surfaces of the pectoral fins. Indeed, this behavioral feature was in the origin of the species name. The records in the literature suggest that the parasite tends to occur with considerably regularity and high numbers on its host.

For details on the species ecology, see the papers below:
Cavaleiro, F. I. & Santos, M. J. (2007) Survey of the metazoan ectoparasites of the European flounder Platichthys flesus (Linnaeus, 1758) along the north-central Portuguese coast. Journal of Parasitology 93, 1218-1222.
Cavaleiro, F. I. & Santos, M. J. (2009) Seasonality of metazoan ectoparasites in marine European flounder Platichthys flesus (Teleostei: Pleuronectidae). Parasitology 136, 855-865.

Contributed by Francisca I. Cavaleiro & Maria J. Santos, Universidade do Porto, Faculdade de Ciências, Departamento de Biologia, Rua do Campo Alegre, s/n, FC4, 4169-007 Porto, Portugal.

October 10 - Microdajus langi

The parasite for today comes from a strange family of ectoparasitic crustaceans called Tantulocarida. There are only a few species within this family and they have a very peculiar development. They are parasitic on a number of deep sea crustaceans, and Microdajus langi itself infects small, shrimp-like crustaceans call tanaids.

Tantulocarids have a very strange life-cycle which is either asexual (which is more common) or sexual (relatively rare). In the asexual cycle, only females larvae are produced. Non-feeding larval stages known as tantulus are released from asexual females which resemble sacs and these larvae can directly attach and infect another host. On the left side of the accompanying photo is an immature female that had just attached onto the host, but once it is attached, it undergoes a strange transformation. On the right side of the photo, you can see a female that has just begun undergoing this development and she eventually develops into a bloated sac filled with eggs.

However, in the sexual cycle both males and females are produced and while males have never been observed alive, they have well-developed swimming legs and sensory organs which allow them to actively seek out and inseminate females. Once fertilised, the female attaches herself onto a crustacean host to start the cycle anew.

Photos from: Boxshall, G.A. and Lincoln, R.J. (1987) The Life Cycle of the Tantulocarida (Crustacea). Philosophical Transactions of the Royal Society of London. Series B 315: 267-303.

Contributed by Tommy Leung.

September 24 - Acanthochondria cornuta

Acanthochondria cornuta (Müller, 1776) is a chondracanthid copepod that infects the European flounder, Platichthys flesus (Linnaeus, 1758) (Teleostei: Pleuronectidae), in different geographic locations, including, the coast of Portugal. It is a site-specific marine ectoparasite that occurs generally with regularity and in high numbers in the branchial chambers of its flatfish host. As in all other species of chondracanthids, the male is dwarf, being usually found attached to the female in the vicinity of the genital region. In other words, he is not found directly attached to the fish host and is called a “hyperparasite”.

See these papers:
1. Cavaleiro, F. I. & Santos, M. J. (2007) Survey of the metazoan ectoparasites of the European flounder Platichthys flesus (Linnaeus, 1758) along the north-central Portuguese coast. Journal of Parasitology 93, 1218-1222.
2. Cavaleiro, F. I. & Santos, M. J. (2009) Seasonality of metazoan ectoparasites in marine European flounder Platichthys flesus (Teleostei: Pleuronectidae). Parasitology 136, 855-865.

Contributed by Francisca I. Cavaleiro & Maria J. Santos.

September 23 - Diphyllobothrium latum

A common item in Jewish cuisine is gefilte fish, small boiled balls of minced fish meat. Unfortunately, though, the preparation of these little treats typically involved testing the gefilte fish as it cooked, meaning early tastes were of undercooked fish. That habit resulted in lots of Jewish grandmothers becoming infected with a tapeworm called Diphyllobothrium latum. Native to Scandanavia and eastern Russia, these parasites were brought to the U.S. with immigrants who settled in Minnesota, Wisconsin and other northern climes all the way to the Pacific Northwest states and the worms easily adapted to the ecosystem there, infecting native fishes. The life cycle is complex and can involve numerous hosts, beginning with copepods that ingest the eggs and then moving up the food chain to larger and larger fish until they are consumed by a person. Many people do not realize that they are infected as the symptoms may, in fact be mild, even though the tapeworms can be more than 10 meters (i.e. more than 30 feet!) long and pump out a million eggs a day. A common one is a severe vitamin B12 deficiency, however. There are two important components to stopping the spread of this parasite: refraining from defecating in lakes and freezing fish before consuming and cooking it properly. These parasites have likely been associated with humans for a very long time - evidence of these worms has been found in settlements along the coast of South America that may be as old as 10,000 years.

Image from the CDC Public Health Image Library.

Read more about this parasite in Robert Desowitz's wonderful book, "New Guinea Tapeworms and Jewish Grandmothers".

September 16 - Balaenophilus manatorum

Balaenophilus manatorum is an ectoparasitic parasite of sea turtles and possibly manatees as well. Recently, specimens of this parasite were obtained from stranded loggerheads on the Spanish coast. Gross morphological and SEM studies could not distinguish these copepods from others that had been found on sea turtles off of Japan and so, for the moment, have been classified as that species. The parasites can be incredibly dense -the authors of this paper note that thousands were found on individual juvenile turtles. Other parasitologists have speculated that this species is the same copepod that has also been found on manatees in the Caribbean. Thus, either this parasite is very much a generalist or there are cryptic species yet to be determined.

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 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 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 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 - 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.

July 24 - Lepeophtheirus salmonis

Here's another species of parasitic copepod, but this one's not going to fish eyes - just feeding off the skin, mucus, and blood of its hosts. Lepeophtheirus salmonis is the salmon louse, which, as the name suggests, infects salmon and marine species of trout. These parasites can cause a great deal of morbidity in their fish hosts and may have severe consequences for both wild and farmed fish populations as very heavy infections of these parasites can kill the hosts. You can read more about these parasites on this site, which is also the source of the image.

July 22 - Ommatokoita elongata

If you find the idea of having something lodged in your eye distressing (ok let's face it, who doesn't?), then today's parasite is probably your worst nightmare. Fortunately for you, it is not a human parasite. The hosts for today's parasite are Greenland sharks (Somniosus microcephalus) and Pacific sleeper sharks (Somniosus pacificus) - both large deep water sharks. Ommatokoita elongata is a parasitic copepod, approximately 5 cm in length (almost 2 inches) with a very specific and truly cringe-worthy preference about where it attaches on to the host.The adult female copepod attaches herself to the shark's eye with an anchoring structure call the bulba, and grazes on the surface of the cornea (see photo, black arrow indicates attachment point), hanging off the eyes of the shark like a grotesque tassle

There are two possible reasons for the copepod's attachment site. Shark skin is covered in microscopic, teeth-like structures call denticles which can make it difficult for parasites to attach themselves to skin (though some species of parasitic copepods
manage). Secondly the eye is considered to be a "immunologically benign environment" for parasites, thus such an attachment is less likely to illicit an immune response.

While the parasite can cause significant damage to the cornea and result in blindness for the host, most sharks seem unaffected by the presence of the parasite and many sharks have the copepod in both eyes, strangely enough. This goes to show when considering the virulence (harmfulness of a parasite to its host) of a parasite, it is worth taking into account the perspective of the host involved - what may seem debilitating to us may not necessarily be the case for the actual organism in question.


Photo source: Borucinska, J.D., Benz, G.W. and Whiteley, H.E. (1998) Ocular lesions associated with attachment of the parasitic copepod Ommatokoita elongata (Grant) to corneas of Greenland sharks, Somniosus microcephalus (Bloch & Schneider) Journal of Fish Diseases, 21:415-422

Also some good photos of live Greenland sharks with the parasite can be seen in Caloyianis, N. "Greenland Sharks." National Geographic 194, no. 3 (1998): 60–71.

Contributed by Tommy Leung.

June 4 - Lernaeocera branchialis

Life is about dealing with changes, but for Lernaeocera branchialis, some of those changes are pretty profound. This parasitic copepod starts out as a free-swimming nauplius, like other crustaceans. Then, it turns into a copepodid and seeks out an intermediate host, something slow and easy to find, like a flounder. It mates with an opposite-sex copepodid on this host and then sets off to find its final host, usually a cod or haddock. It then completely metamorphosizes into a large (4 cm), red, worm-like thing with a big egg sac and "antlers". Its head remains inserted into the gills of the fish where it feeds from the blood and pumps out new eggs.

The photo is from this site.

May 23 - Proteocephalus pinguis

Proteocephalus pinguis parasitizes pike (how about them P's??). These are tapeworms (cestodes) that alternate between their fish hosts and copepod intermediate hosts. They have extremely simple scoleces and are small even as adults. The genus contains many other species that have similar life cycles, alternating between vertebrates and copepods. If the first vertebrate host gets gobbled up by a bigger one, then the tapeworms simply infect this host instead.

The photo is from this website.

March 27 - Haemobaphes diceraus

Haemobaphes diceraus is a parasitic pennellid copepod that is found on a variety of fish species. This is an interesting species because it is a type of crustacean and many people would never think of a crustacean as a parasite. It is also an interesting parasite because it looks nothing like a crustacean in its adult form. This parasitic copepod extends from the gills and into the bulbous ateriosus of the heart where the parasite is anchored. The distinguishing feature of this parasite is the large, spirally coiled egg sacks. These egg sacks project from the gill arch of the host fish. The egg sacks are attached to a trunk which extends into the heart. While some copepods are able to move about freely, this copepod has reduced segmentation and appendages in its adult form (Goater 1996). When the eggs hatch they are released into the water where they undergo a series of molts until they are developed enough to find a host. Pennellids such as the Haemobahes diceraus are unique in that they require an intermediate host. After fertilization of the egg the newly hatched parasite has a free swimming phase. It then locates a fish, attaches itself and grows to adulthood. (Goater and Jepps 2002).

References:
Goater, Tim. 1996. “Parasitic Copepoda.”
Goater, T. and Jepps, S. 2002. Prevalence and Intensity of Haemobaphes diceraus (Copepoda: Pennellidae) from Shiner Perch, Cymatogaster aggregata (Embiotocidae). Journal of Parasitology 88: 194-197.

Contributed by Taylor Phillips, Bucknell University.
Image from this site.