Isorchis cannoni n. sp. (Digenea: Atractotrematidae) from Great Barrier Reef rabbitfishes

This paper came out as an 'online-first-view' last year, and is still languishing in 'in press' purgatory, so I thought I would go ahead and do a quick write up. Here's the citation and link:

2018. Huston, D.C., Cutmore, S.C. and Cribb, T.H. Isorchis cannoni n. sp. (Digenea: Atractotrematidae) from Great Barrier Reef rabbitfishes and the molecular elucidation of its life cycle. The Journal of Helminthology (in press). PDF

This particular story begins with Dr. Lester Cannon’s study of the cerithiid gastropod Clypeomorus batillariaeformis (then called Cerithium moniliferum, a junior synonym) from Heron Island on Australia’s Great Barrier Reef. In his 1978 publication ‘Marine Cercariae from the Gastropod Cerithium moniliferum Keiner at Heron Island, Great Barrier Reef’ Cannon described 10 new trematode cercariae from C. batillariaeformis, and gave each cercariae a placeholder name and a numeral, e.g. Cercariae queenslandae I-X. The morphology of one of these cercariae (Cercaria queenslandae II) aligned closely with those known from the trematode family Haploporidae. In fact, Cannon noted that this cercariae might be that of Atractotrema sigani which was, at that time, considered a member of the Haploporidae, although today it is placed in the haploporid’s sister family Atractotrematidae. Atractotrema sigani parasitises rabbitfishes (family Siganidae), an important group of medium-sized, herbivorous marine fishes, several species of which feed on algae growing on the beachrock along Heron Island where C. batillariaeformis is found.

Cannon was about as close to the mark as one could get in those days, those days being those without molecular sequencing. In the past, elucidating life-cycles was rather difficult, and could only really be accomplished with captive populations and somewhat time-consuming experimental infections. Nowadays it is easy enough to generate molecular sequences from adult and larval trematodes and match them up!

Had molecular tools been available to Dr. Cannon, he would have quickly realised that the cercariae he had found were not those of A. sigani, and actually a species of atractotrematid yet to be discovered! This is what I found when I started a project sequencing the cercariae of C. batillariaeformis from Heron Island. When I began the project in 2015, the adult of Cercariae queenslandae II had not yet been discovered, but in 2017 we found the adults. Cannon was pretty close to the mark again: the definitive hosts turned out to be the same rabbitfishes that host A. sigani, Siganus lineatus and Siganus fuscescens. The twist was that rather than being the cercaria of a species of the genus Atractotrema, the adult match was an undescribed species of the genus Isorchis. We named this species Isorchis cannoni in honour of Dr. Lester Cannon and his work on trematodes of the Great Barrier Reef (and that he pretty much figured out the life-cycle for us already!).

Isorchis cannoni new species. A) Holotype, B) Ovarian complex

Species of Isorchis were previously known only from the milkfish Chanos chanos (family Chanidae) and the scat Selenotoca multifasciata (family Scatophagidae). This was all pretty rad as our study added a new host family to those known to be exploited by species of Isorchis and we revealed the first life-cycle known for the genus (actually the first life-cycle for a species of the Atractotrematidae). This life-cycle information may provide new insights into the evolutionary split between the Atractotrematidae and the Haploporidae, though we need to discover a few more life-cycles before we can truly delve.


References
Cannon, L. (1978) Marine cercariae from the gastropod Cerithium moniliferum Kiener at Heron Island, Great Barrier Reef. Proceedings of the Royal Society of Queensland, 89, 45-57.

 

New publications - New species of Schikhobalotrema (Digenea: Haplosplanchnidae) and a note about Menemerus bivittatus (Araneae: Salticidae)

I'm happy to report I've got two new publications that have come out this month. The first was a long time coming, and includes a molecular phylogeny for the poorly studied digenean family Haplosplanchnidae. I also described a new species in the paper, Schikhobalotrema huffmani which I was very pleased to name after my friend, mentor and masters degree supervisor at Texas State University, Dr. David Huffman. No one deserves the honor more than him. Here is the citation and a link to the paper:

Huston, D.C., S.C. Cutmore, and T.H. Cribb. 2017. Molecular phylogeny of the Haplosplanchnata Olson, Cribb, Tkach, Bray and Littlewood, 2003, with a description of Schikhobalotrema huffmani n. sp. Acta Parasitologica, 62: 502–512. PDF on Researchgate. 

This family has barely been studied on the Great Barrier Reef, even though its looking like the group is a bit more diverse than we thought (more on that coming soon!). There are actually only two species of Haplosplanchnidae reported from the GBR, so this beast makes the third.

Schikhobalotrema huffmani from intestine of Tylosurus crocodilus, Lizard Island, Great Barrier Reef, Australia. A) Dorso-ventral B) Lateral C) Terminal Genitalia

I also included the first record for the species Haplosplanchnus pachysomus from Australia in the same paper. Here's a picture of the worm for your admiration:

Haplosplanchnus pachysomus from the intestine of Mugil cephalus, Moreton Bay, Australia

Parasites are pretty groovy but I'm also a bit of an amateur entomologist, and have published a few short papers and research notes on insects over the last couple years. I just got a short note published in the Australian Entomologist detailing some observations I made of a species of jumping spider, Menemerus bivittatus on the balcony of the old "Queenslander" style home I rented when I first moved to Brisbane. If you don't live in Brisbane, essential background information is that all our homes are infested with these tiny black ants called Technomyrmex sophiae. These critters aren't that much of a problem, and don't really get into your food or anything, but they will build nests in just about any small crevice. They seem to enjoy potted plants the best, but I have personally experienced small colonies living inside the machine bits of a blender, and behind the motherboard of my washing machine. The point here is, they are constantly moving house, and their little wagon trains are great targets for raiders.

Menemerus bivittatus is a pan-tropical species and is pretty common around here in Brisbane. We had them back in Texas as well, which is why they were so easily recognizable to me. Anyway, these spiders have some clever tricks. One such trick is train robbery, stealing the ants' precious larval cargo. The micro-world is a savage one. Check out the video I shot of this behaviour on YouTube.

Be sure to download the paper and give it a read. Heres the citation and a link:
Huston, D.C. Train Robbery: Menemerus bivittatus (Dufour, 1831) (Araneae: Salticidae) steals larvae of Technomyrmex sophiae Forel, 1902 (Hymenoptera: Formicidae) in transit. Australian Entomologist, 44: 85–88. PDF on ResearchGate.

 

Fieldwork in French Polynesia

Parasitology isn’t always glamorous, but I find it comes with perks. I just got back from a month of fieldwork in French Polynesia, and it was awesome.

Approaching Moorea, French Polynesia on the ferry from Tahiti

 

 

 

 

Along with two other students from my lab, I was lucky enough to be invited over by Dr. Pierre Sasal to work on a project examining the parasites of three species of important aquaculture fish in French Polynesia: Chanos chanos, Siganus argenteus, and Platax orbicularis. While we were there we also had plenty of time to collect fish for our own research projects. For me that meant fish of the families Acanthuridae and Kyphosidae. I was also pleasantly surprised to get some interesting trematodes in the family Atractotrematidae from Chanos chanos and Siganus argenteus.

A beautiful Naso vlamingii I collected off Rangiroa in the Tuamotus. Species of Acanthuridae in the genus Naso have some very interesting haplosplanchnid trematodes that I am currently working on.

We spent our first two and our last week at the CRIOBE research facility in Moorea, a small island just off Tahiti.  Moorea is stunningly beautiful, and the water is warm and clear.  If you ever get to visit, be sure to try the local fruit juice. Baguettes are a given.

The bay we set out from each day on our way to the reef.

 Our third week was spent in Rangiroa, a large atoll in the Tuamotus. This place was far out.

Pretty sure I could live here

Although the trematode fauna of French Polynesia is relatively depauperate compared with the Great Barrier Reef, I was still able to make a pretty good collection.  I’ve got a lot of projects on my plate right now, but hopefully I’ll get around to working up my French Polynesian collection soon. French Polynesia was among the most beautiful places I’ve ever been, and being able to spend a month collecting there was a privilege I won’t soon forget.

 

The Life-cyle of Gorgocephalus yaaji (Digenea: Gorgocephalidae)

The complexity of trematode life-cycles was really what first drew me in and fueled my worm obsession.  Thus, I am pleased to say that I have a new paper hot off the press, in which my co-authors and I elucidate the first full life-cycle for a species of the family Gorgocephalidae.  I recommend that you read my paper immediately:

"Huston, D.C., S.C. Cutmore and T.H. Cribb. 2016. The life-cycle of Gorgocephalus yaaji Bray & Cribb, 2005 (Digenea: Gorgocephalidae) with a review of the first intermediate hosts for the superfamily Lepocreadioidea Odhner, 1905. Systematic Parasitology, 93: 653-665." have a quick read on Readcube or go straight to researchgate PDF

The three species that comprise the Gorgocephalidae are true to their namesake (relatively), with little tentacles sticking out of their oral sucker. I reckon they look quite a bit like Graboids from that awesome movie Tremors.  Tremors was one of those flicks which nurtured my love of cheesy monster movies.

The family Gorgocephalidae didn't start out as a family. It was first erected by the American trematodologist H.W. Manter in 1966 as a subfamily of the Lepocreadiidae. Manter called his new subfamily the "Gorgocephalinae" which he created to accommodate the type species, Gorgocephalus kyphosi.  Manter had recovered these odd little worms from the silver drummer Kyphosus sydneyanus which had been caught by Robert Piddington off Adelaide, South Australia.

Gorgocephalus kyphosi Manter, 1966.

Not much happened in regards to these strange worms for some time, though greater glory was destined. In 1971 the most influential trematode taxonomist of all time, Yamaguti, took a look at a couple of Manter's paratypes, and thought they were more unique than their pitiful subfamily designation suggested. The little tentacle mouthed worms finally got that family rank. And so began the Gorgocephalidae Manter, 1966.


Nearly twenty years passed before another gorgocephalid was discovered. In 1983, a second species was described by the Russian trematodologist E.V. Zhukov from Kyphosus sectatrix off of Cuba.  I have never been able to find much information on Zhukov, likely due to majority of his work being published in Russian.  Based on the dates of his Cuban publications however, It looks like Zhukov was in Cuba before the fall of the Soviet Union. However, regardless of the tensions between the USA and the Soviet Union, Zhukov named his new species Gorgocephalus manteri in honor of Manter's contributions to the field.

In 2005, Rod Bray and Tom Cribb described the third (and currently final) species of gorgocephalid from Kyphosus vaigiensis off of Lizard Island on the northern Great Barrier Reef.  They called this species Gorgocephalus yaaji. 

Another ten years passed.

Then, in 2015, something new happened.  During a study of the intramolluscan trematode fauna of the banded periwinkle Austrolittorina unifasciata (Littorinidae) from along the south coast of Australia, O'Dwyer et al. (2015) discovered and described the first known cercariae of the family Gorgocephalidae.  They were able to confirm that these intramolluscan stages belonged to a species of the family based on 28S rDNA sequence data.  While a previous sequence existed for Gorgocephalus kyphosi (Olson et al. 2003) from Lizard Island, O'Dwyer et al. determined that their cercaria most likely represented a separate species, based on differences in the sequence data.

Now, I had just read O'Dwyer et al. (2015) before my first trip to Lizard Island.  This was also my first trip to the Great Barrier Reef, and after my many years working in the freshwater systems of Texas, research in a coral reef ecosystem was exciting and unique.  My original goal for the trip was to study the intramolluscan trematode fauna from gastropods of the family Cerithiidae. However, I found cerithids quite difficult to find.  In fact, I was only able to collect one species in large numbers, Rhinoclavis vertagus.  I began to understand that the trematode fauna of Great Barrier Reef cerithids might be a rather difficult topic, so in frustration I turned my attention to some gastropods that were a bit more common in the area, littorinids.

To keep the narrative of my serendipitous discovery brief, I collected and examined some specimens of Echinolittorina austrotrochoides from the rocks along the beach. By placing these little snails into little cups of seawater, I was able to induce natural emergence of some cercariae, which just so happened to look just like those described by O'Dwyer et al. (2015)!

Larval stages of Gorgocephalus yaaji. A) Cercariae; B) Rediae; C) Metacercariae encysted on algae. From Huston et al. (2016).

It had previously been speculated that the metacercariae of gorgocephalids would be associated with algae due to the algivorous nature of the kyphosid host fishes.  I tested this by placing my cercariae in little cups of seawater with some algae.  They happily obliged, and encysted on the algae within a few hours.  The route of gorgocephalid recruitment into kyphosids was confirmed.

Back in the lab, I generated ITS2 and 28S rDNA molecular sequence data from the cercariae as well as from adult gorgocephalids we collected from Kyphosus cinerascens during the same trip. This allowed me to confirm that the larval stages did indeed belong to Gorgocephalus yaaji.  From there I wrote up a manuscript about the life-cycle, and included a review of the gastropod-trematode relationships for the superfamily Lepocreadioidea.  This review led to some fairly interesting insights, though a discussion on those insights is a bit beyond the scope of this post.  I'll write another post about the other half of the paper some time in the indeterminable future!

References

Bray, R. A., & Cribb, T. H. (2005). Gorgocephalus yaaji n. sp (Digenea: Gorgocephalidae) from the brassy chub Kyphosus vaigiensis (Perciformes: Kyphosidae) off Lizard Island, northern Great Barrier Reef and further records of G. kyphosi. Zootaxa, 1068, 39-46.

Olson, P., Cribb, T., Tkach, V., Bray, R., & Littlewood, D. (2003). Phylogeny and classification of the Digenea (Platyhelminthes: Trematoda). International Journal for Parasitology, 33, 733-755.

O’Dwyer, K., Faltýnková, A., Georgieva, S., & Kostadinova, A. (2015). An integrative taxonomic investigation of the diversity of digenean parasites infecting the intertidal snail Austrolittorina unifasciata Gray, 1826 (Gastropoda: Littorinidae) in Australia. Parasitology Research, 114, 2381-2397.

Manter, H. W. (1966). A peculiar trematode, Gorgocephalus kyphosi gen. et sp. n. (Lepocreadiidae: Gorgocephalinae subfam. n.), from a marine fish of South Australia. The Journal of Parasitology, 52, 347-350.

Yamaguti, S. (1971). Synopsis of digenetic trematodes of vertebrates. Keigaku Publishing Co. Tokyo, Vol I, 1074 pp. Vol II, 349 plates.

Zhukov, E. (1983). New representatives of the fauna of trematodes from the fishes of the Gulf of Mexico. Parazitologiia, 17, 112-117.