New paper on a new species of acanthocephalan

I’ve got another recent paper out, another collaboration with the eminent Emeritus Professor Lesley Warner (she publishes under Lesley Smales).

Reference:

Huston, D.C. and Smales, L.R. 2021. Gorgorhynchoides pseudocarangis n. sp. (Acanthocephala: Isthmosacanthidae) from Pseudocaranx dentex (Carangidae) in southeast Queensland, Australia, with comments on the Isthmosacanthidae. Systematic Parasitology, doi: https://doi.org/10.1007/s11230-021-09985-1

Sometimes you can’t fit all your findings into a single paper – there are lots of reasons for this but in my experience, it is usually not an issue of space but more an issue of focus. Anyway, in our 2020 paper (‘Molecular characterisation of acanthocephalans from Australian marine teleosts…’) on the molecular phylogeny of acanthocephalans we determined some of the Gorgorhynchoides specimens we collected likely represented an undescribed species. We didn’t think that this description would really fit into our previous paper, so we decided to publish it separately. This was good as we also had some further comments on our previously proposed transfer (in the 2020 paper) of Gorgorhynchoides and Serrasentis to the family Isthmosacanthidae.  

My magnum opus? A new paper published on Indo-West Pacific trematodes of the family Gorgocephalidae

All the hoops which need to be jumped through to get a piece of research published often leaves me feeling rather over the project once they actually appear nicely formatted in a journal somewhere. I just find it difficult to get excited about seeing my papers in print after I have already read them over and over again writing, editing, proofing, revising etc. However, I am still finding myself rather chuffed over one of my most recent papers:

2021. Huston, D.C., Cutmore, S.C., Miller, T.L., Sasal, P., Smit, N.J. and Cribb, T.H. Gorgocephalidae (Digenea: Lepocreadioidea) in the Indo-West Pacific: new species, life-cycle data and perspectives on species delineation over geographic range. Zoological Journal of the Linnean Society, doi: https://doi.org/10.1093/zoolinnean/zlab002.

This paper is the final result of something I started at the beginning of my PhD in 2015, and represents over 5 years of effort – collecting specimens, sequencing specimens, studying the morphology of specimens, banging my head against the keyboard as I searched for real morphometric differences, learning how to operate a scanning electron microscope, writing grants to travel and collect more specimens, on and on. It was a really great undertaking, and I think it is easily my best piece of work to date.

All that effort was really worth it. I collected specimens of the family Gorgocephalidae from all around Australia, and from the eastern and western extremes of the Indo-West Pacific marine region (French Polynesia and South Africa, respectively). As far as I am aware, this is the very first paper on marine digeneans to include data from specimens collected from the breadth of the Indo-West Pacific. Perhaps the most important thing I found was that it appears one species of the genus (Gorgocephalus yaaji) spans the entire range of the Indo-West Pacific! This has important implications, because the within-species genetic variation we observed could easily be misinterpreted as between-species genetic variation if other aspects (morphology and hosts) were ignored.

It is possible that the trematode taxonomy community (and that includes me) might be going a bit overboard with the proposal of cryptic species. Don’t get me wrong, I 100% accept the existence of true cryptic species, but we need to be more careful in proposing them. Cryptic species are easy to detect if they are occurring in sympatry. However, if you find a trematode at locality A that is morphologically indistinguishable from a trematode at locality B, but has some molecular differences, how do you know that the molecular difference is sufficient to consider them different, and not representative of natural intraspecific variation? I see a lot of molecular ‘cutoffs’ being thrown around, especially in terms of percent difference, but I never really see strong evidence presented for why 5% or 10% difference in cox1 or ITS or whatever is sufficient to consider one population species A and another species B. Sure, 5% might be a comfortable species-level difference for some trematode lineages, but that does not mean that 5% is going to apply to all trematode lineages. We need more reference datasets before we can have real confidence in such methods – and those reference datasets need to have specimens incorporated from wide geographic ranges!

New Postdoc

I am happy to say I recently took up a new postdoc with CSIRO at the Australian National Insect Collection, in Canberra, Australia. It was tough leaving Tasmania, but hey there is good fly fishing up here as well.

My new project is working on the systematics of plant-parasitic nematodes - so a bit of a change from fish helminths. I am sure I will work on helminth systematics for the rest of my career, but it is pretty exciting to be working on something completely different.

New Paper: Parasite life cycles and mariculture

I got my start in an aquaculture-related field, although it was culturing endangered aquatic species rather than commercial ones. Over the last five years I've had the opportunity to explore another passion of mine - the complex life cycles of marine parasites. Well, in one of my recently released papers, I got to do a pretty nice mashup of those two concepts:

Huston, D.C., Ogawa, K., Shirakashi, S. & Nowak, B.F. 2020. Metazoan Parasite life cycles: significance for fish mariculure. Trends in Parasitology. DOI:https://doi.org/10.1016/j.pt.2020.07.011

Aquaculture is expanding rapidly offshore into the sea and open oceans (aka mariculture). One of the most popular methods being employed by the finfish industry is the use of suspended cages or net pens moored offshore which allow constant water exchange for the farmed fish. This seems to be working great for a lot of reasons, but it does allow parasites to rather easily enter the net pens. 

In our paper we discuss how a renewed focus on basic parasite biology, especially life-cycle characteristics, can be used to manage parasitic infection in net-pen mariculture without the use of chemical treatment. We hope that our paper will renew interest in understanding basic aspects of marine parasite life-histories and promote research focused on elucidating parasite life cycles.

Phylogenetic evidence for a new Acanthocephalan family?

Phylogenetic evidence for a new Acanthocephalan family?

In my previous paper on acanthocephalans we proposed a new family (the Pyriproboscidae) based on phylogenetic evidence. In a follow up article, Lesley and I argue for the recognition of a new genus and another new family, Spinulacorpus and the Spinulacorpidae, respectively.

Huston, D.C. and Smales, L.R. 2020. Proposal of Spinulacorpus biforme (Smales, 2014) n. g., n. comb. and the Spinulacorpidae n. fam. to resolve paraphyly of the acanthocephalan family Rhadinorhynchidae Lühe, 1912. Systematic Parasitology. https://doi.org/10.1007/s11230-020-09923-7

One of the things we observed in our previous project was the species Rhadinorhynchus biformis Smales, 2014, resolved basal to the families Rhadinorhynchidae + Transvenidae, resulting in a paraphyletic Rhadinorhynchidae. In the original description, Smales (2014) noted that the trunk spine pattern in R. biformis was unlike any other species described in the genus. So it seemed like we had phylogenetic and potentially morphological evidence that R. biformis didn’t truly belong in the Rhadinorhynchidae (so long as we continue to consider the Transvenidae as distinct from the Rhadinorhynchidae). We didn’t have enough specimens at the time of our first paper to get into this particular problem, but later we examined additional specimens and did some far more intensive phylogenetic analyses. Overall, we found sufficient evidence to consider R. biformis as distinct from the Rhadinorhynchidae, and thus proposed our new genus and family.

Our aim with this paper was to help bring the Rhadinorhynchidae towards a modern classification scheme based on integrated molecular and morphological data. We think we’ve done this, but I suspect that there is much left to do. The Acanthocephala as a whole just keeps throwing up surprises and morphology and molecules seem to clash in the Acanthocephala much more than the other groups I have worked on.