Caruncle in Megalomma Johansson, 1925 (Polychaeta: Sabellidae) and the description of a new species from the Eastern Tropical Pacific

Abstract

The presence of a caruncle in the polychaete family Sabellidae is documented. It is placed dorsally above the mouth, between the dorsal lips, supported with hyaline cartilage constituted by a homogeneous eosinophilic matrix and it is innervated directly from the cerebral ganglion. The caruncle surface has four longitudinal ciliated bands; the cilia from the lateral bands are hypertrophied, wider distally, tongue‐like, forming a ciliated curtain or membranella. The genus Megalomma is emended based on the presence of a caruncle, a long dorsalmost radiolar pair, a high number of radiolar skeletal cells, and the presence of interramal eyespots. We describe a new species from Acapulco in the Tropical Eastern Pacific –Megalomma carunculata sp. nov. It has a caruncle, subtriangular ventral lappets, well developed dorsal pockets, compound eyes in all radioles, and interramal eyespots in the thoracic and abdominal segments.

Keywords:

• compound eyes
• interramal eyespots
• new species
• sabellids
• sense organs

Acknowledgements

We are grateful for the guidance and support of Teresa Sosa‐Rodríguez and Pilar Torres‐García (Laboratorio de Invertebrados, Facultad de Ciencias, UNAM) for the histological work; to Guadalupe Nieto (ECOSUR–Tapachula) for help in processing scanning electron micrographs. Humberto Bahena Basave (ECOSUR–Chetumal) took the pictures for Figure 1A,D and Beatriz Yáñez (ECOSUR–Chetumal) shared with us histological sections of Hermodice carunculata. Special thanks are due to Rolando Bastida‐Zavala (UMAR) who provided specimens for comparison. This study was susported by CONACYT 61609.