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

Changes of phosphatidylcholine and fatty acids in germ cells during testicular maturation in three developmental male morphotypes of Macrobrachium rosenbergii revealed by imaging mass spectrometry.

Testis maturation, germ cell development and function of sperm, are related to lipid composition. Phosphatidylcholines (PCs) play a key role in the structure and function of testes. As well, increases of polyunsaturated fatty acids (PUFA) and highly unsaturated fatty acids (HUFA), especially arachidonic acid (ARA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) are essential for male fertility. This study is the first report to show the composition and distribution of PCs and total fatty acids (FAs) in three groups of seminiferous tubules (STs) classified by cellular associations [i.e., A (STs with mostly early germ cells), B (STs with mostly spermatids), and C (STs with spermatozoa)], in three morphotypes of Macrobrachium rosenbergii, [i.e., small male (SM), orange claw male (OC), and blue claw male (BC)]. Thin layer chromatography exhibited levels of PCs reaching maxima in STs of group B. Imaging mass spectrometry showed remarkably high signals corresponding to PC (16:0/18:1), PC (18:0/18:2), PC (18:2/20:5), and PC (16:0/22:6) in STs of groups A and B. Moreover, most signals were detected in the early developing cells and the intertubular area, but not at the area containing spermatozoa. Finally, gas chromatography-mass spectrometry indicated that the major FAs present in the testes were composed of 14:0, 16:0, 17:0, 18:0, 16:1, 18:1, 18:2, 20:1, 20:2, 20:4, 20:5, and 22:6. The testes of OC contained the greatest amounts of these FAs while the testes of BC contained the least amounts of these FAs, and there was more EPA (20:5) in the testes of SM and OC than those in the BC. The increasing amounts of FAs in the SM and OC indicate that they are important for spermatogenesis and spermiogenesis. This knowledge will be useful in formulating diets containing PUFA and HUFA for prawn broodstocks in order to improve testis development, and lead to increased male fecundity