Salinity effects on the development of embryos and larvae of a high-valued sea urchin, Tripneustes gratilla (Linnaeus, 1758)

Abstract

Aim: Methodology:Results: Interpretation:To investigate the standard salinity levels on the embryonic and larval development that will be helpful for the optimum growth and larval development in the seed production of for aquaculture and conservation.Gametes were collected by injecting 0.5 M KCl into coelomic cavity of the adult sea urchin, and insemination was done using 10 'dry' sperm dilution from where around 500 fertilized eggs were transferred into eight transparent plastic tubes containing 50 ml artificial seawater each with different salinities (19‰, 22‰, 25‰ 28‰, 31‰, 34‰, 37‰ and 40‰). To set up this experiment, 31‰ salinity was considered as a control treatment containing normal sea water. Hatching rate with required time at each salinity level were studied. Each treatment of this experiment was conducted with three replications at 26.0 ± 1.0°C. All the developmental stages of embryos and larvae were observed at time intervals after insemination until attaining the metamorphic competent stage, and the duration of different development stages was also estimated.Fertilization rate was highest at 28‰, followed by those obtained at 28‰, 34‰, 25‰, 37‰, 22‰, and 40‰, while the lowest rate was achieved at 19‰ salinity level, decreased with increasing and decreasing salinities (p < 0.05). The development times of 16-cell and morula stages were significantly different at 31‰ and 28‰ salinity than those at 34‰ and 37‰ salinity, whereas, in blastula, there was no significant difference (p > 0.05) among 31‰, 28‰ and 34‰. The developmental times in the early prism, 2-arm and 4-arm pluteus stages showed significant differences at the salinity levels of 31‰ and 37‰. There were no significant differences (p > 0.05) recognized on the length and width of prism larva in these salinity levels at all. However, the differences were found to be significant (p < 0.05) in all the morphological characteristics of the 2-and 4-armed pluteus larvae of .To date, this is the first effort to study the influence of salinity on embryonic and larval morphometric development, and survival and growth in tropical sea urchin, in Malaysia. The results obtained from this study would be helpful towards the development of induced breeding, larval rearing and seed production of this high-valued sea urchins for commercial aquaculture and biodiversity conservation.

Influence of Salinity on Copper Toxicity in Paracentrotus lividus and Arbacia lixula Embryos

“…Sarifudin et al (2014; [52,53] found that Diadema setosum and Salmacis sphaeroides successfully grow and develop within the salinity range from 28 to 37‰ and from 25 to 35‰, respectively. A similar optimal range of salinity (28 to 34‰) was observed in Tripneustes gratilla by Shamim Parvez et al (2018) [54], whereas Greenwood and Bennet (1981) [55], studying the effect of 45 temperature-salinity combinations on the fertilization success of the gametes of the sea urchin Parechinus angulosus, observed that temperature had the greatest effect on sperm, whereas low salinities relevantly affected the ova, but had little apparent effect on sperm. Even in Heliocidaris crassispina, low salinity and high temperature had interactive effects in reducing larval survivorship [16], whereas Metaxas (1998) [56] reported for Echinometra lucunter short-term (24 h) and long-term (over the entire developmental period) effects of salinity on larval survival and rate of development.…”

Combined Effects of Temperature and Salinity on Hatching and Larval Survival of Commercially Important Tropical Sea urchin, Tripneustes gratilla (Linnaeus, 1758)

“…A decrease in salinity depressed the fertilization ability of the collector sea urchin, especially in combination with the lowest (24°C) and the highest (36°C) temperatures, while a salinity of 23‰ inhibited it. However, fertilization was still possible in this minimal salinity (i.e., 23‰) that matched with the lower limit of resistance of adult individuals of the collector sea urchin [40,41]. A similar phenomenon was also recorded in other echinoderms, such as cucumaria sea cucumber (Eupentacta fraudatrix), and sea stars (Asterias amurensis and Asterina pecinifera), although fertilization in these species was still observed at the minimum salinity levels (20‰ and 18‰, respectively), which were lower than in T. gratilla [42,43,44,45].…”

Cryopreservation of the collector urchin embryo,Tripneustes gratilla

“…Large-scale T. gratilla fisheries, responsible for catching hundreds of tons of urchins, have been reported in the Philippines, Fiji and Japan [3]. Urchin gonads, known as roe, are a luxury delicacy that can command astronomical prices, over US$1000/kg, making them one of the most expensive seafood products in the world [11,58]. With the ever-increasing demand for roe and the general decline in sea urchin fisheries, an opportunity for aquaculture and stock enhancement is bourgeoning [40,65].…”