A comprehensive evaluation of utilization potential of semiterrestrial isopods, Ligia exotica in China: a new aquatic feed?

Abstract Background: The semiterrestrial isopod, Ligia exotica represents one of the oldest documented species introductions of marine organisms and is known as an intermediate form between marine and strictly terrestrial isopods. In order to explore the practical value for food & feed of Ligia, this study focused on growth rate under laboratory rearing conditions and detailed analysis of the overall nutrient content of the species in comparison to two other aquatic food media (krill and fish meal). Results: Evaluation of the growth rate of juveniles suggests it is a relatively fast-growing species of the Ligiidae family. The essential amino acids content Ligia meal is the lowest but the proportion of flavor amino acids was higher. In particular, the content of taurine was much higher. Amino acid score and chemical score show that the most restricted amino acids of isopod meal are methionine and cysteine. The extremely unbalanced amino acid composition may affect the absorption and utilization by consumers. In terms of fatty acids, the total polyunsaturated fatty acids in isopod is very low. A total of 12 vitamins were examined. The VK1, VE, VB2, VB3, VB5 content of isopod meal were significantly higher than those of krill meal and fish meal. Similarly, most of the 11 mineral elements are the highest in isopod meal. Conclusions: Ligia offers potential as an alternative natural food source especially in aquaculture given the growth rate under culture and the overall nutrient content. But Ligia collected in most of the field would be deemed unfit for human consumption because of the relatively low nutritional value and heavy metal content exceeding the provided standard. Ligia isopods offer some potential to become a crustacean model animal for commercial aquaculture crustaceans, further study is warranted to elucidate its biological characteristics.