Maturation and reproductive cycle of female armorhead Pseudopentaceros wheeleri from the southern Emperor-northern Hawaiian Ridge Seamounts

Abstract

The stage of ovarian development and annual reproductive cycle of female armorhead Pseudopentaceros wheeleri collected from seamounts of the southern Emperor—northern Hawaiian Ridge in 1993 and 1995–1996 was investigated through use of the gonadal somatic index (GSI) and ovarian histology. The stages of oocyte development were classified into eight developmental stages (perinucleolus, cortical alveolus, oil droplet, early yolk globule, late yolk globule, migratory nucleolus, prematuration, and maturation) based on histological characteristics. Oocytes of different size and developmental stage were present within ovaries during the spawning season. Oocyte development appears to be asynchronous and armorhead apparently spawn several times during the spawning season. The stage of the most developed oocyte was used to classify the stage of ovarian maturation. The GSI increased gradually with ovarian development. Oocytes in the perinucleolus, cortical alveolus, and oil droplet stages were present in ovaries throughout the year. Early and late yolk globule stages appeared during August–September indicating that yolk formation begins during late summer. The migratory nucleolus through maturation stages were detected during November–January. Post ovulatory follices were present during November–March, and GSI values rapidly decreased in February. Results indicate that spawning occurs during November–February and peaks during December–January.