The deep‐sea chiton Nierstraszella (Mollusca: Polyplacophora: Lepidopleurida) in the Indo‐West Pacific: taxonomy, morphology and a bizarre ectosymbiont

Abstract

This study investigated the taxonomy and distribution of the deep‐sea polyplacophoran mollusc Nierstraszella Sirenko, 1992 in the Indo‐West Pacific, based on a collection of 516 specimens collected in the Philippines and Solomon Islands. Although seven species names have historically been proposed in this group of chitons, all have been considered as synonyms of the monotypic N. lineata (Nierstrasz, 1905). Morphological examination of this new material reveals the presence of two species. N. lineata is distinct from N. andamanica (Smith, 1906), based on morphological characters given in the original species description and very distinctly different morphology of aesthete pores in the shell surface. Furthermore, populations of N. andamanica in the Philippines and Solomon Islands are locally colonized with the epibiotic (ectoparasitic) bryozoan Pseudobathyalozoon profundum d'Hondt, 2006. These bryozoans attach ventrally to the girdle of the host chiton and the erect zooids feed within the pallial cavity, among the chiton's gills.

Keywords:

• Lepidopleurida
• Nierstraszellidae
• deep‐sea chitons
• epibiont

Acknowledgements

I thank Philippe Bouchet (MNHN) who organized the expeditions that produced the material described here. B. Sirenko and two anonymous reviewers provided helpful and constructive comments that improved this manuscript. Funding support for this work was provided by the European Commission SYNTHESYS programme (awards FR‐TAF‐1157, NL‐TAF‐437, NL‐TAF‐5088, DE‐TAF‐407 and GB‐TAF‐436). R. Moolenbeek (ITZ), J. Goud (RMNH), M. Glaubrecht (ZMB), K. Way (BMNH) and V. Héros (MNHN) kindly provided access to collections. J. Goud (RMNH) and P. Maestrati (MNHN) also provided assistance with SEM imaging.