The morphology and life cycle of the gill monogenean (Pseudorhabdosynochus lantauensis) on orange-spotted grouper (Epinephelus coioides) cultured in the Philippines
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The morphology of Pseudorhabdosynochus lantauensis is described. It is the most numerous parasite recovered from the gills of cultured orange-spotted grouper Epinephelus coioides in the Philippines and is smaller compared with similar species reported in Hong Kong, Malaysia and Indonesia. This species is characterized by having an overlapping dorsal bar and short copulatory organ. The life cycle of the gill monogenean is also described. One mature parasite lays at least 10-22 eggs/day. Eggs are oval (0.021-0.120 mm) with a spiral filament attached to one end. Eggs hatch into free-swimming larvae (oncomiracidia) within 2-6 d at 30°C and 30 ppt. The rate of hatching of various eggs is highly variable, that is, some eggs hatch in 2 d while others take 6 d. The oncomiracidium can attach to the grouper host within 8 h. Upon attachment, the oncomiracidium metamorphoses to an adult parasite in 4-7 d. The parasite becomes fully mature and delivers eggs in 7 d. Without a host, the life span of oncomiracidium is only 4-8 h. The life cycle is complete in 13-20 days (eggs to oncomiracidium 2-6 d; oncomiracidium to adult parasite 4-7 d; adult to fully mature and egg delivery parasite 7 d). This is the first report on the morphology and life cycle of P. lantauensis from the Philippines.
CitationErazo-Pagador, G., & Cruz-Lacierda, E. R. (2010). The morphology and life cycle of the gill monogenean (Pseudorhabdosynochus lantauensis) on orange-spotted grouper (Epinephelus coioides) cultured in the Philippines.
PublisherEuropean Association of Fish Pathologists
The authors express their gratitude to Francisco Gernade, Susan Torrento and Fely Torreta for technical assistance, Prof. Kazuya Nagasawa for technical guidance; and Dr. Elena Catap and Ms. Milagros Castaños for helpful criticism and editorial comments. This study was funded by the Government of Japan, Trust Fund under the Regional Fish Disease Project.
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Conference paperK Fukusho - In TU Bagarinao & EEC Flores (Eds.), Towards sustainable aquaculture in Southeast Asia and Japan: Proceedings of the Seminar-Workshop on Aquaculture Development in Southeast Asia, Iloilo City, Philippines, 26-28 July, 1994, 1995 - SEAFDEC Aquaculture DepartmentAquaculture production in Japan in 1993 was 1,351,000 tons, 15.6% of the total fisheries production. About 93.6% came from mariculture and 6.4% from freshwater aquaculture. The per cent contribution of aquaculture to total production has increased in recent years but partly because marine fisheries,especially of sardine and pollack, have decreased. Aquaculture has reached a plateau, and decreased slightly between 1992 and 1993. Diverse marine and freshwater species are cultured in Japan — various fishes, crustaceans, mollusks, seaweeds, sea squirt, sea urchin, and others. Research and development in mariculture focus on finding substitutes for animal protein in feeds, improvement of fish quality, protection of the culture environment, use of offshore floating culture systems, and protection from diseases. Research in freshwater aquaculture has expanded to include recreational fishing, the propagation and preservation of endangered species, and the construction of fish ladders for salmonids and other migratory species.
The sulfide tolerance of milkfish and tilapia in relation to fish kills in farms and natural waters in the Philippines Fish kills of milkfish Chanos chanos and tilapia Oreochromis spp. now occur frequently in brackish, marine, and freshwater farms (ponds, pens, and cages) in the Philippines. Aquafarms with high organic load, limited water exchange and circulation, no aeration, and high stocking and feeding rates can become oxygen-depleted and allow sulfide from the sediments to appear in the water column and poison free-swimming fish. The sulfide tolerance of 2-5 g milkfish and 5-8 g O. mossambicus was determined in 25-liter aquaria with flow-through sea water (100 ml min-1) at 26-30 °C and sulfide stock solutions pumped in at 1ml min-1. Total sulfide concentrations in the aquaria were measured by the methylene blue method and used in the regression against the probits of % survival. Four experiments showed that the two species have similar sulfide tolerance. In sea water of pH 8-8.5, about 163 ± 68 μM or 5.2 ± 2.2 mg l-1 total sulfide (mean ± 2 se) or 10 μM or 313 μg l-1 H2S was lethal to 50% of the fish in 4-8 h, and 61 ± 3 μM total sulfide or 4 μM H2S in 24-96 h (to convert all sulfide concentrations: 1 μM = 32 μg l-1). Earthen pond bottoms had 0-382 μM total dissolved sulfide (mean ± sd - 54 ± 79 μM, n - 76); a tenth of the samples had >200 μM. The water column may have such sulfide levels under hypoxic or anoxic conditions. To simulate some of the conditions during fish kills, 5-12 g milkfish were exposed to an abrupt increase in sulfide, alone or in combination with progressive respiratory hypoxia and decreasing pH. The tests were done in the same flow-through set-up but with sulfide pumped in at 25 ml min-1. The lethal concentration for 50% of the fish was 197 μM total sulfide or 12 μM H2S at 2 h, but 28-53 μM sulfide allowed fish to survive 6-10 h. Milkfish in aquaria with no aeration nor flow-through sea water died of respiratory hypoxia in 5-8 h when oxygen dropped from 6 to 1 mg l-1. Under respiratory hypoxia with 30-115 μM sulfide, the fish died in 2.5-4 h. Tests with low pH were done by pumping a weak sulfuric acid solution at 25 ml min-1 into aquaria with flow-through sea water such that the pH dropped from 8 to 4 in 5 h. Under these conditions, milkfish died in 7-9 h when the pH was 3.5. When 30-93 μM sulfide was pumped in with the acid, the fish died in 2-6 h when the pH was still 4.5-6.3. Thus, sulfide, hypoxia, and low pH are each toxic to milkfish at particular levels and aggravate each other's toxicity. Aquafarms must be well oxygenated to prevent sulfide toxicity and fish kills.
Advanced broodstock diets for the mangrove red snapper and a potential importance of arachidonic acid in eggs and fry AC Emata, HY Ogata, ES Garibay & H Furuita -
Fish Physiology and Biochemistry, 2003 - Springer VerlagMangrove red snapper fed advanced broodstock diets containing squid meal and squid oil exhibited higher hatching rates, cumulative survival and survival activity index than those fed a basal diet or a basal diet supplemented with mixture of antioxidants. On the other hand, fatty acid analyses of ovaries and fry of wild fish and eggs and larvae of broodstock fed raw fish revealed high arachidonic acid (ARA) and docosahexaenoic acid (DHA) levels and relatively lower eicosapentaenoic acid (EPA) levels consequently showing high ARA/EPA and DHA/EPA ratios compared to cold water species. This suggests that ARA may be nutritionally more important for egg and larval development and survival in tropical marine fish and its supplementation in broodstock diets may enhance reproductive performance of mangrove red snapper.