Sexual reproduction of the shallow-water black coral Cirrhipathes anguina (Dana, 1846) from Madagascar

ABSTRACT

Random sampling of shallow-water black corals colonies of Cirrhipathes anguina was carried out over a period of 13 months near the Great Reef of Toliara in southwest Madagascar. Small pieces of tissue were collected monthly from the base and apex of each colony. A total of 114 sets of upper and lower sections were observed. There were 37 males and 39 females for a sex ratio of 0.95, which was not significantly different from 1:1. On female and male colonies, 56% and 60% of the polyps, respectively, were showing developing gametes and no embryo nor larvae. Based on these samples, the species was determined to be gonochoric with broadcast spawning. The development of female and male gametes was divided into 3 stages, with stage 0 referring to unsexable colonies, and stage 2 referring to a high abundance of fully developed gametes inside the reproductive mesenteries. Gametes are released seasonally, with a major increase in the maturity and oocyte size when the temperature and the precipitation were at their highest in January. Intra-colonial differences were observed regarding maturing polyps. A few polyps living on the highest part of the colonies were showing gametes all year long. Their presence may be the result of unspawned gametes and residual mature polyps. All results are in line with previous hypotheses about the sexual reproduction of Cirrhipathes anguina based on the ultrastructure of the gametes or random observation events. An up to date summary of the current knowledge about black coral reproduction is also presented.

KEYWORDS:

• Antipatharia
• Madagascar
• reproduction
• black corals

Acknowledgements

The authors are thankful to the reviewers for their very interesting comments and remarks that improved the quality of the manuscript. Many thanks are expressed to the Institut Halieutique et des Sciences Marines (University of Toliara) for providing facilities and especially to Gildas Todinanahary and Malagasy students for their help during the monthly sampling on the field. Lucas Terrana is funded by the FRIA (FNRS).

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Lucas Terrana http://orcid.org/0000-0001-5767-3220

Additional information

Funding

This work was supported by Fonds pour la Formation à la Recherche dans l’Industrie et dans l’Agriculture [grant number MCF/XH/FC-16752].