Unique tagging of small echinoderms: a case study using the cushion star <i>Parvulastra exigua</i>

Abstract

Summary Tagging animals is essential to evaluate animal population dynamics and behaviour. Using unique marks requires that tags must last for the duration of the study and not affect animal behaviour and health. Echinoderms, especially smaller species, are usually considered intractable for tagging because they readily discard both internal and external tags. We compared the utility of two tagging techniques for marking the small starfish Parvulastra exigua : (i) branding with a soldering iron, and (ii) injection of visible implant elastomer ( VIE ) of different colours. The efficiency of these techniques was evaluated by assessing (i) the effects of the tag on the mortality, growth and mobility of P. exigua ; and (ii) the persistence of the tags over 30 days. VIE had no detectable effect on any variable tested, whereas brand marks caused a decrease in mobility. In addition, 95% of the starfish tagged with VIE were still tagged after 1 month. This technique will facilitate research on the ecology of this and other small asteroid species, and is also relevant for ecological studies of other small soft‐bodied invertebrates. The combination of VIE colours plus the viability to track individuals offers a wide range of opportunities to investigate the ecology and behaviour of small invertebrates in the field.