Research Product

During the molt from third- to fourth-stage, larvae of Homarus americanus metamorphose into their adult form and pigmentation. In the course of the fourth stage, their pelagic life changes to a benthic existence. Artificial substrate choice experiments and qualitative illumination experiments show that during the early fourth stage the phototactic response reverses from positive to negative. Together with positive thigmotaxis, this results in a choice of dark crevices. Among natural substrate choices, preferential settlement occurred on macroalgal-covered rocks, followed by rocks on sand, mud, and sand. Moreover, when no choice was given, settling occurred most rapidly on macroalgal-covered rocks (34 h), followed by scattered rocks on sand (38 h), and mud (62 h); no settling occurred on sand even two weeks after the last animal had settled on all other substrates. These animals continued to explore the sand substrate with dives to the bottom. Although mud was not a preferred substrate in choice tests, the animals that chose mud and those that were presented only with mud settled successfully and were immediately efficient in their burrowing behavior, constructing U-shaped tunnels when in the center of the aquarium without using a pebble or rock as a starting point. These laboratory tests confirm field observations that lobsters can successfully exploit a variety of substrates. They show that a substrate can be manipulated to make suitable burrows.