Rockhopper blenny nests on land

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Scientists have described the reproduction of a species of blenny that lays its eggs in a nest on land.

According to a new study which has just been published in the Journal of Zoology, males of the Rockhopper blenny, Andamia tetradactyla, build nests between crevices in rocks in the high intertidal zone, at the upper limit of waves.

The scientists who studied the blennies observed females gathering in large numbers on patches of algae in the wave-splashed zones and saw them approach the nests on both rising and falling tides during daylight hours.

The males and females took part in elaborate courtship displays as the tide went in and out, and this was apparently most vigorous when the waves splashed the nests.

The authors wrote: "Females spawned eggs in a single layer on air-exposed rock surfaces inside nests. Andamia tetradactyla did not mate in the tidal conditions in which nests were either underwater or completely dried up.

"Territorial males stayed all day in the nests to guard eggs, even though nests emerged above water for c. 12 h each day."

By measuring the humidity with a thermohygrometer, the scientists learnt that the humidity in the nests was greater than the air outside.

Although the fish spawned out of water, the authors believe that their courtship is similar to that of other blennies: "A. tetradactyla maintains reproduction out of water, retaining humid habitats on supralittoral reefs, in mating styles that are probably not drastically changed from their ancestral blenniid fishes."

For more information see the paper: Shimizu, N, Y Sakai, H Hashimoto and K Gushima (2006) - Terrestrial reproduction by the air-breathing fish Andamia tetradactyla (Pisces; Blenniidae) on supralittoral reefs. Journal of Zoology 269: 357-364.