Coral kin aggregations exhibit mixed allogeneic reactions and enhanced fitness during early ontogeny

<p>Abstract</p> <p>Background</p> <p>Aggregated settlement of kin larvae in sessile marine invertebrates may result in a complex array of compatible and incompatible allogeneic responses within each assemblage. Each such aggregate can, therefore, be considered as a distinct self-organizing biological entity representing adaptations that have evolved to maximize the potential benefits of gregarious settlement. However, only sparse information exists on the selective forces and ecological consequences of allogeneic coalescence.</p> <p>Results</p> <p>We studied the consequences of aggregated settlement of kin larvae of <it>Stylophora pistillata </it>(a Red Sea stony coral), under controlled laboratory settings. When spat came into contact, they either fused, establishing a chimera, or rejected one another. A one-year study on growth and survivorship of 544 settled <it>S. pistillata </it>genotypes revealed six types of biological entities: (1) Single genotypes (SG); (2) Bi-chimeras (BC); (3) Bi-rejecting genotypes (BR); (4) Tri-chimera entities (TC); (5) Three-rejecting genotypes (TR); and (6) Multi-partner entities (MP; consisting of 7.5 ± 2.6 partners). Analysis of allorecognition responses revealed an array of effector mechanisms: real tissue fusions, transitory fusions and six other histoincompatible reactions (borderline formation, sutures, overgrowth, bleaching, rejection, and partner death), disclosing unalike onsets of ontogeny and complex modes of appearance within each aggregate. Evaluations at the entity level revealed that MP entities were the largest, especially in the first two months (compared with SG: 571% in the first month and 162% in the seventh month). However, at the genotype level, the SG entities were the largest and the colonies with the highest-cost-per-genotype were the TR and the MP colonies. The cost was calculated as reduced average genotype size, from 27% and 12% in the first month to 67% and 64% in the seventh month, respectively. In general, MP exhibited the highest survivorship rate (85%, after one year) and SG the lowest (54%).</p> <p>Conclusion</p> <p>In view of the above, we suggest that the driving force behind gregarious kin settlements in <it>Stylophora pistillata </it>stems from gained benefits associated with the immediate and long-term increase in total size of the MP entity, whereas survivorship rates did not draw a parallel link. Furthermore, the biological organization of MP entity exhibits, simultaneously, an intricate network of rejecting and fusible interactions in a single allogeneic intimate arena, where proposed benefits surpass costs incurred by discord among founders. Above results and documentations on gregarious settlement in other marine taxa bring us to suggest that the 'group level' of kin aggregates may serve as a ubiquitous legitimate selection entity in the evolution of a sessile mode of life in marine organisms.</p

Seychelles Lagoon Provides Corals with a Refuge from Bleaching

An extensive bleaching event in the summer of the year 1997-1998 affected most reefs along East Africa's shores. In the aftermath of that episode, the reefs of Île Alphonse in the Seychelles were examined and it was found that reefs along the seaward slopes of the island lost >95% of their branching coral colonies, with considerably higher survival of massive species. Île Alphonse features a nearly circular shallow lagoon, with steep seaward slopes. Contrary to our expectations, mortality in the warmer lagoon was far lower than of coral colonies on the surrounding slopes, bathed in deeper and cooler waters. We suggest that corals in the lagoon were protected from UV radiation by leachate stemming from seagrass leaves steeped in the lagoon. Our measurements in the lagoon showed a strong attenuation of ultraviolet radiation, not observed in the waters outside the lagoon, and laboratory examination confirmed that the strong UV absorption of substances leached into seawater from decomposing leaves of the seagrass Thalassodendron (=Cymodocea) testudinaceum. Our findings demonstrate the synergism between elevated seawater temperature and UV radiation in triggering bleaching on shallow reefs

INTERSPECIFIC AGGRESSIVE BEHAVIOR OF THE CORALLIMORPHARIAN CORYNACTIS CALIFORNICA (CNIDARIA: ANTHOZOA): EFFECTS ON SYMPATRIC CORALS AND SEA ANEMONES

Volume: 173Start Page: 110End Page: 12

Phosphate excretion by anemonefish and uptake by giant sea anemones: demand outstrips supply

International audiencehigh biodiversity on coral reefs results in part from tight nutrient cycling among symbiotic organisms, such as within the obligate associations among some damselfishes, cnidarians, and zooxanthellae. Some anemonefish excrete ammonia 20-50× faster than host anemones can absorb this nutrient, leading to significant growth of the anemones and their zooxanthellae. In contrast, little is known about phosphate transfer in this major coral reef mutualism. We determined rates of phosphate excretion by anemonefish and uptake by giant sea anemones under laboratory conditions, and compared them with known rates of ammonia transfer in this symbiosis. Immediately after feeding with a phosphate-rich diet, anemonefish excreted phosphate at slow rates of 0.07 ± 0.01 µmol P g-1 d-1 , which did not vary significantly with body size. Starved anemones that had been cultured with phosphate supplements absorbed phosphate at a significantly slower rate (0.18 ± 0.03 µmol P g-1 d-1) than did those cultured with either no supplements or with anemonefish, which absorbed phosphate at similarly rapid rates (0.54 ± 0.01 and 0.51 ± 0.14 µmol P g-1 d-1 respectively). We conclude that under laboratory conditions, anemones absorb phosphate up to 6.6× faster than the rate at which it is excreted by their anemonefish, and thus fish do not appear to provide sufficient phosphate to their hosts through this pathway. Anemones may get most of their phosphorus via ingestion of fish feces and/or mucus, or via the ingestion of prey

Effects of Allogeneic Contact on Life-History Traits of the Colonial Ascidian Botryllus schlosseri in Monterey Bay

Volume: 205Start Page: 133End Page: 14

Variation in the abundance of <i>Diadema antillarum</i> and other sea urchin species grouped (<i>Arbacia punctulata</i> and <i>Eucidaris tribuloides</i>) among patch reefs ranked by level of snorkeling in Akumal Bay, Mexico.

<p>N = 10 transects examined per reef.</p

Spatial and temporal variation in visitor abundance at Akumal Bay, Mexico, during July 2015.

<p>Shown are numbers of visitors ( ± SE, N = 5 d) observed every 2 h between sunrise (06:00) and near sunset (18:00) in: (a) 4 on-land beach sections, and (b) 6 in-water sections (also referred to as snorkelers). See map (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0184175#pone.0184175.g001" target="_blank">Fig 1</a>) and text for details.</p

Results of simultaneous tests for general linear hypotheses of variation in visitor abundance among sections of Akumal Bay, Mexico.

<p>Shown are Z and P values respectively for post-hoc pairwise comparisons between bay sections: (a) on land during peak use at 14:00 each day in 4 sections (A-D), and (b) in the water during peak use at 16:00 each day in 6 sections (E-J).</p

Variation in the percent cover of stony corals (left) and macroalgae (right) among patch reefs ranked by level of snorkeling in Akumal Bay, Mexico.

<p>N = 10 transects examined per reef.</p