Larval Development of Euphausia similis (Crustacea, Euphausiacea) in Sagami Bay, Central Japan

Abstract

The larvae of Euphausia similis G. O. Sars in Sagami Bay, Central Japan, aredescribed. Nauplius, metanauplius, calyptopis and furcilia stages are included. In the furciliastage, six forms are identified on the basis of the form of the pleopods and the number ofterminal telson spines. Furcilia I: a pair of non-setose pleopods and seven terminal telsonspines. Furcilia II: a pair of setose and three pairs of non-setose pleopods and seven terminalspines. Furcilia III: four pairs of setose and a pair of non-setose pleopods and seventerminal spines. Furcilia IV: five pairs of setose pleopods and five terminal telson spines.Furcilia V: five pairs of setose pleopods and three terminal telson spines. Furcilia VI: fivepairs of setose pleopods and one terminal telson spine. On the basis of the developmentalpathway of the larvae, E. similis is suggested to be related to E. spinifera, E. longirostris, E. hanseni and the E. gibboides group species. The size of E. similis larvae, expressed astotal length, in Sagami Bay varied according to month. The sizes of calyptopis III and furciliaI-V stages were smallest in November and March and largest in May.