Sex pheromones and ovarian development in teleost fish

Acetochlor affects zebrafish ovarian development by producing estrogen effects and inducing oxidative stress

Acetochlor is one of the most widely used pesticides worldwide and widely distributed in the water environment. However, studies on the reproductive influence of acetochlor are still limited. To investigate the impact and potential mechanism of acetochlor on fish ovarian development, zebrafish were utilized as experiment models. The ovarian histology, ovarian development-related genes, and plasma oxidative stress-related indexes were investigated following acetochlor (at nominal concentration 1, 10, and 100 μg/L) exposure for 7 and 21 days. Results showed that low-dose acetochlor had estrogen effect and induced zebrafish estradiol (E₂) and ovarian vitellogenin (Vtg) synthesis and promoted ovarian development, while long-term exposure to higher doses of acetochlor reduced the ability of ovarian resistance to oxidative stress and destroyed the development of the ovary. Moreover, bone morphogenetic protein 15 (bmp15) and growth differentiation factor 9 (gdf9) were also involved in the influence of acetochlor on the ovarian development of zebrafish.

Sexually mature European eels (Anguilla anguilla L.) stimulate gonadal development of neighbouring males: possible involvement of chemical communication

This study was aimed to investigate whether sexual maturation of immature male eels could be stimulated indirectly by placing them in contact with either male (Minj) or female (Finj) eels in which sexual maturation had been stimulated directly by weekly injections of human chorionic gonadotropin (hCG) or salmon pituitary extract (SPE), respectively. Untreated males were placed either in the same tank or in a separate tank that was linked to the injected fish via a recirculation system. The hormonal treatments stimulated spermatogenesis and spermiation in Minj, and ovulation in Finj as well as an increase of the ocular (Io) and gonadosomatic (GSI) indices in both sexes. Plasma levels of testosterone (T) and 11-ketotestosterone (11-KT) increased in Minj and T and 17beta-estradiol (E2) in Finj. A small peak of plasma 17,20beta-dihydroxypregn-4-en-3-one (17,20betaP) occurred during ovulation, while the plasma levels of 17alpha-hydroxypregn-4-ene-3,20-dione (17P) were undetectable in both males and females. The water conditioned by Minj and Finj induced significant, though relatively minor, increases in Io and GSI in uninjected males. In addition, uninjected fish showed small changes in plasma T and 11-KT levels, apparently related to the timing of spermiation and ovulation of Minj and Finj, respectively, as well as an activation of spermatogenesis (but not spermiation). Injected fish released free and conjugated T, 11-KT and E2 into the water, although immature eels were unable to smell (by electro-olfactogram) any of these steroids or prostaglandin F2alpha. However, immature males were highly sensitive to water extracts conditioned by spermiating Minj and pre-ovulatory and ovulated Finj. These preliminary results suggest the existence of chemical communication between maturing eels and immature males that stimulates gonad development, although the putative pheromone(s) involved has/have not yet been identified.

Molecular cloning and characterization of a hemolymph clottable protein from tiger shrimp (Penaeus monodon)

To investigate the coagulation system in crustacean decapoda, a homodimeric glycoprotein of 380 kDa was purified from the hemolymph of tiger shrimp (Penaeus monodon) by sequential DEAE anion exchange chromatography. The purified protein was coagulated by the shrimp hemocyte transglutaminase in the presence of Ca2+. The clottable protein contains 44% alpha helices and 26% beta sheets as determined by circular dichroism spectra. Its conformation is stable in buffer of pH 4-9. To solve its primary structure, partial sequences of the purified polypeptides from cyanogen bromide cleavage and endopeptidase digestion were also determined. A shrimp cDNA expression library was constructed. By combination with antibody screening, reverse transcriptase PCR using degenerate primers from determined amino acid sequences and cDNA library screening with digoxigenin-labeled DNA probes, the entire cDNA of 6124 bp was obtained. This cDNA encodes a protein of 1670 amino acids, including a 14-amino acid signal peptide. With four potential N-glycosylation sites, the clottable protein was found to contain 3.8% high-mannose glycan; and Man8GlcNAc and Man9GlcNAc were released upon endo-beta-N-acetylglucosaminidase hydrolysis. Upon conducting a protein sequence database survey, the shrimp clottable protein shows 36% identities to the crayfish clotting protein and lower similarities to members of insect vitellogenins, apolipoprotein B and mammalian von Willebrand factor. Notably, a region rich in Gln residues, a polyGln motif and five Ser-Lys-Thr-Ser repeats are present in the shrimp protein, suggesting this protein might be a transglutaminase substrate. Northern blot analysis revealed that the clottable protein is expressed in most of the shrimp tissues but not in the mature hemocytes.

Pheromone-induced spawning of Pacific herring. I. Behavioral characterization

A spawning pheromone in the milt (semen) and testes of the Pacific herring, Clupea harengus pallasi, triggers spawning in sexually mature fish of both sexes and is thought to facilitate school spawning of this species. We found the response to the pheromone to be a stereotyped behavioral sequence consisting of a graded extension of the gonadal papilla, release of gametes, and spawn deposition behavior. The response is triggered by an olfactory stimulus, as demonstrated by the elimination of the response by occlusion of the nares. Stimulus concentrations of an approximate 1:500 dilution of fresh milt or the equivalent of 0.02 g of fully mature testes per milliliter were required to elicit a response in 50% of ripe herring that are responsive to the pheromone. Female fish appeared to be less sensitive to the pheromone in milt than males early in the spawning season, but not thereafter. The average duration of responses of male fish was longer after exposure to concentrated milt than to testes extracts, but no consistent difference in response times of the two sexes was detected. Factors other than the spawning pheromone, maturity of the fish, and stress also were found to influence the spawning response. For example, exposure to shallow (3 cm) water in a small tank induced "spontaneous" papilla extension and spawning approximately 20 min after refilling the tank; occluding the nares prevented this response. Also, the presence of floating kelp (Macrocystis) resulted in prolonged spawning in a large tank after pheromonal stimulation.

When is a butterfly like an elephant?

The behaviours of organisms as diverse as elephants and butterflies are affected by pheromones with identical or similar structures. Recent developments in the molecular biology of pheromone detection suggest why.

Characterization of a clotting protein, isolated from plasma of the freshwater crayfish Pacifastacus leniusculus

A protein responsible for clot formation was isolated from plasma of the crayfish Pacifastacus leniusculus, by repeated precipitation at low ionic strength, pH 6.0. The protein, here named clotting protein (CP), is a lipoglycoprotein, which consists of two 210-kDa subunits, covalently associated by disulfide bonds. Preparations of the CP can form stable clots in the presence of crayfish haemocyte lysate supernatant, which contains endogenous, Ca(2+)-dependent transglutaminase (TGase) activity. The covalent, TGase-mediated polymerization of CP could clearly be visualized in SDS/PAGE under reducing conditions, where the 210-kDa subunit is covalently cross-linked into dimeric, trimeric and higher polymeric forms. The CP was shown to be a substrate for transglutaminases, since two different fluorescent TGase substrates, namely dansylcadaverine and a dansylated glutamine-containing peptide, were incorporated into the CP subunit by active TGase. This indicates the presence of both glutamine and lysine residues in the CP, accessible for TGase cross-linking. The amino acid composition and the N-terminal amino acid sequence of the clotting protein was determined.