The effects of manipulating water temperature, photoperiod, and eyestalk ablation on gonad maturation of the swimming crab, Portunus trituberculatus

Abstract

An experiment to induce maturation and spawning of Portunus trituberculatus by manipulating seawater temperature, photoperiod, and eyestalk ablation, and to study the effect these factors have on the variation of nucleic acid content in gonadal tissue, was conducted. Non-incubating adult females were divided among three temperature treatments (natural, 10 • C, and 20 • C) and two photoperiod treatments (15 h and 9 h daylight periods per day, respectively). Within each temperature-photoperiod combination, subjects were further divided into each of two groups, i.e., unilaterally eyestalk ablated and unablated. The gonadosomatic index, spawning rate, and nucleic acid variation were examined for each treatment at 3-week intervals. Holding ablated females at 20 • C and providing 15 h of light photoperiod had the most profound effect on the induction of ovarian maturation and spawning. Gonad maturation also occurred in the unablated, 20 • C, 15 h light group, although to a lower extent. Gonad maturation did not take place for groups exposed to lower temperatures, despite either ablation or photoperiod treatments.RNA to DNA ratios were strongly correlated to the state of gonad maturation, with the highest values obtained for the ablated groups held at temperatures under 20 • C for the 15 h light photoperiod. Under these conditions, increasing DNA concentration, reflecting gonad differentiation (small cell size and a large number of cells per unit of tissue), began three weeks earlier than for the other treatments. These results suggest that P. trituberculatus requires not only a raised temperature but also another stimulus, such as eyestalk ablation or a long photoperiod, to induce off-season maturation and spawning.

Comparative transcriptome reveals the potential modulation mechanisms of estradiol affecting ovarian development of female Portunus trituberculatus

“…The swimming crab, Portunus trituberculatus , is an important marine-culture crab widely distributed in the coastal water area of East Asia, including Korea, Japan, Philippines and China [23, 24]. Previous studies in our group have shown that estradiol widely distributed in various endocrine organs of P .…”

Effects of short‐term temperature changes on the physiology, biochemistry and feeding behaviour of the juvenile yellow seahorse— Hippopotamus kuda Bleeker

“…In recent years, with the wild seahorse resources had been slumped and the drastic increase in market demand for seahorse, the seahorse breeding industry is growth and booming. However, there are still many problems restricting the production efficiency in the current breeding industry, most of which are caused by environmental stresses within the aquaculture system (Jang et al, 2010; Li & Xiang, 1999; Nicieza & Metcalfe, 1997; Wang et al, 2008). Due to high density in the artificial system, the cultured organisms were in different water layers and positions, in which the environmental factors (such as light, temperature, salinity) were different.…”