Absorption of dissolved and dispersed nutrients from sea-water by Panulirus japonicus phyllosoma larvae

This study examined the capacity of Japanese spiny lobster Panulirus japoni cus phyllosoma larvae to absorb nutrients directly from the surrounding wat er. For this purpose, 48-, 81-, 124-, 160-, and 264-day-old intermoult larv ae were starved for 48 h, held for 30 min to 4 h in 0.05 g L-1 solutions or dispersions of cholesterol, peanut oil, saccharose and horseradish peroxid ase in seawater, and subsequently examined by histological and ultrastructu ral methods. Lipids, carbohydrate, and protein were detected in either the lumen of the midgut gland tubules, the midgut gland cells, the haemolymph o r in the cells of the epidermis of all larvae examined after each experimen tal period, with general improvement of the cell and tissue characteristics over unfed controls. The lipids were also found in the cuticle. Thus, the results provide evidence of nutrient absorption via the digestive tract, an d possibly also via the integument. Structural adaptations that may be invo lved in the process of absorption were tentatively identified. Our observat ions suggest the possibility that particulate organic matter (POM) and diss olved organic matter (DOM) can be utilized by the P. japonicus phyllosoma l arvae, perhaps as supplementary sources of nutrients to macroscopic diets.