Post‐larval American lobsters(Homarus americanus)living in burrows may be suspension feeding

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Abstract
Laboratory experiments were conducted to study the ability of post‐larval lobsters (Homarus americanus) to feed on planktonic organisms in suspension. Late Stage IV or early Stage V lobsters were suspended above the bottom of jars in glass tubes which mimicked burrows and prevented the lobsters from obtaining settled food particles. Plankton, vitally stained with fluorescent dye, were introduced into the experimental jars, while dyed, filtered seawater was placed into the control jars. Three sizes of live plankton were tested: 500–1000 μm, 250–500 μm, and 125–250 μm and the plankton typically consisted of copepods, invertebrate eggs and larvae, and diatoms. The lobsters were allowed 60–90 min to capture and consume the plankton after drawing them into their tubes by pleopod fanning. The lobsters were then removed from their tubes and examined under an ultraviolet light in darkness for the presence of dye in their stomachs or intestinal tract. Fifty to 100% of the experimental lobsters were found to feed on the plankton. None of the controls were ever scored as containing dye in any part of their digestive tract. These results demonstrate that lobsters are capable of removing swimming plankton from the water column. Removal of smaller particles (100, 70, 40, and 12–20 μm) was tested using fluorescently coloured beads. Over a 4 h period 30 to 35% of the lobsters removed beads of 100 μm; 20 to 55% of the lobsters removed beads of 70 μm; and 0% of the lobsters were able to remove beads of 40 and 12–20 μm size. These results indicate that lobsters are capable of removing particles in the size ranges of many algal cells or aggregations and of many juvenile zooplankters. Both experiments combined suggest that burrowed post‐larval lobsters may suspension feed in addition to their demonstrated ability to feed raptorially on benthic organisms.