External malformations in the green sea urchin Arbacia dufresnii (Blainville, 1825) in populations from Golfo Nuevo, Patagonia, Argentina

Abstract

Malformations in sea urchins can manifest in various forms, often influenced by environmental and biological factors. Adult Arbacia dufresnii (Blainville, 1825) exhibit pentaradial symmetry, spines in the ambulacral areas, absence of spines in the interambulacral areas, and a rhomboidal periproct composed of four ossicles. This report aims to document the presence of external malformations in the green sea urchin Arbacia dufresnii in the population of Golfo Nuevo, Patagonia, Argentina (42°42′ S 64°30′ W). A total of 319 specimens were collected, out of which 5 showed malformations. The malformation include: absence of pentaradial symmetry, spines in the interambulacral areas, and non-rhomboidal periprocts covered by three supraanal plates. These findings suggest the need for monitoring external malformations in populations of A. dufresnii and other Echinoidea, as they could provide crucial information abouth the health and status of these populations. Malformations may serve as biomarkers of environmental stress, pollution, or habitat condition changes, which is essential for effective conservation measures.