Stenosoma stephenseni sp. n. (Isopoda, Idoteidae), from the southwestern Mediterranean, with a note on the nomenclatural status of Synisoma Collinge, 1917

António Santos,Madalena Branco,Saliha Zenboudji,Tristao Branco,Raquel Xavier

doi:10.3897/zookeys.141.1376

Abstract

Recent collections of isopods in Alboran Island and Algeria included several specimens of the species Stenosoma stephenseni sp. n. This is the fourteenth species described in the genus Stenosoma Leach, 1814. Examination of two specimens collected during the Danish oceanographic cruises of the Thor (1908–10) close to the Galite Islands, and identified as Stenosoma acuminatum Leach, 1814, revealed that both belong to Stenosoma stephenseni sp. n. In light of these findings, the Mediterranean records of Stenosoma acuminatum are revised, and it is proposed that Stenosoma acuminatum is a strictly Atlantic species. An updated diagnosis for the genus Stenosoma is given, together with a key for the identification of its species. The nomenclatural status of the name Synisoma Collinge, 1917 is addressed, and although it is in prevailing usage, it is shown that Stenosoma Leach, 1814 is the valid name of the genus.

Highlights

In his work on the isopods collected during the Danish oceanographic cruises of the Thor (1908–10) in the Mediterranean and the Black Sea, Stephensen (1915) identified three species belonging to the genus Stenosoma Leach, 1814 (=Synisoma Collinge, 1917): two specimens of S. acuminatum Leach, 1814, from the Galite Islands, two specimens of S. capito (Rathke, 1837), from the Aegean Sea, and one specimen of S. appendiculatum (Risso, 1826), from Cabo da Gata (Spain)
We describe a new species of Stenosoma, in which we include the specimens of Stephensen (1915) from the Galite Islands, and we discuss the implications of Stenosoma stephenseni sp. n. (Isopoda, Idoteidae), from the southwestern Mediterranean.. 31 this finding on the distribution of S. acuminatum in the Mediterranean
The epithet honours Knud Hensch Stephensen (1882–1947), former curator of the crustacean collections at the ZMUC, who first noticed that some specimens he placed in S. acuminatum were likely to be a new species from the Mediterranean (Stephensen, 1915)

Summary

Introduction

In his work on the isopods collected during the Danish oceanographic cruises of the Thor (1908–10) in the Mediterranean and the Black Sea, Stephensen (1915) identified three species belonging to the genus Stenosoma Leach, 1814 (=Synisoma Collinge, 1917): two specimens of S. acuminatum Leach, 1814, from the Galite Islands (northern Tunisia), two specimens of S. capito (Rathke, 1837), from the Aegean Sea, and one specimen of S. appendiculatum (Risso, 1826), from Cabo da Gata (Spain). Stephensen noted that the two specimens from the Galite Islands agreed broadly with the figures and descriptions of S. acuminatum provided by Dollfus (1896) and Tattersall (1911), they were “somewhat broader” and the abdomen was “[...] by no means so sharply pointed” Upon dissection, he noted that “there is a considerably similarity to S. capito (Rathke, 1837), the appendages being, far thicker and heavier”. Successful sampling of adults from Algeria in 2009 allowed us to start a detailed morphological analysis of this lineage Morphological similarities between these recently collected individuals and Stephensen’s description of S. acuminatum, led us to request the material from the Thor campaign (1908–10), deposited at the ZMUC. An amended key is given for the species of the genus Stenosoma based on the one provided by Castellanos and Junoy (2005)

Material and methods

Discussion