MEPS 300:105-115 (2005)  -  doi:10.3354/meps300105

Blind dating—mate finding in planktonic copepods. I. Tracking the pheromone trail of Centropages typicus

Espen Bagøien1,2,*, Thomas Kiørboe1

1Danish Institute for Fisheries Research, Department of Marine Ecology and Aquaculture, Kavalergården 6, 2920 Charlottenlund, Denmark
2Present address: Department of Biology, University of Oslo, PO Box 1066 Blindern, 0316 Oslo, Norway

ABSTRACT: Mate-finding behaviour in the marine copepod Centropages typicus was investigated by 3-dimensional video analysis. Females leave a chemical trail in their wake and a male intercepting a fresh trail initiates a characteristic tracking behaviour in which he increases his speed from ~10 to ~30 mm s–1 and races up the female trail while displaying a tight zigzag motion. Within seconds the male overtakes the female and attempts to catch her. Males faithfully follow even very convoluted trails and successfully track down females after pursuing trails up to 31 s old and 17 cm long. The probability of detecting a trail is inversely related to trail age and length. Males often start tracking female trails in the wrong direction before correcting themselves, and the frequency of directional errors increases with increasing trail age. Complicated or disrupted signal trails may cause males to lose the trail. This induces a distinct signal-scanning behaviour characterised by further enhanced swimming speeds of 50 to 70 mm s–1, and frequent shifts of direction. The male scans a restricted volume around the point where the trail was lost and often regains the trail and resumes normal tracking behaviour. This behaviour may help males follow trails that are broken by turbulence. A simple generic model of pheromone trails that is consistent with the tracking behaviour of males in C. typicus and other species of copepods was used to explore the characteristics of pheromone trails. Model considerations suggest that these pheromones are small molecules, e.g. amino acids, and that the investment in pheromone production, both in terms of elements and metabolic energy, represents only a small fraction of the females’ ingestion and metabolic rate.

KEY WORDS: Mating behaviour · Mate detection · Chemical signals · Encounter rates

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