Feeding behavior under dark conditions in larvae of sutchi catfish Pangasianodon hypophthalmus

Abstract

Sutchi catfish Pangasianodon hypophthalmus hatch with morphologically immature sensory organs; however, sensory organs develop rapidly with larval growth. Two-day-old larvae commenced ingesting Artemia nauplii. The larvae displayed many taste buds on the barbels, the head surface, and in the buccal cavity. Other sense organs were also well developed at this stage. Feeding experiments revealed that 2-day-old larvae ingested Artemia under both light and dark conditions, moreover, the larvae could ingest frozen dead Artemia. The ingestion rates for 4-and 7-day-old larvae were significantly higher under dark conditions than under light conditions. The rates using frozen dead Artemia were mostly higher than the rates using live Artemia. Therefore, feeding behavior under dark conditions is most likely not mediated by visual or mechanical senses, but rather by chemosensory senses, such as taste buds. Larval fish are vulnerable to predators; thus, if they can search for and eat food at night, they can avoid diurnal predators. The behavior observed here appears to represent their survival strategy. Moreover, these results suggest a new possibility that sutchi catfish larvae can be reared under dark or dim light conditions in order to improve survival and growth rates as in the case of African catfish Clarias gariepinus.

Development of sensory organs and changes of behavior in larvae of the sutchi catfish, Pangasianodon hypophthalmus

“…In sutchi catfish, the larvae had many taste buds at the commencement of feeding behavior. Seed production of sutchi catfish is required to reduce cannibalism, thus there is a possibility that dark conditions could be used to reduce cannibalism [24]. of Education of Malaysia and the e-Science Fund (05-01-10-SF0054) of the Ministry of Science, Technology, and Innovation of Malaysia.…”

“…However, the details of the development of sensory organs in sutchi catfish larvae remain largely unknown. Mukai et al [24] tried to reconstruct the early life history of sutchi catfish using limited morphological data, but the interpretation in that study is limited. Detailed analysis of sutchi catfish sensory organ morphogenesis will contribute to better understanding of the early life cycle in the wild and to the development of more efficient larval rearing techniques in hatcheries [22].…”

Remarkably high survival rates under dim light conditions in sutchi catfish Pangasianodon hypophthalmus larvae

“…Larval rearing of sutchi catfish has been studied previously [2,3], but the role of sensory organs in feeding behavior has not been explored, except in a preliminary report by Mukai et al [15]. In this study, sutchi catfish were found to have numerous taste buds on the surface of their skin.…”

“…The larvae were left for 20 min to recover from the stress of handling. Following the recovery period, 30 Artemia (0.1 individual/ml, the same density as in the previous study of Mukai et al [15]) were placed in each beaker, and the larvae were left in the beakers to feed for 30 min. Larvae were subsequently anesthetized with Transmore (Nika Trading Co.) to stop ingestion, and the remaining Artemia were counted in order to determine the number consumed by each larva (n = 30).…”

“…In this study, sutchi catfish were found to have numerous taste buds on the surface of their skin. Mukai et al [15] demonstrated that sutchi catfish larvae could ingest live and dead Artemia under dark conditions, and therefore predicted that feeding behavior is mediated by chemosensing.…”