RICHARD ( OUTSIDE THE TYPE LOCALITY ) WITH NOTES ON DIAGNOSTIC CHARACTERS AND SEXUAL DIMORPHISM

Studies on the shrimp resources of the genus Caridina H. Milne Edwards. 1837 of Kerala is limited (Natarajan, 1942; Pillai, 1964; Tiwari and Pillai, 1968; Thomas et al., 1973; Jayachandran, 2005; 2006; Jayachandran et al., 2006). Recently, Mariappan and Richard (2006) have described a new species, Caridina jalihali, from the River Arani at Periyapalayam and a lake at Thenneri and also from ponds situated at Maduranmangalam, Marimangalam, Redipalayam, Roshan Nagar and Singaperumalkoli of Thiruvalluvar district of Tamil Nadu. This species is small sized (grows up to 29 mm). During a recent survey, the authors have collected the species from Anchal (Kollam District, Kerala State). The present paper hence fonns the first report of the species outside the type locality from Kerala state. The paper reveals important taxonomic data on the comparison of characters with original description and also discusses on sexual dimorphism and the possibilities of the species for utilization as a candidate species for aquarium.


INTRODUCTION
Studies on the shrimp resources of the genus Caridina H. Milne Edwards.1837 of Kerala is limited (Natarajan, 1942;Pillai, 1964;Tiwari and Pillai, 1968;Thomas et al., 1973;Jayachandran, 2005;2006;Jayachandran et al., 2006).Recently, Mariappan and Richard (2006) have described a new species, Caridina jalihali, from the River Arani at Periyapalayam and a lake at Thenneri and also from ponds situated at Maduranmangalam, Marimangalam, Redipalayam, Roshan Nagar and Singaperumalkoli of Thiruvalluvar district of Tamil Nadu.This species is small sized (grows up to 29 mm).During a recent survey, the authors have collected the species from Anchal (Kollam District, Kerala State).The present paper hence fonns the first report of the species outside the type locality from Kerala state.The paper reveals important taxonomic data on the comparison of characters with original description and also discusses on sexual dimorphism and the possibilities of the species for utilization as a candidate species for aquarium.

OBSERV A TION AND DISCUSSiON
The characters of the specimens of the present collection fully agree with that of Mariappan and Richard (2006).Table I shows a comparison of characters of the two collections.The rostral *E-mail: chandrankvj@yahoo.co.uk formula, spinules on the different segments of 3 rd and 5 th pereiopods come within the reported range already made for the species.Table 2 provides details of sexual dimorphism for the species and it reveals that it exhibits sexual dimorphism in characters like, total length, length of rostrum, relation between rostrum length and post-ocular carapace length, spinules on the ischium and merus of 5 th pereiopods and appendix intema and appendix masculina of 1 st and 2 nd pleopods.
With this report the distribution range of the species has been extended further south.
The species co-habits with C. gurney; lalihal et ai., 1984 at Dharwar, Karnataka State (lalihal et ai., 1984) and C. weberi var.sumatrensis at Madras (Mariappan and Richard, 2006).In Kerala waters, it co-habits with C. natarajani Tiwari and Pillai, 1968.C. jalihali is more benthic in habitat and C. Ilatarajani occupies preferably on the upper regions of the water bodies.
The species exhibits excellent colour pattern and is in general agreement with the colour described for the species by Mariappan and Richard (2006).The authors have maintained the species in aquarium along with fishes like guppy, gold fish, angel fish and gouramy and found quite suitable for community aquarium.Therefore, this is a new addition of shrimps in aquarium.Recently a few I prawns and shrimps were introduced into the aquaria Macrobrachium iatimanus, M. gurudeve, M. ornatus, M. idella, C. natarajani by layachandran et at.(2005) and layachandran (2006).The advantageous characters of the present species are-1.Beautiful steel black colouration with off-white lines on the dorsal and lateral sides 2. Scavengers, feeds on detritus and faecal matter of fishes in a community tank.
3. Benthic fonns hence avoid competition with fishes for food and space 4. Do not attack other organisms in the tank

Compatible with other aquarium fishes
Colour photographs of the species is given for easy identification of the species and for helping those breeders who would like to propagate the species for aquarium trade (Plate I, Figs. 1, 2).
Maximum size: 18.0 mm (male), 29.0 mm (female) In the light of the above discussion, a revised diagnosis of the species is given as : small sized shrimps, with short rostrum extending between middle of 2 nd segment to the middle of 3 rd segment of antennular peduncle, tip of rostrum directed forwards, dorsal margin with 15-29 teeth (usually 17-22) of which 3-6 teeth (usually 4-5) post-orbital, ventral margin with 3-9 teeth placed more towards the distal part; ischium, merus, carpus and dactylus of third pereiopod with 1, 4-5, 1 and 6-7 spinules respectively on the inner side; ischium, merus, carpus and dactylus of fifth pereiopod with 0-1, 2-4, 1 and 30-60 spinules respectively on the inner side; telson broad with or without median tenninal spine, dorsal surface with 5-6 pairs of spines and distal margin with 3-5 pairs of spinules; first pleopod of male with appendix interna and uropod with 17-20 spinules on the diaeresis.The animal is steel black in colour with distinct off-white bands on the dorsal and lateral sides of the abdomen.

Table 1 A
comparison of characters of C. ja/iha/i Mariappan & Richard from Madras and Kerala for analyzing the regional variations if any.