Pseudopulex jurassicus

This is the seventh and final posts in a series of posts written by students from my third year Evolutionary Parasitology unit (ZOOL329/529) class of 2015. This particular post was written by Maxine Walter and it is about the fossils of some "giant fleas" dating from the Mesozoic period which might have fed on dinosaurs (Note: But see also this new paper which questions the interpretation of Pseudopulex as a "flea") (you can check out the previous post about how different parasitoid wasps induce different web-building behaviour in their zombified spider hosts here).

Reconstruction of Pseudopulex jurassicus 
by Wang Cheng via Oregon State University

Ever had an itch you just can’t scratch? Was it inappropriately placed while you were in pleasant company? Was it hard to reach? Or were your hands just otherwise occupied with day-to-day tasks? If you answered yes to any of the above, you must be familiar with the insanity-driving BURN that accompanies an un-neutralised itch. It’s no wonder that even the undisputed monster of Mesozoic beasts, the King of Dinosaurs and ruler of reptiles - Tyrannosaurus rex, was bugged by, er, bugs! Our beloved pooches scratch incessantly when infested by fleas. But spare a thought for the puny-armed Tyrant Reptile King himself!

But these were not your average bugs. Like the dinosaurs themselves, the parasites of the pre-mammalian reign were oversized with functional weaponry to match! A few years ago, a group of paleontologists uncovered evidence for up to three separate species of parasites categorized into the new genus Pseudopulex. This generic name has roots in Latin meaning “with visual similarity to flea(s)”. The three species P. jurassicus, P. magnus and P. tanlan appear to have plagued dinosaurs (and others) from the late Middle Jurassic (P. jurassicus) through to the early Cretaceous period (P. magnus and P. tanlan).

These giant ancient flea-like animals, possibly the first of their blood-sucking kind, featured many characteristics typical of an external (or ecto-) parasite including; a wingless, flattened body for wedging into the natural contours of the dinosaurs’ skin/feathers; reduced eyes (because how on Earth can you miss a giant walking buffet?); mouthparts for piercing thick hide; and scythe-like claws for added purchase and avoiding dislodgement.

Photo of Pseudopulex fossil from this paper

The striking piercing and blood-sucking apparatus that was the Pseudopulex's mouthparts, has been described by Entomology Curator Michael Engel as having saw-like projections, and zoologist George Poinar Jr. as “a large beak [that] looks like a syringe when you go to the doctor to get a shot… a flea shot if not a flu shot”. The unusually robust and sturdy nature of these siphon mouths is what led scientists such as Dr. Andre Nel from the Natural History Museum, France, to the idea that these parasites possibly attacked dinosaurs and their high flying pterosaurian counterparts. Although fleas were originally thought to have co-evolved alongside mammals, the large (and easily dislodged on small animals) size of these "fleas" indicates they likely feasted on thick skinned and/or feathered animals, such as Rex and other dinosaurs, rather than the small mammals that also existed during the time.

Of their striking dissimilarity to modern fleas though, is the non-existence of rear jumping legs in these ancient forms. With the lack of springy legs, and the addition of a thick elongate mouth, led scientists like Engel to suggest that Pseudopulex ambushed their large victims. Pseudopulex would have spent much of their lives anchored to hosts with their claws and mouthparts and possessed little running or jumping ability.

The exciting discovery of these three flea-like species has resulted in a massive re-think of scientific theory concerning flea evolution, and finally closes the circle on Mesozoic biodiversity and the intricacies of ancient food chains.

Reference:
Gao, T., Shih, C., Xu, X., Wang, S., & Ren, D. (2012). Mid-Mesozoic flea-like ectoparasites of feathered of haired vertebrates. Current Biology 22, 732-735.

This post was written by Maxine Walter

That does it for ZOOL329 class of 2015 - I'd like to thank all the students for their posts! Next month, it's back to writing my usual posts about newly published and interesting parasite papers which you might have missed, and/or not as widely covered by the usual news and media outlets - so stay tuned!

December 13 - Eudynamys scolopaceus

This beautiful bird, commonly known as the Asian Koel, is a brood parasite in the cuckoo family. Eudynamys scolopaceus is found in southern Asia and primarily uses crows as hosts for its young. Although the female will sometimes remove one of the host's eggs when she lays hers, unlike many other brood parasites, the Asian Koel young usually do not kill or evict their nest mates, but rather beg their host parents in calls resembling those of baby crows. Their common name comes from the calls that the adults make, though their Sanskrit name, seen in literature that is more than 4000 years old, is Anya-Vapa which translates to "that was raised by others". Thus, the Asian Koel may be the first documented brood parasite known.

November 9 - Meloe franciscanus

Today's parasite is the larval stage of the blister beetle Meloe franciscanus. The beetle larvae are brood parasites that feed on eggs and the young of the solitary bee Habropoda pallida. The problem is, how do they get into the nest of a female bee on the first place? Well they do it by imitating the real thing. They gather into a swarm and climb to the tip of a grass stem. Once there, they clump together to form a small brown blob. While it might not look like much to you, but beetles give off a smell and produce vibrations that fool a male bee into thinking that the blob is one fine hottie. For the beetle larvae, it's a collective effort - the more of them there are in the blob, the more attractive they appear to a male bee. As soon as the bee comes into range expecting to get lucky, all the beetle larvae jump onboard. The experience leaves the bee slightly shaken, but unstirred, and he continue on his quest to find a female bee. However, once he does find a real female, he also ends up passing on his sticky hitch-hikers as a sexually transmitted infection. Once the beetles are all onboard the poor female, they cling on for dear life, eventually disembarking at her nest where they will be surrounded by all the food they'll ever need to grow up.

Photo credit: SFSU

Contributed by Tommy Leung.

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.

July 30 - Anomalospiza imberbis

This pretty little African bird is commonly called the Cuckoo Finch or Parasitic Weaver and is a member of a family of African birds known as Viduidae, or the indigobirds or whydahs (now there's a good Scrabble word!). These birds are like cuckoos in that they lay their eggs in the nests of other birds and the hosts for Anomalospiza imberbis eggs are usually warblers. The females apparently remove any resident eggs before laying their own and then the little parasitic weavers convince their adoptive parents to feed them for several weeks before heading off to find a mate or join flocks of their own species.

April 4 - Synodontis multipunctatus

Well, we've had cuckoo birds on this blog before, which most people would at least have heard of, but what about the cuckoo catfish? The cuckoo catfish, Synodontis multipunctatus, a popular ornamental fish that is somewhat well-known amongst aquarium enthusiasts. It is originally from Lake Tanganyika in Africa which is hotspot of cichlid fish biodiversity. The cuckoo catfish has a rather unusual breeding habit, it is a brood parasite of mouthbrooding cichlids found in Lake Tanganyika. Just like their bird namesake, the cuckoo catfish displaces the legitimate offspring of its host, forcing the cichlid to rear its young, and they have a rather clever way of accomplishing this. The catfish is attracted by the scent of the brooding cichlids, and as soon as they detect any such brooding cichlid in the vicinity, they race to the scene of the coupling. The catfish mob the pair of spawning cichlids and as soon as their eggs are fertilised, a mating pair of cuckoo catfish dash in, the female laying her own eggs amidst the brood, with the male following closely behind to fertilise them. When the brooding cichlid scoop up the clutch of eggs to brood them in its mouth, it's a mixed-bag of cichlid and catfish eggs. The catfish fry hatch a few days earlier than the cichlid fry and proceed to feed on the host's eggs with which they are sharing the brood chamber. So the cichlid is unknowingly and unwittingly carry a brood composed of juvenile catfish - imagine seeing a mouthbrooding cichlid open its mouth and out swim a swarm of splotchy little catfish!


The paper that originally described this fishy brood parasite is:
Sato, T. 1986. A brood parasitic catfish of mouthbrooding cichlid fishes in Lake Tanganyika. Nature 323:58-59

Contributed by Tommy Leung.

March 15 – Molothrus ater

One of these eggs is not like the other…one of these eggs just doesn’t belong. We can see this very obviously, but for some songbirds, not noticing this different egg can have very negative consequences. The different egg is that of a Brown-headed Cowbird, Molothrus ater, a brood parasite. These birds range widely across North America and as adults, they feed primarily on insects, often following grazing animals to eat the insects that they stir up and attract. These brood parasites have been documented using over 200 different species of birds as hosts. Though they’re lazy parents, they are very demanding parasites and check back on their eggs' progress. And, these birds can also demonstrate a very nasty retaliatory behavior. If the host bird recognizes the Cowbird egg and kicks it out, the Cowbird will often trash the host nest, punishing the discriminating host. You can read more about this here.

See photos of the adult birds here.

February 8 - Coelioxys coturnix

A female Coelioxys (Allocoelioxys) coturnix Pérez bee dashes into the nest of another bee species, Megachile minutissima Radoszkowski, and lays an egg on top of her host’s. She has waited—loitering outside the nest while assessing the whereabouts of the other female —for the other’s moment of weakness: leaving the nest to collect the last bit of material to close the brood chamber containing her egg and the pollen and nectar provisions for the larva that will emerge from the egg. Coelioxys coturnix is a cleptoparasitic (sometimes spelled “kleptoparasitic”) bee, an entomological version of the cuckoo bird, that does not collect food or nesting material for her offspring but uses the nests and, in bees, larval provisions of other species. Depending on the species of parasitic bee, its newly hatched larva might have disproportionately large, fang-like jaws to kill the host’s brood, might feed on the host’s egg, or might (in one very unusual species from Florida currently being described) wait until it is almost too late, during its last larval stage, to do away with the competition. Cleptoparasitism has evolved many times among bees using different pathways, according to Jerry Rozen, a Curator at the American Museum of Natural History for nearly 50 years, who has studied these bee species for much of his career.

Contributed by Kristin Phillips.
Photography by Rollin Coville.

January 14 - Cuculus canorus

Parasites aren't all squirmy worms or microscopic organisms. Sometimes they are devious birds. The common cuckoo, Cuculus canorus, is the classic example of a brood parasite - an organism that lets another raise its offspring. Female cuckoos lay their eggs in the nests of other birds, tossing out one of the host's eggs (because birds are very good at counting!). The young cuckoos often hatch first, grow larger, and will kick out the baby host birds. Cuckoos have even evolved the capacity to mimic the eggs of most of their hosts.