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 Unfortunately, most of these data remain unpublished which limits our understanding of regional and global reproductive patterns.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 The CSD includes 6178 observations (3085 of which were unpublished) of the time or day of spawning for over 300 scleractinian species in 61 genera from 101 sites in the Indo-Pacific.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.
Multi-species spawning is reported in the coral genus Acropora, but hybridization in nature rarely occurs because of the incompatibility of gametes and the timing of spawning. However, the evolutionary relationships between gamete compatibility and spawning time are obscure. Investigations of gamete compatibility in sister species that spawn at different times may provide clues to answering this question. Acropora sp. 1 has been defined as a cryptic species of Acropora digitifera, and they are morphologically similar, but spawn in different months, suggesting that they are either a cryptic species or a different species. We examined the morphology and conducted crossing experiments using cryopreserved sperm. The morphologies (branch length, branch width, and outer diameter of axial corallites) of A. digitifera and Acropora sp. 1 differed significantly. A phylogenetic tree of partial Pax-C nuclear sequences from A. digitifera and Acropora sp. 1 shows that they are monophyletic and closely related genetically, based on F ST values and P-distance. These results imply that these two species originated recently from a common ancestor. In addition, cryopreserved sperm from both A. digitifera and Acropora sp. 1 showed bidirectional inter-crossing (cryopreserved sperm of A. digitifera and eggs of Acropora sp. 1 from Sesoko: 32.1 ± 6.7 %, control-conspecific cryopreserved sperm and eggs: 46.1 ± 10.6 %; cryopreserved sperm of Acropora sp. 1 and eggs of A. digitifera from Oku: 63.3 ± 16.6 %, control: 83.6 ± 6.0 %). The results suggest that the gametes of these two species are compatible and that the pre-zygotic isolation mechanism is relaxed because their gametes do not interact. Overall, these two species should be classified as distinct species, and changes in spawning time are related to speciation in a similar gamete recognition system.
The Type III flagellar protein export apparatus of bacteria consists of five or six membrane proteins, notably FlhA, which controls the export of other proteins and is homologous to the large family of FHIPEP export proteins. FHIPEP proteins contain a highly-conserved cytoplasmic domain. We mutagenized the cloned Salmonella flhA gene for the 692 amino acid FlhA, changing a single, conserved amino acid in the 68-amino acid FHIPEP region. Fifty-two mutations at 30 positions mostly led to loss of motility and total disappearance of microscopically visible flagella, also Western blot protein/protein hybridization showed no detectable export of hook protein and flagellin. There were two exceptions: a D199A mutant strain, which produced short-stubby flagella; and a V151L mutant strain, which did not produce flagella and excreted mainly un-polymerized hook protein. The V151L mutant strain also exported a reduced amount of hook-cap protein FlgD, but when grown with exogenous FlgD it produced polyhooks and polyhook-filaments. A suppressor mutant in the cytoplasmic domain of the export apparatus membrane protein FlhB rescued export of hook-length control protein FliK and facilitated growth of full-length flagella. These results suggested that the FHIPEP region is part of the gate regulating substrate entry into the export apparatus pore.
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