Highly seasonal reproduction in deep-water emergent Desmophyllum dianthus (Scleractinia: Caryophylliidae) from the Northern Patagonian Fjords

Abstract

Desmophyllum dianthus is a cosmopolitan species usually found at 1000–2500 m depth in the deep ocean, but in the Patagonian fjords can be found in shallow waters up to 8 m due to deep-water emergence. The purpose of this study was to determine the reproductive biology and seasonality of the scleractinian cup coral D. dianthus from the Chilean fjord region using histological techniques. Corals were collected via SCUBA approximately every 3 months from August 2012 to September 2013 from three sites—Lilihuapi (n = 76) and Punta Huinay (n = 59) in the Comau Fjord; and Morro Gonzalo (n = 44) in the Renihue Fjord (42.0°S–42.35°S). This study determined that D. dianthus is dioecious, and reproduction is highly seasonal, spawning at the end of austral winter (August) and beginning gamete production in early spring (September). Gametogenesis tracks with known fjord primary productivity and the fjords were coolest and most saline in August, potentially cueing spawning. Owing to the presence of late-stage oocytes in August 2012 and the absence of larvae, we hypothesize that D. dianthus’s mode of reproduction is broadcast spawning. Oogenesis starts in September with previtellogenic oocytes (25–200 μm) that slowly develop into vitellogenic oocytes (200–380 μm) by June. Fecundity is high compared to other deep-sea scleractinians, ranging from 2448 (± 5.13 SE) to 172,328 (± 103.67 SE) potential oocytes per polyp. This research provides the first insight into Desmophyllum dianthus’s reproductive biology and yields an important baseline for continuing work on this benthic habitat builder.