Corallite Morphology Research Articles

First record of a fossil coral (Anthozoa) from Pleistocene deposits at Terra Ceia, North Carolina

A fossil coral of the genus Solenastrea Milne Edwards & Haime (Anthozoa: Scleractinia: Faviidae) is reported from Pleistocene deposits exposed near the town of Terra Ceia in Beaufort County, North Carolina. The specimen is similar in gross and corallite morphology to Solenastrea hyades (Dana) which is common in Neogene and Quaternary sediments of North Carolina, but has been altered by vadose diagenesis, making confident assignment to species challenging. The specimen is the first coral recovered from the Terra Ceia locality which has, up to now, yielded only mollusks.

Deciphering the composite morphological diversity ofLophelia pertusa, a cosmopolitan deep‐water ecosystem engineer

AbstractCold‐water coral reefs constitute important biodiversity hotspots in aphotic waters around the world. The complex, highly variable morphology of the reef habitat‐forming species has important implications for the communities they harbor and for the physical processes occurring therein.Lophelia pertusa(Desmophyllum pertusum) is one of the most common reef‐building cold‐water corals, but its morphological diversity has never been characterized on a broad scale. We qualitatively and quantitatively explored the patterns of morphological variation of this species over a wide geographic and ecological range, addressing corallite and colony traits and their interrelation. Geographic variation is evident at both corallite and colony level, although with distinct trends. By linking branching patterns to colony morphology, we identified three main morphotypes (asymmetrical, bushy, and columnar) with substantial geometric and architectural differences, which suggest high functional diversity of cold‐water coral reefs across regions. Colony morphology appears strongly governed by asexual budding of individual polyps, but largely decoupled from corallite morphology. We hypothesize that colony morphology is primarily driven by local hydrodynamic conditions and associated food supply.

Distinct Phenotypes Associated with Mangrove and Lagoon Habitats in Two Widespread Caribbean Corals, Porites astreoides and Porites divaricata

AbstractAs coral reefs experience dramatic declines in coral cover throughout the tropics, there is an urgent need to understand the role that non-reef habitats, such as mangroves, play in the ecological niche of corals. Mangrove habitats present a challenge to reef-dwelling corals because they can differ dramatically from adjacent reef habitats with respect to key environmental parameters, such as light. Because variation in light within reef habitats is known to drive intraspecific differences in coral phenotype, we hypothesized that coral species that can exploit both reef and mangrove habitats will exhibit predictable differences in phenotypes between habitats. To investigate how intraspecific variation, driven by either local adaptation or phenotypic plasticity, might enable particular coral species to exploit these two qualitatively different habitat types, we compared the phenotypes of two widespread Caribbean corals, Porites divaricata and Porites astreoides, in mangrove versus lagoon habitats on Turneffe Atoll, Belize. We document significant differences in colony size, color, structural complexity, and corallite morphology between habitats. In every instance, the phenotypic differences between mangrove prop root and lagoon corals exhibited consistent trends in both P. divaricata and P. astreoides. We believe this study is the first to document intraspecific phenotypic diversity in corals occupying mangrove prop root versus lagoonal patch reef habitats. A difference in the capacity to adopt an alternative phenotype that is well suited to the mangrove habitat may explain why some reef coral species can exploit mangroves, while others cannot.

Occurrence of the azooxanthellate coral Phyllangia pequegnatae (Scleractinia: Caryophylliidae) in the Colombian Caribbean Sea: hidden diversity or another invasive species?

As part of a baseline biodiversity study of the marine fauna associated with the Marina of Puerto Velero (PVM) in the Colombian Caribbean, we record the presence of the azooxanthellate coral Phyllangia pequegnatae Cairns, 2000. This new record extends the geographic distribution of this species to the southwestern Caribbean and increases its bathymetric range to the shallow 0.3 m depth as this species was previously known between 48 and 112 m depth. The colony of P. pequegnatae consists of 15 corallites and it was collected from underneath one of the main docks (concrete). Images of live extended polyps and detailed corallite morphology illustrate the differences between the recorded species P. pequegnatae with respect to its congeneric Phyllangia americana americana Milne Edwards & Haime, 1849. We discussed two hypothetical scenarios for the occurrence of P. pequegnatae in the Colombian Caribbean: the expansion of the bathymetric range of a previously overlooked native species or its introduction via the fouling community of small vessels.

Morphology, lipid composition, and reproduction in growth anomalies of the reef-building coral Porites evermanni and Porites lobata

Growth anomalies (GAs) are protuberant masses found on many coral species; their presence may be linked to increased ocean temperatures and bleaching stress. In 2014 and 2015, Hawai‘i experienced back-to-back beaching events, after which an increased number of growth anomalies were noted on massive Porites colonies. GAs and normal tissues were sampled from 19 P. evermanni and P. lobata colonies in 2015 and from each of 15 separate P. evermanni colonies on six dates from June 2016 to August 2017, encompassing two annual reproductive cycles. Compared to normal tissue, GAs had significantly larger corallites in all dimensions in both P. evermanni and P. lobata. GAs of P. evermanni also had reduced amounts of lipid and lower functional lipid ratios across all time points. Across tissue types, lipid content was generally higher in winter (December) and spring (April) than in summer months (June/July), but was not correlated with reproductive condition. While GAs are generally non-reproductive in other corals, GA tissues in P. evermanni contained elevated numbers of oocytes in 2017. Compared to normal tissue, GAs in P. evermanni had aberrant corallite morphology and likely committed proportionally more energy to growth and less to energy storage.

Montastraea cavernosa corallite structure demonstrates distinct morphotypes across shallow and mesophotic depth zones in the Gulf of Mexico.

This study assessed morphological variation of the depth-generalist coral Montastraea cavernosa across shallow and mesophotic coral ecosystems in the Gulf of Mexico (GOM) using thirteen corallite metrics. While corallite structure differed significantly across sites, we observed that mean corallite diameters were smaller and spacing was greater in mesophotic corals as compared to shallow corals. Additional corallite variation, including greater mean corallite height of mesophotic samples, are hypothesized to be photoadaptive responses to low light environments. Multivariate analyses also revealed two distinct morphotypes identified by significant variation in corallite spacing with >90% accuracy. A ‘shallow’ morphotype was characterized by larger, more closely-spaced corallites, while a ‘depth-generalist’ type exhibited smaller, further-spaced corallites. Variable presence of morphotypes within some sites suggests genotypic influence on corallite morphology as there was a slight, but significant, impact of morphotype on genetic structure within shallow zones in the Flower Garden Banks. Patterns of increased algal symbiont (Symbiodiniaceae) density and chlorophyll concentration were retained in the depth-generalist morphotype even in shallow zones, identifying multiple photoadaptive strategies between morphotypes. The results of this study suggest that morphological variation among M. cavernosa represents a combination of genotypic variation and phenotypic plasticity rather than responses to environmental stimuli alone.

Corallite skeletal morphological variation in Hawaiian Porites lobata

Due to their high morphological plasticity and complex evolutionary history, the species boundaries of many reef-building corals are poorly understood. The skeletal structures of corals have traditionally been used for species identification, but these structures can be highly variable, and currently we lack knowledge regarding the extent of morphological variation within species. Porites species are notorious for their taxonomic difficulties, both morphologically and genetically, and currently there are several unresolved species complexes in the Pacific. Despite its ubiquitous presence and broad use in coral research, Porites lobata belongs to one such unresolved species complex. To understand the degree of intraspecific variation in skeletal morphology, 120 corallites from the Hawaiian P. lobata were examined. A subset of samples from two genetically differentiated populations from contrasting high- and low-stress environments in Maunalua Bay, Hawaii, were then quantitatively analyzed using multivariate morphometrics. Our observations revealed high intraspecific variation in corallite morphology, as well as significant morphological differences between the two populations of P. lobata. Additionally, significant correlation was found between the morphological and genetic distances calculated from approximately 18,000 loci generated from restriction site-associated DNA sequencing. The unique morphological characters observed from the genetically differentiated population under environmental stress suggest that these characters may have adaptive values, but how such traits relate to fitness and how much plasticity they can exhibit remain to be determined by future studies. Relatively simple morphometric analyses used in our study can be useful in clarifying the existing ambiguity in skeletal architecture, thus contributing to resolving species issues in corals.

Comparison between Colony Morphology and Molecular Phylogeny in the Caribbean Scleractinian Coral Genus Madracis

A major challenge in coral biology is to find the most adequate and phylogenetically informative characters that allow for distinction of closely related coral species. Therefore, data on corallite morphology and genetic data are often combined to increase phylogenetic resolution. In this study, we address the question to which degree genetic data and quantitative information on overall coral colony morphologies identify similar groupings within closely related morphospecies of the Caribbean coral genus Madracis. Such comparison of phylogenies based on colony morphology and genetic data will also provide insight into the degree to which genotype and phenotype overlap. We have measured morphological features of three closely related Caribbean coral species of the genus Madracis (M. formosa, M. decactis and M. carmabi). Morphological differences were then compared with phylogenies of the same species based on two nuclear DNA markers, i.e. ATPSα and SRP54. Our analysis showed that phylogenetic trees based on (macroscopical) morphological properties and phylogenetic trees based on DNA markers ATPSα and SRP54 are partially similar indicating that morphological characteristics at the colony level provide another axis, in addition to commonly used features such as corallite morphology and ecological information, to delineate genetically different coral species. We discuss this new method that allows systematic quantitative comparison between morphological characteristics of entire colonies and genetic data.

Changes in scleractinian coral Seriatopora hystrix morphology and its endocellular Symbiodinium characteristics along a bathymetric gradient from shallow to mesophotic reef

The algae living endosymbiotically within coral are thought to increase algal pigmentation with increasing depth to capture the diminishing light. Here, we follow distribution of the hermatypic coral Seriatopora hystrix along a 60-m bathymetric gradient in the Gulf of Eilat, Red Sea, to study coral ecophysiology and response to light regimes. Combining work on coral morphology, pigment content and genotyping of the photosymbiont, we found that total chlorophyll concentration per zooxanthellae cell and the dark- and light-acclimated quantum yield of photosystem II did not vary significantly along the 60-m gradient. However, the chlorophyll a/c ratio increased with depth. This suggests that the symbiotic algae in S. hystrix possess a mechanism for acclimatization or adaptation that differs from previously described pathways. The accepted photoacclimatory process involves an increase in chlorophyll content per alga as light intensity decreases. Based on corallite and branch morphology, this research suggests that S. hystrix has two depth-dependent ecophenotypes. Above 10 m depth, S. hystrix exhibits sturdier colony configurations with thick branches, while below 30 m depth, colonies are characterized by thin branches and the presence of a larger polyp area. Between 10 and 30 m depth, both ecophenotypes are present, suggesting that corallite morphology may act as another axis of photoacclimation with depth.

American Samoa’s island of giants: massive Porites colonies at Ta’u island

[Extract] One of the largest and oldest single hermatypic coral colonies known is a massive Porites coral located on the southwest corner of Ta'u island (14°15S, 169°30W) in the Manu'a group of American Samoa. The coral is believed to be Porites lutea based on colony and corallite morphology; however, Porites taxonomy is notoriously difficult and recent genetic work has revealed surprising levels of cryptic diversity (Forsman et al.2009). Small (1 cm) cores were collected for genetic and microscopic work, and to determine skeletal density. DNA sequence for mitochondrial (COI, COIII) and nuclear (ITS region) markers were deposited in GenBank (accession numbers ITS-FJ416523-6, mt COI-FJ423967, and mt control FJ427369), and skeletal voucher specimens have been deposited at the Bishop Museum (SC4164).

Skeletal response of Lophelia pertusa (Scleractinia) to bioeroding sponge infestation visualised with micro-computed tomography

The skeleton morphology of the azooxanthellate cold-water coral Lophelia pertusa can be strongly influenced by invasive boring sponges that infest corallites in the still living part of the colony. Atypically swollen corallites of live Lophelia pertusa from the Galway Mound (Belgica Carbonate Mound Province, Porcupine Seabight, NE Atlantic), heavily excavated by boring organisms, have been examined with a wide range of non-destructive and destructive methods: micro-computed tomography, macro- and microscopic observations of the outer coral skeleton, longitudinal and transversal thin sections and SEM analyses of coral skeleton casts. As a result, three excavating sponge species have been distinguished within the coral skeleton: Alectona millari, Spiroxya heteroclita and Aka infesta. Furthermore, four main coral/sponge growth stages have been recognised: (1) cylindrical juvenile corallite/no sponge cavities; (2) flared juvenile corallite/linear sponge cavities (if present); (3) slightly swollen adult corallites/chambered oval sponge cavities; (4) very swollen adult corallites/widespread cavities. The inferred correlation between corallite morphology and boring sponge infestation has been detected in micro-computed tomography (micro-CT) images and confirmed in sponge trace casts and peculiar features of coral skeleton microstructure.

Modelling variations in corallite morphology of Galaxea fascicularis coral colonies with depth and light on coastal fringing reefs in the Wakatobi Marine National Park (S.E. Sulawesi, Indonesia)

Coastal environments in the tropics can suffer from high sedimentation and low light levels. Galaxea fascicularis is a hermatypic coral that is relatively resilient to stress from bleaching and from sedimentation. Corallite dimensions – width, height, corallite densities and inter-corallite distances – of Galaxea fascicularis colonies varied significantly with depth, and so with incident light at the Sampela reef in the Wakatobi Marine National Park, S.E. Sulawesi, Indonesia. Modelling studies based on our data showed that corallite width decreased with the amount of incident light, while corallite height increased with the amount of incident light ( r 2 values of 0.835 for width and 0.869 for height). In all colonies, inter-corallite distance decreased significantly with the amount of incident light ( r 2 = 0.89). Colony width/height ratio increased in a linear fashion with inter-corallite distance for all colonies studied ( r 2 = 0.65). Current flow as judged using tags did not appear to be a factor in variations of corallite dimensions. Our results suggest that under low light conditions, distribution and size of corallites may optimise heterotrophic nutrition, while in conditions where light is not limiting, distribution and size of corallites may be optimal for photosynthesis.

An aquarium experiment for identifying the physical factors inducing morphological change in two massive scleractinian corals

Previous research has demonstrated that the massive corals Favia speciosa (Dana, 1846) and Diploastrea heliopora (Lamark, 1816) are phenotypically plastic, i.e. the phenotype of these species can be altered by environmental conditions within their life span. Many researchers have suggested that light, water movement and/or sediment can affect coral morphology, but no work to date has attempted to separate these variables in a controlled aquarium experiment. To ascertain whether any of these three factors could induce morphological change in F. speciosa and D. heliopora, fragments (clone-mates) of both species were maintained in five aquarium tanks, representing: high water energy, high sedimentation, and three different light regimes. After 4 months, the architecture of 12 randomly chosen corallites from each fragment was measured. Reaction norms suggest a relationship between corallite morphology and light, but no consistent pattern could be detected for fragments kept in the sediment regime tank or the high water energy tank. Corallites expand, extend and deepen in high light conditions and possible functional explanations for this response are presented. However, more research is necessary to confirm that light is the primary controlling factor inducing small-scale morphological change in F. speciosa and D. heliopora.

The relationship between corallite morphology and colony shape in some massive reef-corals

Multivariate statistical tests are performed on three coral species to determine if a relationship exists between colony shape and corallite morphology. Hemispherical to branched colony shapes are emphasized. The material consists of specimens of Montastraea annularis and M. cavernosa from modern reef habitats in Jamaica. Colonies of the more “branched” M. limbata from the Neogene of the Dominican Republic are analyzed for comparison. The characters studied consist largely of linear measurements of colony dimensions and corallite structures in transverse thin-sections. The results show that different complexes of corallite characters vary within each species. With the possible exception of a complex describing theca thickness in M. annularis, none of these corallite complexes is related to variation in colony shape within species. Colony shape variation within species is related to upward colony growth rate. These results indicate that corallite morphology and colony shape can be represented by two different vectors of variation within species. Comparisons of intraspecific with interspecific patterns suggest that a strong genetic component explains colony shape variation in corals.