Effect of different salinities on trilobite larvae of Malaysian horseshoe crab (Tachypleus gigas; Muller) for their better survival under controlled conditions

Abstract

A Malaysian horseshoe crab, Tachyplues gigas (Millier, 1785) are commercially harvested for production of Tachypleus Amoebocyte Lysate (TAL) and food other than being exported to Thailand. Ho.wever, there is no legislation or harvest regulations have been implemented to protect the horseshoe crab in Malaysia. Therefore, successful cultures of horseshoe crab are highly desirable and will depend on the basic information for their better survival. Laboratory experiments were carried out to study the effect of different salinity on the survival of trilobite larvae and their successful molting into juvenile stage. The trilobite larvae were obtained in February, 2012 from The Horseshoe Crab Aquaculture Farm at Sedili Kecil, Kota Tinggi, Johor. Triplicates of five different salinities (0, 10, 20, 30 and 40 ppt) were chosen for the experiments under laboratory conditions (28± I 0C). 30 ppt treatment was conducted as control. All larvae were fed with Artemia cysts. The number of survival and molting larvae during the 15 days of observations were recorded. Highest percentage of survival was found at 20 and 30 ppt (100±0%) followed by l O and 40 ppt (98±2%). The lowest survival occurred at O ppt (60±30%). Molting frequency of trilobite larvae into juvenile is influenced by salinity. The larvae maintained at 20 and 30 ppt shows a high number of molting, but no molting larvae were observed at O and 40 ppt. Salinity may affected the early larval development of Malaysian horseshoe crab, but its seemed tolerable.