Sex reversal and growth performance in juvenile females of the freshwater crayfish Cherax quadricarinatus (Parastacidae): effect of increasing temperature and androgenic gland extract in the diet

Abstract

Monosex male culture of C. quadricarinatus is proposed for increasing yields because males reach a larger size at harvest than females. An experiment was done to evaluate the effects of androgenic gland extract and temperature on sex reversal and somatic growth in early juvenile females. Females were exposed to the following experimental conditions: C: control food and temperature maintained at 26 ± 1°C; HT (high temperature): control food and temperature maintained at 28.5 ± 1°C; VHT (very high temperature): control food and temperature maintained at 31 ± 1°C; AG: food with enriched with androgenic gland (1/10 dose for each juvenile per day) and temperature maintained at (26 ± 1)°C. The juveniles were weighed, sexed, and growth increment (GI) and growth rate (GR) were calculated twice a month. The HT and AG groups differed from the C group in GI and GR indicating a greater somatic growth. At the end of the experiment, the HT and AG groups had similar weight but only the HT group had enhanced oocyte diameter, with some vitellogenic oocytes compared to the C group. In the HT group, there was significant sex reversal, as indicated by development of male and intersex male characteristics in different individuals. Both temperature and AG diet have a high potential for culture of this species because of their enhancement of somatic growth; higher temperature increases the proportion of males, a desirable characteristic of cultured populations.

Effect of attractant stimuli, starvation period and food availability on digestive enzymes in the redclaw crayfish Cherax quadricarinatus (Parastacidae)

“…The temperature was maintained at 27 ± 1°C by Altman water heaters (100 W, precision 1°C), and the photoperiod was 14 h light:10 h dark cycle. Each aquarium was provided with a PVC tube (10 cm diameter, 25 cm long) as a shelter (Jones 1995 ) according to Bugnot &López Greco (2009) andSánchez De Bock &. At stage 3, juveniles became independent (Levi et al 1999) and were separated from 6 mothers, then pooled and maintained under the same conditions mentioned above (based on previous studies; Vazquez et al 2008, Stumpf et al 2010, Tropea et al 2010, Calvo et al 2013) until they reached the desired weight.…”

Sex reversal of juvenile freshwater crayfish (Cherax quadricarinatus) influenced by steroid extract of sea cucumber and 17α-methyltestosterone hormone at different temperatures

“…Juvenile freshwater crayfish were reared for 50 d. During nursery rearing, juveniles were observed under a stereoscopic microscope to determine sex, using the presence or absence of the genital openings at the base of the third pair of walking legs (females), genital papillae at the base of the fifth pair of walking legs (males), or both structures in an individual (intersex) [13].…”

“…Temperature affects the rate of metabolism in the body [12]. Increased temperature can speed up the metabolism process so that the crayfish appetite also increases [13]. This certainly can help the absorption of steroid hormones contained in the feed to enter the body effectively.…”

“…Optimal water temperature will affect various mechanisms in the body, especially during the period of sexual differentiation, which is very sensitive to hormonal stimulation and temperature. Conversely, if the temperature is too low, it will cause gonadal sensitivity in the formation of genitals to be slower [13].…”

Effect of different diets on digestive enzyme activities, in vitro digestibility, and midgut gland structure in juvenile crayfish, Cherax quadricarinatus

“…Females were fed daily ad libitum with Elodea sp. and dry commercial pellets (TetraColor ® Tropical), according to previous studies (Bugnot and L opez Greco 2009;S anchez de Bock and L opez Greco 2010). When juveniles became independent at stage 3 (Levi et al 1999), they were separated from their mothers and were maintained under the same experimental conditions, as previously described until they reached the desired weight.…”