Abstract
This study presents some basic biology of Uroteuthis (Photololigo) duvauceli, the most often caught species during sampling in the area of study, such as the sex ratio and length-frequency, allometric growth of various parts of the body, with particular interest in allometric relationship of eye shape against other parts of the body. Samples were collected from Cirebon in West Java, Kendal and Semarang in Central Java and Tuban waters in East Java. During 4 mo sampling from May to August 2015, four species were identified including Uroteuthis (Photololigo) duvauceli (d’Orbigny, 1835), Octopus sp, Sepiella inermis (Ferussac &’d’Orbigny, 1848), and Sepioteuthis cf. lessoniana (Ferussac, 1830). In all four populations, males dominated in number, the sex ratios ranged from 1:1.21 to 1:1.95 in favour of male individuals. Allometric growth of juveniles and mature individuals (60 mm to152 mm dorsal mantle length, DML) showed that U. (P.) duvauceli grew its length faster than any other part of the body except its fin (P < 0.01). Eyes grew according to its long axis than to its height. Head length and eye shape (eye length and height) grew significantly slower compared to the body length (P < 0.01). This means that since early juveniles U. (P.) duvauceli concerned more to the fin growth and development than to its eye size, even though newly hatch squid seemed to have shown big eyes compare to its overall body size. Previous studies on this species elsewhere substantiated that the length-weight relationship of U. (P) duvauceli do not follow ideal cube law. The fact in this study that wet body weight was always negatively allometric (P < 0.01) compared to any part of the body, not only its length, suggesting that U (P.) duvauceli is indeed a real swimmer, shaping a very light, slim and slender body with fully developed fin since early juveniles, balance feature for a predator escaping predation.
