Section outline

    •  表層クロロフィルa:surface Chlorophyll a, 出現個体数:number of appearance individuals, 雌個体に占める割合:proportion of female individuals, 雄個体に占める割合:proportion of male individuals, 予想産卵期:Expected spawning season







      Looking at the number of individuals appearing at each developmental stage, it can be seen that there are many C1 stages from June to August.

      A separate egg-nauplius rearing experiment revealed that it takes 51 days for egg hatching and nauplii development under the field environment.

      Taking these into account, it was found that the reproduction (egg laying) of this species almost coincided with the high season of chlorophyll a in the surface layer.


      Growth from C1 to C3 could be traced clearly.


      After C4, this species has different developmental times in both sexes, and females spend a long time in C6 (parental adult).


      Expediting a long time in the adult state of a female is an advantageous life history strategy in that it rapidly shifts to egg laying in response to an increase in the number of food particles settling from the surface layer.

    • [Open Access] Yamaguchi & Ikeda, 2000, Marine Biology URL