Hemolymph vitellogenin levels during final maturation and post-spawning in the female kuruma prawn, Marsupenaeus japonicus

A vitellogenin (VTG) ELISA was developed to clarify the relationship between hemolymph VTG levels and spawning conditions in female kuruma prawns. Hemolymph VTG was measured at the final maturation and spent stages. Collected hemolymph and oocytes were assessed for the 5 consecutive days of the spawning test. Of gravid females, 22.7% were broodstock, ready-to-spawn with cortical rods in oocytes. A negative correlation (r2=0.71) was found between the release rate of eggs and the hemolymph VTG concentration 1 day before spawning. Hemolymph VTG levels did not fluctuate significantly through the late granule, pre-maturation, and maturation stages. Late perinucleolus oocytes, which have already accumulated vitellin (Vn) in the cytoplasm, were found at the maturation stage. Positive immunoreactions against the anti-Vn serum were observed in the ovarian sections at the spent stage just after spawning. These results indicate that female prawns are preparing for the next spawning just before and after spawning, resulting in a high levels of hemolymph VTG throughout the late maturation and spent stages.