Oogenesis and ovarian development in female
Panulirus japonicus were examined by light and electron
microscopy. Eight substages (oogonium, bouquet, chromatin nucleolus, oil
globule, pre-yolk platelet, yolk platelet, pre-maturation and maturation) were
distinguished in the typical process of oogenesis (multiplication,
pre-vitellogenesis, vitellogenesis and maturation stages). Yolk accumulation
started at the late pre-yolk platelet substage, when electron-dense granules
appeared. Yolk granules seemed to be accumulated in two ways, being produced
endogenously by the abundant rough endoplasmic reticulum during vitellogenesis
and exogenously by micropinocytosis from the yolk platelet to pre-maturation
substages. Ovulation occurred after oocytes became mature (i.e. after the
metaphase of the primary maturation division was reached). The diameter of
mature oocytes was 465–477 µm.
The seasonal ovarian development cycle was divided into seven stages:
inactive, developing, ripe, re- developing, re-ripe, spawned and recovery. The
morphological characteristics relating to the gonadosomatic index (GSI) of
each stage are described (GSI was calculated by the formula
I = W ×
105/L3,
where I represents GSI, W is the
gonad weight in grams, and L is the carapace length in
millimetres). Estimated GSI values ranged from 11.3 to 12.4 in individuals
with mature oocytes, and the 99% confidence intervals for GSI values of
adjacent oogenesis substages did not overlap. GSI values at the developing and
ripe stages were significantly larger than those at the re-developing and
re-ripe stages, respectively.
Cooling-Induced Activation of the Pericardial Organs of the Spiny Lobster, Panulirus japonicus