Marine Citizen Science and the Conservation of Mediterranean Corals: The Relevance of Training, Expert Validation, and Robust Sampling Protocols

Marine Citizen Science (MCS) has emerged as a promising tool to enhance conservation efforts. Although the quality of volunteer data has been questioned, the design of specific protocols, effective training programs, and data validation by experts have enabled us to overcome these quality concerns, thus ensuring data reliability. Here, we validated the effectiveness of volunteer training in assessing the conservation status of Mediterranean coral species. We conducted a comparative analysis of data collected by volunteers with different levels of expertise, demonstrating improvements in data precision and accuracy with only one training session, thereby achieving values equivalent to those obtained by scientists. These outcomes align with the feedback received from volunteers through a qualitative survey. Finally, we analysed the data generated by volunteers and validated by experts using the developed protocol in the Coral Alert project from the Observadores del Mar MCS initiative. Our findings highlight the importance of proper training, expert validation, robust sampling protocols, and a well-structured platform to ensure the success of long-term MCS projects. Overall, our results stress the key role MCS plays in enhancing the conservation and management strategies designed to mitigate the ongoing environmental crisis.

Bamboozled! Resolving deep evolutionary nodes within the phylogeny of bamboo corals (Octocorallia: Scleralcyonacea: Keratoisididae)

Keratoisididae is a globally distributed, and exclusively deep-sea, family of octocorals that contains species and genera that are polyphyletic. An alphanumeric system, based on a three-gene-region phylogeny, is widely used to describe the biodiversity within this family. That phylogeny identified 12 major groups although it did not have enough signal to explore the relationships among groups. Using increased phylogenomic resolution generated from Ultraconserved Elements and exons (i.e. conserved elements), we aim to resolve deeper nodes within the family and investigate the relationships among those predefined groups. In total, 109 libraries of conserved elements were generated from individuals representing both the genetic and morphological diversity of our keratoisidids. In addition, the conserved element data of 12 individuals from previous studies were included. Our taxon sampling included 11 of the 12 keratoisidid groups. We present two phylogenies, constructed from a 75% (231 loci) and 50% (1729 loci) taxon occupancy matrix respectively, using both Maximum Likelihood and Multiple Species Coalescence methods. These trees were congruent at deep nodes. As expected, S1 keratoisidids were recovered as a well-supported sister clade to the rest of the bamboo corals. S1 corals do not share the same mitochondrial gene arrangement found in other members of Keratoisididae. All other bamboo corals were recovered within two major clades. Clade I comprises individuals assigned to alphanumeric groups B1, C1, D1&D2, F1, H1, I4, and J3 while Clade II contains representatives from A1, I1, and M1. By combining genomics with already published morphological data, we provide evidence that group H1 is not monophyletic, and that the division between other groups - D1 and D2, and A1 and M1 - needs to be reconsidered. Overall, there is a lack of robust morphological markers within Keratoisididae, but subtle characters such as sclerite microstructure and ornamentation seem to be shared within groups and warrant further investigation as taxonomically diagnostic characters.

Individual and combined effect of organic eutrophication (DOC) and ocean warming on the ecophysiology of the Octocoral Pinnigorgia flava

Dissolved organic carbon (DOC) enrichment and ocean warming both negatively affect hard corals, but studies on their combined effects on other reef organisms are scarce. Octocorals are likely to become key players in future reef communities, but they are still highly under-investigated with regard to their responses to global and local environmental changes. Thus, we evaluated the individual and combined effects of DOC enrichment (10, 20 and 40 mg L^-1 DOC, added as glucose) and warming (stepwise from 26 to 32 °C) on the widespread Indo-Pacific gorgonian Pinnigorgia flava in a 45-day laboratory experiment. Oxygen fluxes (net photosynthesis and respiration), as well as Symbiodiniaceae cell density and coral growth were assessed. Our results highlight a differential ecophysiological response to DOC enrichment and warming as well as their combination. Individual DOC addition did not significantly affect oxygen fluxes nor Symbiodiniaceae cell density and growth, while warming significantly decreased photosynthesis rates and Symbiodiniaceae cell density. When DOC enrichment and warming were combined, no effect on P. flava oxygen fluxes was observed while growth responded to certain DOC conditions depending on the temperature. Our findings indicate that P. flava is insensitive to the individual effect of DOC enrichment, but not to warming and the two stressors combined. This suggests that, if temperature remains below certain thresholds, this gorgonian species may gain a competitive advantage over coral species that are reportedly more affected by DOC eutrophication. However, under the expected increasing temperature scenarios, it is also likely that this octocoral species will be negatively affected, with potential consequences on community structure. This study contributes to our understanding of the conditions that drive phase shift dynamics in coastal coral reef ecosystemds.

An alternative and effective method for extracting skeletal organic matrix adapted to the red coral Corallium rubrum

Skeleton formation in corals is a biologically controlled process in which an extracellular organic matrix (OM) is entrapped inside the calcified structure. The analysis of OM requires a time-consuming and tedious extraction that includes grinding, demineralization, multiple rinsing and concentration steps. Here we present an alternative and straightforward method for the red coral Corallium rubrum that requires little equipment and saving steps. The entire skeleton is directly demineralized to produce a tractable material called ghost, which is further rinsed and melted at 80 °C in water. The comparative analysis of the standard and alternative methods by electrophoresis, Western blot, and FTIR of C. rubrum OM, shows that the "alternative OM" is of higher quality. Advantages and limitations of both methods are discussed.

Changes in coral forest microbiomes predict the impact of marine heatwaves on habitat-forming species down to mesophotic depths

Global warming is causing the increase in intensity and frequency of heatwaves, which are often associated with mass mortality events of marine organisms from shallow and mesophotic rocky habitats, including gorgonians and other sessile organisms. We investigated the microbiome responses of the gorgonians Paramuricea clavata, Eunicella cavolini, and the red coral Corallium rubrum to the episodic temperature anomalies detected in the North Western Mediterranean, during August 2011. Although the investigated corals showed no signs of visible necrosis, the abundance of associated Bacteria and Archaea increased with increasing seawater temperature, suggesting their temperature-dependent proliferation. Coral microbiomes were highly sensitive to thermal anomaly amplitude and exhibited increased bacterial diversity to greater thermal shifts. This effect was explained by the decline of dominant bacterial members and the increase of new, rare and opportunistic taxa, including pathogens, revealing a direct effect of heatwave-induced alteration of the microbiomes and not a secondary consequence of coral necrosis.

Effects of nanostructure antifouling biocides towards a coral species in the context of global changes

Biofouling prevention is one of the biggest challenges faced by the maritime industry, but antifouling agents commonly impact marine ecosystems. Advances in antifouling technology include the use of nanomaterials. Herein we test an antifouling nano-additive based on the encapsulation of the biocide 4,5-dichloro-2-octyl-4-isothiazolin-3-one (DCOIT) in engineered silica nanocontainers (SiNC). The work aims to assess the biochemical and physiological effects on the symbiotic coral Sarcophyton cf. glaucum caused by (1) thermal stress and (2) DCOIT exposure (free or nanoencapsulated forms), in a climate change scenario. Accordingly, the following hypotheses were addressed: (H1) ocean warming can cause toxicity on S. cf. glaucum; (H2) the nanoencapsulation process decreases DCOIT toxicity towards this species; (H3) the biocide toxicity, free or encapsulated forms, can be affected by ocean warming. Coral fragments were exposed for seven days to DCOIT in both free and encapsulated forms, SiNC and negative controls, under two water temperature regimes (26 °C and 30.5 °C). Coral polyp behavior and photosynthetic efficiency were determined in the holobiont, while biochemical markers were assessed individually in the endosymbiont and coral host. Results showed transient coral polyp retraction and diminished photosynthetic efficiency in the presence of heat stress or free DCOIT, with effects being magnified in the presence of both stressors. The activity of catalase and glutathione-S-transferase were modulated by temperature in each partner of the symbiosis. The shifts in enzymatic activity were more pronounced in the presence of free DCOIT, but to a lower extent for encapsulated DCOIT. Increased levels of oxidative damage were detected under heat conditions. The findings highlight the physiological constrains elicited by the increase of seawater temperature to symbiotic corals and demonstrate that DCOIT toxicity can be minimized through encapsulation in SiNC. The presence of both stressors magnifies toxicity and confirm that ocean warming enhances the vulnerability of tropical photosynthetic corals to local stressors.

Seasonal trends of the polyp expansion and nutritional condition of Alcyonium acaule (Octocorallia, Alcyonacea)

The ecological physiology of anthozoans, as well as their resistance to stressors, are strongly influenced by environmental factors and the availability of resources. The energy budget of anthozoans can vary seasonally in order to find an equilibrium between the available resources and respiration, polyp activity, growth, and reproduction processes. The variation in the biochemical composition of the animal tissues in these organisms results from a combination of the productivity processes of the water column coupled with the reproductive effort and potential starvation periods of the anthozoans. Here, the seasonal variation in the polyp activity of a slow-growing passive suspension feeder, the octocoral Alcyonium acaule, as well as their carbohydrate, protein and lipid contents, was investigated in a warm temperate environment using in-situ observations and biochemical analyses. Polyp activity exhibited a significant variability that was moderately dependent on season, while an aestivation phenomenon in A. acaule (i.e., a resting period in which the anthozoan is not capable of any polyp activity) during the warmer months is clearly observed. Carbohydrate concentrations in the coral species showed a significant increase in the late winter and spring seasons, and the lipid content increased during the spring. A higher abundance of lipids and carbohydrates coincided with a higher primary productivity in the water column, as well as with the octocoral reproduction period. In late autumn, there was a depletion of these biomolecules, with protein levels exhibiting great variability across sampling times. Complex alterations driven by climate change could affect the energy fluxes that depend on the dead or alive particles that are intercepted by marine animal forests. The obtained findings show a food shortage in late summer and autumn of the benthic suspension feeder A. acaule through the integrative descriptors of the ecophysiology of these anthozoans. This research contributes to the knowledge of energy storage capabilities in benthic suspension feeders in general, highlighting the importance of understanding the limits of resistance to starvation periods through these indicators.

Functional metagenomics reveals differential chitin degradation and utilization features across free-living and host-associated marine microbiomes

BACKGROUND

Chitin ranks as the most abundant polysaccharide in the oceans yet knowledge of shifts in structure and diversity of chitin-degrading communities across marine niches is scarce. Here, we integrate cultivation-dependent and -independent approaches to shed light on the chitin processing potential within the microbiomes of marine sponges, octocorals, sediments, and seawater.

RESULTS

We found that cultivatable host-associated bacteria in the genera Aquimarina, Enterovibrio, Microbulbifer, Pseudoalteromonas, Shewanella, and Vibrio were able to degrade colloidal chitin in vitro. Congruent with enzymatic activity bioassays, genome-wide inspection of cultivated symbionts revealed that Vibrio and Aquimarina species, particularly, possess several endo- and exo-chitinase-encoding genes underlying their ability to cleave the large chitin polymer into oligomers and dimers. Conversely, Alphaproteobacteria species were found to specialize in the utilization of the chitin monomer N-acetylglucosamine more often. Phylogenetic assessments uncovered a high degree of within-genome diversification of multiple, full-length endo-chitinase genes for Aquimarina and Vibrio strains, suggestive of a versatile chitin catabolism aptitude. We then analyzed the abundance distributions of chitin metabolism-related genes across 30 Illumina-sequenced microbial metagenomes and found that the endosymbiotic consortium of Spongia officinalis is enriched in polysaccharide deacetylases, suggesting the ability of the marine sponge microbiome to convert chitin into its deacetylated-and biotechnologically versatile-form chitosan. Instead, the abundance of endo-chitinase and chitin-binding protein-encoding genes in healthy octocorals leveled up with those from the surrounding environment but was found to be depleted in necrotic octocoral tissue. Using cultivation-independent, taxonomic assignments of endo-chitinase encoding genes, we unveiled previously unsuspected richness and divergent structures of chitinolytic communities across host-associated and free-living biotopes, revealing putative roles for uncultivated Gammaproteobacteria and Chloroflexi symbionts in chitin processing within sessile marine invertebrates.

CONCLUSIONS

Our findings suggest that differential chitin degradation pathways, utilization, and turnover dictate the processing of chitin across marine micro-niches and support the hypothesis that inter-species cross-feeding could facilitate the co-existence of chitin utilizers within marine invertebrate microbiomes. We further identified chitin metabolism functions which may serve as indicators of microbiome integrity/dysbiosis in corals and reveal putative novel chitinolytic enzymes in the genus Aquimarina that may find applications in the blue biotechnology sector. Video abstract.

High ecological resilience of the sea fan Gorgonia ventalina during two severe hurricanes

Since about the turn of the millennium, octocorals have been increasing in abundance on Caribbean reefs. The mechanisms underlying this trend have not been resolved, but the emergent species assemblage appears to be more resilient than the scleractinians they are replacing. The sea fan Gorgonia ventalina is an iconic species in the contemporary octocoral fauna, and here its population dynamics are described from St. John, US Virgin Islands, from 2013 to 2019. Mean densities of G. ventalina at Yawzi Point (9-m depth) varied from 1.4-1.5 colonies m-2, and their mean heights from 24-30 cm; nearby at Tektite (14-m depth), they varied from 0.6-0.8 colonies m-2 and from 25-33 cm. These reefs were impacted by two Category 5 hurricanes in 2017, but neither the density of G. ventalina, the density of their recruits (< 5-cm tall), nor the height of colonies, differed among years, although growth was depressed after the hurricanes. Nevertheless, at Tektite, colony height trended upwards over time, in part because colonies 10.1-20 cm tall were reduced in abundance after the hurricanes. These trends were sustained without density-associated effects mediating recruitment or self-thinning of adults. The dynamics of G. ventalina over seven years reveals the high resilience of this species that will contribute to the persistence of octocorals as a dominant state on Caribbean reefs.

Octocoral populations and connectivity in continental Ecuador and Galápagos, Eastern Pacific

Octocorals are important zoobenthic organisms, contributing to structural heterogeneity and species diversity on hardgrounds. Their persistence amidst global coral reef degradation and ocean acidification, has prompted renewed interest in this taxon. Octocoral assemblages at 52 sites in continental Ecuador and Galápagos (23 species, 3742 colonies) were examined for composition, size distributions within and among populations, and connectivity patterns based on ocean current models. Species richness varied from 1 to 14 species per site, with the richest sites on the continent. Three assemblage clusters were recognised based on species richness and population size, one with a mix of sites from the mainland and Galápagos (defined by Muricea fruticosa and Leptogorgia alba, Muricea plantaginea and Pacifigorgia darwinii), the second from Santa Elena in southern Ecuador (defined by M. plantaginea and L. alba) and the third from the northernmost sites on the continent, in Esmeraldas (defined by Muricea fruticosa, Heterogorgia hickmani, Leptogorgia manabiensis). Based on biophysical larval flow models with 30, 60, 90-day Pelagic Larval Duration, good connectivity existed along the South American mainland, and from the continent to Galápagos. Connectivity between Galápagos, Cocos, Malpelo and the Colombian mainland may explain the wide distribution of L. alba. Muricea plantaginea had the densest populations with the largest colonies and therewith was an important habitat provider both in continental Ecuador and Galápagos. Continental Ecuador harbours the most speciose populations of octocorals so far recorded in the southern Eastern Tropical Pacific (ETP). Most species were uncommon and possibly vulnerable to local extirpation. The present study may serve as a base line to determine local and regional impacts of future disturbances on ETP octocorals.

Polyp expansion of passive suspension feeders: a red coral case study

Polyp activity in passive suspension feeders has been considered to be affected by several environmental factors such as hydrodynamics, water temperature and food concentration. To better elucidate the driving forces controlling polyp expansion in these organisms and the potential role of particle concentration, the octocoral Corallium rubrum was investigated in accordance with two approaches: (1) high-frequency in-situ observations examining various environmental and biological variables affecting the water column, and (2) video-recorded flume-controlled laboratory experiments performed under a range of environmental and biological conditions, in terms of water temperature, flow speed, chemical signals and zooplankton. In the field, C. rubrum polyp expansion correlated positively with particle (seston and zooplankton) concentration and current speed. This observation was confirmed by the flume video records of the laboratory experiments, which showed differences in polyp activity due to changes in temperature and current speed, but especially in response to increasing nutritional stimuli. The maximum activity was observed at the highest level of nutritional stimulus consisting of zooplankton. Zooplankton and water movement appeared to be the main factors controlling polyp expansion. These results suggest that the energy budget of passive suspension feeders (and probably the benthic community as a whole) may rely on their ability to maximise prey capture during food pulses. The latter, which may be described as discontinuous organic matter (dead or alive) input, may be the key to a better understanding of benthic-pelagic coupling processes and trophic impacts on animal forests composed of sessile suspension feeders.

The influence of different deep-sea coral habitats on sediment macrofaunal community structure and function

Deep-sea corals can create a highly complex, three-dimensional structure that facilitates sediment accumulation and influences adjacent sediment environments through altered hydrodynamic regimes. Infaunal communities adjacent to different coral types, including reef-building scleractinian corals and individual colonies of octocorals, are known to exhibit higher macrofaunal densities and distinct community structure when compared to non-coral soft-sediment communities. However, the coral types have different morphologies, which may modify the adjacent sediment communities in discrete ways. Here we address: (1) how infaunal communities and their associated sediment geochemistry compare among deep-sea coral types (Lophelia pertusa, Madrepora oculata, and octocorals) and (2) do infaunal communities adjacent to coral habitats exhibit typical regional and depth-related patterns observed in the Gulf of Mexico (GOM). Sediment push cores were collected to assess diversity, composition, numerical abundance, and functional traits of macrofauna (>300 µm) across 450 kilometers in the GOM at depths ranging from 263–1,095 m. Macrofaunal density was highest in L. pertusa habitats, but similar between M. oculata and octocorals habitats. Density overall exhibited a unimodal relationship with depth, with maximum densities between 600 and 800 m. Diversity and evenness were highest in octocoral habitats; however, there was no relationship between diversity and depth. Infaunal assemblages and functional traits differed among coral habitats, with L. pertusa habitats the most distinct from both M. oculata and octocorals. These patterns could relate to differences in sediment geochemistry as L. pertusa habitats contained high organic carbon content but low proportions of mud compared to both M. oculata and octocoral habitats. Distance-based linear modeling revealed depth, mud content, and organic carbon as the primary factors in driving coral infaunal community structure, while geographic location (longitude) was the primary factor in functional trait composition, highlighting both the location and ecological differences of L. pertusa habitats from other coral habitats. Enhanced habitat structural complexity associated with L. pertusa and differences in localized hydrodynamic flow may contribute to the dissimilarities in the communities found among the coral types. Our results suggest a decoupling for infaunal coral communities from the typical depth-related density and diversity patterns present throughout soft-sediment habitats in the GOM, highlighting the importance of deep-sea corals in structuring unique communities in the nearby benthos.

Part 1: Suborder Calcaxonia

Thirteen species of deep-water calcaxonian octocorals belonging to the families Primnoidae, Chrysogorgiidae, and Isididae collected from off the Galápagos and Cocos Islands are described and figured. Seven of these species are described as new; nine of the 13 are not known outside the Galápagos region. Of the four species occurring elsewhere, two also occur in the eastern Pacific, one off Hawaii, and one from off Antarctica. A key to the 22 Indo-Pacific species of Callogorgia is provided to help distinguish those species.

Coral Food, Feeding, Nutrition, and Secretion: A Review

Tropical scleractinian corals are dependent to varying degrees on their photosymbiotic partners. Under normal levels of temperature and irradiance, they can provide most, but not all, of the host's nutritional requirements. Heterotrophy is required to adequately supply critical nutrients, especially nitrogen and phosphorus. Scleractinian corals are known as mesozooplankton predators, and most employ tentacle capture. The ability to trap nano- and picoplankton has been demonstrated by several coral species and appears to fulfill a substantial proportion of their daily metabolic requirements. The mechanism of capture likely involves mucociliary activity or extracoelenteric digestion, but the relative contribution of these avenues have not been evaluated. Many corals employ mesenterial filaments to procure food in various forms, but the functional morphology and chemical activities of these structures have been poorly documented. Corals are capable of acquiring nutrition from particulate and dissolved organic matter, although the degree of reliance on these sources generally has not been established. Corals, including tropical, deep- and cold-water species, are known as a major source of carbon and other nutrients for benthic communities through the secretion of mucus, despite wide variation in chemical composition. Mucus is cycled through the planktonic microbial loop, the benthos, and the microbial community within the sediments. The consensus indicates that the dissolved organic fraction of mucus usually exceeds the insoluble portion, and both serve as sources for the growth of nano- and picoplankton. As many corals employ mucus to trap food, a portion is taken back during feeding. The net gain or loss has not been evaluated, although production is generally thought to exceed consumption. The same is true for the net uptake and loss of dissolved organic matter by mucus secretion. Octocorals are thought not to employ mucus capture or mesenterial filaments during feeding and generally rely on tentacular filtration of weakly swimming mesozooplankton, particulates, dissolved organic matter, and picoplankton. Nonsymbiotic species in the tropics favor phytoplankton and weakly swimming zooplankton. Azooxanthellate soft corals are opportunistic feeders and shift their diet according to the season from phyto- and nanoplankton in summer to primarily particulate organic matter (POM) in winter. Cold-water species favor POM, phytodetritus, microplankton, and larger zooplankton when available. Antipatharians apparently feed on mesozooplankton but also use mucus nets, possibly for capture of POM. Feeding modes in this group are poorly known.

Ordinary kriging vs inverse distance weighting: spatial interpolation of the sessile community of Madagascar reef, Gulf of Mexico

Information about the distribution and abundance of the habitat-forming sessile organisms in marine ecosystems is of great importance for conservation and natural resource managers. Spatial interpolation methodologies can be useful to generate this information from in situ sampling points, especially in circumstances where remote sensing methodologies cannot be applied due to small-scale spatial variability of the natural communities and low light penetration in the water column. Interpolation methods are widely used in environmental sciences; however, published studies using these methodologies in coral reef science are scarce. We compared the accuracy of the two most commonly used interpolation methods in all disciplines, inverse distance weighting (IDW) and ordinary kriging (OK), to predict the distribution and abundance of hard corals, octocorals, macroalgae, sponges and zoantharians and identify hotspots of these habitat-forming organisms using data sampled at three different spatial scales (5, 10 and 20 m) in Madagascar reef, Gulf of Mexico. The deeper sandy environments of the leeward and windward regions of Madagascar reef were dominated by macroalgae and seconded by octocorals. However, the shallow rocky environments of the reef crest had the highest richness of habitat-forming groups of organisms; here, we registered high abundances of octocorals and macroalgae, with sponges, Millepora alcicornis and zoantharians dominating in some patches, creating high levels of habitat heterogeneity. IDW and OK generated similar maps of distribution for all the taxa; however, cross-validation tests showed that IDW outperformed OK in the prediction of their abundances. When the sampling distance was at 20 m, both interpolation techniques performed poorly, but as the sampling was done at shorter distances prediction accuracies increased, especially for IDW. OK had higher mean prediction errors and failed to correctly interpolate the highest abundance values measured in situ, except for macroalgae, whereas IDW had lower mean prediction errors and high correlations between predicted and measured values in all cases when sampling was every 5 m. The accurate spatial interpolations created using IDW allowed us to see the spatial variability of each taxa at a biological and spatial resolution that remote sensing would not have been able to produce. Our study sets the basis for further research projects and conservation management in Madagascar reef and encourages similar studies in the region and other parts of the world where remote sensing technologies are not suitable for use.

Comparative mitogenomics, phylogeny and evolutionary history of Leptogorgia (Gorgoniidae)

Molecular analyses of the ecologically important gorgonian octocoral genus Leptogorgia are scant and mostly deal with few species from restricted geographical regions. Here we explore the phylogenetic relationships and the evolutionary history of Leptogorgia using the complete mitochondrial genomes of six Leptogorgia species from different localities in the Atlantic, Mediterranean and eastern Pacific as well as four other genera of Gorgoniidae and Plexauridae. Our mitogenomic analyses showed high inter-specific diversity, variable nucleotide substitution rates and, for some species, novel genomic features such as ORFs of unknown function. The phylogenetic analyses using complete mitogenomes and an extended mtMutS dataset recovered Leptogorgia as polyphyletic, and the species considered in the analyses were split into two defined groups corresponding to different geographic regions, namely the eastern Pacific and the Atlantic-Mediterranean. Our phylogenetic analysis based on mtMutS also showed a clear separation between the eastern Atlantic and South African Leptogorgia, suggesting the need of a taxonomic revision for these forms. A time-calibrated phylogeny showed that the separation of eastern Pacific and western Atlantic species started ca. 20Mya and suggested a recent divergence for eastern Pacific species and for L. sarmentosa-L. capverdensis. Our results also revealed high inter-specific diversity among eastern Atlantic and South African species, highlighting a potential role of the geographical diversification processes and geological events occurring during the last 30Ma in the Atlantic on the evolutionary history of these organisms.

Mitochondrial RNA processing in absence of tRNA punctuations in octocorals

BACKGROUND

Mitogenome diversity is staggering among early branching animals with respect to size, gene density, content and order, and number of tRNA genes, especially in cnidarians. This last point is of special interest as tRNA cleavage drives the maturation of mitochondrial mRNAs and is a primary mechanism for mt-RNA processing in animals. Mitochondrial RNA processing in non-bilaterian metazoans, some of which possess a single tRNA gene in their mitogenomes, is essentially unstudied despite its importance in understanding the evolution of mitochondrial transcription in animals.

RESULTS

We characterized the mature mitochondrial mRNA transcripts in a species of the octocoral genus Sinularia (Alcyoniidae: Octocorallia), and defined precise boundaries of transcription units using different molecular methods. Most mt-mRNAs were polycistronic units containing two or three genes and 5' and/or 3' untranslated regions of varied length. The octocoral specific, mtDNA-encoded mismatch repair gene, the mtMutS, was found to undergo alternative polyadenylation, and exhibited differential expression of alternate transcripts suggesting a unique regulatory mechanism for this gene. In addition, a long noncoding RNA complementary to the ATP6 gene (lncATP6) potentially involved in antisense regulation was detected.

CONCLUSIONS

Mt-mRNA processing in octocorals possessing a single mt-tRNA is complex. Considering the variety of mitogenome arrangements known in cnidarians, and in general among non-bilaterian metazoans, our findings provide a first glimpse into the complex mtDNA transcription, mt-mRNA processing, and regulation among early branching animals and represent a first step towards understanding its functional and evolutionary implications.

The Identification of Octocorals from the Northern Region of Straits of Malacca

Coral reefs in the northern region of the Straits of Malacca have a diverse group of octocorals growing on its bed. The octocorals identified in this study are from islands along the Straits. In this study, 23 specimens were identified, belonging to 4 sub-orders, which have been subdivided into 8 families. From these 8 families, 15 different genera have been identified. The identification process for this research was conducted based on five important keys; the external form and colouration, polyps or colonial and fundamental structure of colonies, monomorphic or dimorphic, the arrangement of polyps, and the arrangement of sclerites.