Sexual reproductive cycle of the epibiotic soft coral Alcyonium coralloides (Octocorallia, Alcyonacea)

Abstract

Alcyonium coralloides is an epibiotic soft coral overgrowing living colonies of Mediterranean gorgonians. The main features of the sexual reproductive cycle of this soft coral species are described and quantified for the first time, in a population found at 18 to 22 m depth off the Medes Islands (NW Mediterranean). A. coralloides is a gonochoric internal brooder. The sexual cycle showed a single reproductive event per year. Gametogenesis took 5 to 6 mo, which is the shortest known gametogenesis in littoral octocorals (especially for oogenesis). The maximum mean ± SD diameter was 365 ± 86 µm for spermatic cysts and 632 ± 125 µm for mature oocytes. Sperm was released in spring (late May). Average male and female fecundity in this last phase of the cycle was 15 ± 9 spermatic cysts and 7 ± 4 oocytes per polyp, respectively. Larvae of about 1000 µm in length were observed in the gastrovascular cavities of female colonies in May, before they were released in June. We suggest that the remarkable short gametogenesis and timing shown by A. coralloides is an adaptation to optimize the colonization of its host (in this case the gorgonian octocoral Paramuricea clavata). We conclude that A. coralloides larvae could be ready to settle in early summer when the host P. clavata is probably more vulnerable as a result of its own reproductive cycle coming to an end.

Who’s Next? Non-Indigenous Cnidarian and Ctenophoran Species Approaching to the Italian Waters

“…Probably one of the keys to understand the successful invasion of this anthozoan is related to its early sexual reproduction (1-2 years, [95]) and the bailout propagation of the species [99]. Gametogenesis is fast, taking five months in the case of female colonies and three months in the case of male colonies [101], similar to the parasitic alcyonarian Alcyonium coralloides [102]. This kind of reproduction may be an advantage in a fast-changing sea in which cnidarians may have problems in the stabilization of their populations due to climate change [103].…”

The Diversity, Structure, and Development of the Epibiont Community of Paramuricea clavata (Risso, 1826) (Cnidaria, Anthozoa)

“…The Alcyonacea A. coralloides, a typical parasite of many gorgonians, grows by fouling ("runner" type) the apical axis of colonies [61,62]. A. coralloides exploit the stressed conditions of its host due to the reproductive window and oligotrophy of the water column during summertime, synchronizing its reproduction cycle with those of P. clavata [63]. Indeed, the emission of sexual products by A. coralloides has been documented in the Tavolara MPA area in the middle of May (Figure 2g), with the settling of recruits a couple of weeks after (ET, unpublished), occurring simultaneously with the spawning of P. clavata.…”

Some Observations on the Reproductive Biology of the Mediterranean Pennatulacean Pteroeides Spinosum (Ellis and Solander, 1786) (Cnidaria: Octocorallia: Pennatulacea)

“…Many of the reproductive features observed in our colonies of Pteroeides spinosum are shared with the population of Pteroeides sp. studied by Duncan (1998) from Fiorland (New Zealand), as well other Mediterranean pennatulaceans (as Veretillum cynomorium, see Lopes et al 2012) and alcyonaceans such as Eunicella singularis, Paramuricea clavata, Alcyonium acaule or Alcyonium coralloides (see Theodor 1967;Weinberg and Weinberg 1979;Coma et al 1995a, b;Fiorillo et al 2013;Quintanilla et al 2013). All of them had spermatocysts and oocytes at different sizes corresponding to different stages of maturity, as well as a distinguishable bi-or tri-modal oocyte size distribution and a high reproductive effort at colony level.…”