Influence of conspecific contact upon blood sex steroid levels and the dynamics of ovarian development in female red-bellied tilapia, Tilapia zillii
Coward K., Bromage NR.
Provision of visual and chemical (pheromonal) contact with adjacent conspecific males (following a period of deprivation) significantly increased circulating levels of serum testosterone (P < 0.05) but not 17β-estradiol (P ≥ 0.05) in a group of female red-bellied tilapia, Tilapia zillii, held in individually-partitioned recirculating aquaria. Male contact also resulted in a significant increase (P < 0.05) in the relative proportions of stage 4 (cortical alveolar) and stage 5 (early vitellogenic) oocytes in the ovary. Visual/chemical contact with a male appeared to induce the recruitment of a cohort of pre-vitellogenic oocytes into vitellogenic growth. Results suggest that the degree of contact between male and female tilapia is likely to be a crucial factor in the determination of the inter-spawn interval and is, therefore, an important consideration for successful broodstock management. [Article copies available for a fee from The Haworth Document Delivery Service: 1-800-342-9678. E-mail address: firstname.lastname@example.org 〈Website: http://www.haworthpressinc.com〉].