The eyestalk hormone, crustacean female sex hormone (CFSH), regulates the development of female secondary sexual characteristics in the blue crab Callinectes sapidus. After its discovery, several ...CFSH gene orthologs have been identified in some species of the suborder Pleocyemata as well. Similarly, in species of another suborder (Dendrobranchiata), an ortholog (Maj-CFSH) has been characterized as an eyestalk factor expressed in both females and males of the kuruma prawn, Marsupenaeus japonicus. In this study, another novel CFSH isoform was identified in the same species using cDNA cloning, expression analysis, and recombinant protein production. The isoform has “CFSH-family” structural characteristics but is dominantly expressed in the ovary, and was therefore designated as Maj-CFSH-ov. Its mRNA and protein levels in vitellogenic ovaries are higher than those in non-vitellogenic ovaries. In the vitellogenic ovary, both mRNA and protein expression of Maj-CFSH-ov are localized to oogonia and previtellogenic oocytes that occupy a small portion of vitellogenic ovaries, but not to the major developing oocytes. A vitellogenesis-inhibiting peptide of M. japonicus (Pej-SGP-I) reduced the expression of vitellogenin in incubated ovarian fragments, but not that of Maj-CFSH-ov. These results indicate that M. japonicus possesses two CFSH isoforms that are derived from distinct tissues, the central X-organ/sinus gland complex and peripheral ovaries. The expression profile of Maj-CFSH-ov suggests its involvement in some reproductive process other than vitellogenesis.
Molecules related to the insulin signaling pathway are widely conserved in the animal kingdom and are responsible for the regulation of various biological functions including growth, metabolism, and ...reproduction. Information on insulin-like peptides (ILPs) is, however, limited to insulin-like androgenic factor (IAG) in crustaceans. To date, in the kuruma prawn
Marsupenaeus japonicus
, only Maj-IAG, which is thought to be a crustacean androgen, and ovarian-specific Maj-ILP1 are the only members of the insulin family that have been reported. In this study, we identified two additional ILPs, Maj-ILP2 and Maj-gonadulin (Maj-GON), from the transcriptome data of
M. japonicus
.
Maj-ILP2
gene expression was observed in the brain ganglia of both sexes and testis, while
Maj-GON
gene expression was limited to the testis. A more detailed tissue expression analysis of three male-dominant ILPs showed clear site-specific gene expression patterns in the gonads:
Maj-ILP2
in the testis,
Maj-GON
in the vas deferens, and
Maj-IAG
in the androgenic gland attaching to the seminal vesicle. The results of this study show that, in addition to Maj-IAG, a crustacean androgen, there are two more ILP molecular species in the male gonad of
M. japonicus
, and suggest that they may serve as signaling molecules involved in the regulation of some male-specific functions.
Crustacean reproduction has been hypothesized to be under complex endocrinological regulation by peptide hormones. To further improve our understanding of the mechanisms underlying this complex ...regulation, knowledge is needed regarding the hormones not only of the central nervous system (CNS) such as the X-organ/sinus gland (XOSG), brain, and thoracic ganglia, but also the peripheral gonadal tissues. For example, in vertebrates, some gonadal peptide hormones including activin, inhibin, follistatin, and relaxin are known to be involved in the reproductive physiology. Therefore, it is highly likely that some peptide factors from the ovary are serving as the signals among peripheral tissues and central nervous tissues in crustaceans. In this work, we sought to find gonadal peptide hormones and peptide hormone receptors by analyzing the transcriptome of the ovary of the kuruma prawn
. The generated ovarian transcriptome data led to the identification of five possible peptide hormones, including bursicon-α and -β, the crustacean hyperglycemic hormone (CHH)-like peptide, insulin-like peptide (ILP), and neuroparsin-like peptide (NPLP). Dominant gene expressions for the bursicons were observed in the thoracic ganglia and the ovary, in the CNS for the CHH-like peptide, in the heart for NPLP, and in the ovary for ILP. Since the gene expressions of CHH-like peptide and NPLP were affected by a CHH (
sinus gland peptide-I) from XOSG, we produced recombinant peptides for CHH-like peptide and NPLP using
expression system to examine their possible peripheral regulation. As a result, we found that the recombinant NPLP increased vitellogenin gene expression in incubated ovarian tissue fragments. Moreover, contigs encoding putative receptors for insulin-like androgenic gland factor, insulin, neuroparsin, and neuropeptide Y/F, as well as several contigs encoding orphan G-protein coupled receptors and receptor-type guanylyl cyclases were also identified in the ovarian transcriptome. These results suggest that reproductive physiology in crustaceans is regulated by various gonadal peptide hormones, akin to vertebrates.
The greasyback shrimp
Metapenaeus ensis
is widely distributed along the coast of India and the West Pacific where it is an important fisheries species. We have examined seasonal changes in ovarian ...development, spermatogenesis, and mating of
Me. ensis
in histological studies and by external observations on specimens collected in Ise Bay, its northernmost habitat. Ovaries were found to be previtellogenic from February to May, with the first signs of development being the accumulation of yolk in oocytes in late May. Ovarian shadow ratios were high during the period late July to mid-September. The formation of cortical rods in the peripheries of oocytes and germinal vesicle breakdown were observed in ovaries from late June to September. Male shrimps had sperm in the testes during the period early June to early October, and female shrimps had spermatophores in spermatheca after early July. In late July, some post-spawn female shrimps had exogenous vitellogenic oocytes in their ovaries, indicating that ovarian development had been repeated in preparation for the next spawning. Ovarian shadow ratios, which were positively correlated with gonadosomatic indices and ovarian development, seem to be a useful marker to determine ovarian development. Our results indicate that mating in
Me. ensis
started in early July and that the spawning season ranged from July to September with more than two cycles of spawning in Ise Bay.
Heavy rainfall can reduce salinity and increase turbidity in coastal waters, creating stressful conditions for the organisms found there, especially for the early stages of their ontogeny. The ...effects of salinity and turbidity on the embryonic stages of red sea bream
Pagrus major
were examined under controlled laboratory conditions. In the first experiment, eggs of red sea bream were exposed to different salinity stresses 34 (control), 30, 26, 22, 18, 14 psu for 3 h. In the second experiment, eggs were exposed to higher turbidity levels of 100, 300, 500, and 700 NTU from 0 NTU (control) obtained by dissolving kaolin clay for the same duration as in the first experiment. The results showed that the embryos of red sea bream are tolerant to short-term exposure to low salinity stress. There were no significant differences in the hatching rate, yolk sac consumption of newly hatched larvae, or survival of larvae at 6 days post-hatching. However, the short exposure to turbidity stress reduced the hatching rate, total length, and yolk sac volume of newly hatched larvae, and larval viability of red sea bream. Turbidity had a significant impact on the abnormality rate at hatching, with higher values observed for elevated turbidity.
Recent research on decapod crustaceans revealed the presence of multiple vitellogenin genes within a single species. Characterizing their expression dynamics and regulatory mechanisms is helpful for ...the sustainability of commercially relevant decapods through a greater comprehension of vitellogenesis. However, it is unclear whether multiple vitellogenin genes exist in the kuruma prawn
Marsupenaeus japonicus
, an essential species in several Asian countries. This study determined the full-length cDNA sequence of the new vitellogenin (Maj-Vg2) using transcriptome analysis and cDNA cloning. The deduced Maj-Vg2 consisted of 2,554 amino acids and shared only 53.8% identity with Maj-Vg1, the known vitellogenin of this species. The Maj-Vg1 gene (
Maj-Vg1
) was expressed in both the hepatopancreas and ovary, whereas the Maj-Vg2 gene (
Maj-Vg2
) was expressed only in the hepatopancreas.
Maj-Vg2
expression in the hepatopancreas was low during the previtellogenic stage and increased during the early and late yolk globule stages
.
When eyestalks were ablated from immature prawns,
Maj-Vg2
expression in the hepatopancreas increased significantly, like
Maj-Vg1
expression in the ovary, suggesting possible regulation by hormones from the eyestalk ganglia. These results suggested that
Maj-Vg2
and
Maj-Vg1
are involved in vitellogenesis in this species
.
The embryonic developmental response of two abalone species (disk abalone
Haliotis discus discus
, giant abalone
Haliotis gigantea
) to a drop in salinity with different exposure times was ...investigated to gain a better understanding of the reasons for the decrease in natural stock populations. Two experimental designs—first, combinations of two salinities (34 and 17 psu) and four exposure times (0, 1, 2 and 4 h), and second, combinations of three salinities (34, 24 and 14 psu) and four exposure times (0, 1, 3 and 6 h)—were tested on disk and giant abalone eggs to determine the effects on hatching onset time, hatching success, percentage of abnormality and survival rate. Hatching onset time increased significantly for both species as salinity dropped and exposure time increased. Both species followed a decreasing trend in terms of hatching success as exposure time increased at low salinity levels. As for abnormality, both species showed a significant negative effect of low salinity and long exposure times. Giant abalone showed better adaptability to long exposure time at low salinity levels, and hence a higher survival rate, than disk abalone.
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Insulin-like androgenic gland factor (IAG) is presumed to be a sex differentiation factor so-called androgenic gland hormone (AGH) in decapod crustacean, although the function of IAG ...peptide has not yet been reported. In this study, we synthesized IAG from the prawn, Marsupenaeus japonicus, and its function was assessed by an in vitro bioassay. As a result, IAG with the insulin-type disulfide bond arrangement showed biological activity, whereas its disulfide isomer did not. These results strongly suggest that the native IAG peptide has an insulin-type disulfide, and it is the decapod AGH.
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