Quantifying the colony shape of the Montastraea annularis species complex

The reef coral Montastraea annularis has been used in a wide range of investigations. Recently, it has been recognized as a complex of three species based on field observations of the variation in colony shape. These observations have also been confirmed by molecular methods as well as morphometrics on individual corallites in the colonies. This paper presents a new quantitative method for measuring overall colony shape based on geostatistics. Seventeen colonies collected from San Blas, Panama in 1995 and 1996 were examined using the Polhemus 3SPACE FASTRAK system to construct three-dimensional coordinates of the center of several hundred corallites in each colony. This method measures the larger bumps or “ridges” as well as the smaller bumps or “lumps” of the colonies. Variograms were then calculated for all the specimens and the lag distances and the values of the variogram were used in a multivariate statistical analysis. Overall, this method indicated that M. annularis and Montastaea faveolata overlap in their relative amount of bumpiness in colony shape while Montastraea franksi is distinct from the other two species. This method has implications for both the modern and fossil record of Montastraea as well as other organisms with similar shapes.     

The complete mitochondrial genome of the black coral Chrysopathes formosa (Cnidaria:Anthozoa:Antipatharia) supports classification of antipatharians within the subclass Hexacorallia

Black corals comprise a globally distributed shallow- and deep-water taxon whose phylogenetic position within the Anthozoa has been debated. We sequenced the complete mitochondrial genome of the antipatharian Chrysopathes formosa to further evaluate its phylogenetic relationships. The circular mitochondrial genome (18,398 bp) consists of 13 energy pathway protein-coding genes and two ribosomal RNAs, but only two transfer RNA genes (trnM and trnW), as well as a group I intron within the nad5 gene that contains the only copies of nad1 and nad3. No novel genes were found in the antipatharian mitochondrial genome. Gene order and genome content are most similar to those of the sea anemone Metridium senile (subclass Hexacorallia), with differences being the relative location of three contiguous genes (cox2-nad4-nad6) and absence (from the antipatharian) of a group I intron within the cox1 gene. Phylogenetic analyses of multiple protein-coding genes support classifying the Antipatharia within the subclass Hexacorallia and not the subclass Ceriantipatharia; however, the sister-taxon relationships of black corals within Hexacorallia remain inconclusive.     

DNA sequences of the mitochondrial COI gene have low levels of divergence among deep-sea octocorals (Cnidaria: Anthozoa)

We are analyzing genetic diversity in deep-seamount octocorals with the ultimate goal of studying the effect of retention and dispersal of larvae on genetic population structure. Here we report on the sequence diversity of the mitochondrial cytochrome oxidase I (COI) gene among 11 species. Uncorrected pairwise sequence divergences ranged from 0.4–10.3% for comparisons among species spanning the intrageneric to interordinal levels. Relative to other invertebrates, these divergences are very low, suggesting that COI may not be useful as a genetic marker for studying dispersal among deep-sea octocoral populations. Possible explanations for the reduced rates of divergence observed include a lower rate of evolution for octocoral mitochondrial genomes and the presence of a gene, mtMSH, which may code for a mitochondrial DNA mismatch-repair system. We report the finding of mtMSH in three deep-sea octocorals (Acanthogorgia sp., Corallium ducale, and Paramuricea sp.), which brings the total published observations of this gene to six species, all in the subclass Octocorallia.     

A study of the spirocytes from the Ceriantharia and Actiniaria (Cnidaria: Anthozoa)

Summary The structure and ultrastructure of ceriantharian and actiniarian spirocysts were compared. In the ceriantharian spirocyst, the apical cap consisted of two layers and the wall consisted of three, whereas in the actiniarian spirocyst, the number of layers was reversed. The inner wall of the ceriantharian spirocyst was smooth in longitudinal section whilst that of the actiniarian was serrated. The apical ends of ceriantharian spirocytes posessed either a set of microvilli or an arrangement that included both microvilli and a flagellum. The actiniarian spirocyte possessed only microvilli. Fine tubules occupying the undischarged tube of the ceriantharian spirocysts were of both moderate and strong electron densities, whilst those of the actiniarian were consistently electrondense. Undischarged ceriantharian spirocytes possessed tubules situated in the pleats and in the centre of the tube, whilst the tubes of undischarged actiniarian spirocytes possessed only centrally placed tubules. Fine electron-dense filaments linking the cell membrane to the spirocyst were present at the apical ends of actiniarian spirocytes. A different electron-dense network of filaments was present in the apical end of ceriantharian spirocytes. All cnidae of ceriantharians lacked tripartite opercula whilst the nematocysts of actiniarians possessed them. Primitive features of ceriantharian cnidae are discussed.     

Pachyseris inattesa sp. n. (Cnidaria,Anthozoa, Scleractinia): a new reef coral species from the Red Sea and its phylogenetic relationships

A new scleractinian coral species, Pachyseris inattesa sp. n., is described from the Red Sea. Despite a superficial resemblance with some species in the agariciid genus Leptoseris with which it has been previously confused, P. inattesa sp. n. has micro-morphological characters typical of the genus Pachyseris. This genus, once part of the Agariciidae, is comprised of five extant species and is widely distributed throughout the tropical Indo-Pacific. It is currently incertae sedis as a result of recent molecular analysis and appears to be closely related to the Euphylliidae. A molecular phylogenetic reconstruction including P. inattesa sp. n., the genus type species P. rugosa, and P. speciosa, all present in the Red Sea, was performed using the mitochondrial intergenic spacer between COI and 16S-rRNA. The results confirm that P. inattesa sp. n. is a monophyletic lineage closely related to the other Pachyseris species examined.     

Examination of the Montastraea annularis Species Complex (Cnidaria: Scleractinia) Using ITS and COI Sequences

The Caribbean coral Montastraea annularis has recently been proposed to be a complex of at least three sibling species. To test the validity of this proposal, we sequenced the ITS region of the nuclear ribosomal RNA gene family (ITS-1, 5.8S, and ITS-2), and a portion of the mitochondrial DNA gene cytochrome c oxidase subunit I (COI) from the three proposed species (M. annularis, M. faveolata, and M. franksi) from Florida reefs. The ITS fragment was 665 nucleotides long and had 19 variable sites, of which 6 were parsimony-informative sites. None of these sites was fixed within the proposed species. The COI fragment was 658 nucleotides long with only two sites variable in one individual. Thus, under both the biological species concept and the phylogenetic species concept, the molecular evidence gathered in this study indicates the Montastraea annularis species complex to be a single evolutionary entity as opposed to three distinct species. The three proposed Montastraea species can interbreed, ruling out prezygotic barriers to gene flow (biological species concept), and the criterion of monophyly is not satisfied if hybridization is occurring among taxa (phylogenetic species concept). Received January 20, 1998; accepted September 30, 1998.     

Cyphastrea kausti sp. n. (Cnidaria,Anthozoa, Scleractinia), a new species of reef coral from the Red Sea

A new scleractinian coral species, Cyphastrea kausti sp. n., is described from 13 specimens from the Red Sea. It is characterised by the presence of eight primary septa, unlike the other species of the genus, which have six, ten or 12 primary septa. The new species has morphological affinities with Cyphastrea microphthalma, from which it can be distinguished by the lower number of septa (on average eight instead of ten), and smaller calices and corallites. This species was observed in the northern and central Red Sea and appears to be absent from the southern Red Sea.     

Effects of pressure on swimming behavior in planula larvae of the coral Porites astreoides (Cnidaria, Scleractinia)

Mechanisms governing the behavior of coral planulae are not well understood, particularly those manifesting themselves between the time when the larvae are released and when they settle. Larvae from the hermatypic coral Porites astreoides Lamarck were exposed to different levels of hydrostatic pressure—103.4, 206.9, 310.3, 413.8, and 517.1 kPa (including ambient pressure). Data were collected at stops of the above pressures for 15 min each, respectively. This was done in both an increasing sequence and a decreasing one. When exposed to increases in pressure from 103.4 kPa, larvae swam upward (negative barotaxis) in a spiraling motion. Upon exposure to decreasing pressure from 517.1 kPa, larvae moved downward (positive barotaxis), but the magnitude of the vertical movement was much less than in the case of increasing pressure. This suggests that these larvae are more sensitive to increased pressure than decreasing pressure. High variance was also observed in the responses of these larvae at both the intra- and inter-colony levels. Thus, this behavioral trait is variable within the population. The trait may be genetically based, and thus may be susceptible to alteration by natural selection, although this remains to be demonstrated. This study is the first to document these behavioral mechanisms in coral larvae.     

Two new dimorphic soft-coral species (Anthozoa: Octocorallia) from Antarctica

Sphaeralcyon shackletonisp. nov. and Sphaeralcyon scottisp. nov. are described and illustrated from material collected at the Scotia Sea and Weddell Sea on the Polarstern cruises ANT XIX/3 (ANDEEP-I), ANT XIX/5 (LAMPOS), and ANT XXI/2 (BENDEX). With the discovery of Sphaeralcyon shackletoni and S. scotti, three species are now known in the genus Sphaeralcyon, all them reported from the Southern Ocean. The diagnosis of the genus has been slightly modified to accommodate some of the characters of the new species.     

Patterns of association between Symbiodinium and members of the Montastraea annularis species complex on spatial scales ranging from within colonies to between geographic regions

Patterns of associations between coral colonies and the major clades of zooxanthellae can vary across scales ranging from individual colonies to widely separated geographic regions. This is exemplified in this study of the Montastraea annularis species complex from six sites on the Mesoamerican Reef, Belize and nine sites in the Bocas del Toro archipelago, Panama. Restriction fragment length polymorphism (RFLP) analysis of small subunit ribosomal DNA (SSU rDNA) was used to identify the zooxanthellae. In Belize (M. annularis), Symbiodinium B (79% of the colonies), Symbiodinium A, and Symbiodinium C were observed. In Panama (primarily M. franksi, but also M. annularis and M. faveolata), there was greater diversity and evenness with Symbiodinium A, B, C, C′ (a new symbiont) and D all being common in at least some host/habitat combinations. Non-metric multidimensional scaling ordinations showed that distribution patterns of symbionts across sites are best explained by enclosure (relative influence of open ocean vs. coastal water) and total suspended solids. Because members of clade D are known to be temperature resistant and Symbiodinium C′ was found in environments characterized by high sedimentation, these Panamanian reefs may have importance from a management perspective as reservoirs of corals better able to tolerate human impacts.     

Spawning of the colonial coral <Emphasis Type=Italic>Cladocora caespitosa</Emphasis> (Anthozoa,Scleractinia) in the Southern Adriatic Sea

Data on sexual reproduction of scleractinian coral species living in temperate zones, particularly in the Mediterranean Sea, are quite scarce. This paper describes sexual reproduction of the colonial coral Cladocora caespitosa from Veliko jezero (Mljet Island) in the Adriatic Sea. Spawned orange eggs and white sperm bundles were observed on the coral bank of C. caespitosa two nights before the full moon (20 June 2005) coinciding with increasing water temperature and correlated with the lunar cycle. Spawning was observed during five nights, involving about 30% of the colonies from the coral bank. Different colonies on the bank released only one type of gamete during the reproductive period. The diameter of the sperm bundles ranged from 100 to 200 μm (average 163 μm; SD = 47.08), while the female gametes diameter ranged from 300 to 500 μm (average 416 μm; SD = 73.12).     

Serial reconstruction of the mitochondrial reticulum in the coccolithophorid,Pleurochrysis carterae (Prymnesiophyceae)

Summary A serial reconstruction of the chondriome ofPleurochrysis carterae (Braarudet Fagerland) Christensen has revealed a single, reticulated mitochondrion branching throughout the cell. The occurrence of a single mitochondrion in unicellular algae is briefly reviewed and its phylogenetic significance is discussed.     

Evolutionary origins of germline segregation in Metazoa: evidence for a germ stem cell lineage in the coral Orbicella faveolata (Cnidaria,Anthozoa)

The ability to segregate a committed germ stem cell (GSC) lineage distinct from somatic cell lineages is a characteristic of bilaterian Metazoans. However, the occurrence of GSC lineage specification in basally branching Metazoan phyla, such as Cnidaria, is uncertain. Without an independently segregated GSC lineage, germ cells and their precursors must be specified throughout adulthood from continuously dividing somatic stem cells, generating the risk of propagating somatic mutations within the individual and its gametes. To address the potential for existence of a GSC lineage in Anthozoa, the sister-group to all remaining Cnidaria, we identified moderate- to high-frequency somatic mutations and their potential for gametic transfer in the long-lived coral Orbicella faveolata (Anthozoa, Cnidaria) using a 2b-RAD sequencing approach. Our results demonstrate that somatic mutations can drift to high frequencies (up to 50%) and can also generate substantial intracolonial genetic diversity. However, these somatic mutations are not transferable to gametes, signifying the potential for an independently segregated GSC lineage in O. faveolata. In conjunction with previous research on germ cell development in other basally branching Metazoan species, our results suggest that the GSC system may be a Eumetazoan characteristic that evolved in association with the emergence of greater complexity in animal body plan organization and greater specificity of stem cell functions.     

A phylogeny of Chinese species in the genus Phrynocephalus (Agamidae) inferred from mitochondrial DNA sequences

We investigated the phylogenetic relationships among most Chinese species of lizards in the genus Phrynocephalus (118 individuals collected from 56 populations of 14 well-defined species and several unidentified specimens) using four mitochondrial gene fragments (12S rRNA, 16S rRNA, cytochrome b, and ND4-tRNA(LEU)). The partition-homogeneity tests indicated that the combined dataset was homogeneous, and maximum-parsimony (MP), neighbor-joining (NJ), maximum-likelihood (ML) and Bayesian (BI) analyses were performed on this combined dataset (49 haplotypes including outgroups for 2058bp in total). The maximum-parsimony analysis resulted in 24 equally parsimonious trees, and their strict consensus tree shows that there are two major clades representing the Chinese Phrynocephalus species: the viviparous group (Clade A) and the oviparous group (Clade B). The trees derived from Bayesian, ML, and NJ analyses were topologically identical to the MP analysis except for the position of P. mystaceus. All analyses left the nodes for the oviparous group, the most basal clade within the oviparous group, and P. mystaceus unresolved. The phylogenies further suggest that the monophyly of the viviparous species may have resulted from vicariance, while recent dispersal may have been important in generating the pattern of variation among the oviparous species.     

Serial reconstruction of the mitochondrial reticulum in the antarctic flagellate,Pyramimonas gelidicola (Prasinophyceae,Chlorophyta)

Summary A serial reconstruction ofPyramimonas gelidicola McFadden, Moestrup andWetherbee has revealed a large reticulated mitochondrion branching throughout the cell. The possibility of single mitochondria in other members of thePrasinophyceae and the uniformity of the morphology of this organelle within the class is discussed.     

The complete mitochondrial DNA sequence of the cestode Echinococcus multilocularis (Cyclophyllidea: Taeniidae)

The 13,738 bp mitochondrial DNA from the cestode Echinococcus multilocularis has been sequenced. It contains two major noncoding regions and 36 genes (12 for proteins involved in oxidative phosphorylation, two for rRNAs and 22 for tRNAs) but a gene for ATPase subunit 8 is missing. All genes are transcribed in the same direction. Putative secondary structures of tRNAs indicate that most of them are conventional clover leaves but the dihydrouridine arm is unpaired in tRNA(Ser(AGN)), tRNA(Ser(UCN)), tRNA(Arg) and tRNA(Cys). The base composition at the wobble positions of fourfold degenerate codon families is highly biased toward U and against C.