Ardavan Farhadi

Effects of 17β-estradiol injection on the reproductive efficiency of freshwater crayfish, Astacus leptodactylus (Eschscholtz, 1823)

ABSTRACT The effects of 17β-estradiol injection (10−7mol/crayfish) in adult female Astacus leptodactylus on the reproductive efficiency (i.e., pleopodal egg and stage 1 juvenile numbers) were investigated. In addition, hepatosomatic index, gonodosomatic index, and 17β-estradiol (E2) levels of crayfish ovary, hepatopancreas, and heamolymph before and after injections were also determined. Results showed that E2 injection to females enhances the reproductive efficiency of A.leptodctylus. E2 injection significantly increased pleopodal egg and stage 1 juvenile numbers, GSI, HSI, and concentrations of E2 in heamolymph, ovary, and hepatopancreas. However, E2 injection did not accelerate time of mating and proportion of pleopodal egg-berried females at the first week of reproduction season in this species. This study highlights that to improve the reproductive efficiency of A.leptodctylus by using hormones to regulate the ovarian cycle, E2 should be used at least 1.5 months before the commencement of the breeding season.

Optimization of the incubation time and temperature for spermatozoa extraction in freshwater crayfish Pontastacus leptodactylus (Eschscholtz, 1823)

Determination and control of spermatozoa quality in crustacean aquaculture is an important issue for successful and controlled reproduction. Investigation of spermatozoa number in spermatophores is a basic and common parameter for determining the reproductive quality in farmed decapods. In the present study, spermatozoa extraction from spermatophores located in the ductus deferens was conducted in Pontastacus leptodactylus using different incubation times and temperatures. The results indicate that the duration of incubation and temperature affected (P < 0.05) spermatozoa extraction. Greater temperatures (40 and 75 °C) resulted in a reduction (P < 0.05) in number of extracted spermatozoa. In contrast, more spermatozoa were extracted when the 4 and 23 °C temperatures were imposed. After 4 h of incubation, the number of extracted spermatozoa were greatest in number at 23 °C. In conclusion, the greater numbers of crayfish spermatozoa can be obtained when the ductus deferens containing spermatophores is incubated at 23 °C for 4 h as compared with other temperatures and incubation durations. The results of present study are useful for assessing spermatozoa quality in aquaculture as well as the extraction of spermatozoa for research purposes.

Effects of different methods and times of 17β-estradiol treatment on the feminization success in the narrow-clawed crayfish Astacus leptodactylus (Eschscholtz, 1823)

Abstract Sex differentiation is a profitable technique in crayfish aquaculture. Most of the studies have focused on sex differentiation in crayfish by ablation or implantation of androgenic glands. There is no research on sex differentiation using hormones in crayfish. In the present study, the effects of 17β-estradiol (E2) injections (10−7 mol/crayfish) to females and baths (50 μg 17β-estradiol/L) to pleopodal eggs and stage1, 2, and 3 juveniles on the feminization of freshwater crayfish, Astacus leptodactylus were investigated. Results showed that E2 injection to females, bath to pleopodal eggs and bath to stage 1, 2, and 3 juveniles increased feminization rate significantly (p < 0.05) in comparison to the control in A. leptodactylus. Best feminization rate (male to female, 0.25:1) was observed after hormonal injection to the females combined with application of both for their both pleopodal eggs and stage 1, 2, and 3 juveniles. In conclusion, it is possible to obtain 75% females A. leptodactylus by E2 injection to females and bath to pleopodal eggs and stage 1, 2, and 3 juveniles. However, future studies are needed to investigate the mechanism of E2 in crayfish feminization and the sexual development of juveniles obtained from feminization.

A Review of the Marine Crab Fisheries in the Turkish Seas

Abstract The paper presents a review of the distribution of marine crabs (Brachyura) along the Turkish coast and the amount of economically important marine crabs harvested between 1967 and 2016. Previous records reported that Turkey had 102 brachyuran crab species, only five of them being economically important, but this review identifies two more species, Inachus phalangium and Ashtoret lunaris. The Aegean Sea has more crab species than the Mediterranean, the Black Sea and the Sea of Marmara. The most harvested species are Callinectes sapidus, Maja squinado, Eriphia verrucosa, Carcinus aestuarii and Portunus segnis, respectively. This review shows that there have been fluctuations in the harvest of marine crabs between years, the lowest being 5 tonnes in 2015 and the highest, 2116 tonnes in 1984. The information provided in this review provides a basis for potential profitable development of conservation and management strategies of marine crabs in Turkey.

Importance of Gammarus in aquaculture

In recent years, there have been significant increases in the production and breeding of aquaculture species; for example, the gilt-head (sea) bream and seabass in salt water and trout, carp, and tilapia in fresh water., Amphipods in the genus Gammarus are used as a rich source of protein to feed various pet animals such as aquarium fish, lizards, and turtles, as well as in aquatic ecotoxicology and water quality assessment. Gammarus meal is used as a partial replacement (10–20%) of fish meal. However, the reproduction and rearing of Gammarus in intensive or semi-intensive conditions has not yet been carried out. Gammarus products (live, dried flakes, or powdered) transported to the markets are constituted from wild caught Gammarus. Due to the high price of these products, Gammarus aquaculture potentially has great economic benefits. Therefore, there is a need to focus on the importance of Gammarus in aquaculture. In the present review, the ecology and distribution of Gammarus, its importance in aquatic ecotoxicology and water quality assessment, the chemical analysis of Gammarus and factors affecting chemical composition of it, and the importance of Gammarus in fish nutrition are discussed. In addition, the economic importance and culture methods of Gammarus are also reviewed. This review will be beneficial for scientific investigators and fish-crustacean farmers.

Feminization strategies in crustacean aquaculture

Crustacean aquaculture production has developed rapidly in recent years because there has been an increase in crustacean market demands in different regions of the world. The growth rate of the most cultured crustacean species depends on genders. Therefore, monosex crustacean aquaculture, all male or all female, is more suitable for achieving higher yields, with the ecological benefits of reducing the risk of cannibalism. In addition, feminization is also appropriate for increasing individual number in populations because males are able to copulate with more females. For this reason, sexual manipulations are important in crustacean reproduction units. This review focuses on the sex differentiation mechanism and the use of different strategies for feminization of economically important crustaceans. In this review, feminization strategies are divided into two main methods: direct feminization and indirect feminization (masculinization). Direct feminization includes (1) ablation of androgenic gland (AG), (2) silencing and suppression AG and androgenic gland hormones (AGHs), (3) hormone therapy (i.e., 17β-estradiol), and (4) polyploidy induction. This review also emphasizes how feminization is carried out for crustaceans belonging to the different sex determination systems (ZW or XY) by using indirect method. The intension of controlling sexual differentiation for crustaceans will continue to increase in the next a few years, either for basic research or for its utilization to crustacean aquaculture; hence, this review will be profitable for crustacean farmers and researches.