AUTHOR=Marchini Chiara , Tortorelli Giada , Guidi Elena , Airi Valentina , Falini Giuseppe , Dubinsky Zvy , Goffredo Stefano 

TITLE=Reproduction of the Azooxanthellate Coral Caryophyllia inornata Is Not Affected by Temperature Along an 850 km Gradient on the Western Italian Coast

JOURNAL=Frontiers in Marine Science

VOLUME=Volume 6 - 2019

YEAR=2020

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2019.00785

DOI=10.3389/fmars.2019.00785

ISSN=2296-7745

ABSTRACT=The IPCC predicted that ocean surface temperature will rise of 0.6-2.0 °C by 2100. Ocean warming is expected to produce strong impacts on marine ecosystems such as coral reefs, affecting their physiological events including reproductive processes. To date, relatively few studies have examined the effects of climate change on the reproductive success of temperate corals and even less in the azooxanthellate ones. This study examined the reproductive output of the azooxanthellate Mediterranean coral Caryophyllia inornata along a wide latitudinal gradient of seawater temperature and solar radiation. A total of 260 samples, collected from five populations along the Western Italian coast, have been analyzed through histological techniques. The intriguing aspects characterizing all populations of C. inornata along the latitudinal gradient are a strong male-biased sex ratio and the presence of embryos in all stages of development throughout the year in females, males and sexually inactive individuals. This peculiarity could suggest a mixed strategy of sexual and asexual reproduction in this species as has been observed for some anemones of the genus Actinia. Fecundity and spermary abundance (i.e., the number of reproductive elements per body volume unit), gonadal index (i.e., the percentage of body volume occupied by the germ cells) and fertility (i.e., the number of embryos per body volume unit) in females, males and sexually inactive individuals were unrelated to solar radiation and temperature along the latitudinal gradient. Only gamete diameters were influenced by environmental parameters but without a clear trend, suggesting that C. inornata is tolerant to increased solar radiation and temperature. The lack of zooxanthellae could make this species less dependent on these environmental parameters, as previously hypothesized for another azooxanthellate species, Leptopsammia pruvoti, investigated along the same gradient.