Location, location, location: finding a suitable home among the noise

Abstract

While sound is a useful cue for guiding the onshore orientation of larvae because it travels long distances underwater, it also has the potential to convey valuable information about the quality and type of the habitat at the source. Here, we provide, to our knowledge, the first evidence that settlement-stage coastal crab species can interpret and show a strong settlement and metamorphosis response to habitat-related differences in natural underwater sound. Laboratory- and field-based experiments demonstrated that time to metamorphosis in the settlement-stage larvae of common coastal crab species varied in response to different underwater sound signatures produced by different habitat types. The megalopae of five species of both temperate and tropical crabs showed a significant decrease in time to metamorphosis, when exposed to sound from their optimal settlement habitat type compared with other habitat types. These results indicate that sounds emanating from specific underwater habitats may play a major role in determining spatial patterns of recruitment in coastal crab species.

Figure 1.

Percentage of total number of megalopae that metamorphosed over time (hour) in laboratory-based experiments: (a) Hemigrapsus sexdentatus; (b) Cyclograpsus lavauxi; (c) Cymo andreossyi; (d) Schizophrys aspera and (e) Grapsus tenuicrustatus. Key for (a,b): circles with solid line, North Reef; circles with dotted line, Mahurangi Harbour; inverted triangles with dashed line, Pakiri Beach; triangles with dot dashed line, silent. Key for (c,d,e): circles with solid line, Coconut Reef; circles with dotted line, Horseshoe Reef; inverted triangles with dashed line, Lagoon; triangles with dot dashed line, silent.

Figure 2.

Percentage of total number of megalopae metamorphosed over time (h) in the field-based experiments: (a) H. sexdentatus; (b) Cyclograpsus lavauxi; (c) Cymo andreossyi; (d) S. aspera and (e) G. tenuicrustatus. Key for (a,b): circles with solid line, Waterfall Reef; circles with dotted line, Whangateau Harbour; inverted triangle with dashed line, Pakiri Beach. Key for (c,d,e): circles with solid line, Horseshoe Reef; circles with dotted line, Loomis Beach Lagoon.