Enhanced growth of juvenile Tachypleus tridentatus (Chelicerata: Xiphosura) in the laboratory: a step towards population restocking for conservation of the species

Abstract

Juveniles of artificially bred Tachypleus tridentatus were reared in the laboratory for 15.5 mo. Fast growth (at least 3 times faster than in previous studies) and low mortality were observed, with juveniles reaching the 9th instar stage and having a cumulative mortality of 61.3% at the end of the rearing period. Such enhanced growth can potentially be attributed to high seawater temperature, sufficient living space and constant water flow. Isometric growth of prosomal width and other growth parameters including opisthosoma width, eye distance and prosomal length was found. Two distinct growth phases were detected for the opisthosoma length, with zero growth from the 1st to 2nd instar but isometric growth from the 2nd to 9th instar stage. Growth in telson length was pos- itively allometric from the 1st to 3rd instar and isometric from the 3rd to 9th instar stage. The increase in wet weight and prosomal width was isometric throughout the 9 developmental stages. Based on the allometric growth patterns, the juveniles can reach adult size within 4 yr. The results may serve as a basis for the large-scale culture of this species for the purposes of restocking and restoration of natural populations.