Biology subjects

Andrade, S. C. S.

Publications and source records attributed to Andrade, S. C. S..

2 recordsLinked to original sources

bioRxiv2023

Venomous Noodles: evolution of toxins in Nemertea through positive selection and gene duplication

Some, probably most and perhaps all, members of the phylum Nemertea are venomous, documented so far from marine and benthic specimens. Although the toxicity of these animals has been long known, systematic studies on characterization of toxins, mechanisms of toxicity and toxin evolution for this group are relatively scarce compared to other venomous groups. Here we present the first investigation of the molecular evolution of toxins in Nemertea. Using a proteo-transcriptomic approach, we described toxins in the body and poisonous mucus of the pilidiophoran Lineus sanguineus and the hoplonemertean Nemertopsis pamelaroeae. Using these new and publicly available transcriptomes, we investigated the molecular evolution of six selected toxin gene families. In addition, we have also characterized in silico the toxin genes found in the interstitial hoplonemertean, Ototyphlonemertes erneba, a first record for meiofaunal taxa. We identified 99 toxin transcripts in the pilidiophoran L. sanguineus, including previously known toxins, such as the alpha-nemertides and the Cytotoxins-A. However, for each of the hoplonemerteans, no more than 30 toxin transcripts were found. Genomic alignments and tree reconciliation methods supported the occurrence of at least one gene duplication in each analyzed toxin gene. Evidence of positive selection was observed in all investigated toxin genes. We hypothesized that an increased rate of gene duplications observed for Pilidiophora could be involved with the origin and expansion of toxin genes. Studies concerning the natural history of Nemertea are still needed to understand the evolution of their toxins. Nevertheless, our results show evolutionary mechanisms similar to those observed in other venomous groups.

evolutionary biology↗

bioRxiv2021

Hoplonemertean larvae are planktonic predators that capture and devour active animal prey

The superficially-simple ciliated planktonic larvae of hoplonemerteans have been assumed to be lecithotrophic direct developers, even though many develop from such small eggs that it is hard to imagine how they could give rise to a viable juvenile without some phase of larval feeding. Indeed, attempts to raise such larvae to settlement without food invariably fail. Observations that some hoplonemertean larvae are found in plankton samples at a range of sizes, and much larger than hatchlings, suggests they must indeed feed somehow. Since these "planuliform" larvae lack apparent means to concentrate suspended algae or other unicellular food, one alternative hypothesis is that they are planktonic predators that hunt large prey. Here we provide direct evidence that this is indeed the case for six distinct species of hoplonemerteans. We recorded wild-caught larvae of Paranemertes californica, Paranemertes sp., Gurjanovella littoralis, Emplectonema viride, Carcinonemertes epialti, and Ototyphlonemertes sp. attacking, subduing, and devouring pelagic crustaceans, including barnacle nauplii, cyprids, copepods and their nauplii, and others. While there is no doubt that some hoplonemerteans are genuine lecithotrophs, our evidence suggests that many species in this group both feed and grow during an extended planktonic larval period. This conclusion has important consequences for biogeographic and life-history studies in this group, because it implies enhanced potential for long-distance dispersal. More broadly, the possibility that many animal larvae are actually carnivores invites reconsideration of prevailing stereotypes about metazoan developmental modes and the trade-offs between them.

zoology↗