Symbiosis

ABSTRACT: Corals harbor a complex suite of beneficial microbial symbionts. Shuffling the composition of these symbionts could, in theory, help the host withstand rapidly emerging or geographically varying stressors without requiring genetic change to the coral itself. The relative impact of host qualities on microbiome (bacteria) composition should provide insight into the extent that shifting microbial symbionts can play in resilience to environmental disturbance on reefs. We sought to assess the differences in microbiome composition across a large spatial scale (between Puerto Rico and Bonaire; >700 km apart) and in response to localized anthropogenic impacts in 2 co-occurring Caribbean soft corals (Eunicea flexuosa and Gorgonia ventalina) with well-documented differing degrees of population genetic differentiation. Host species was the strongest determinant of microbiome composition, with between-hosts distinction due largely to differences in the abundant genera Endozoicomonas and Mycoplasma. Interestingly, the microbiome of the more genetically subdivided G. ventalina showed stronger differentiation between islands and in response to local anthropogenic impacts than the less subdivided E. flexuosa. For both hosts, anthropogenic impacts on microbiome composition were stronger in Bonaire. Again, Endozoicomonas was responsible for much of the differentiation between and within islands and included host- and island-specific sequence variants. The level of intra-species microbiome variation mirrored the known geographic differentiation of their hosts, a trend that is consistent in the literature for 8 other coral species. Thus, while potentially adaptive bacteria may shuffle in response to environmental changes, our findings suggest that most changes to microbiomes are likely constrained by host genetics.

The colonial stony coral genus Madracis is cosmopolitan, lives in shallow and deep water habitats, and includes zooxanthellate, azooxanthellate and facultative symbiotic species. One of its species, Madracis pharensis, has been recorded from the Mediterranean and East Atlantic, where it forms small knobby and facultative zooxanthellate colonies (also named M. pharensis f. pharensis), and from the tropical Caribbean, where it also occurs in a massive and zooxanthellate form (named M. pharensis f. luciphila by some). These two forms have been previously found to host different Symbiodinium species. In this study, species boundaries and phylogenetic relationships between these two Madracis pharensis forms (from the Mediterranean Sea and the Caribbean), M. senaria, and the Indo-west Pacific M. kirbyi were analyzed through an integrated systematics approach, including corallite dimensions, micromorphology and two molecular markers (ITS and ATP8). Significant genetic and morphological differences were found between all the examined Madracis species, and between M. pharensis from the Mediterranean Sea and M. pharensis f. luciphila from the Caribbean in particular. Based on these results, the latter does not represent a zooxanthellate ecomorph of the former but a different species. Its identity remains to be ascertained and its relationship with the Caribbean M. decactis, with which it bears morphologic resemblance, must be investigated in further studies. Overall, the presence of cryptic Madracis species in the Easter and Central Atlantic remains to be evaluated.

Abstract

Coral reefs are known to be among the most biodiverse marine ecosystems and one of the richest in terms of associations and species interactions, especially those involving invertebrates such as corals and sponges. Despite that, our knowledge about cryptic fauna and their ecological role remains remarkably scarce. This study aimed to address this gap by defining for the first time the spatial ecology of the association between the epibiont hydrozoan Nemalecium lighti and the Porifera community of shallow coral reef systems at Bonaire. In particular, the host range, prevalence, and distribution of the association were examined in relation to different sites, depths, and dimensions of the sponge hosts. We report Nemalecium lighti to be in association with 9 out of 16 genera of sponges encountered and 15 out of 16 of the dive sites examined. The prevalence of the hydroid–sponge association in Bonaire reef was 6.55%, with a maximum value of over 30%. This hydrozoan has been found to be a generalist symbiont, displaying a strong preference for sponges of the genus Aplysina, with no significant preference in relation to depth. On the contrary, the size of the host appeared to influence the prevalence of association, with large tubular sponges found to be the preferred host. Although further studies are needed to better understand the biological and ecological reason for these results, this study improved our knowledge of Bonaire’s coral reef cryptofauna diversity and its interspecific associations. View Full-Text

Hexactinellid sponges are important members of deep-sea benthic ecosystems because they provide available hard substrate habitats for filter-feeding invertebrates. However, symbioses between hexactinellid sponges and their symbionts are poorly known. Zoantharians associated with hexactinellid sponges have been reported widely from deep-sea marine ecosystems, either on the bodies or stalks of hexactinellid sponges. Despite these records, there has been a lack of research on their diversity and phylogenetic relationships. In this study, 20 specimens associated with amphidiscophoran and hexasterophoran sponges were collected from the waters of Australia and Japan in the Pacific, and from Curaçao in the southern Caribbean, and these were examined in addition to museum specimens. Based on molecular phylogenetic analyses and morphological observations, we formally describe two new genera and three new species of Zoantharia and report several previously described species. The results suggest at least two independent origins for the symbioses between hexactinellid sponges and zoantharians. Our results demonstrate that the diversity of hexactinellid sponge-associated zoantharians is much higher than has been previously thought. The new taxa described in this work further reconfirm that the deep-sea harbours high levels of undescribed zoantharian diversity.

Hexactinellid sponges are important members of deep-sea benthic ecosystems because they provide available hard substrate habitats for filter-feeding invertebrates. However, symbioses between hexactinellid sponges and their symbionts are poorly known. Zoantharians associated with hexactinellid sponges have been reported widely from deep-sea marine ecosystems, either on the bodies or stalks of hexactinellid sponges. Despite these records, there has been a lack of research on their diversity and phylogenetic relationships. In this study, 20 specimens associated with amphidiscophoran and hexasterophoran sponges were collected from the waters of Australia and Japan in the Pacific, and from Curaçao in the southern Caribbean, and these were examined in addition to museum specimens. Based on molecular phylogenetic analyses and morphological observations, we formally describe two new genera and three new species of Zoantharia and report several previously described species. The results suggest at least two independent origins for the symbioses between hexactinellid sponges and zoantharians. Our results demonstrate that the diversity of hexactinellid sponge-associated zoantharians is much higher than has been previously thought. The new taxa described in this work further reconfirm that the deep-sea harbours high levels of undescribed zoantharian diversity.

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Mutualistic symbiosis is a finely tuned relationship between two species in which each receives a service that increases its own fitness in exchange for providing service to another. The evolutionary stability of such a relationship is dependent on all species performing in an honest manner. However, many species that participate in mutualistic symbiosis have been observed cheating, or taking benefits beyond those evolutionarily agreed upon. This study attempted to identify factors that contribute to the frequency of cheating at cleaning stations on coral reefs. In these relationships, small fish and crustaceans clean parasites from larger host organisms. Client abundance and proximity of cleaning stations were examined as indicators for competition between cleaners and client choice. These factors put pressure on cleaners to cooperate by creating competition for clients. It was found that there was a greater abundance of clients at stations where cheating occurred less frequently, suggesting that clients may have chosen those stations for the higher quality service demonstrated. Proximity of cleaning stations did not seem to influence the frequency of cheating. Finally, obligate cleaners spent more time cleaning individual clients and cheated less frequently than facultative cleaners, demonstrating their higher dependence on the relationship. Understanding the factors that motivate cleaners and clients to cooperate at cleaning stations is an important component to comprehending community dynamics on reefs, but it is not as clear of a relationship as is commonly described.

This student research was retrieved from Physis: Journal of Marine Science XIV (Fall 2013)19: 33-40 from CIEE Bonaire.

Mutualisms and symbiotic relationships are common in the marine environment. Relationships between cleaner species, their hosts, and their client species are prime examples of these types of relationships. Cleaner shrimp, which are typically found in association with sea anemones, exhibit mutualistic behavior through the removal and consumption of parasites, injured tissue and various other particles from their client fish. The shrimp may inhabit their host anemone alone, or in groups ranging up to more than ten individuals. This study focused on the cleaner shrimp species Ancylomenes pedersoni and examined the relationship between the number of shrimp present at cleaning stations and the number of client fish visiting that station. The relationship between the number of shrimp present and the size of the host anemone was also investigated; the data collected did not support any significant relationships between the variables tested. All data was collected through observational studies and video analysis of specimens in the field. Because cleaner species are crucial to the heath of their clients and therefore to the overall heath of the reef, enhanced understanding of the behavior of A. pedersoni will contribute to better conservation of the species and consequently their client fish.

This student research was retrieved from Physis: Journal of Marine Science XV (Spring 2014)19: 1-8 from CIEE Bonaire.

Symbiotic Copepoda comprise a widespread, diverse, and abundant ecological group of small crustaceans associat- ed with various invertebrates, including octocorals. Some copepods, such as Lamippidae, are morphologically high- ly modified endoparasites found in galls or other cavities of various species of octocorals (Buhl-Mortensen and Mortensen 2004). Despite previous investigations of sym- biotic copepods inside Caribbean octocorals (Stock 1973), lamippid copepods associated with the common shallow-water sea fan Gorgonia ventalina Linnaeus, 1758, have not been reported so far. 

The detrimental effect of climate change induced bleaching on Caribbean coral reefs has been widely documented in recent decades. Several studies have suggested that increases in the abundance of thermally tolerant endosymbionts may ameliorate the effect of climate change on reefs. Symbionts that confer tolerance to temperature also reduce the growth rate of their coral host. Here, we show, using a spatial ecosystem model, that an increment in the abundance of a thermally tolerant endosymbiont (D1a) is unlikely to ensure the persistence of Caribbean reefs, or to reduce their rate of decline, due to the concomitant reduction in growth rate under current thermal stress predictive scenarios. Furthermore, our results suggest that given the documented vital rates of D1a-dominated corals, increasing dominance of D1a in coral hosts may have a detrimental effect by reducing the resilience of Caribbean reefs, and preventing their long-term recovery. This is because Caribbean ecosystems appear to be highly sensitive to changes in the somatic growth rate of corals. Alternative outcomes might be expected in systems with different community-level dynamics such as reefs in the Indo-Pacific, where the ecological costs of reduced growth rate might be far smaller.