Chanyut Sudtongkong, Sinlapachai Senarat, Gen Kaneko, and Chamnan Para

DOI: 10.14456/sjst-psu.2021.8

pp. 50 - 56

Abstract

The sesarmid crab Episesarma singaporense is an economically important crab in Thailand. In this study, we
associated the integrated classification of oocyte development with ovarian morphology and the gonadosomatic index (GSI). All
specimens were collected in October 2018 and January – February 2019. The germinative centers of the ovary contained oocytes
in oogonia proliferation and primary growth phases (previtellogenic stage; Oc1), whereas peripheral germinal zones contained
those in the secondary growth phase: early vitellogenic stage (Oc2), late vitellogenic stage (Oc3), and mature stage (Oc4). The
developing ovary was classified into four stages. Stage I ovary (immature stage, GSI = 0.17±0.09, n=58) was characterized by
translucent color and oocytes at the oogonia proliferation and primary growth phases. Stage II ovary (developing stage; GSI =
0.59±0.09, n=49) had creamy white color and mainly contained Oc2 oocytes. In Stage III (developed stage; GSI = 1.38±0.09,
n=62), ovary color turned into bright orange and Oc3/Oc4 oocytes were prominently observed. Stage IV ovary (mature stage;
GSI = 2.54±0.46, n=84) showed deep yellow to red/orange color and was dominantly composed of mature oocytes. These data
provide useful information to estimate the oocyte development from ovarian morphology.