Hatching, growth and hatchling dietary preference in Hemifusus ternatanus (Gmelin, 1791)

The copulation, spawning and hatching of gastropod Hemifusus ternatanus under laboratory conditions were described. After copulation, the female whelks laid trapezoidal egg capsules on the hard surface of the aquarium at about 40 min per capsule. The number of eggs (280–300 μm in size) in the capsules ranged from 1500 to 3000, positively correlated with the size of capsule. The hatchlings crawled out of the capsules over a 58-day incubation period at 21–23 °C. The hatchlings were 3.00–6.04 mm in total shell length and 4.15–21.4 mg in wet body weight, and could hang upside down the water by their feet. In an artificial culture, cutting the capsules as soon as cleft is found at the apical area may help prevent mortality. Six diets were provided over a ten-week period to compare their effects on post-hatching growth and survival. At the end of the experiment, the hatchlings fed with live clam Meretrix meretrix had the highest growth and survival rates, followed by those fed with frozen oyster Crassostrea rivularis, and was significantly higher than those fed with frozen mackerel Pneumatophorus japonicas, frozen shrimp Penaeus vannamei, eel feed, and microalgae Chlorella pyrenoidsa (P < 0.01). Although mackerels have higher protein and amino acid content than clams and oysters, the growth and survival rates of mackerel-fed hatchlings were significantly lower (P < 0.01), suggesting that other hatchling-preferred substances besides umami amino acids may be present in bivalves. In a subsequent 140-day rearing, clam-fed whelks showed a nearly linear growth (about 12 mm per month), indicating the potential of H. ternatanus for aquaculture.

► The whelk Hemifusus ternatanus is a direct developer.
► In artificial culture, cutting the capsules once cleft is found at the apical area may help prevent mortality.
► Hatchlings of H. ternatanus preferred bivalves to shrimp, mackerel, compound feed and microalgae.
► Owing to its good taste and higher growth rate (12 mm per month), the whelk is a potential species for aquaculture.