The effects of biogenic amines, gonadotropin-releasing hormones and corazonin on spermatogenesis in sexually mature small giant freshwater prawns, Macrobrachium rosenbergii (De Man, 1879)

Neurotransmitters such as the serotonin (5-HT) and dopamine (DA), as well as the neurohormones gonadotropin-releasing hormones (GnRHs) and corazonin (Crz), are known to have various effects on decapod crustaceans, including ovarian maturation and spermatogenesis. The effects of these neurotransmitters and neurohormones on spermatogenesis in the small male freshwater prawns, Macrobrachium rosenbergii, have not been reported. So, we undertook histological and histochemical observations, as well as germ cell proliferation assays to examine the effects of 5-HT, DA, two exogenous GnRH isoforms (l-GnRH-III and oct-GnRH) and Crz. Ten experimental groups were injected with 5-HT and DA at 2.5 × 10−7 and 2.5 × 10−6 mol/prawn, and l-GnRH-III, oct-GnRH and Crz at 50 and 500 ng/gBW, at 4-day intervals from days 0 to 16. We found that prawns treated with 5-HT and GnRH isoforms exhibited significant increases in their testis-somatic index (TSI), seminiferous tubules at early maturation, i.e., stages I and III, with increased diameter of the tubules (DST), and germ cell proliferation, by days 4, 12 and 16, compared with saline control groups. In contrast, prawns treated with DA and Crz showed mostly seminiferous tubules at late maturation stages VIII and IX, and decreases of TSI, DST, and cell proliferation, by day 12, compared with saline control groups. By day 16 the Crz-treated prawns had died. These data indicate that 5-HT and GnRHs can stimulate spermatogenesis, while DA and Crz inhibit spermatogenesis. Consequently, hormonal treatment of male broodstocks in aquaculture with 5-HT and GnRHs could provide valuable tools to enhance reproduction by accelerating testicular maturation, leading to increased production of sperm