February 28 - Edwardsiella lineata

It seems that just about every group of organisms has evolved parasitism, but we haven't seen one of these yet - a parasitic sea anemone. And what do parasitic sea anemones feast on? (Don't be afraid...) Ctenophores - or comb jellies - are the hosts to these parasites. It's just the larvae of Edwardsiella lineata that are parasitic and the evidence is such that it's thought that this is a very recent strategy as all other members of the family have free-living larvae. Larval E. lineata embed themselves in their ctenophore hosts (they can do this from either direction - they can burrow in from the outside, or they can go through the gut if the ctenophore eats them first!). Once in position, they extend their mouths right into the ctenophore's gut, and ingest anything that the comb jelly has worked hard to eat. When it's had its fill, it simply removes itself and transforms into a regular looking sea anemone larva. Is it content to stop there? No, not always, as it turns out. Sometimes it is – and develops into a polyp (the anemone-looking thing). But sometimes it actually invades a second ctenophore and reverts back to the parasitic body form while it sucks away at more of the new host’s food. Greedy little buggers, aren't they?

Image and more info from this paper.
Click on the image to enlarge.

February 27 - Myrmeconema neotropicum

Yesterday, the parasite was saving coffee berries, today the parasite is making ants look like berries. Myrmeconema neotropicum is another nematode parasite that infects the ant, Cephalotes atratus in South America. The life cycle is somewhat similar to that of yesterday's parasite. Foraging ants pick up the nematode's eggs which have been shed in bird feces and feed them to their larvae. Inside the ant pupa, the worms hatch, mature and mate. As the embryos inside the female nematode mature, the gaster, or abdomen of the ant, swells and goes from being black, to translucent, to bright red. Adult ants then walk around with bright red abdomens held up into the air and are also slower and "clumsier" - perfect targets for frugivorous birds. The species, described in 2008, also changed the taxonomy of the ant hosts. Over a century before, a variety of tropical ants had been described based on their unusual red abdomens. We now know that they were just parasitized individuals. Makes me wonder how many other "species" have been erected based on parasite-induced morphological changes...

Image from figure of the paper.

You can read the original paper here.

February 26 - Metaparasitylenchus hypothenemi

It’s been a long week for me here at the AMNH. We’ve just finished up the interviews for prospective students for our Richard Gilder Graduate School and I am definitely in need of an extra cup of coffee this morning. So, perhaps it’s fitting to finish up this week of newly described Mexican parasites with Metaparasitylenchus hypothenemi (you’ll need a cup of coffee - or eight cups -to wrap your tongue around that moniker!). These are nematode parasites that infect coffee berry borers, beetles that are one of the most important coffee pests. The free-living adult worms are thought to mate in the coffee berries themselves and then the female nematodes penetrate into the larval beetles’ cuticles. There they wait, as the beetles proceed through their own developmental process, though pupal stage into the adult form. Like many nematodes, the eggs hatch within their mother (the photo shows a female filled with eggs and first-stage larvae) and even go through their first molt within the egg or soon after. Third-stage larvae leave the beetle hosts via the typical exit routes – the gastrointestinal and/or genital openings.

These nematodes pose an interesting biogeographic question as well. The coffee borer itself is native to Africa, so it is possible that the beetles brought this parasite to the New World with them, but it is also possible that the nematodes were native to the New World and hopped into these hosts when they encountered them. It is currently being studied as a possible biocontrol agent for these coffee pests. Go parasites! I need my coffee!

February 25 - Rallicola deckeri

Rallicola deckeri is a new species of chewing louse that was recently discovered on a Ruddy Woodcreeper in Campeche, Mexico. The other lice that have graced this site, Pediculus humanus humanus and Pediculus humanus capitis were both sucking lice. Chewing lice (Mallophaga) typically feed on skin or feathers and most commonly parasitize birds. They often have elongated bodies, but wide, flat heads.

February 24 - Gnathostoma lamothei

This nematode, with spines and hooks covering its body lives attached inside the stomach of racoons in Southern Mexico. These worms lay their eggs in the host’s stomach and the eggs find their way to outside when the vertabrates poop. If this happens close to freshwater and the parasite is lucky enough, a free-living larva is liberated from each egg. These larvae can live for a few days in the water until it dies or… is swallow by a copepod. The nematode then penetrates the digestive system of the copepod and lives there until the copepod is ingested by a fish. Once in the fish, the nematode again penetrate the intestine and finds its way into the muscles where it encysts. The life cycle of Gnathostoma lamothei comes full circle when a racoon eats fish flesh with the parasite encysted in the muscles. Inside the raccoon, the parasite penetrates the intestine, spends some time there, and then finally enters the stomach to start the cycle again.

The life cycle of G. lamothei is fascinating but in reality is much more complicated. Larvae allocated in the muscle of fish can infect an extraordinary number of animals other that dogs and cats. For example, if a frog or snake eats the infected fish, the nematode penetrates the intestine again to encyst in the muscles. The nematode larvae can move from animal to animal until it reaches a racoon.

Humans can be infected by this parasite or by closely related species while eating raw freshwater fish. Human gnathostomiosis is a common food-borne parasitic disease in several countries of Asia and now is becoming a serious health problem in some areas of Latin America. In most of the cases the larvae of Gnathostoma don’t encyst in humans. On the contrary, the larva migrates erratically throughout the body, most of the cases close to the skin. Remember, the next time you eat sushi, sashimi, ceviche or any kind of raw fish, be sure that is not fresh-water fish!!

You can read more about it here.

Contributed by Alejandro Oceguera-Figueroa.

February 23 - Sciruodendrium bravohollisae

This new species of nematode was discovered infecting red-bellied squirrels (Sciurus aureogaster) as part of a survey in Morelos, Mexico in 2003. Both squirrels that were examined had these parasites in quite high numbers. These parasites are part of the suborder Strongylida, which are typically gastro-intestinal parasites of mammals.

February 22 - Thaumasioscolex didelphidis

Up until the point at which this parasite was found, tapeworms in the group Proteocephalidea were thought to only infect fishes, amphibians and reptiles. But, in the late 1990’s, these cestodes were found in black-eared opossums in Veracruz, Mexico. The authors erected a new genus for these tapeworms, calling it Thaumasioscolex, from the Greek “thaumasio” which means “to surprise” because of its presence in a mammal and then described this single species in that genus, Thaumasioscolex didelphidis. Molecular data were consistent with the parasite’s relatedness to members of the Proteocephalidea that infect fishes. The life cycle is not yet known, though aquatic intermediate hosts including crustaceans and frogs are suspected.

February 21 - Tricophyton rubrum

Tricophyton rubrum is a dermatophyte - a fungus that is an obligate parasite of the skin or other keratinized tissues like nails. This species is the most frequent culprit behind the most common fungal infections of humans - ringworm, athlete's foot and jock itch. The fungi typically only colonize the outermost layers of skin and do not invade the true living tissues beneath. They make us itch when our immune systems respond to the metabolic waste they exude out. Although ringworm isn't usually a severe health threat to an infected person, and can be treated with aggressive topical medications, it's often horrifically hard it can be to get rid of in one's house. The fungi can remain in clothes, on sheets, even on furniture and other parts of the environment for over a year and transmission can occur between humans and pets. It's very common in showers and locker rooms so wearing flip-flops is always a good idea in these public places. The name "ringworm" comes from the tendency of the fungus to form a ring in the skin, though they do not always do this.

February 20 - Zeylanicobdella arugamensis

The piscicolid leeches inhabit marine environments and take their blood meals from fish hosts. Recently, these leeches were found on mudskippers – unusual fish in the goby family that are amphibious, spending part of their time out of the water. Zeylanicobdella arugamensis was discovered feeding from the mudskipper Scartelaos tenuis, which lives in the Persian Gulf and leeches also readily attached to a second species, Periophthalmus waltoni, in aquaria (shown in photo). Although this second fish species is sympatric with S. tenuis, the authors of the paper did not find any leeches on them in the wild. They proposed that perhaps in nature, P. waltoni spends too much time out of the water and thus the leeches prefer the more aquatic S. tenuis. Z. arugamensis has a wide distribution in the Indian Ocean and infects numerous species of fish, but this was the first time one had ever been found on mudskippers.

Photo kindly provided by Gianluca Polgar.

February 19 - Pterygodermatites peromysci

Pterygodermatites peromysci is a common intestinal nematode of Peromyscus leucopus, the white-footed mouse and Peromyscus maniculatus, the deer mouse. P. peromysci inhabits the small intestines of these two rodents where it lives out its days feeding on the nutrients taken in by the mouse. The life cycle of this parasite is complex and requires passage through an intermediate host Ceuthophilus pallidipes, the camel cricket. Eggs are shed in the mouse faeces and ingested by the cricket. The nematode develops inside of the crickets hemocoel, or body cavity where it floats around encysted inside gut epithelium until a hungry mouse gobbles up the tasty cricket treat, continuing the parasites life cycle. The parasite in the photo was isolated from Peromyscus maniculatus captured in the Great Basin desert in Utah.

Contributed by Craig Gritzen.