Morphological and molecular differences between the Amphiamerican populations of Antillesoma (Sipuncula: Antillesomatidae), with the description of a new species

Abstract

Introduction: The sipunculans are a group of marine invertebrates that have been little studied in the tropical eastern Pacific (TEP). Antillesoma antillarum is a species belonging to the monospecific family Antillesomatidae, considered widely distributed in tropical and subtropical localities across the globe. Objective: The main objective of this work was to examine the morphological and molecular differences between specimens from both coasts of tropical America to clarify the taxonomy of this species. Methods: We examined the morphology with material from the Mexican Caribbean and southern Mexican Pacific. To perform molecular analyses, two sequences of the COI molecular marker were obtained from specimens collected in Panteón Beach, Oaxaca, southern Mexican Pacific, and compared with four sequences identified as A. antillarum in GenBank, all of them from different localities. A phylogenetic reconstruction was performed with the maximum likelihood method and genetic distances were calculated with the Kimura 2P model and compared to reference values. Results: The phylogenetic analysis revealed three different lineages of Antillesoma that are well supported by bootstrap values: Antillesoma antillarum sensu stricto from the Caribbean Sea and Florida; a sister group to the one represented by our samples from the Mexican Pacific; and a third group from Thailand. Conclusion: Based on morphological traits and molecular data, Antillesoma mexicanum sp. nov. is described from the Mexican Pacific, differing from A. antillarum in the trunk papillae, color patterns and, additionally, the specimens from the Caribbean attain significantly bigger trunk sizes than the ones Pacific.

Reinstatement ofPhascolosoma(Phascolosoma)variansKeferstein, 1865 (Sipuncula: Phascolosomatidae) based on morphological and molecular data

“…nigrescens from Israel, South Africa and, Broome, Australia, varies from 18% to 26% regarding Phascolosoma ( Phascolosoma ) varians from the Greater Caribbean. These values are similar to the results of Silva-Morales et al (2019) , where they found a genetic distance of 19% between Antillesoma antillarum (Greater Caribbean) and A. mexicanum (Southern Mexican Pacific). The present analysis reveals that Phascolosoma ( Phascolosoma ) nigrescens is a species complex resulting from the incipient morphological analysis.…”

“…However, recent molecular analyses revealed potential taxonomic problems at the species level, where small morphological differences also were shown to correspond with distinct species, thus rejecting previously assumed wide distributions for some of those species ( Staton & Rice, 1999 ; Kawauchi & Giribet, 2010 ; Schulze et al, 2012 ; Kawauchi & Giribet, 2014 ; Johnson et al, 2016 ; Silva-Morales et al, 2019 ). Because of this, Kawauchi, Sharma & Giribet (2012) proposed to clarify the taxonomic status of each species through a meticulous case-by-case analysis, integrating molecular data while considering that some species names that are currently hidden under synonyms deserve to be restored.…”

“…The reduced number of sipunculan taxa may call into question previous records, lead to possible taxonomic errors among field investigators, and suggest that most, if not all, species have been accounted for. However, after 1994, 13 new species have been described (Kawauchi & Rice, 2009;Hylleberg, 2013;Saiz et al, 2015;Silva-Morales et al, 2019). Importantly, in the Greater Caribbean region alone, 38 valid species have been recorded, of which 40% correspond to species with type localities outside of the Greater Caribbean, with seven of those species belonging to Phascolosomatidae (Quiroz-Ruiz & Londoño-Mesa, 2015).…”

First records and two new species of sipunculans (Sipuncula) from the Southern Mexican Pacific

“…polymyotus become available, the name S. natans could be revalidated. This hypothesis is based on some recent papers where the use of molecular data has rejected the supposed wide distribution of some species (Staton & Rice 1999;Kawauchi & Giribet 2010, 2014Schulze et al 2012;Johnson et al 2016;Silva-Morales et al 2019).…”

“…Also, no identification key or updated list of the sipunculans from TEP exist. The presence of this group in the Southern Mexican Pacific (SMP) is completely unknown (Bastida-Zavala et al 2013); a single record of one new species in the SMP was made by Silva-Morales et al (2019). Therefore, the main objective of this work was to determine the composition of species of the phylum Sipuncula present in the study area.…”