Development and function of the filter-press in spiny lobster, Sagmariasus verreauxi, phyllosoma

Mass propagation of spiny lobster phyllosoma is a critical bottleneck for the development of spiny lobster aquaculture. Eastern spiny lobster Sagmariasus verreauxi has been identified as a good candidate for temperate culture with a relatively short life cycle lasting 6 to 8months and 17 stages. We investigated the development and functionality of the filter-press of S. verreauxi phyllosoma to better understand the size and quantity of dietary particles ingested over the entire larval cycle. Filter-press morphometrics were obtained from live phyllosoma larvae throughout development, and filtration capacity was ascertained using fluorescent microspheres and the rare earth metal markers yttrium oxide and ytterbium oxide. The filter-press of phyllosoma larvae was fully functional from stage 3, fully developed from stage 4, and the numbers (8 to 50), lengths (79 to 384μm), and widths (14.8 to 20.3μm) of food grooves increased with the development stage to accommodate a larger volume of ingested food. In contrast, there was no change in the widths of the lower ampullary setae (1.28±0.16μm) or the widths of the gap between these setae (0.91±0.07μm). Lower ampullary setae were arranged in a single layer perpendicular to the food grooves and restricted the entry of food particles into the digestive gland. From stage 3, the filter-press selectively excluded more than 99% of particles of >1μm from reaching the digestive gland and demonstrated that only particles of ≤1μm are available for digestion. In the absence of a gastric mill, phyllosoma larvae have no obvious structure for internally grinding prey and the present study shows that phyllosoma larvae are well adapted to feed from the body fluids of wild preys over their entire larval cycle. The results have important practical applications for the development of formulated feeds for spiny lobster larvae. ► Hatchery propagation is a critical bottleneck for aquaculture of spiny lobster. ► The filter-press structure and function in Eastern rock lobster larvae was studied. ► The filter-press increases in size and complexity throughout larval development. ► The filter-press excluded 99% of particles of > 1 µm from the digestive gland. ► Phyllosoma are adapted to feed on preys’ body fluids over their entire larval cycle.