Reproduction and development of the brooding sea urchin Austrocidaris canaliculata from deep-sea off Argentina

Abstract

Even though brooding behavior show an unusual high level of incidence in Austral cidaroids, the genus Austrocidaris has a particularly original developmental feature, is the only cidaroid to brood its young on the aboral side of the test. This study describes several features of the reproductive and development mode of the widely distributed sea urchin Austrocidaris canaliculata (Agassiz, 1863). For this, 216 specimens were collected from deep-sea off Argentina including the Mar del Plata submarine canyon area and the Marine Protected Area Namuncurá/Burdwood Bank. Histological analyses revealed specimens presenting gonads at different stages of development. Ovaries contained oocytes at different stages of gametogenesis; the largest intra-ovarian oocyte recorded was 1300 µm in diameter. Fully testes were found showing spermatozoa with elongated heads (9 µm in length). Eleven brooding females were collected. A single mother was recorded carrying up to 536 broods simultaneously. All the offspring in the same marsupium were at a single stage of development. The deepest record for A. canaliculata (up to 1398 m) is also reported in this study. The main finding confirm that A. canaliculata is a brooding cidaroid with a direct, lecithotrophic developmental mode from the Southwestern Atlantic Ocean.