جستجوی مقالات مرتبط با کلیدواژه "sea urchin" در نشریات گروه "شیلات"

Gonads of sea urchin attract consumers due to its high nutritional value than any other seafood delicacies. Aquaculturists are also very keen on developing larval culture methods for large-scale cultivation. The present investigation systematically examined the larval rearing, development, survival and growth rate of Salmacis bicolor fed with various microalgal diets under laboratory condition. Fertilization rate was estimated as 95%. The blastula and gastrula stages attained at 8.25 h and 23.10 h post-fertilization. The 4 - armed pluteus larvae were formed with two well - developed post-oral arms at 44.20 h following post-fertilization. The 8 - armed pluteus attained at 9 days post fertilization. The competent larva with complete rudiment growth was developed on 25th days post - fertilization. Monodiet algal feed - Chaetoceros calcitrans and Dunaliella salina resulted medium (50.6 ± 2.7%) and low survival rate (36.8 ± 1.7%) of S. bicolor larvae. However, combination algal feed – Isochrysis galbana and Chaetoceros calcitrans has promoted high survival rate (68.3 ± 2.5%) which was significantly different between the mono and combination diet. From the observations of the study, combination diet could be adopted as an effective feed measure to promote the production of nutritionally valuable roes of S. bicolor.

In this study, we tested the effect of two agar-based biocomposites (differing for the fish meal source), on the Paracentrotus lividus gonad cycle progression and biochemical composition, in an offshore pilot scale trial. The purpose of this study was to identify a feeding regime for P. lividus that would allow adequate gonadal growth without accelerating the gamete maturation, in order to extend the market period. The purpose was pursued through the use of agar as a binding agent in the manufacturing of biocomposites to be used as feed for P. lividus and the realization of special offshore cages. The gonad index, histology, biochemical composition of fatty acids (FA) and free amino acids (FAA) and volatile molecule fingerprint were evaluated. Both the gonad index and the histological analysis showed a slower gametogenesis progression in the gonads of caged sea urchins with respect to the field collected ones, consistent with our previous results obtained testing a similar feed composition in a recirculating system. The amount and the relative proportions of FA and FAA in the gonads of wild and cultured gonads were similar, while the analysis of the volatile substances of the gonads of the sea urchin conducted using the electronic nose, shows that they vary as a result of the different feeding treatments. These results show that P. lividus sea urchins can be housed, under this feeding regime during the recovery phase of the gonads, without acceleration of the maturation of the gametes and thus in conditions to allow the extension of the market period. Moreover, the here tested agar-based biocomposites make it possible to reduce the management costs of the rearing system as they need to be replaced only once a week, and its environmental impact as they guarantee a limited nutrient dispersion in the water.

This study attempted to describe the length and weight frequency, and length-weight relationship in the black sea urchin, Stomopneustes variolaris, in Sri Lanka. The sampling sites Mount-Lavinia (n=43), Beruwala (n=99) and Tangalle (n=55) were selected from South-west coast in Sri Lanka. The shell length and body weight were measured separately for three sampling sites. The mean length and weight of S. variolaris were 5.55±1.04 cm, 101.40±57.76 g; 6.54±0.86 cm, 147.90±50.40 g, and 6.41±1.05 cm, 150.50±59.45 for Mount-Lavinia, Beruwala and Tangalle, respectively. In addition, the length-weight relationship of S. variolaris were W=0.9953*L2.6472, W=0.9651*L2.6536 and W=1.4665*L2.4637 for Mount-Lavinia, Beruwala and Tangalle, respectively.

Diadema setosum (Leske, 1778), is one of the common echinoids widely distributed in the Indo-West Pacific Ocean, where it occurs from the Red Sea, Persian Gulf and the east coast of Africa to Japan, Australia and Malaysia. To investigate the developmental basis of morphological changes in embryos and larvae, we documented the ontogeny of D. setosum in a controlled laboratory condition at the Institute of Bioscience, Universiti Putra Malaysia, during July–September, 2012. Matured gametes were obtained from the adult individuals and the eggs fertilized at limited sperm concentration (10-5 dilution). The obtained embryos were then reared at 24-25oC. First cleavage (2-cell), 4-cell, 8-cell, 16-cell, 32-cell and multi-cell (Morulla) stages were attained at 01.20, 02.14, 02.44, 03.09, 03.32 and 03.54 h after fertilization, respectively. Blastulae with a mean length of 111.47±1.88 µm (mean±SD) hatched 08.45 h after sperm entry. Gastrula formed 16.36 h post-fertilization and the archenteron extended constantly, while the ectodermal red-pigmented cells migrated synchronously to the apical plate. The pluteus larva started to feed unicellular algae (Chaetoceros calcitrans) in 2 d, grew continuously, and finally attained metamorphic competence within 35 d after fertilization. Induction of metamorphosis took approximately 1 h 30 min from attachment on the substratum to the complete resorption of larval tissues and the development of complete juvenile structure with adult spines, extended tubefeet and well-developed pedicellaria, the whole event usually took place within 1 d post-settlement. The newly formed juvenile (473.16 ± 6.96 µm, n=30) with a complete adult structure then grew on coralline algae to 3-month old juvenile, which represents the “sea urchin seed” for stocking in grow-out culture. This study represents the first successful investigation on embryonic, larval and early juvenile development of D. setosum. The findings would greatly be helpful towards the development of breeding and seed production techniques for aquaculture of sea urchins.

This study investigated the effects of increasing mercury (Hg) concentration on early developmental stages of sea urchin, Echinomethra mathaei, as a bioindicator. The toxicity test was carried out after the gamete released induction and fertilization in six concentrations of mercury within the range of 4, 8, 16, 32, 64 and 128 µg/L. Embryos samples were incubated for 30 h in control and test solutions. After incubation, the percentage of developed 4-arm pluteus larvae was recorded in each group and embryonic abnormalities were studied by a microscope. Results of this study indicate that exposure of embryos to increasing mercury concentrations lead to abnormalities such as changes to shape and size of pluteus larval arms and also arrested development in early embryonic stages. Furthermore, embryos were analyzed to determine mercury absorption by cold vapour atomic absorption spectrometry method (AAS). The median effective concentration (EC50) value calculated for mercury was 17/42 µg/L.

Sea Urchin is one of the most useful tools in developmental biology studies because this organism has the simplest kind of developmental stages. We aimed to determine developmental stages and timetable of Echinometra mathaei embryo (the species of Persian Gulf). The spawning of E. mathaei was induced by 0.5M KCl injection (1ml) into the coelomic cavity. After fertilization, embryos were placed in beakers and were incubated at 29◦C and a salinity of 39 ppt until embryos reached the pluteus stage. The developmental stages of embryos and the timing of each stage including cleavage, morulae, blastula, gastrula, prism and pluteus larvae were studied under the microscope. Our results showed that after 30 hours from fertilization time, the embryos developed to pluteus larvae. E. mathaei had the shorter development time in comparison to the other Sea Urchin species. Therefore, it may be appropriate as a model organism in biological researches.