Back to Laevistrombus …

It’s April, and we’re on to Blog 4. Progress is ever-onward, and I can’t believe how quickly the time is flying! Continuing with the current theme of marine gastropods, I’m going to continue with the story of Laevistrombus, discussing a paper that Stephen published in 2017. Yes, I know, I haven’t said anything about his masters thesis yet. All in good time!

Laevistrombus canarium (Maxwell et al. 2019)

Sex-ratio bias is common in gastropods, particularly in the Strombidae, with generally 0.75 males per female. In addition, this sex imbalance is variable on both spatial and temporal scales. Currently, the mechanisms driving sex-ratio bias are little explored. Therefore, in this paper, published in Memoirs of the Queensland Museum - Nature, we explored some of these mechanisms in Laevistrombus canarium (Fig. 1) from two populations.

Four Mile Beach and Alexandra Reefs (Google Maps; 14/04/2019)

We sampled individuals from two reefs in Far North Queensland, Australia, with different benthic compositions, namely Four Mile Beach and Alexandra Reef (Fig. 2). Snails were sampled over nine trips at low tide between June 2013 and May 2016. We collected individuals from bot mating and non-mating clusters when possible. For each individual, we recorded the substrate it occurred on and its sex.

We also found a strong bias towards females, which was consistent across both locations and across benthic substrates (Table 1). Our findings suggest that inherent genetic factors (possibly related to either ZQ-ZZ or XX-XY sex determination mechanisms) regulate natural patterns of sex imbalance in L. canarium. These findings also suggest that some life-history characteristics, yet to be clearly established, are associated with the origin and maintenance of this sex-ratio bias in L. canarium.

* Taken from Maxwell et al. 2017

Again, I hope that you realise that marine snails provide a really rich area for scientific scrutiny. And who knows how much more we will learn in the future. Perhaps the most important lesson that I take out of this paper is not a specific conclusion, or anything that is going to shatter the core of scientific thinking. I suggest that we shouldn’t just assume that patterns will be the same across closely related species. I suggest that we should explore with an open mind, and not just generalise that a snail will behave like any other snail. We really should admire these species, and indeed populations and even individuals within species, for what they are: unique.

You can read more about my research in my publications, listed on my blog. You can also find me on ResearchGate, the James Cook University website and Twitter.

Recent news on the snail story …

It’s March, and we’re on to Blog 3, so still going strong. Continuing with the current theme of marine gastropods, we’ve just had a new piece that recent master’s graduate (and now PhD candidate) Stephen has had published. We still have to get onto a discussion of his masters thesis, but that will come in time!

Stephen’s third paper was published in Zootaxa, and evaluates the taxonomy of marine snails belonging to the genus Laevistrombus (Fig. 1). After the first major revision of the family Strombidae (Abbott 1960), Laevistrombus was considered monospecific (that is, only one extant species in the genus). This is where we could have a whole discussion on whether to lump or split organisms into distinct species. Abbott (1960) was a lumper, whereas recent revisions on this genus have considered Abbott (1960) to have been too conservative. While later authors suggest that there are three extant species, we suggest that further splitting is needed, proposing that L. taeniatus and L. vankorensis be elevated to species. We provide descriptions on the morphology and distribution to do this.

Fig. 1. The five extant members of the Laevistrombus: A) L. turturella; B) L. taeniatus; C) L. guidoi; D) L. canarium; and E) L. vanikorensis

Fig. 2. Morphology of a snail

We provide the description of five species of Laevistrombus in the paper. For each, we provide the taxonomic identification, the definition, type locality and distribution. We also identify the type material. Comparative analyses of this complex have been problematic specifically because there has been a lack of designation of the type material.  The shells of these animals are quite beautiful (Fig. 1). They are smooth, solid and quite round. The outer lip is quite thick and smooth, becoming a bit harder and rougher (calloused) towards the head region. The columella (the spiral bit that goes through the middle, Fig. 2) is smooth and thickened in the middle. To see what makes each of these species different, you can check out the paper by clicking on the link under List of Publications.

Hopefully you can see that there’s a lot more to marine snails that you probably thought. And there will definitely be more to come in the future. I think one of the most important lessons out of this paper is that lumping or splitting is perhaps a matter of opinion when there isn’t solid evidence or appropriate descriptions. If you state specifically why you think something is different to something else, and you provide evidence to support that observation, then there is no ambiguity in your rationale for splitting or lumping. However, if you just say that things look alike, and lump them together without taking a holistic view, then you introduce ambiguity, which causes confusion. 

You can read more about my research in my publications, listed on my blog. You can also find me on ResearchGate, the JamesCook University website and Twitter.

Snail tales continued …

So far so good. It’s February, and we’re on to Blog 2. I’m going to continue on the current theme of marine gastropods, moving on to a second piece that my master’s student Stephen completed. Stephen has just completed his masters, which warrants discussion itself, but more on that another time!

Fig. 1. Priabonian age (Ma = millions of years ago)

Stephen’s second paper was accepted in Paleontological Journal, and describes a new species of Paraseraphs from the Priabonian (37.8 – 33.9 Ma; Fig. 1) white limestone formation of Jamaica. Paraseraphs are extinct gastropods, so perhaps you’re wondering why it’s important that this paper was published. Well, really the only way that fossils can be designated to species is morphologically. However, there is a risk in saying that two animals are the same species just because they look the same. In this paper, while we used morphology, we also looked at the spatial and temporal distribution of the species in relation to others.

The description of Paraseraphs cantamessae is based on morphology (Fig. 2). It has a slender shell with slightly concave whorls, and there is distinct elongation of the shell on later whorls. The base of the shell is anteriorly quadrate. The shell spire is acute and the sutures are well defined. While it occurred sympatrically with another species, P. procerum, P. cantamessae is cylindrically elongated, larger, and more dorsoventrally convex. Two additional species occurs in the region. However, they are separated temporally from P. cantamessae. Both P. texanopsis and P. erratica occurred roughly 47.8 - 41.2 Ma (Lutetian). Several other species are morphologically similar to P. cantamessae, but they are separated both spatially (P. armoricensis and P. propedistortum occurred in Europe) and temporally (41.2 – 37.8 Ma and 47.8 - 41.2 Ma, respectively).

Fig. 2. Type material for Paraseraphs cantamessa sp. nov.: (a) holotype USNM, no. 135097A; (b) paratype USNM, no. 135097B; (c) paratype USNM, no. 135097C. (Details and image taken from publication: Maxwell et al. 2018)

So, there you have it. Hopefully you now know even more than you did from the last blog. I think one of the most important lessons out of this paper is that we shouldn’t just think that one species conception is the answer to everything. If we just used morphology in this instance, all the fossils might be considered one species. However, if we take into account other factors, like spatial or temporal distributions, we can begin to see that things might be a little more complicated than they originally appeared. By taking a look at the organism in context, we gain a greater understanding about how it lived in relation to other organisms. 

You can read more about my research in my publications, listed on my blog. You can also find me on ResearchGate, the James CookUniversity website and Twitter.

Let’s start again …

It seems that this is something that happens yearly. I start with good intentions of trying to blog, which lasts a few months and then withers to nothing as work takes over. So, I’m going to just keep on trying and hopefully sometime it will stick and become more of a routine.

So, what approach should I take this year? Well, I thought I might update you on some of my recent works. Let’s start with a look at snails.

Fig. 1. The three extant members of the Terebellum. 1)  T.  terebellum (A-H). 2) T. delicatum (I-K). 3) T. hubrechti (L-M). (Image taken from publication: Maxwell et al. 201

So, my master’s student, Stephen has been working hard, and recently submitted his thesis for examination. He’s recently had a paper accepted in Proceedings of the Royal Society of Queensland, which provides a revision of Terebellum delicatum Kuroda and Kawamoto in Kawamoto and Tanabe, 1956 (Gastropoda, Seraphsidae). One of the primary purposes of this review was to give a higher level of taxonomic clarity, as there are at least three species of Terebellum that can be confusing to distinguish (Fig. 1). Although the paper hasn’t come out online yet, it’s a happy achievement all round.

Fig. 2. Contrasting T. terebellum and T. delicatum (Image taken from publication: Maxwell et al. 2018)

T. delicatulum’s (Fig. 2) new description is based on morphology, particularly colour. Generally, the shell has a base colour of tan, with circular white spotting. A single dark spot, smaller than each larger one, can be observed within each large white one. The resulting outcome is a white crescent shape that partially surround the darker spot. The axial ridge in the middle of the columella is also thickened, and white, being roughly 7-9mm long. However, adults may not show this thickening. T. delicatulum’s spire only bears 2.5 whorls, and it is quite long. The last whorl is cylindrical, but more straight-sided than in its sister taxon T. terebellum.

So, there you have it. If you didn’t know much about marine snails, hopefully you now know a little bit more than you did. One of the lessons out of this paper, I think, is that revisions and reviews are necessary to keep things in perspective. Whether you are a splitter or a lumper when it comes to taxonomic theory, it is always good to go back to the beginning and review the original author’s intentions. In some cases, looking a little different might not mean a new species. In other cases, this may be the opposite. Revisions give us new perspectives and allow us to learn more about the organisms that make our world so beautiful.

You can read more about my research in my publications, listed on my blog. You can also find me on ResearchGate, the James Cook University website and Twitter.