Sex Determination in Heterotis Niloticus (Cuvier 1829) Based on Morphometric Features

Abstract

This study examined the morphometric and meristic characters of African Bony Tongue (Heterotis niloticus) in order to identify possible phenotypic sex markers in this potential aquaculture species. The ratios of external measurements of the dorsal length, the pre-dorsal length, the head length, the peduncle length, the anal length, the pectoral length, the pelvic length and the caudal length to the  standard length was determined. The inter-orbital length of head length and the snout length of head length were also analyzed. The analyses were done in thirty (30) specimens of Heterotis niloticus. Only two of the morphological ratios namely peduncle length of the standard length and the inter-orbital length of the head length indicated significantly higher values (P<0.05) in the females. The ratio of  peduncle length to the standard length in the female was 5.13 ± 0.56 and 4.89 ± 0.43 was recorded in the male, while the ratio of inter-orbital length to head length in the female was 39.35 ± 2.16 and 37.54 ± 2.05 was recorded in the male. Sensory pits count on both the right and the left opercula plates were higher in the male than the female though, the difference was not significant enough for sensory pits count to form the basis for   sexual dimorphism. The dimorphism so indicated in peduncle length and inter-orbital length is not readily observable by visual examination and may require simple measurements, which may not be easily carried out for routine sex determination on the field. However, it can be used to separate the broodstock population into different male and female holding facilities, while exteriorization of sexual products by catheterization or hand stripping can be used to confirm the sex of the selected broodstock and their readiness to spawn during the breeding season.