A NEW SPECIES OF CARIDINA H. MILNE EDWARDS, 1837 (, , ) FROM THE BETSIBOKA RIVER BASIN, MADAGASCAR

BY

JASMINE RICHARD1) and PAUL F. CLARK2) Department of Zoology, The Natural History Museum, Cromwell Road, London SW7 5BD, England

ABSTRACT

A new species of Caridina H. Milne Edwards, 1837 is described from the Betsiboka River Basin in Madagascar. This freshwater shrimp is unique in possessing a straight rostrum bearing either 1-14 teeth on the proximal part of the dorsal margin leaving 0.3-3.9 of the distal end unarmed or the entire margin devoid of teeth. When the dorsal margin is devoid of teeth, the new species is similar to Caridina typus H. Milne Edwards, 1837, in its rostral morphology. However, the new species differs from C. typus in possessing a telson with a rounded, protruding posterior margin bearing 4-6 pairs or 7 or 9 spines that increase in length towards the centre and in having ca. 30 eggs of 1.17-1.19 times 0.7-0.8 mm in size. Caridina typus differs from the new species by the posterior margin of the telson being rounded with a median protuberance bearing 2-4 pairs or 7 or 9 plumose processes and in having over 3000 eggs (ca. 3700 eggs counted on one female from India) of 0.35-0.39 × 0.23-0.25 mm in size.

RÉSUMÉ

Une nouvelle espèce de Caridina H. Milne Edwards, 1837 est décrite à partir de spécimens du bassin de la rivière Betsiboka à Madagascar. Cette crevette d’eau douce est unique par son rostre droit portant de 1 à 14 dents sur la partie proximale du bord dorsal, laissant les 0.3- 3.9 du bout distal sans dents ou le bord entier dépourvu de dents. Quand la marge dorsale est dépourvue de dents, la nouvelle espèce est similaire à Caridina typus H. Milne Edwards, 1837 en raison de sa morphologie rostrale. Cependant, la nouvelle espèce diffère de C. typus par son telson dont le bord postérieur est arrondi et saillant et qui porte de 4 à 6 paires d’épines ou 7 ou 9 épines dont la longueur s’accroît vers le centre et en ayant environ 30 œufs de 1.17-1.19 mm de long et 0.7-0.8 mm de large. Caridina typus se distingue de la nouvelle espèce par le bord

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© Koninklijke Brill NV, Leiden, 2010 Studies on : 637-644 638 CRM 014 – Fransen et al. (eds.), LIPKE BIJDELEY HOLTHUIS MEMORIAL VOLUME postérieur du telson qui est arrondi avec une protubérance médiane portant de 2 à 4 paires ou 7 ou 9 de processus plumeux et en ayant plus de 3000 oeufs (environ 3700 œufs comptés sur une femelle de l’Inde) de 0,35-0,39 de long et 0,23-0,25 mm de large.

INTRODUCTION

Caridina freshwater shrimps from Madagascar have been studied and described for over a century with contributions from Coutière (1899, 1900), Bouvier (1904, 1905, 1912, 1913, 1919, 1925), Lenz (1905, 1910), Nobili (1905), J. Roux (1929, 1934), Holthuis (1956a, b, 1965), Gurney (1984), and Cai (2005). The is widely distributed throughout the many water catchments, which radiate throughout this unique southwest Indian Ocean Island. Roux (1929) listed 20 Caridina species that were described to that date, listing 12 as endemic to Madagascar. Later, Holthuis (1965) provided a key to 16 species and recently Goodman & Benstead (2003) recognised 21 species and confirmed that 15 Caridina are endemic to the island. Recently, Cai (2005) described a new species, C. steineri from western Madagascar and this too is probably endemic. Since 1991, Jean-Marc Elouard and colleagues Michel Sartori, Francois Gibon and Jean-Luc Gattilotat have extensively sampled over 600 different freshwater (see Sartori et al., 2000) sites around Madagascar for their study of mayflies (Insecta, Ephemeroptera) as part of a major project entitled “Bio- diversité et biotypologie des eaux continentales malagaches”. This extremely successful programme initiated the formation of the Laboratoire de Recherche sur les Systèmes Aquatiques et leur Environnement (LRSAE), in Madagas- car by the Institut de Recherche pour le Développement and is now organ- ised jointly with the Malagasy Centre National de la Recherche Appliquée au Développement Rural (CNRE). A collection of Crustacea collected by Jean- Marc Elouard and his colleagues was donated to the Field Museum of Natural History (FMNH), Chicago by Steven Goodman and is comprised mostly of freshwater crabs (see Cumberlidge & Sternberg, 2003). However, in with the Brachyura were some freshwater shrimps partially identified as Caridina sp. by Christopher B. Boyko in 2000. As the authors of this present study are currently working on a collection of Caridina shrimps from Madagascar, they requested that this FMNH material be sent on loan to London for examination. The FMNH Caridina specimens are considered to be an undescribed species, therefore the purpose of this study is to fully describe and illustrate this material. Moreover as Professor Holthuis (1956a, b, 1965) worked on