Feeding activity and the morphology of the digestive tract in stage-I phyllosoma larvae of the rock lobster Jasus edwardsii

First-stage phyllosoma larvae of the rock lobster Jasus edwardsii attached to and fed on larvae of the Tasmanian trumpeter fish, Latris lineata, when the two were placed together in an aerated, through-circulating, sea-water aquarium. Scanning electron micrographs of the mouthparts showed adaptations suitable for scraping and cutting soft substrata. Phyllosomas removed from the fish while feeding had pigment particles from the fish integument throughout their digestive tracts. The behaviour of these phyllosomas, swimming in a Petri dish, was recorded with a microscope and video system. The presence of the pigment particles made it possible to see the lumen of the gut diverticulae and parts of them undergoing regular contractions. Transmission electron micrographs of the gut showed that the parts of the gut that contracted in the video records have well developed muscle bands associated with them. The ultrastructure of the digestive tract is relatively uniform throughout and is lined by cells resembling the undifferentiated (E) cells of other scyllarid and palinurid larvae. Extensive folding of the wall, together with a brush border on the digestive cells, results in a large surface area for absorption. There is no grinding or filtering apparatus in the digestive tract. The behaviour of the phyllosoma, structure of the mouthparts, and ultrastructure of the digestive tract, suggest that the first-stage phyllosoma of J. edwardsii is adapted for removing soft tissue from gelatinous organisms and pumping it around the digestive tract.