Influence of 17β-oestradiol (E2) and 17α-hydroxyprogesterone (OHP) on ovarian maturation in Penaeus semisulcatus De Haan, 1844 (Decapoda, Dendrobranchiata, Penaeidae) from the Mediterranean Sea off Alexandria, Egypt

This study searches to provide appropriate conditions to trigger spawning in Penaeus semisulcatus in aquaculture. The aim was to test the effect of 17β-oestradiol and 17α-hydroxyprogesterone on ovarian maturation and to study the correlation between the different stages of ovarian maturation and hormonal levels in the ovaries, hepatopancreas, and haemolymph. Female shrimps were collected from Ras El-Tin beach and the fishing port to Abu Qir Bay of the Mediterranean Sea off Alexandria, Egypt from June 2018-August 2019. Shrimps were individually weighed and subsequently killed by thermal shock at a maximum temperature of 45°C. Gonadosomatic and hepatosomatic indices were calculated. The correlation between the gonadosomatic and hepatosomatic indices indicates the presence of endogenous and exogenous vitellogenesis. The haemolymph, hepatopancreas, and ovaries were studied by stereo- and electron microscopy. From 15 females in each season the mentioned tissues were isolated for the extraction and quantification of steroid hormones during the different stages of gonadal maturation using radioimmunoassay. An ecdysteroid- and steroid-extraction protocol was applied. Aliquots were collected from the haemolymph to identify 17β-oestradiol and 17α-hydroxyprogesterone by mass spectrometry. Five stages of gonadal maturation were observed. The hepatopancreas was formed by a set of tubules lined with pseudostratified epithelium composed of five cell types, cell E (undifferentiated), cell F (fibrillar), cell B (vesicular), R (reabsorbing), and M (basal) cells. Steroidogenic tissues were small in size and numerous. The ultrastructure of the ovary and hepatopancreas were studied during oocyte development. There was a high concentration of 17β-oestradiol and 17α-hydroxyprogesterone in stages I and II of ovarian maturation, coinciding with the preparation phase for vitellogenesis. A progressive decrease of these steroid hormones occurred during the course of gonadal maturation, and reached its lowest concentration in the spawning period. The ecdysone concentration did not fluctuate in ripe females. Its level increases from stages I-IV of vitellogenesis onward.

Modulation of the PGE2-Mediated Pathway in the Eclosion Blocking Effect of Flumethrin and Terpenoid Subfraction Isolated from Artemesia nilagirica in Rhipicephalus annulatus

Prostaglandins are a group of important cell-signaling molecules involved in the regulation of ovarian maturation, oocyte development, egg laying and associated behaviors in invertebrates. However, the presence of prostaglandin E2 (PGE2), the key enzymes for PGE2 biosynthesis and its interference by drugs were not investigated previously in the ovary of ticks. The present study was undertaken to assess the modulation of the PGE2-mediated pathway in the eclosion blocking effect of flumethrin and terpenoid subfraction isolated from Artemisia nilagirica in Rhipicephalus annulatus ticks. The acaricidal activities and chemical profiling of the terpenoid subfraction were performed. The localization of the cyclooxygenase1 (COX1) and prostaglandin E synthase (PGES) enzymes and the quantification of PGE2 in the ovaries of the ticks treated with methanol (control), flumethrin and terpenoid subfraction were also undertaken. In addition, the vitellogenin concentration in hemolymph was also assayed. Both flumethrin and the terpenoid subfraction of A. nilagirica elicited a concentration-dependent inhibition of fecundity and blocking of hatching of the eggs. The COX1 could not be detected in the ovaries of treated and control ticks, while there was no significant difference observed in the concentration of vitellogenin (Vg) in them. The presence of PGES in the oocytes of control ticks was confirmed while the immunoreactivities against PGES were absent in the vitellogenic oocytes of ticks treated with flumethrin and terpenoid subfraction. The levels of PGE2 were below the detection limit in the ovaries of the flumethrin-treated ticks, while it was significantly lower in the ovaries of the terpenoid subfraction-treated ticks. Hence, the prostaglandin E synthase and PGE2 were identified as very important mediators for the signaling pathway for ovarian maturation and oviposition in ticks. In addition, the key enzyme for prostaglandin biosynthesis, PGES and the receptors for PGE2 can be exploited as potential drug targets for tick control. The detection of PGES by immunohistochemistry and quantification of PGE2 by LC-MSMS can be employed as valuable tools for screening newer compounds for their eclosion blocking acaricidal effects.

Transcriptome analysis of five ovarian stages reveals gonad maturation in female Macrobrachium nipponense

Background Macrobrachium nipponense is an economically important species of freshwater shrimp in China. Unlike other marine shrimps, the ovaries in adult female M. nipponense can mature rapidly and periodically during the reproductive period, but the resulting high stocking densities and environmental deterioration can negatively impact the harvest yield and economic benefits. To better understand ovary development in female M. nipponense, we performed systematic transcriptome sequencing of five different stages of ovarian maturation. Results We obtained 255,966 Gb of high quality transcriptome data from 15 samples. Of the 105,082 unigenes that were selected, 30,878 were successfully annotated. From these unigenes, we identified 17 differentially expressed genes and identified three distinct gene expression patterns related to different biological processes. We found that cathepins, legumains, and cystatin were enriched in the lysosome pathway, and they are related to vitellogenin hydrolysis. Additionally, we found that myosin heavy chain 67 participated in oocyte excretion. Conclusions We provide the first detailed transcriptome data relating to the ovarian maturation cycle in M. nipponense. Our results provide important reference information about the genomics, molecular biology, physiology, and population genetics of M. nipponense and other crustaceans. It is conducive to further solve the problem of M. nipponense rapid ovarian maturation from the aspects of energy supply and cell division.

Assessment of the Effects of Double-Stranded RNAs Corresponding to Multiple Vitellogenesis-Inhibiting Hormone Subtype I Peptides in Subadult Female Whiteleg Shrimp, Litopenaeus vannamei

Vitellogenesis-inhibiting hormone (VIH) negatively regulates reproduction in shrimp and other decapod crustaceans. In order to assess the effects of transcriptional silencing by multiple VIH subtype I sinus gland peptides (SGPs) on ovarian maturation in female whiteleg shrimp, Litopenaeus vannamei, we synthesized five dsRNAs targeting Liv-SGP-A, −B, −C, −F, and −G and injected them into subadults. The following treatments were employed: sgpG-dsRNA (targeting Liv-SGP-G), sgpC-dsRNA (targeting Liv-SGP-C), and mixed-dsRNA (targeting Liv-SGP-A, −B, and −F). The expression of Liv-SGP-G in eyestalks was significantly decreased at 10, 20, and 30 days after the injection of sgpG-dsRNA In addition, it was significantly decreased at 10 and 30 days after the injection of mixed-dsRNA. The expression of vitellogenin (Vg) gene expression in the ovaries, and concentrations of Vg protein in the hemolymph, were not changed by the administration of any dsRNA treatment (the ovaries remained immature in all treated individuals and contained mostly oogonia and previtellogenic oocytes). Although the administration of dsRNAs corresponding to multiple VIHs did not promote ovarian maturation, this is the first report of the co-transcriptional repression of Liv-SGP-G by the injection of dsRNA for homologous genes (Liv-SGP-A, −B, and −F). These results indicate that subadults can respond to the techniques of transcriptional silencing.

Comparative stages of atretic oocytes between Episesarma versicolor and E. singaporense from Thailand: Implication on the reproductive success

Informative reviews on the oocyte atresia referring to degeneration and resorptive mechanism are warranted in common animals, but it is rarely still found in carbs. In this current study, we focused on characteristics and stage of the atretic oocyte from two important female sesarmid carbs (violet vinegar crab, Episesarma versicolor, and Singapore vinegar crab, E. singaporense) during ovarian maturation. A total of 30 female samples in each carb species were collected from the Palian mangrove area of Trang province, Thailand. The results shared among those carb samples that both primary growth (PGs) and secondary growth (SGs) phases underwent a degenerative process of atresia. The latter of atresia during SGs was also divided into five stages (I, II, III, IV, and V). The degeneration of follicular cell and yolk architecture identifying in the SGs were highlighted. The number of atresias was slightly compared between E. versicolor and E. singaporense; therefore, there were no significant differences. Our observation suggested that the low number of atresia might be associated with the increased reproductive success of two female sesarmid carb living in natural habitats.