Corals of the world

Systema Naturae includes representatives of every major lineage of the animal phylum Cnidaria.  However, Linnaeus did not classify the members of the phylum as is now done, and the diversity of the group is not well represented.  We contrast the Linnaean perspective on cnidarian diversity with the modern, phylogenetic perspective.  For each order, we detail diversity at the family level, providing phylogenetic context where possible.

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The phylum Cnidaria: A review of phylogenetic patterns and diversity 300 years after Linnaeus

Food webs are descriptions of who eats whom in an ecosystem. Although extremely complex and variable, their structure possesses basic regularities1,2,3,4,5,6. A fascinating question is to find a simple model capturing the underlying processes behind these repeatable patterns. Until now, two models have been devised for the description of trophic interactions within a natural community7,8. Both are essentially based on the concept of ecological niche, with the consumers organized along a single niche dimension; for example, prey size8,9. Unfortunately, they fail to describe adequately recent and high-quality data. Here, we propose a new model built on the hypothesis that any species' diet is the consequence of phylogenetic constraints and adaptation. Simple rules incorporating both concepts yield food webs whose structure is very close to real data. Consumers are organized in groups forming a nested hierarchy, which better reflects the complexity and multidimensionality of most natural systems.

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Phylogenetic constraints and adaptation explain food-web structure

Taxonomic classification of the reef coral family Mussidae (Cnidaria: Anthozoa: Scleractinia)

In spite of more than one century and half of studies, mechanisms of coral biomineralization, leading to coral growth and reef formation, still remain poorly known, although major global threats to coral reefs, such as ocean acidification, primarily affect this process. Coral skeletons are used as environmental archives but the vital processes that govern incorporation of trace elements and stable isotope are still unknown. Our knowledge on coral physiology is restricted to the organismal level due to the lack of appropriate cell model, however the advent of new approaches, such as coral genomic, is changing drastically our knowledge on these animals even if only a few data are available concerning the field of biomineralization. This chapter reviews our present knowledge and discusses the different theories on coral calcification, from the molecular to the reef level. Conclusion is presented in a list of key issues to be resolved in order to understand the intimate mechanisms of calcification of corals, essential to determine the origin of the sensitivity of corals to ocean acidification, to improve paleoceanographic reconstructions or coral reef management, or “just” to understand how genes of a soft organism control the formation of an extracellular 3D-skeleton.

Coral Calcification, Cells to Reefs

The focus of this paper is to provide an overview of historical and modern accounts of scleractinian evolutionary relationships and classification. Scleractinian evolutionary relationships proposed in the 19th and the beginning of the 20th centuries were based mainly on skeletal data. More in-depth observations of the coral skeleton showed that the gross-morphology could be highly confusing. Profound differences in microstructural and microarchitectural characters of e.g., Mesozoic microsolenine, pachythecaliine, stylophylline, stylinine, and rhipidogyrine corals compared with nominotypic representatives of higher-rank units in which they were classified suggest their separate (?subordinal) taxonomic status. Recent application of molecular techniques resulted in hypotheses of evolutionary relationships that differed from traditional ones. The emergence of new and promising research methods such as high-resolution morphometrics, analysis of biochemical skeletal data, and refined microstructural ob...

/pdf/towards-a-new-synthesis-of-evolutionary-relationships-and-cbbg7adkq7.pdf

Towards a new synthesis of evolutionary relationships and classification of scleractinia

INVITED: Discovery of a Cretaceous scleractinian coral with a calcitic skeleton

Study of the crystallographic architecture of corals at the nanoscale by scanning transmission X-ray microscopy and transmission electron microscopy.

The Early Carnian (Upper Triassic) phaceloid coral originally described by Volz (1896) as Hexastraea fritschi, type species of Quenstedtiphyllia Melnikova, 1975, reproduced asexually by ''Taschenknospung'' (pocket-budding), a process documented herein for the first time. This type of budding is recognized only in the Amphiastraeidae, a family thus far recorded only from Jurassic- Cretaceous strata. Similar to amphiastraeids, Quenstedtiphyllia fritschi (Volz, 1896) has separate septal calcification centers and a mid- septal zone built of serially arranged trabeculae. The most important discriminating characters of the new amphiastraeid subfamily Quenstedtiphylliinae are one-zonalendotheca and radial symmetry of the corallite in the adult stage (in contrast to two-zonal and bilateral symmetry in the adult stage in Amphiastraeinae). Quenstedtiphyllia fritschi shares several primitive skeletal characters (plesiomorphies) with representatives of Triassic Zardinophyllidae and, possibly, Paleozoic plerophylline rugosans: e.g., thick epithecal wall and strongly bilateral early blastogenetic stages with the earliest corallite having one axial initial septum. To interpret the phylogenetic status of amphiastraeid corals, we performed two analyses using plerophylline rugosans and the solitary scleractinian Protoheterastraea,respec- tively, as the outgroups. The resulting phylogenetic hypotheses support grouping the Zardinophyllidae with the Amphiastraeidae in the clade Pachythecaliina (synapomorphy: presence of pachytheca). Taschenknospung is considered an autapomorphy for the Amphiastraei- dae. This study is the first attempt to analyze the relationships of the Triassic corals cladistically.

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J. Stolarski

Papers

Towards a new synthesis of evolutionary relationships and classification of scleractinia

INVITED: Discovery of a Cretaceous scleractinian coral with a calcitic skeleton

Study of the crystallographic architecture of corals at the nanoscale by scanning transmission X-ray microscopy and transmission electron microscopy.

Triassic roots of the amphiastraeid scleractinian corals