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Reef-building corals are found across > 30° of latitude from tropical to temperate regions, where they occupy habitats greatly differing in seawater temperature and light regimes. It remains largely unknown, however, how the demography of corals differs across this gradient of environmental conditions. Variation in coral growth is especially important to coral populations, because aspects of coral demography are dependent on colony size, with both fecundity and survivorship increasing with larger colonies. Here we tested for latitudinal variation in annual growth rate and survival of juvenile corals, using 11 study locations extending from 17° S to 33° N in the West and South Pacific. Regression analyses revealed a significant decline in annual growth rates with increasing latitude, whereas no significant latitudinal pattern was detected in annual survival. Seawater temperature showed a significant and positive association with annual growth rates. Growth rates varied among the four common genera, allowing them to be ranked Acropora > Pocillopora > Porites > Dipsastraea. Acropora and Pocillopora showed more variation in growth rates across latitudes than Porites and Dipsastraea. Although the present data have limitations with regard to difference in depths, survey periods, and replication among locations, they provide evidence that a higher capacity for growth of individual colonies may facilitate population growth, and hence population recovery following disturbances, at lower latitudes. These trends are likely to be best developed in Acropora and Pocillopora, which have high rates of colony growth.

Molecular cytogenetic investigation was carried out on the scleractinian coral, Acropora pruinosa (A. pruinosa). Conventional Giemsa staining techniques for karyotyping, such as G- and C-banding, were conducted. Karyotype analysis showed mosaicism of cells with two different chromosome numbers, 28 and 29, in the same embryo. The C-band positive portions appeared on the centromeres of most chromosomes and along the entire length of the unpaired chromosome 15 in cells with 29 chromosomes. Fluorescence in situ hybridization (FISH) revealed that the loci of rRNA genes (rDNA), 5S and 18S/28S, were located on chromosomes 4 and 2, respectively. Whole genome hybridization (WGH) with sperm DNA showed distinct signals not only on all centromeric regions but also on a whole unpaired chromosome 15. Comparative genomic hybridization (CGH) using DNAs from sperm and unfertilized eggs revealed that the unpaired chromosome 15 has sperm-specific DNA sequences. We therefore hypothesized the existence of a sex-related chromosome in A. pruinosa. In this study, we have presented a tentative karyotype of this coral, based on banding results, and described FISH, WGH, and CGH results. Moreover, we successfully cloned and sequenced three clones; AP-5S for 5S rDNA, AP-18S for 18S/28S rDNA, and AP-unpaired chromosome 15q for the unpaired chromosome 15-specific DNA. These molecular cytogenetic approaches will help establish a more exact karyotype of corals and promote understanding of coral genetics, including chromosome evolution. These findings will help to verify the method of classification of complex scleractinian corals.

The discovery of multi-species synchronous spawning of scleractinian corals on the Great Barrier Reef in the 1980s stimulated an extraordinary effort to document spawning times in other parts of the globe. Unfortunately, most of these data remain unpublished which limits our understanding of regional and global reproductive patterns. The Coral Spawning Database (CSD) collates much of these disparate data into a single place. The CSD includes 6178 observations (3085 of which were unpublished) of the time or day of spawning for over 300 scleractinian species in 61 genera from 101 sites in the Indo-Pacific. The goal of the CSD is to provide open access to coral spawning data to accelerate our understanding of coral reproductive biology and to provide a baseline against which to evaluate any future changes in reproductive phenology., info:eu-repo/semantics/published