Abstract
Tne development and morphology of lateral scutes in Japanese sticklebacks has been studied for more than 15 years by the author. The present paper is one of those serial works, and deals with the species, Pungitius kaibarae (Tanaka) or in Japanese “minami-tomiyo”. The total of 30 specimens, ranging 18 to 51 mm in total length and collected at Nishioji, Kyoto City in June 1958, were studied. This species is now about to extinguish in this area. In P. kaibarae the scutes develop firstly in the juvenile, no more than 18 mm in total length, instead of 20 and 15 mm as observed in P. sinensis and P. pungitius, respectively. In P. kaibarae the first scutes appear on the caudal peduncle followed by those on the dorsolateral part of body above pectoral fin, and then each group grow forward and backward respectively, eventually formulating the Trachuran series of scutes; such pattern of scute formation, though observed in the species of Gasterosteus, is not traced in the species of Pungitius except in P. kaibarae. The feathershaped scutes in P. kaibarae are more blunt than in P. sinensis, and the central ridge on the rhomboid scutes in the former species develops in later stage than in the latter. The scutes in P. kaibarae, like in P. sinensis, P. pungitius and P. sp.(“musashi-tomiyo”, Japanese name), were ranged in a single series; the scutes in the present species seldom overlapped one another, sometimes, completely iso-lated anteriorly. Those findings favor to recognize P. kaibarae as a distinct species, which some authors have treated as a subspecies of P. sinensis or P. pungitius.
