First evidence of asexual recruitment of Pocillopora acuta in Okinawa Island using genotypic identification

Abstract

Okinawa Island is located near the center of the Nansei Islands (∼24–31°N), at a relatively high latitude for coral reefs. Nevertheless, more than 80 coral genera (over 400 species) are abundant in the Nansei Islands. Since March, 2017, scleractinian corals have been held in an outdoor tank at the OIST Marine Science Station at Seragaki, Onna with natural sea water flow-through in order to be used in molecular biological and physiological studies. In January, 2018, we found small pocilloporid-like colonies suspected to have originated asexually. We collected 25 small colonies and measured their sizes and weights. Also, we validated the classification and clonality of the colonies using a mitochondrial locus and nine microsatellite loci. Almost all of the small colonies collected in the outdoor tank were ≤1 cm in both width and height. The weight of dried skeletons ranged from 0.0287 to 0.1807 g. Genetic analysis determined that they were, in fact, Pocillopora acuta. Only one mitochondrial haplotype was shared and two microsatellite multilocus genotypes were detected (20 colonies of one and four colonies of the other). The mitochondrial haplotype and one microsatellite multilocus genotype for 20 colonies corresponded to those of one P. acuta colony being kept in the tank. One small colony matched both multilocus genotypes. This may have been a chimeric colony resulting from allogenic fusion. These small colonies were not produced sexually, because the only potential parent in the tank was the aforementioned P. acuta colony. Instead, they were more likely derived from asexual planula release or polyp bail-out. Corals as Pocillopora acuta have the capacity to produce clonal offspring rapidly and to adapt readily to local environments. This is the first report of asexual reproduction by planulae or expelled polyps in P. acuta at Okinawa Island.

Ploidy variation and its implications for reproduction and population dynamics in two sympatric Hawaiian coral species

“…Our results suggest that the diploid P. acuta are both sexual outbreeders and generate asexual brooded larvae, as previously described (Nakajima et al 2018; Richmond and Jokiel 1984; Schmidt-Roach et al 2014). The evolution of triploid genotypes in this species may be an adaptation to local conditions in Kāne‘ohe Bay, possibly allowing them to outcompete the ancestral diploid genotypes.…”

Reef location has a greater impact than coral bleaching severity on the microbiome of Pocillopora acuta

“…P. acuta is a brooding species, which implies limited dispersal of larvae before settlement, compared to a broadcast spawning species (Torda et al 2013a). In addition, P. acuta exhibits both sexual and asexual reproductive modes (Torda et al 2013a;Schmidt-Roach et al 2014b;Ge ´lin et al 2017;Nakajima et al 2018). Whilst populations in the Palm Island archipelago preferentially use sexual reproduction, particular sites within the Palm Islands received a greater proportion of recruits than others when examined over a period of two years (Torda et al 2013a).…”

“…For instance, it is welldocumented that different coral colonies of a given species, exposed to similar levels of thermal stress at the same location can exhibit varying degrees of bleaching (Swain et al 2016;Green et al 2019); however, we do not know if this mosaic of bleaching phenotypes observed at the colony-level is reflected in the microbiome. To address this question, we used the emerging model species Pocillopora acuta, a reef-building coral with well characterised ecology, reproduction and microbiome (Torda et al 2013a;Schmidt-Roach et al 2014a, b;Nakajima et al 2018;Damjanovic et al 2020b;Ros et al 2021). Previous studies have revealed that the microbiomes of Pocillopora species are generally stable under changing environmental conditions (Pogoreutz et al 2018;Epstein et al 2019), with species such as P. acuta often hosting site-specific microbiomes (Torres et al 2020), perhaps due to the brooding reproductive strategy of the host (Torda et al 2013a).…”

A molecular census of early‐life stage scleractinian corals in shallow and mesophotic zones

“…Recently, P. verrucosa has been found to brood in nearby Philippines (Villanueva et al., 2008) that wintertime P. verrucosa recruits could actually be brooded; however, further study is required. Several other pocilloporids can reproduce asexually, which could provide an alternative explanation for winter recruitment: Pocillopora acuta may generate planula asexually in the absence of sperm (Nakajima et al., 2018; Smith et al., 2019), and P . damicornis may produce clonal larvae, although this behavior may vary along latitudinal gradients (Miller & Ayre, 2004).…”