Effect of different maturation diets on reproductive performance of the broodstock of purple mangrove crab, Scylla tranquebarica

The present study was aimed at evaluating the reproductive performance of the broodstock of purple mangrove crab (Scylla tranquebarica) fed natural food and formulated diets supplemented with astaxanthin and/or DHA. Formulated diets were supplemented with 500 mg kg-1 of astaxanthin (FA), 10 g kg-1 of DHA (FD) and both astaxanthin and DHA (FA+D). Diet without astaxanthin and DHA (FCon) and natural food (NF) consisted of forage fish (Valamugil sp.), shrimp (Penaeid sp.) and mangrove clam (Polymesoda sp.) to serve as control. Female broodstock of initial body weight 129.07±17.03 g were stocked in HDPE tank and cultured under recirculating water system. Broodstock maturation was monitored until spawning. Reproductive performance of female and condition of the larvae were also evaluated. After 50 weeks, broodstock fed FA+D diet showed better maturation percentage, spawning rate, gonadosomatic index, oocytes diameter, molting, molt death syndrome and survival rate than FCon group (P0.05) to the FA+D group but diet FD resulted in better performance than FA. Broodstock fed FA+D diet had the highest hatching rate, number of larvae produced and significantly higher zoea II survival compared to FCon and NF groups (P<0.05). No significant difference was observed in hatching rate and zoea II survival rate when broodstock were fed FA+D, FA and FD diets. This study indicated that DHA as well as astaxanthin improved the reproductive performance of the mangrove crab, and the use of both DHA and astaxanthin further enhanced the maturation performance

Effects of rotifer and Artemia enrichment in the first feeding and larval morphogenesis of purple mud crab, Scylla tranquebarica larvae

The effects of feeding rotifers and Artemia enriched with different types of enrichment in the first feeding and later stages of Scylla tranquebarica larvae were investigated. Two different experiments were conducted each with five enrichment treatments including live and digestible Nannochloropsis sp. and Tetraselmis sp. or commercial product. In Experiment I, the zoea 1 (Z1) larvae were fed with enriched or unenriched rotifers as their first feed until they moulted into the zoea 2 (Z2) stage, while in Experiment II, the zoea 3 (Z3) larvae were fed with enriched or unenriched Artemia until they metamorphosed into megalopa stage. In Experiment I, Z1 fed enriched rotifers showed higher survival, larval stage index (LSI) and carapace length than those in unenriched treatment. However, the highest survival was recorded in larvae fed Nannochloropsis sp. treatment. In Experiment II, Z3 fed Artemia enriched with digestible Tetraselmis sp. exhibited the highest survival and LSI, lowest chela-carapace length ratio and abnormal moulting frequencies. In comparison to live microalgae, digestible treatment resulted in a smaller chela-carapace length ratio with lower abnormal moulting. In conclusion, enrichments tested in this study can be used to enrich rotifers for the first feeding of Z1, while later stage (Z3 onwards) fed Artemia enriched with digestible Tetraselmis sp. improved survival and decreased the abnormal moulting frequencies of Z5 to megalopa stage

Effect of dietary dha and carotenoid on reproductive performance of purple mangrove crab (scylla tranquebarica) broodstock

In mangrove crab seed production, it is important to provide the broodstock with maturation diet that can improve the reproductive performance. For the purple mangrove crab (Scylla tranquebarica), a dominant mangrove crab in Sabah, there are limited study on its maturation diet. Therefore, the present study was conducted to investigate the suitable maturation diet for the purple mangrove crab. Formulated diets (46% crude protein, 12% crude lipid) were prepared by adding astaxanthin (500 mg kg-1) (FA), DHA (10 g kg-1) (FD), both astaxanthin and DHA (FA+D) and without astaxanthin and DHA (Fcon). Natural food (NF) was comprised of trash fish (Valamugil sp.), shrimp (Penaeid sp.) and mangrove clam (Polymesoda sp.). Immatured female broodstock of initial body weight 129.07 ± 17.03 g and male 125.30 ± 14.12 g were cultured under recirculating water system for 50 weeks with the ratio of 1:5 (male:female). Reproductive performance of the broodstock was routinely monitored. Matured females (n=3) were identified and sacrificed for gonadosomatic index (GSI) estimation and biochemical analysis while others were allowed to spawn. The male broodstock (n=3) also sacrificed to determine the sperm viability. Newly hatched larvae (from one hatching) were measured (n=30), subjected to resistance tests (ammonia, dissolve oxygen, salinity and starvation) and reared until zoea II to determine the survival rate. The results revealed that the broodstock fed FA+D showed significantly higher maturation and spawning rate than broodstock fed Fcon, however, it showed no significant different with broodstock fed NF. Broodstock fed FA+D also showed significant better results than Fcon and NF in term of GSI, ovary colour intensity, oocyte diameter, molting rate, molt death syndrome (MDS) and male sperm viability. Broodstock given FD and FA diets resulted in significantly better results than NF group in term of GSI, oocytes diameter and sperm viability (P0.05). On the other hand, broodstock fed FA and FA+D diets showed significantly greater total carotenoid accumulation in the ovary than other treatments corresponding to the ovary colour intensity (P0.05). Broodstock fed FD and FA+D diets also showed significantly higher DHA accumulation in the ovary and hepatopancreas than those fed Fcon diet (P0.05). Larval from broodstock fed FA+D diet showed higher hatching rate, total number of larvae and significantly higher zoea II survival than Fcon group (P<0.05). Likewise, larval resistance tests showed that the larvae produced by broodstock fed FA+D diet showed significantly higher survival rate than Fcon and NF groups in all of the tests. In conclusion, formulated feed that supplemented with DHA and astaxanthin is a better maturation diet than the natural food for purple mangrove crab. The maturation diet provided also affected the early stage larval quality with best quality observed in larvae produced by the broodstock fed DHA and astaxanthin

Effect of background tank color in combination with sand substrate and shelters on survival and growth of Scylla tranquebarica instar

Effect of tank color in combination with substrate-shelters on the survival and growth of the instar of purple mud crab, Scylla tranquebarica (initial body weight of 28.7 ± 2 mg) was investigated. Ten treatments were tested in triplicate with black (B) and white (W) tanks were set as the control, while other tanks were provided with a combination of sand substrate (S), and/or polyvinyl chloride pipes (P) as horizontal and nets (N) as vertical shelter, referred as B, BS, BSP, BSN, BSPN, W, WS, WSP, WSN and WSPN, respectively. Survival of the instar in black tanks (26.7 to 60.0%) was higher than in white tanks (20.0 to 46.7%) (P = 0.052). Survival in the horizontal shelter treatments (46.7 and 63.3%) exceeded that in the vertical shelter groups (30.0 and 50.0%) (P = 0.068). The final body weight of the instar in black tank (2.4 to 3.8 g) was significantly lower than white tank (2.6 to 4.8 g) (P = 0.02). Specific growth rate was significantly greater in sand substrate treatments (8.4 to 9.1%/day) than in controls (7.9 and 8.0%/day) (P = 0.015). In conclusion, horizontal shelter was better than vertical type, and black tank with substrate and horizontal shelter was more suitable for culture of purple mud crab instar.This work was partially funded by Universiti Malaysia Sabah (UMS) under grant SDK0028-2018