MALE SIZE POLYMORPHISM IN NATURAL HABITATS OF POECILIA (LIMIA) PERUGIAE (PISCES, POECILIIDAE) ENDEMIC TO HISPANIOLA

Individual fish of Poecilia (Limia) perugiae from seven different coll ection sites southwest from Santo Domingo, Dominican Republic, were ca ught and measured immediately after draught. This species appears both in pure fresh waters and in habitats with high salinity. The occurren ce of three different male morphs (large males with more than 25 mm, i ntermediate males varying between 21 and 25 mm, and small males with l ess than 21 mm total length) confirmed our previous findings on the in heritance of these male morphs in laboratory stocks of Poecilia perugi ae. Every ten (males) or nine (females) measures were taken from each fish. From these continuous variables 15 (males) or 13 (females) body proportions were determined. Females normally exhibit another body sha pe with a deeper caudal peduncle as compared to males of the same coll ection site. The higher ratio of gonopodium to body length of smaller males seems not to be correlated with their courtship strategy. Apart from these morphological differences between males and females as well as between those of the three male morphs, fish of the same morph fro m different habitats sometimes also differed in their body proportions : At high salinity the fish develop a relatively longer head, longer g onopodium, higher ratio of ventral to anal length, and generally seem to be more compact and high-backed than freshwater fish. There are, ho wever, still other environmental parameters (e. g. food supply) which might influence the body shape of fishes from different habitats.