Abstract
Abalone (Haliotis spp.) are typical nocturnal creatures but Haliotis discus hannai is bold and active in the nighttime whereas H. gigantea tends to be timid and inactive. In this study, we quantified and compared differences in movement, feeding, and digestive physiology between H. discus hannai and H. gigantea as well as the potential molecular mechanisms on the basis of video observations and expression levels of genes related to feeding regulation. The feeding behaviors of both species were characterized by significant circadian rhythms (P < 0.05). However, the distance moved and the cumulative duration of movement were 2.61 and 1.94 times higher, respectively, in H. discus hannai than in H. gigantea over the 24-h cycle. The cumulative duration of feeding by H. discus hannai was only 1.15 times that by H. gigantea, but the feeding time as a percentage of the cumulative duration of movement (FTP) was up to 94.6% for H. gigantea and only 56.0% for H. discus hannai. The peaks for α-amylase activity and NPF expression levels in both species as well as the peak OX2R expression level in H. gigantea occurred during 20:00–00:00 h. By contrast, the peaks for alginate lyase activity and NPYR expression levels in H. discus hannai occurred at 16:00 h, when the FTP was significantly higher for H. discus hannai than for H. gigantea. These initial findings quantify specific behavior parameters and thus provide a reference for the selection of appropriate feeding strategies and the proliferation of abalone via bottom sowing.
Highlights
Pacific abalone (Haliotis discus hannai) is one of the most economically important marine shellfish in China and is widely distributed in the Yellow Sea and along the coastline of the Northwest Pacific
Over 24 h, the summed distance moved by H. discus hannai was 2.61 times the distance moved by H. gigantea
We found that the feeding behaviors of H. discus hannai and H. gigantea exhibited significant circadian rhythms according to video analysis
Summary
Pacific abalone (Haliotis discus hannai) is one of the most economically important marine shellfish in China and is widely distributed in the Yellow Sea and along the coastline of the Northwest Pacific. Digestive Physiology of Abalones industry, Haliotis gigantea, a species distributed along the coastline of Japan and South Korea, was introduced into China in 2003, which reduced the risk level for the national aquaculture industry (Luo et al, 2006). H. discus hannai is a bold and active nocturnal creature that rapidly crawls around after leaving the water before searching for a place to hide (Gao et al, 2020). Quantification of the behavioral characteristics and circadian feeding rhythms of nocturnal abalone is considered crucial for the development of a reasonable feeding strategy
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