FAULKES, Z.; University of Texas – Pan American: Do shovel-nosed lobsters shovel with their noses?
Aquatic digging is a poorly understood form of locomotion that typically involves moving through sand. Sand is a granular material with complex physical properties: for example, granular materials can switch between solid-like and liquid-like properties. Because the physics of granular materials are poorly understood, it is difficult to make predictions about aquatic digging from general principles. Descriptions of aquatic digging behaviour, however, might suggest such general principles. Shovel-nosed lobsters (Ibacus peronii) live in sandy habitats, and anecdotes suggest that they dig using their “noses” (antennae) as shovels. Ibacus peronii in aquaria were videotaped digging into fine sand. Contrary to their suggestive name, shovel-nosed lobsters do not dig with their antennae. Instead, they use the legs to drive the abdomen into sand like a wedge. At the start of a digging sequence, digging behaviour consists of abdominal extension immediately followed by abdominal flexion. As digging continues, the behaviour becomes more complex, consisting of abdominal extension, repositioning the legs during extension, abdominal flexion, and pausing before the next abdominal extension. Digging occasionally ends with tailflips, which cause a small avalanche of sand that often covers the animal. Ibacus peronii are slow diggers, often requiring over four minutes to submerge (mean = 276.3 s; n = 9), suggesting that digging by �wedging� is mechanically inefficient. Although I. peronii can dig into a wide range of substrates, animals showed a statistically significant preference for fine sand (~0.3 mm diameter) over shell grit (~5 mm diameter) when presented with a choice between the two (Χ2 = 14.23, df = 1, p < 0.01). Animals did not show a statistically significant preference for fine sand or coarse sand (~1 mm diameter) when presented with a choice between them (Χ2 = 1.48, df = 1, p = 0.22). Research supported by NSERC (Canada).
