Preferential settlement in concavities (Rugophilic behaviour) by larvae of the brachiopodWaltonia inconspicua(Sowerby, 1846)

Abstract

Juvenile brachiopods attached in valve grooves or on valve ridges were counted on 20 large specimens of the corrugated rhynchonellid brachiopod Notosaria nigricans (Sowerby 1846). There were 606 small juveniles of undetermined species in the grooves and only 5 on ridges. Corresponding numbers for larger juveniles identified as Waltonia inconspicuu (Sowerby 1846) were 51 and 1. The same procedure was used on 20 large specimens of the smooth terebratellid brachiopod Waltonia inconspicua. There were 27 small juveniles of undetermined species in grooves and 1 larger one identified as Waltonia inconspicua. No juveniles were found on ridged or flattish areas of the valves. Both series of adults were collected from populations living in an intertidal rock pool in Lyttelton Harbour, South Island, New Zealand. The greater number of juvenile brachiopods found in grooves, particularly in the Notosaria series, is attributed to rugophilic behaviour by the settling larvae. This phenomenon does not appear to have been recorded previously for brachiopod larvae, but has been reported for the larvae of certain spirorbid tubeworms, barnacles, and polyzoans.