<i>Centropages abdominalis</i> SATOのノープリアス幼生

Abstract

The Copepoda nauplii are herbivore, preyed by the larvae of Pisces, Crustacea, Sagittoidea and the others which prey upon the nauplii. They may assume an important rôle in the food chain in the sea. Centropages abdominalis SATO occurs usually in rather large numbers in January, in the north western coast of Kyushu. In this season the plankton community is dominated by Bacillariaceae, especially by Thalassiosira subtilis (OSTENFELD). In rearing the female specimens of C. abdominalis were placed in the jars filled with the water (Cl--19.06‰). Skeletonema costatum (GREVILLE) and Stephanophixis palmeliana (GREVILLE) GRUNOW were placed in the jars for a fresh supply of the food or oxygen. The number of eggs produced by C. abdominalis ranged from 120 to 130 with an average of 122 eggs per brood. The egg is semitranslucent with light green in colour. The pelagic egg is 0.075mm in diameter having many setae on the surface. The length of the setae is from 0.02mm to 0.04mm. The egg is very similar to Haliocladus (Radiolaria) in structure. The nauplius is pyriform, and slight pointed posteriorly and quite rounded anteriorly. The nauplius retains red brown in the posterior region. The dark red eye-spot is comparatively large at the proximal portion of the rostrum. The nauplius is very similar in structure to that nauplius of Centropages hamatus (LILLJEBORG) described by M. OBERG (1906). After hatching, the larva developed into the nauplius VI which is the final stage of nauplius within about 10 days at the water temperature 15.4°C.