Diastylis fabrizioi, a new species and brief redescription of D. planifrons Calman, 1912 (Crustacea: Cumacea: Diastylidae) from South America

Abstract

A new cumacean from the southwestern Atlantic, Diastylis fabrizioi, is fully described. This species is closely allied to Diastylis planifrons Calman, 1912, whose description is also completed. D. fabrizioi n. sp. can be easily distinguished from D. planifrons by having: (1) a wide pentagonal figure on the posterior part of the female carapace (a narrower pentagonal figure in D. planifrons), (2) a uniformly arched outline of the plateau when the carapace is seen from above (interrupted by two prominent blunt projections in D. planifrons), and (3) a telson with two divergent cuspidate setae distally (in close apposition in D. planifrons). Specimens housing nicothoid copepods inside their branchial chambers were observed in both species herein studied. One of these infested branchial chambers also contained two cryptoniscus larvae (Isopoda, Epicaridea).

Keywords:

• Diastylis
• Cumacea
• nicothoid copepods
• cryptoniscus larvae
• South America

Acknowledgements

Our deepest appreciation goes to Fabrizio Scarabino for making a large amount of specimens from the Argentine‐Uruguayan common fishing zone available for this study. We are also grateful to José Dadon, Liliana Forneris, Diego Giberto, Pamela González Salvo, Juan López Gappa, José María (Lobo) Orensanz, Catalina Pastor de Ward, Peter Rehm, and Diego Zelaya for providing many other specimens examined in the present work; to Ute Mühlenhardt‐Siegel for reviewing and improving our manuscript; and to Angelika Brandt for the loan of material collected during the “Victor Hensen” 1994 campaign. Lastly we want to address our thanks to Teresa Kurokawa for her constructive editorial comments, Fabián Tricárico for his assistance with scanning electron microscopy, and Ignacio Chiesa and Brenda Doti for sorting many of the specimens examined in this study. This research was partially funded by the Agencia Nacional de Promoción Científica y Técnica, Argentina (ANPCyT, PICT 02‐11180), the Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina (CONICET), and the Universidad de Buenos Aires (UBACyT X162).