36 DECEMBER 2024 • WORLD AQUACULTURE • WWW.WAS.ORG a conical tank inside of which a mesh-bottomed container (generally a bucket) is attached. The animals are released inside the container and a constant supply of aerated and clean sea water is maintained. The spawning process is called “nuptial dance,” wherein the male and female go in circular motions around each other by vigorously beating their posterior segments, resulting in a feathery movement. These worms have gamete sacs attached to their body segments and as they spawn, these segments rupture and release the gametes directly into the water (Poltana et al. 2007). Dead animals are removed and constant aeration is provided in the tank. Once fertilization takes place, embryonic development and cleavage starts inside the vitelline membrane after one hour. First and second cleavage will be observed at 1-2 and 3-4 hours, respectively, after spawning. The sixteen-cell stage will be reached within 18 hours. The embryo develops an equatorial ring of cilia at 24 hours, and becomes a mono-trochophore moving inside the egg jelly. At 30 hours the mono-trochophore becomes a trochophore, which grows by elongation of the trunk, and subsequently three pairs of chaetigerous sacs will appear laterally. At 36 hours after spawning, the trochophore hatches, becoming a meta-trochophore and swimming freely. The nectochaete stage with three chaetigerous segments follows, by 48 hours post-spawning. Larvae are fed the same commercial diet as used for adults, but crushed to a fine powder and enriched with 10 percent spirulina powder. The survival rate from fertilized eggs to the nectochaete stage varies from 50 to 60 percent. Nectochaetes stop swimming and settle down into the sand bed, growing up to juveniles and eventually becoming adults within five months (Poltana et al., 2007; Murugesan and Balasubramanian, 2021). The level of sediment is generally 5 - 6 cm in the beginning stages, due to the minuscule size of the larvae. As they advance in growth, the sediment level is increased to 20 - 25 cm as it is the recommended sediment depth for the juveniles to thrive properly. Once they reach an appropriate size, juveniles are fed the same diet used for adult polychaetes. The larval units used in our facilities are FRP tanks fitted with outlets and inlets. Directed matings of specific individuals are also possible under controlled conditions. Oocytes are collected by removing a single parapodium from a mature female and pouring the contents (≈ 1000 eggs) into a 0.2- to 0.5 mm screen container submerged in artificial seawater filtered through a 0.25- to 0.5 mm cartridge filter, at 30-32 ppt. This screen is used to wash oocytes initially. The oocytes are then washed three more times in a 100 mm petri dish and maintained in artificial seawater. “Dry sperm” is extracted using a pipette and diluted 1:1000 with artificial saltwater. When the sperm suspension is checked under a stereomicroscope and shown to be motile, 1 to 3 drops are introduced to the petri dish holding the eggs. Swimming, ciliated trochophores will form in 12 hours at room temperature. These can then be moved to pelagic culture tanks (Murugesan and Balasubramanian 2021). The concentrated larvae are gently placed back into the larval rearing tank, once the water has been run through a 0.2- to 0.5 mm screen, and the screen is cleaned with a sequential bottle of filtered saltwater to release any larvae stuck on it. The larvae are then allowed to develop in the rearing tank until they reach the juvenile stage. Conclusions Results to date on breeding success show the possibility of cultivating potentially SPF polychaetes at Lakshadweep, which could be a significant step forward in both the aquaculture industry and the sustainable management of marine resources and livelihood enhancement for islanders (Figure 5). The unique, relatively unpolluted environment of Lakshadweep makes it an ideal location for such endeavours, minimizing the risks associated with pathogen contamination. Moreover, the development of SPF polychaete culture can provide alternative livelihoods for local communities, especially women, while preserving the region’s biodiversity. By balancing ecological preservation with commercial viability, the cultivation of SPF polychaetes in Lakshadweep holds great promise for the future of Indian aquaculture. Such activities will enhance the country’s compliance to a number of sustainable development goals. FIGURE 5. Cultivation of SPF polychaetes in Lakshadweep holds great promise for the future of Indian aquaculture. FIGURE 4. Polychaete brooder tank. Results to date on breeding success show the possibility of cultivating potentially SPF polychaetes at Lakshadweep, which could be a significant step forward in both the aquaculture industry and the sustainable management of marine resources and livelihood enhancement for islanders.
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