Bilateral eyestalk-ablation of the blue swimmer crab, Portunus pelagicus, produces hypertrophy of the androgenic gland and an increase of cells producing insulin-like androgenic gland hormone

The androgenic glands (AG) of male decapod crustaceans produce insulin-like androgenic gland (IAG) hormone that controls male sex differentiation, growth and behavior. Functions of the AG are inhibited by gonad-inhibiting hormone originating from X-organ-sinus gland complex in the eyestalk. The AG, and its interaction with the eyestalk, had not been studied in the blue swimmer crab, Portunus pelagicus, so we investigated the AG structure, and then changes of the AG and IAG-producing cells following eyestalk ablation. The AG of P. pelagicus is a small endrocrine organ ensheathed in a connective tissue and attached to the distal part of spermatic duct and ejaculatory bulb. The gland is composed of several lobules, each containing two major cell types. Type I cells are located near the periphery of each lobule, and distinguished as small globular cells of 5–7 μm in diameter, with nuclei containing mostly heterochromatin. Type II cells are 13–15 μm in diameter, with nuclei containing mostly euchromatin and prominent nucleoli. Both cell types were immunoreactive with anti-IAG. Following bilateral eyestalk ablation, the AG underwent hypertrophy, and at day 8 had increased approximately 3-fold in size. The percentage of type I cells had increased more than twice compared with controls, while type II cells showed a corresponding decrease

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

Expression of the male reproduction-related gene (Mar-Mrr) in the spermatic duct of the giant freshwater prawn, Macrobrachium rosenbergii

Phosphorylated sperm proteins are crucial for sperm maturation and capacitation as a priori to their fertilization with eggs. In the freshwater prawn, Macrobrachium rosenbergii, a male reproduction-related protein (Mar-Mrr) was known to be expressed only in the spermatic ducts as a protein with putative phosphorylation and may be involved in sperm capacitation in this species. We investigated further the temporal and spatial expression of the Mar-Mrr gene using RT-PCR and in situ hybridization and the characteristics and fate of the protein using immunblotting and immunocytochemistry. The Mar-Mrr gene was first expressed in 4-week-old post larvae and the protein was produced in epithelial cells lining the spermatic ducts, at the highest level in the proximal region and decreased in the middle and distal parts. The native protein had a MW of 17 kDa and a high degree of serine/threonine phosphorylation. It was transferred from the epithelial cells to become a major protein at the anterior region of the sperm. We suggest that it is involved in sperm capacitation and fertilization in this open thelycal species and this is being investigated