Synopsis of the knowledge on the Brazilian aplacophorans (Mollusca: Caudofoveata & Solenogastres)

Abstract

Aplacophorans are well known as exclusively marine benthic molluscs with a vermiform body covered by aragonitic sclerites (also called spicules), whose species are widely distributed from the sublittoral down to the abyss. Currently, only nine species are known from Brazil (one Solenogastres and eight Caudofoveata), but these very few records are no longer a reflection of an existing low diversity. Sampling in deep waters has been conducted recently in oil-rich areas of the Brazilian coast, and the museum collections have now many aplacophoran lots. There is a need to learn about and/or install some microscopical facilities in Brazilian institutions, to form expertise for the investigations on these generally small animals. With studies on taxonomy, phylogeny, biogeography and ecology, important questions will be surely answered about the diversity, distribution, and the relationship among the deep-sea fauna from Brazil and from other places.

Estado atual de conhecimento das principais características dos Moluscos / Current state of knowledge of the main characteristics of mollusks

“…Os solenogastres ou neomeniomorfas, são organismos estritamente marinhos, desprovidos de concha e olhos, possui parede corpórea com presença de quitina e esclerito calcário e corpo vermiforme espiculado, normalmente com rádula. As brânquias verdadeiras estão ausentes, as trocas gasosas ocorrem por estruturas no manto pregueado denominadas de papilas respiratórias (PASSOS et al, 2019).…”

“…Importantes achados despertaram o interesse em compreender melhor a evolução do grupo (TEBBLE, 1967;LOWENSTAM, 1967;WILSON et al, 2010) diante de uma expressiva diversidade fisiológica, morfológica, genética, biogeográfica, comportamental e dos distintos ambientes que o grupo conseguiu colonizar, sucessivas e independentes vezes (RUPPER et al, 2005;PASSOS et al, 2019).…”

“…Por outro lado, o Mesonychoteuthis hamiltoni (Robson, 1925) mede cerca de 14 m de comprimento, Brazilian Journal of Development, Curitiba, v.7, n.4, p. 40950-40963 apr 2021 obtendo o título de maior molusco vivente (MORTON et al, 2015). Além disso, os moluscos apresentam uma ampla distribuição biogeográfica (PASSAMANECK et al;2004;PONDER, 2008;PASSOS et al, 2019).…”

Better Alone Than in Bad Company: New Species of Caudofoveate Limifossorid (Mollusca, Aplacophora) Unravels Patterns of Distribution Hidden in the Deep Atlantic

“…As it occurs with other deep-water animals, Aplacophora is a clear example of lesser-known group. However, especially in the last decade, this scenario is rapidly changing (Todt, 2013;Passos et al, 2019). Some techniques, like SEM and birefringence microscopy, particularly important for the study of these animals, are becoming more accessible (e.g., Corrêa et al, 2014Corrêa et al, , 2018Passos et al, 2018;Saito, 2020), making the descriptions more detailed; moreover, previous molecular obstacles have been surpassed (e.g., Kocot et al, 2011;Mikkelsen et al, 2018Mikkelsen et al, , 2019Bergmeier et al, 2021).…”

“…For the Brazilian coast (Southwestern Atlantic), in particular, eight species are known: Chevroderma turnerae Scheltema, 1985 recorded by Scheltema (1985) and Ivanov and Scheltema (2008), and Spathoderma bulbosum Ivanov and Scheltema, 2008 by Ivanov and Scheltema (2008); Falcidens targatus Salvini-Plawen, 1992 and F. acutargatus Salvini-Plawen, 1992 studied by Corrêa et al (2014); Claviderma amplum Ivanov and Scheltema, 2008, C. crassum Ivanov and Scheltema, 2008and C. virium Corrêa, Miranda and Passos, 2018 investigated by Corrêa et al (2018); and F. australocaudatus Passos, Corrêa and Todt, 2016 described by Passos et al (2018). Passos et al (2019) have summarized all the records of aplacophorans from Brazilian waters up to that time, pointing out that most of them are from restricted oil-rich areas, there remaining large parts of its coast in which these molluscs were never reported (as its southernmost and northernmost portions), and that there are many other species to be investigated.…”