Leptin-like immunoreactivity in the central nervous system, digestive organs, and gonads of the giant freshwater prawn, Macrobrachium rosenbergii

Distribution of abalone egg-laying hormone-like peptide in the central nervous system and reproductive tract of the male mud crab, Scylla olivacea

The mud crab, Scylla olivacea, is a high value economic marine animal in Thailand. However, collection of these crabs from natural habitat for local consumption and export has caused rapid population decline. Hence, aquaculture of this species is required and to this measure understanding of endocrine control of their reproduction must be understood. Egg laying hormone (ELH) is a neuropeptide synthesized by the bag cells (neurons) in the abdominal ganglia of Aplysia gastropods. It plays a critical role in controlling egg production and laying in gastropods, and its possible homolog (ELH-like peptide) was reported in the neural and ovarian tissues of prawns and recently in female reproductive tract of the blue swimming crab, Portunus pelagicus. In this study, we have studied the histology of the male reproductive tract in Scylla olivacea which are comprised of anterior testis, posterior testis, early proximal spermatic duct (ePSD), proximal spermatic duct (PSD), middle spermatic duct (MSD) and distal spermatic duct (DSD), by immunohistochemistry, detected an abalone ELH- immunoreactivity (aELH-ir) in epithelium of ducts in posterior testis and epithelium of all parts of spermatic duct. Furthermore, we could detect aELH-ir in neurons of cluster 9, 11, olfactory neuropil (ON) in the brain and in the small neurons located between the third and the fourth thoracic neuropils (T3-T4) and between the fourth and the fifth thoracic neuropils (T4-T5) of thoracic ganglia. Thus, the presence of aELH in male S. olivacea was designated the role of female egg laying behavior in the male mud crab.

Molecular cloning and expression analysis of a prawn (Macrobrachium rosenbergii) juvenile hormone esterase-like carboxylesterase following immune challenge

Methyl farnesoate (MF), the crustacean juvenile hormone (JH), plays critical roles in various physiological processes in crustaceans. The titer of MF is precisely regulated by specific carboxylesterase. Here, we report for the first time that the cloning and expression analysis of a JH esterase-like carboxylesterase from the prawn Macrobrachium rosenbergii (named as MrCXE). MrCXE contained a 1935-bp open reading frame (ORF) conceptually translated into a 644-amino acids protein. MrCXE protein shared the highest identity (36%) with JH esterase-like carboxylesterase from the swimming crab, Portunus trituberculatus and exhibited the typical motifs of JH esterase-like carboxylesterases. MrCXE was most abundantly expressed in hepatopancreas, the major tissue for MF metabolism. MrCXE was expressed at a low level in gut and was not detected in other tissues. Additionally, MrCXE expression was upregulated in hepatopancreas by eyestalk ablation to increase MF level. Furthermore, the mRNA level of MrCXE was significantly increased in the hepatopancreas when challenged by the bacterial pathogens Aeromonas hydrophila and Vibrio parahaemolyticus. To our knowledge, this is the first report that the JH esterase-like carboxylesterase is involved in the innate immune response of the crustaceans.

The expression and distribution of a leptin receptor in the central nervous system, digestive organs, and gonads of the giant freshwater prawn, Macrobrachium rosenbergii

In the present study, the presence and distribution of leptin receptor (LEP-R) in central nervous system, digestive organs, gonads of giant freshwater prawn, Macrobrachium rosenbergii, were investigated with Western blot and immunohistochemistry. By Western blot a LEP-R with a molecular weight (MW) of 100 kDa was detected in the brain, thoracic ganglia, abdominal ganglia, hepatopancreas, all parts of the gastrointestinal tract, ovaries, and testes. In hepatopancreas and foregut, another intense positive band was detected at molecular weight of 30 kDa, which could be an isotype of LEP-R. By immunohistochemistry, LEP-R-ir was detected in the neurons, and neuropils in the brain, thoracic ganglia, and abdominal ganglia. In the gastrointestinal tract, there was intense LEP-R-ir in the apical part of the epithelial cells of the foregut, midgut, and hindgut. In addition, LEP-R-ir was found in the Restzellen(R)cells and Fibrillenzellen(F) cells in the hepatopancreas. In the ovary, LEP-R-ir was detected in early stage of oocytes and mature oocytes. Intense LEP-R-ir was observed in spermatogonia and spermatocytes of the small and orange claw male prawns. In addition, LEP-R was seen in the high epithelium of spermatic ducts from all male morphotypes. In summary, the detection of the LEP-R-ir suggests the existence of a LEP-R in several organs of M. rosenbergii. Through binding with leptin peptide, LEP-R may be an important signaling molecule that has critical functions in modulating and controlling food intake, energy expenditure, and reproduction in this prawn.