Ovarian development and hemolymph vitellogenin levels in laboratory-maintained protandric shrimp, Pandalus hypsinotus: Measurement by a newly developed time-resolved fluoroimmunoassay (TR-FIA)

Abstract

Most pandalid shrimps exhibit protandric hermaphroditism, and detailed information on ovarian development of pandalid species is important for a better understanding of vitellogenesis in crustacean species. In the present study, we characterized ovarian development under light and electron microscopy and examined the hemolymph vitellogenin levels in the coonstriped shrimp, Pandalus hypsinotus under laboratory conditions. To measure vitellogenin levels, a time-resolved fluoroimmunoassay (TR-FIA) was developed after purification of vitellin and production of the anti-vitellin antiserum. The TR-FIA showed wide assay range (0.98-2000 ng/ml), high sensitivity (0.5 ng/ml), and low assay variability (0.9-6.4% of intraassay coefficients, 1.4-5.1% for interassay coefficients). Female P. hypsinotus had non-vitellogenic ovaries in March after the eggs attached to the abdomen hatched, and started yolk accumulation in the ovaries during April-October. During yolk accumulation, yolk globules appeared and increased in the ooplasm. After yolk accumulation, gonadosomatic index (GSI) reached 8.3-8.5 just before oviposition. Females spawned and were ovigerous during June-July of the next year. Hemolymph vitellogenin levels were low (0.006±0.008 mg/ml, mean±SD) before the yolk accumulation, and became significantly higher (2.66±0.93 mg/ml) during yolk accumulation (GSI, 2-8). Just before oviposition, levels declined to low levels (0.040±0.012 mg/ml). Vitellogenin levels were significantly correlated to GSI during the yolk accumulation. The obtained results show that the process of vitellogenesis during the female phase of P. hypsinotus is similar to other crustacean species that do not change sex.