Morphometry and morphological phylogeny of Sepia pharaonis Ehrenberg, 1831 complex in Thai waters

Abstract

Three hundred and fifty-eight specimens of pharaoh cuttlefish, Sepia pharaonis, Ehrenberg, 1831 were collected from 30 localities in Thai waters, Gulf of Thailand (Pacific Ocean) and the Andaman Sea (Indian Ocean). Specimens were grouped according to sex, habitats and four categorised types of colour patterns on the dorsal mantle based on the number of stripes on the middle and lateral parts. Morphometry of 70 characters from five character sets of external, cuttlebone, digestive system, reproductive system and hectocotylus morphology were compared. The male and female cuttlefish were significantly different in 38 characters. Four types of males and females were significantly different in 29 and 19 characters. Overall, differences in colour patterns were more prominent in males than in females. Phylogenetic analyses of seven high-weighted characters revealed four likely clades of populations, corresponding to four types of colour patterns on the dorsal mantle.