Abstract
While juvenile cannibalism plays an important role in the evolution of organisms in natural populations, it is a serious problem in aquaculture. A number of genetic and environmental factors result in different rates of cannibalism. Whether there is kin recognition in juvenile cannibalism in fish is poorly understood. We studied cannibalism and kinship recognition in juveniles of Asian seabass using molecular parentage analysis with polymorphic microsatellites. In the three mass crosses, under an ordinary feeding scheme without size grading, the rate of juvenile loss due to cannibalism was 1.08% per day. In the group without feeding for 24 h, 2.30% ± 0.43% of offspring per day were lost within 24 h due to cannibalism. We detected that juveniles avoided cannibalizing their siblings when they were not hungry, whereas cannibalism among siblings increased when they were hungry. These data suggest that there is kin discrimination in fish cannibalism. Raising genetically closely related offspring in the same tanks and appropriate levels of feeding may reduce the rate of cannibalism. We hypothesized that the chemical cues for kin discrimination might be secreted by fish skins. To test this hypothesis, we analyzed gene expression profiles in the skins of juveniles under slightly and very hungry conditions using RNA sequencing and bioinformatics analysis. Genes differently expressed under slightly and very hungry conditions were identified. Among them, genes from the trypsin family were significantly down-regulated under starved conditions, suggesting that they may play a role in kin discrimination.
Highlights
Asian seabass (Lates calcarifer) is an important marine food fish species and has been cultured for over 30 years in Southeast Asia (Jerry, 2013; Yue, Li, Chao, Chou, & Orban, 2002) and recently in Australia (Domingos, Smith-Keune, & Jerry, 2014; Domingos et al, 2013; Qin, Mittiga, & Ottolenghi, 2004)
Kin recognition has been studied in fishes (Pfennig, 1997; Smith & Reay, 1991) and there is evidence that kin selection plays a role in egg-cannibalism in fish (DeWoody, Fletcher, Wilkins, & Avise, 2001), whether kin recognition plays a role in fish cannibalism remains largely unknown
We found that juveniles avoided cannibalizing their siblings when they were not hungry, whereas cannibalism among siblings increased when they were hungry, suggesting that there is kin discrimination in fish cannibalism
Summary
Asian seabass (Lates calcarifer) is an important marine food fish species and has been cultured for over 30 years in Southeast Asia (Jerry, 2013; Yue, Li, Chao, Chou, & Orban, 2002) and recently in Australia (Domingos, Smith-Keune, & Jerry, 2014; Domingos et al, 2013; Qin, Mittiga, & Ottolenghi, 2004). Genetic factors that cause cannibalism range from inherent differences in growth rates to a genetic predisposition for cannibalistic behavior (Baras et al, 2000; Hecht & Pienaar, 1993). A number of methods have been suggested to reduce the rate of cannibalism in hatcheries These include supplying shelter (Moksnes et al, 1998), reducing light density (Qin et al, 2004), decreasing culture density (Sukumaran et al, 2011), feeding enough (Kailasam et al, 2011), and size grading (Loughnan et al, 2013). Further studies on environmental and genetic factors influencing the rate of cannibalism may bring new methods and ideas in mitigating cannibalism. Kin recognition has been studied in fishes (Pfennig, 1997; Smith & Reay, 1991) and there is evidence that kin selection plays a role in egg-cannibalism in fish (DeWoody, Fletcher, Wilkins, & Avise, 2001), whether kin recognition plays a role in fish cannibalism remains largely unknown
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