Spawning, embryogenesis, settlement, and post‐settlement development of the gorgonian <i>Plexaura homomalla</i>

Tonra, Kaitlyn J.; Wells, Christopher D.; Lasker, Howard R.

doi:10.1111/ivb.12319

Cited by 6 publications

(5 citation statements)

References 31 publications

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“…We observed elevated settlement approximately ten days after the full moon, which is approximately five days after predicted spawning for a number of octocoral species (Kahng, Benayahu, and Lasker 2011), indicating that octocorals prefer to settle as soon as they are competent. This timing matches the findings of Tonra, Wells, and Lasker (2021) and Lasker and Kim (1996), where Caribbean plexaurid octocorals took five days for median competency. Plexaurids are the most abundant family of octocorals that spawned during the time of this study (Kahng, Benayahu, and Lasker 2011).…”

Section: Discussionsupporting

confidence: 85%

Grazers and predators mediate the post-settlement bottleneck in Caribbean octocoral forests

Wells

Benz

Tonra

et al. 2022

Preprint

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Caribbean octocorals have not suffered the decades long decline in abundance that has plagued reef-building scleractinian corals. Their success and the formation of octocoral forests has been attributed to their continuing recruitment to reef habitats. Assessing the processes controlling recruitment is essential to the understanding the success of octocorals and predicting their future. Benthic grazers on coral reefs can facilitate the growth and recruitment of corals by reducing the abundance of competitive algal turfs and macroalgae or hinder corals through predation of coral tissue and recruits. We assessed the effects of grazing by fishes and the sea urchin Diadema antillarum and mesofaunal predation on octocoral recruitment in a series of manipulative experiments using varying grazer/predator exclusion and inclusion conditions in in situ and ex situ experiments. Exposure to fish and urchin grazing significantly reduced survival and recruitment of single-polyp octocorals, while turf-associated mesofauna did not significantly affect neither recruitment nor survival. We also found a positive relationship between octocoral recruitment and turf algae, a potential related response to the deleterious effect of grazing exposure. These data suggest that grazers and predators mediate the mortality bottleneck characteristic of recruitment. Thus, the declines in the abundance of grazing fishes and urchins throughout the Caribbean may have contributed to the increase in abundance of octocorals in the Caribbean, concurrent with the loss of scleractinians.

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Section: Discussionsupporting

confidence: 85%

Grazers and predators mediate the post-settlement bottleneck in Caribbean octocoral forests

Wells

Benz

Tonra

et al. 2022

Preprint

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“…Previous work at Europa and Grootpan Bays found that newly metamorphosed Plexaura homomalla polyps that settled on unglazed stoneware clay tiles suffered 87% mortality over 59 d ( Martínez-Quintana & Lasker, 2021 ). Tonra, Wells & Lasker (2021) observed P. homomalla recruits reached three polyps (2–3 mm) in 10 weeks. If we assume recruits within the 0.3–0.5 cm size class were at least 1–2 months old, adding 1–2 months mortality would reduce our estimates of survival to the juvenile stage an additional 65–87%.…”

Section: Discussionmentioning

confidence: 75%

“…These forms all start their benthic lives as single polyps, which we refer to as primary polyps. Primary polyps are unambiguously recruits and some species can start budding new polyps within weeks of metamorphosis ( Tonra, Wells & Lasker, 2021 ), but some may take months ( Hwang & Song, 2007 ; Sun, Hamel & Mercier, 2011 ). Most studies of recruitment among octocorals have sampled on scales greater than the time needed for many recruits to bud, and therefore have included small single branch colonies as recruits, i.e.…”

Section: Introductionmentioning

confidence: 99%

“…Censuses of in situ populations, while characterizing recruitment in a more natural setting, also require the investigator to distinguish recruits from small but older colonies. Single-polyp recruits persist in that state for weeks to months before dividing and becoming colonial ( Tonra, Wells & Lasker, 2021 ). Only censuses in which recruits are mapped, or those performed at short intervals can unambiguously distinguish recruits from small juveniles, i.e ., small and not reproductive colonies that are older than 1 year.…”

Section: Introductionmentioning

confidence: 99%

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Growing up is hard to do: a demographic model of survival and growth of Caribbean octocoral recruits

Lasker

Martínez-Quintana

2022

PeerJ

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Background Among species with size structured demography, population structure is determined by size specific survival and growth rates. This interplay is particularly important among recently settled colonial invertebrates for which survival is low and growth is the only way of escaping the high mortality that small colonies are subject to. Gorgonian corals settling on reefs can grow into colonies of millions of polyps and can be meters tall. However, all colonies start their benthic lives as single polyps, which are subject to high mortality rates. Annual survival among these species increases with size, reflecting the ability of colonies to increasingly survive partial mortality as they grow larger. Methods Data on survival and growth of gorgonian recruits in the genera Eunicea and Pseudoplexaura at two sites on the southern coast of St John, US Virgin Islands were used to generate a stage structured model that characterizes growth of recruits from 0.3 cm until they reach 5 cm height. The model used the frequency distributions of colony growth rates to incorporate variability into the model. Results High probabilities of zero and negative growth increase the time necessary to reach 5 cm and extends the demographic bottleneck caused by high mortality to multiple years. Only 5% of the recruits in the model survived and reached 5 cm height and, on average, recruits required 3 y to reach 5 cm height. Field measurements of recruitment rates often use colony height to differentiate recruits from older colonies, but height cannot unambiguously identify recruits due to the highly variable nature of colony growth. Our model shows how recruitment rates based on height average recruitment and survival across more than a single year, but size-based definitions of recruitment if consistently used can characterize the role of supply and early survival in the population dynamics of species.

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“…In sea tables, P. homomalla started releasing eggs between 21:00 and 21:30, with different colonies (males and females) starting at different times over a 60 min period. Release continued for approximately 2 h. Eggs collected during the spawning events developed into planulae which successfully settled (see Tonra et al 2021 for more details).…”

Section: Reproductionmentioning

confidence: 99%

Fine-scale morphological, genomic, reproductive, and symbiont differences delimit the Caribbean octocorals Plexaura homomalla and P. kükenthali

et al. 2021

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Octocorals are conspicuous members of coral reefs and deep-sea ecosystems. Yet, species boundaries and taxonomic relationships within this group remain poorly understood, hindering our understanding of this essential component of the marine fauna. We used a multifaceted approach to revisit the systematics of the Caribbean octocorals Plexaura homomalla and Plexaura kükenthali, two taxa that have a long history of taxonomic revisions. We integrated morphological and reproductive analyses with high-throughput sequencing technology to clarify the relationship between these common gorgonians. Although size and shape of the sclerites are significantly different, there is overlap in the distributions making identification based on sclerites alone difficult. Differences in reproductive timing and mode of larval development were detected, suggesting possible mechanisms of pre-zygotic isolation. Furthermore, there are substantial genetic differences and clear separation of the two species in nuclear introns and single-nucleotide polymorphisms obtained from de novo assembled transcriptomes. Despite these differences, analyses with SNPs suggest that hybridization is still possible between the two groups. The two nascent species also differed in their symbiont communities (genus Breviolum) across multiple sampling sites in the Caribbean. Despite a complicated history of taxonomic revisions, our results support the differentiation of P. homomalla and P. kükenthali, emphasizing that integrative approaches are essential for Anthozoan systematics.

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Spawning, embryogenesis, settlement, and post‐settlement development of the gorgonian Plexaura homomalla

Cited by 6 publications

References 31 publications

Grazers and predators mediate the post-settlement bottleneck in Caribbean octocoral forests

Grazers and predators mediate the post-settlement bottleneck in Caribbean octocoral forests

Growing up is hard to do: a demographic model of survival and growth of Caribbean octocoral recruits

Fine-scale morphological, genomic, reproductive, and symbiont differences delimit the Caribbean octocorals Plexaura homomalla and P. kükenthali

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