Emilia T. Quinitio

Midgut gland as monitor organ for the nutritional value of diets in Penaeus monodon (Decapoda)

Midgut gland cells of Penaeus monodon postlarvae were investigated by electron microscopy after starvation and refeeding with different diets. Well nourished postlarvae could be starved for 5 days without irreversible detriment. They recovered easily on a good diet. Only R cells were affected by a short starvation period. After 13 days of food deprivation the structures of all cell types were disintegrated. The postlarvae were able to starve for a maximum of 15 days. The most diversified ultrastructure was obtained by refeeding with cod liver oil and 2s (mixed diet). Casein was not well utilized. Sucrose was the poorest diet. The midgut gland of Penaeus monodon seems to be lipid oriented. Only fat was used as storage material; glycogen was lacking. Different ultrastructures were induced in R cells by a given diet after longer starvation periods. The reestablishment of their ultrastructure by means of a definite diet seems to be impossible after a certain period of starvation (point of no return). R cells are very sensitive to different diets. B cells show slight reactions, while F and E cells remain relatively unchanged. This indicates that R cells could be used to monitor the nutritional value of prawn diets in aquaculture.

Isolation and characterization of vitellin from the ovary of Penaeus monodon

Summary Female-specific protein (FSP, vitellogenin) in Penaeus monodon hemolymph and its related ovarian protein (vitellin, lipovitellin) were identified and characterized using electrophoretical and immunological procedures. The purification of vitellin from mature ovaries was carried out using hydroxylapatite and Sepharose 6B columns. Results indicated that there are two proteins specifically existing in the hemolymph of the mature female which are immunologically identical to ovarian protein. These are absent in the male. The isolated vitellin has a molecular weight of approximately 540 kDa and is composed of 4 major (polypeptide) subunits, 74, 83, 104 and 168 kDa and 1 minor (polypeptide) subunit, 90 kDa. The purified protein stained positively with periodic acid-Schiff and Sudan black B and thus is a glycolipoprotein. Results of double immunodiffusion demonstrate the cross-reactivity of P. monodon vitellin antiserum with the ovarian extract from mature females of Penaeus indicus, Penaeus merguiensis ...

Runt-Deformity Syndrome in cultured giant tiger prawn Penaeus monodon.

Abstract A total of 24 morphological abnormalities associated with the Runt-Deformity Syndrome (RDS) is reported for the first time in 17- to 18-mo old F3 generation Penaeus monodon (>40 mm CL) belonging to three breeding families. Although diagnosed as positive for the infectious hypodermal and hematopoietic necrosis virus (IHHNV), the shrimp appeared normal at 9 to 10 mo when they were procured from a commercial facility in Antique, central Philippines, in September 1996. The abnormalities affected either specific shrimp organs and appendages (e.g., rostrum, antennae, uropods) or the whole body (e.g., shell color and hardness). A two-way analysis of variance was used to evaluate differences in the morphometric characters rostral length (RL), carapace length (CL), abdominal length (AL), body length (BL), total length (TL), carapace width (CW), 1st abdominal segment width (AS1W), and body weight (BW) and the morphometric ratios RL:CL, CL:AL, and CW:AS1W by sex and stock (3 families and wild controls). Female P. monodon had significantly larger CL, AL, BL, TL, CW, and BW than males, regardless of stock. Wild females had longer BL and TL than cultured ones, whereas wild male shrimp had shorter CL, CW, and BW than cultured male P. monodon. Cultured shrimp had significantly higher CL:AL and CW:AS1W ratios and lower RL:CL ratio compared to wild P. monodon. The shorter and narrower abdomen relative to the carapace gave the shrimp a “runted” or dwarf appearance characteristic of RDS earlier described in Litopenaeus vannamei with IHHNV. Confirmed by parallel studies, IHHNV infection of the cultured P. monodon may account for their cuticular deformities, slower growth, and smaller sizes. The appearance of deformities in older (and bigger) P. monodon suggests that RDS expression is dependent on age and size. Examination for external abnormalities and evaluation of the three morphometric ratios may complement existing screening protocols for diseases and growth rates in shrimp breeding programs. Cultured giant tiger prawn also had lower sperm count, greater proportion of dead and abnormal sperm, and lower incidence of mating (absence of sperm in thelyca) compared to wild P. monodon.

Changes in the steroid hormone and vitellogenin levels during the gametogenic cycle of the giant tiger shrimp, Penaeus monodon

Abstract The levels of estradiol-17β, and progesterone in the hemolymph, ovaries and hepatopancreas, in relation to the vitellogenin levels of captive female Penaeus monodon, were determined during the gametogenic cycle. Estradiol in the hemolymph was detected in fully mature shrimps (Stage 5) only. The ovarian estradiol levels were quite variable but showed no significant differences in the mature (Stages 4 and 5) and spent stage (Stage 6). In the hepatopancreas, a peak in estradiol level was noted in mature shrimps (Stage 5). The progesterone levels in the hemolymph were high in shrimps with mature ovaries (Stages 4 and 5) while those with immature ovaries (Stages 2, 3 and spent) were low or undetectable. The progesterone levels in both ovaries and hepatopancreas were significantly high in mature shrimps. The vitellogenin levels increased simultaneously with ovarian development and reached maximum levels during the final stage of vitellogenesis. A decrease in levels was observed after egg release. The correlation between the levels of progesterone and vitellogenin may indicate a positive effect of this steroid on vitellogenin production

The effects of diets on reproductive performance of eyestalk ablated and intact mud crab Scylla serrata

Abstract The reproductive performance of female mud crabs was evaluated as affected by various diets. Dietary treatments were as follows: D 1 — natural diet (mussel meat, squid, trash fish); D 2 — combination of natural and formulated diets; D 3 — formulated diet. Pond-sourced broodstock, with initial body weight of 300–400 g, were tagged in their carapace then stocked in three units of 10 m 3 broodstock tanks at eight females per tank. Half of the females were ablated and the other half were intact. Spawnings were monitored and berried females were transferred to individual 500-l tanks for incubation of eggs. Four experimental runs were conducted. Broodstock response in terms of number of spawnings, spawnings with hatching, fecundity, egg fertilization rate, total zoea produced and broodstock survival was enhanced in females fed the mixed diet (D 2 ) compared to those fed the natural diet (D 1 ) or the formulated diet (D 3 ). Larval quality measured as larval stage index followed the same trend. Results further showed that intact females fed diets D 1 and D 2 gave higher numerical values in reproductive performance and zoea growth index than ablated females while ablated females fed diet D 3 performed better than their intact counterparts. This may be attributed to presence of essential nutrients and vitamins A, C, E in the formulated diet. Latent period from gonadal maturation to first spawning was shortened by eyestalk ablation. Use of a combined diet would ensure the production of good quality eggs and large numbers of zoea with the best chance of completing the larval stages and thus, would serve as an appropriate starting point in establishing a viable mud crab aquaculture.

Ovarian development in relation to changes in the external genitalia in captive Penaeus monodon

Abstract Hatchery-reared Penaeus monodon postlarvae were cultured in ponds until they attained adult size. Thereafter, the shrimps were transferred to concrete broodstock tanks for maturation. During the culture period, the morphological changes of the ovary in relation to the development of the external genitalia and other quantitative parameters were examined. Based on histology, primordial germ cell and chromatin nucleolus in the early stages of ovarian development were reported in addition to the stages that have been described earlier on adult specimens, thus completing the description of ovarian development on P. monodon . Females with ovaries at the perinucleolus stage can be impregnated as long as the thelycum is structurally developed to receive the spermatophores. Females with cortical rod stage ovaries either spawned or resorbed their eggs before molting, indicating that the molting cycle overrides reproductive activity in first-maturing females.

Evaluation of hatchery-based enhancement of the mud crab, Scylla spp., fisheries in mangroves: comparison of species and release strategies

Ranching, stock enhancement and restocking are management approaches involving the release of wild or hatchery-bred organisms to enhance, conserve or restore fisheries. The present study, conducted from April 2002 to November 2005, evaluated the effectiveness of releasing wild and hatchery-reared (HR) mud crabs in the mangroves of Ibajay, Aklan, Philippines where preliminary studies demonstrated declining fishery yields, abundance and size of crabs. Comparison of survival and growth of wild-released and HR Scylla olivacea and HR Scylla serrata demonstrated the effect of nursery conditioning, size-at-release and species differences. Overall yield and catch per unit effort (CPUE) increased by 46% after stock enhancement trials. Recapture rates of released crabs were highest in wild-released S. olivacea and in crabs measuring 65.0–69.9 mm carapace width (CW) and lowest in non-conditioned HR S. serrata. Growth rates were highest for conditioned HR S. olivacea and lowest for conditioned HR S. serrata (11.7 and 3.7 mm month–1 respectively). Fishing mortality was highest for S. olivacea, whereas natural mortality was greater for S. serrata. Conditioning hatchery-bred animals before release is also important in obtaining higher survival. S. olivacea was the more appropriate of the two species for release in mangrove habitats inundated with low-salinity water. However, there is a need for site-specific studies to evaluate the effectiveness of releases.

Transport of Scylla serrata megalopae at various densities and durations

Abstract The optimal conditions for transport of Scylla serrata megalopae were determined. Loading densities of 50, 100 and 150 ind l −1 of hatchery-reared megalopae were studied over a 6-h simulated transport, including shaking. Survival immediately after transport was significantly higher at 50 ind l −1 (99.3±1.6%) (mean± x %) than at 100 (93.0±5.0) and 150 ind l −1 (94.0±3.8%). The same trend was noted 15 h after transport. Another experiment compared survival of megalopae packed at 50 and 100 ind l −1 with simulated transport of various durations (3, 6, and 9 h) at mobile and stationary conditions. Regardless of the duration and condition of transport, survival was again significantly higher at 50 ind l −1 (86.7±2.4%) compared to 100 ind l −1 (79.7±2.1%). Megalopae that were shaken or remained unshaken for 3 or 6 h had similar survival through transport as those shaken for 9 h. Megalopae that remained unshaken for 9 h gave the lowest survival among treatment groups (38.7±0.2%). Due to cannibalistic behavior, stationary transport conditions may have provided the megalopae with a chance to grasp each other. In a third experiment, a batch of megalopae was packed at water temperature levels of 20, 24, and 28°C (ambient) at 50 and 100 ind l −1 for 6 h simulated transport, including shaking. Density and temperature separately influenced survival. Survival was lower at 28°C than 24°C. Although megalopae were less active at 20°C, survival was similar to that at 24°C and 28°C. These results provide useful information for megalopae transport from hatchery to ponds.

Stock Enhancement of Threatened Species in Southeast Asia

Natural populations of global inshore fisheries are coming under heavy pressure, primarily due to overexploitation and habitat degradation. Stock enhancement of hatchery-reared seeds is perceived as an alternative strategy to enhance the regeneration process. The Aquaculture Department of the Southeast Asian Fisheries Development Center in the Philippines has been implementing activities related to stock enhancement of donkeys ear abalone (Haliotis asinina), mud crabs (Scylla spp.), giant clam (Tridacna gigas), and seahorses (Hippocampus spp.). Seed production techniques for abalone including a diet tagging method were established, and juvenile abalone were released and monitored in a marine protected area. Mud crabs conditioned before release had higher recapture rates compared to the non-conditioned crabs, which can be translated to higher survivorship. Giant clams stocked at 8–10 cm shell length have high survival 4 mo after stocking (90%), with initial mortalities occurring within the first few days due to transportation stress. Seed production trials for seahorse have begun.