Sea cucumbers belonging to the phylum Echinodermata are important marine invertebrates, generally occur in the sandy substrates and rocky shores near the bottom of sea. This review work has been attempted to make an interlink between biological and socio-economical perspectives of sea cucumber because of the high demand in the present world. The outer body part of sea cucumber (bêche-de-mer) has been recognized for producing secondary metabolites including vitamins and triterpenoid glycoside saponins that have profound ecological and bio-medicinal significance. Sea cucumbers are also used to remove arthritis pain, exert wound healing, and nowadays, are utilized in human health therapeutics and Asian folk medicine. Due to higher pharmaceutical, cosmeceutical and nutraceutical values, sea cucumber has become one of the most essential products, and fetched higher market prices and therefore, provide a significant earning source and employment opportunity to the coastal communities in many countries. The sea cucumber and its product have been considered to be the excellent bioresource in the invertebrate fishery, whose harvestings, transporting, handlings, processing and maintenance are easy, convenient and cost-effective. Historically, bêche-de-mer were harvested from the multi-species capture fishery and stored for long times for selling to the businessmen and traders directly on the site. As like other lucrative and expensive food items viz., fish-maws, shark-fins and abalones, sea cucumbers are taken into the account as the high-valued products in the world seafood markets. Nevertheless, bêche-de-mer product supply in the South-East Asian countries has been decreasing day by day because of unstrained harvesting and overexploitation. On the other hand, the marketing structure in these countries is typically ineffective and the trading networks are multifaceted. Due to the lack of proper information, fishermen are not usually getting proper values and actual prices from the sea cucumber products, whereas other distributors and value-chain members have made complex systems, which have led to high cost of the products. The sea cucumber products will still have higher possibility of trading throughout the world markets, that might eventually contribute to the global economy in a very worthwhile, significant and sustainable manner.

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.

The combined effects of temperature and salinity on percent hatching, normal larval rate at hatching, and survival of fasting larvae after hatching (survival activity index; SAI) of the commercial species of collector sea urchin, Tripneustes gratilla were investigated in a captive laboratory condition. The study was conducted by setting different levels of temperatures (24°C to 36°C) and salinities (38‰ to 23‰). Within the range of temperature from 24 to 36°C and at 32‰ salinity, hatching and normal larval rates, and SAI values were highest at 24 and 27°C. The highest hatching and normal larval rates were found at 35 and 38‰ within the salinity range of 23-38‰; however, SAI value was the highest at 26‰. The results of the experiments in each level of temperature (24, 27 and 30°C) with each salinity (32, 35 and 38‰) indicated interactive effects of temperature and salinity, and within the experimental protocols of 24°C at 38‰ gave an optimal combination for highest hatching and survival of T. gratilla. The findings obtained from the present research would not only be immensely helpful towards the understanding of the suitable temperature-salinity interactions but also facilitate the development of captive breeding, larval raising and mass seed production of this high-valued sea urchin for commercial aquaculture.

The present study investigated the influence of different temperature levels (16, 19, 22, 25, 28, 31 and 34 o C) on embryonic and early larval development of the tropical sea urchin, Tripneustes gratilla (Linnaeus, 1758) in a controlled laboratory condition. The critical lower and higher temperature for embryonic development was found to be 16 and 34 o C, respectively. Embryos reared in these temperatures exhibited 100% abnormality within 48 h post-insemination. The time required to reach embryonic and larval stages was increased with temperature from 28 o C followed by 31, 25, 22 and 19 o C. The developmental time of 2-cell to 4-arm pluteus larvae showed significant (p<0.05) differences. The survival (%) of larvae at the prism, 2-arm and 4-arm stages were observed as dissimilar from 22 to 34 o C, and the highest values (100% or near 100%) were found at 25 and 28 o C. The morphometric measurements from prism to 4-arm pluteus larvae at different temperatures differed significantly (p<0.05). However among the temperatures evaluated, 28 o C was found as the best temperature for better growth and development of larvae at all stages. The findings of the study would help to develop captive breeding and seed production programmes for commercial aquaculture of the species.