Morphological development of the swimming and feeding apparatus in larval rabbitfish, Siganus guttatus.

ALSO IN: Compilation of JICA Expert Activities at SEAFDEC, Aquaculture Department (1986-1990) and additional (since 1974) by S. Fukumoto, vol.2, Japan International Cooperation Agency (JICA) 1990, pp44-50.The development of body parts for swimming and feeding in Siganus guttatus larvae was studied in samples reared in the laboratory at temperatures of 27.3-30 degree C. From the observations, the larval stage of S. guttatus may be divided into three phases: (1) inactive swimming and feeding by swallowing (to about 4-5 mm TL); (2) the transitional phase (to about 7-8 mm TL); and active swimming and feeding (8 mm TL and beyond). A change in feeding habits may be expected in S. guttatus larvae at sizes 7-8 mm TL as shown by this study

Feeding habits of larval rabbitfish, Siganus guttatus in the laboratory

ALSO IN: Compilation of JICA Expert Activities at SEAFDEC, Aquaculture Department (1986-1990) and additional (since 1974) by S. Fukumoto, vol.2, Japan International Cooperation Agency (JICA) 1990, pp143-148.The feeding habits of Siganus guttatus larvae were determined in laboratory rearing studies at 23.8-30.3 degree C by examination of digestive tract contents of larvae given rotifers and/or brine shrimp. Larvae were initially fed on rotifers at a total length (TL) of 2.6 mm (day 2 from hatching), and on brine shrimp at 4.4 mm TL (day 12). A change in feeding habits, seen as the flexion point in the relationship between larval TL and maximum amount of prey, occurred at about 7.0-9.5 mm TL with rotifers as prey, and at 7.2 mm TL with brine shrimp. Higher preference for brine shrimp over rotifers was seen in larvae 8-9 mm TL and larger. These changes in habit coincided with the full osteological development of the feeding apparatus in larvae at 7-8 mm TL. S. guttatus larvae exhibited a diurnal feeding pattern at day 9 (mean 3.7 mm TL), day 15 (5.8 mm TL) and day 21 (7.9 mm TL)

Morphological aspects of the development of swimming and feeding functions in the milkfish Chanos chanos

Contribution No. 213 of the SEAFDEC Aquaculture Department.Development of swimming and feeding abilities based on morphological development of larval and early juvenileChanos chanos was investigated. In larvae smaller than about 6.5 mm SL, mechanical supports of fins and branchial arches were in a primordial stage of development. Supports and rays of the vertical fins and branchial arches rapidly developed from 6.5 mm SL, and all components appeared by about 10.5 mm SL. Thereafter body depth proportion changed and the supports and rays of the paired fins and gill-rakers developed. These developmental events were nearly or totally completed by about 17 mm SL, and we concluded that the larvae transformed to juveniles at this size. By this time, the mode of swimming of the fish shifted from undulating locomotion to caudal propulsion and that of feeding from swallowing paniculate food to filtering and concentrating substrate food matters using gill-rakers and the epibranchial organ. One of the most characteristic, and well-known, phenomena in the life history ofChanos chanos is the mass occurrence in the surf zone of postlarvae of a limited size range. In view of the scheme of the development of mechanical supports of the body and fins, they may acquire a swimming ability strong enough to move against the current only upon reaching about 10.5 mm SL, and if active shoreward migration of the larvae occurs, it is only during the late period of their journey from the spawning grounds to the shore. The sudden disappearance from the surf zone of larvae larger than 15–16 mm SL is obviously related to a change in food habit