Aspects of the biology of some New Zealand echinoderms : feeding, growth and reproduction in the asteroids, Patiriella regularis (Verrill, 1867) and Coscinasterias calamaria (Gray, 1840).

Abstract

The aims of the present study: Both Patiriella regularis and Coscinasterias calamaria are abundant in the shallow sublittoral of Otago Harbour, where the present study was concentrated, and they frequently occur side by side in the same habitat. Preliminary diving observations showed that the density and size distributions of separate subpopulations of both species vary considerably with the type of habitat in which they are found. Similarly Grace (1967) found that the occurrence and size of Patiriella and Coscinasterias in Whangateau Harbour, Northland, depended on the nature of the substrate, and concluded that "the different feeding habits of the two starfish probably accounts for their different distributions". Very little information, however, was available concerning the feeding behaviour of either species. In the present study the food and feeding behaviour of both species, in three different habitats, were determined by field observations using aqualung diving techniques.

Several previous studies on carnivorous forcipulate asteroids have emphasised the importance of the relationship between energy intake, body size and reproductive strategy. Thus Vevers (1949) has suggested that poorly fed populations of Asterias rubens will survive and show minimum growth and little or no gonad maturity, whereas well fed populations will grow fast and reach breeding condition within one year of metamorphosis. Farmanfarmaian et al (1958) demonstrated an inverse relationship between the size of the gonads and pyloric caeca (food storage organs) in the forcipulates Pisaster ochraceus and P. brevispinus. Mauzey (1966) has shown that this inverse relationship is correlated with seasonal patterns of feeding behaviour, food ingested during the summer being stored in the pyloric caeca during winter months. By contrast, Farmanfarmaian et al (1958) could detect no inverse relation between gonad size and the size of pyloric caeca in the spinulosan Patiria miniata. Pearse (1965) suggested that different populations of the omnivorous phanerozone, Odontaster validus, varied in reproductive activity and pyloric caeca development in relation to local differences in primary production.

The present study was intended primarily as a comparative study of selected parameters of well-being in a spinulosan asterinid and a forcipulate asteriid, which represent fundamentally distinct lines of asteroid evolution. It was of interest to discover whether the relationship between reproductive effort and energy intake is comparable in the two species studied or whether there are fundamental differences between them in this respect. In order to examine the well-being of different sub-populations the relationship between energy intake and reproductive effort was examined in three separate and different habitats. [extract from Introduction]