Unusual Morphotypes of the Giant Barrel Sponge off the Coast of Barbados

Joseph R Pawlik,Patrick M Erwin,Susanna López-Legentil,James S Evans,Denise C Manker

doi:10.3390/d13120663

Joseph R Pawlik, Patrick M Erwin + Show 3 more

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https://doi.org/10.3390/d13120663

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Abstract

Giant barrel sponges (GBSs) belong to a cryptic species complex (Xestospongia spp.) and are found on tropical reefs worldwide. Over their range, including most of the Caribbean, GBSs have a cylindrical shape, with variation in height, diameter and surface complexity. However, off the southwest coast of Barbados, GBSs mostly exhibit a clam shape or a tub shape, interspersed with a few that have the normal barrel morphotype, suggesting that this variation is not due to environmental factors. Haplotype identification (mtDNA-COI) of six clam and six normal sponges indicated no clear genetic differentiation based on morphotype; hence, this morphological variation remains unexplained.

Highlights

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The second most common morphology is similar to a tub (Figure 1c), with the atrium opening widely, and the outer lip exceeding the diameter of the base of the sponge
Morphology has important implications for pumping rates of giant barrel sponges (GBSs) [8], but how these very different morphologies affect water processing is not yet known. Both clam and tub morphotypes are known from other locations in the southeast Caribbean: in Tobago, the clam morphotype is common [9], and the tub form was photographed in Curaçao [10], but all three are present in proximity to each other in Barbados

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Morphological variation is foundational in delimiting species in many animal phyla, with notable exceptions among modular and clonal taxa such as sponges [1]. Giant barrel sponges (GBSs) of the genus Xestospongia have a normal barrel morphology (Figure 1a), with variation in height, diameter, and surface complexity (smooth to highly papillate) [5], and a generally cylindrical inner cavity of the sponge (atrium).

Results

Conclusion