The purpose of this study is to investigate the distribution and growth of the Black-Disease-causing Terpios hoshinota, including the effects of light, depth and nutrient on their growth at Green Island and Orchid Island. We also simulated the future coverage of black disease based on present data. Most T. hoshinota colonies were distributed at 2-3 meters (0-62 ind./100 m2) and the densities decrease with depth (0-5 ind./100 m2, at 10 m). The BD density at north and east coast were higher than that at west coast at Green Island, but no such difference occurred at Orchid Island. There were many small sponges and the number decrease with size. The frequency distribution of log-transformed lengths displayed a normal distribution. In comparing various recruitment models, i.e., normal, uniform, exponential and seasonal, we found that the actual size distribution is only compatible with the exponential temporal pattern. Thus more and more recruits may be entering the population continuously. The average growth rate of T. hoshinota is 0.18 cm/day, therefore the largest sponge at Green Island might have grown for only 2-4 years (340 cm).Two independent nutrient experiments did not detect the effects of nutrient addition on growth rates of the sponge. Comparison of BD densities and house numbers near the reef failed to reveal correlation. Most sponge colonies could not grow normally when shaded. The sponges transported to deeper water (15-20 m) might suffer tissue loss, but if they survived, they grew as fast as those controls at shallow waters (5-10 m). Growth rates of T. hoshinota differed by seasons within our testing period from April to July, 2008. The sponge expanded slower on non-coral substrate, at about 55% the rate, than those on corals. T. hoshinota grow on artificial substrate like glass, antifouling coatings, soft corals and other sponges. Using BD densities, sizes, growth rates and coral coverage, we simulated the BD colony distribution to predict its future coverage. We found that the sponge has the potential to cover the shallow reefs in 3-5 years at Green Island. The actual rate of increase at Gon-guan reef between 2007 and 2008 supports the above prediction.

Porifera (sponge) has been considered the earliest branching group of the metazoan crown, it plays an important role of evolution from protist to multicellular organisms. The sponges do not have tissues and organs. There are 15,000 species of sponges in the world. They contain a rich variety of secondary metabolites which may have the potential of becoming anticancer or antivirus drugs. The morphological characteristics of sponges may be affected by the environmental conditions and cause ambiguity and confusion in sponge identification. The complete mitochondrial DNAs of four Demospongiae sponges, Terpios hoshinota, Xestospongia testudinaria, Petrosia corticata, and Suberea clavata in Green Island were determined by PCR and primer walking. The sequences can be used for evolution and phylogenetic analyses. The complete mitochondrial genomes of the four sponges contain 20498 bp, 18988 bp, 18562 bp and 19559 bp, respectively. The genomes encode 2 rRNA genes (rns, rnl), 14 protein-coding genes (atp6, atp8-9, cox1-3, cob, nad1-6, and nad4L) and 25 tRNAs. All the genes of T. hoshinota, X. testudinaria, P. corticata are transcribed on the same strand. Whereas, some of the genes (nad 4L ~ tRNA-SerUGA) of S. clavata are encoded on the complementary strand. The results showed the differences between the mitochondrial DNA sequences of X. testudinaria and the Atlantic sponge, X. muta, are very limited, therefore, they may be reclassified as the same species. Meanwhile, S. clavata and Aplysina fulva are close phylogenetically. The conflict between molecular and morphology taxonomy should be re-examined.

The encrusting sponge Terpios hoshinota is a cyanobacteriosponge with symbiotic photosynthetic cyanobacteria. It covers live corals causing their death. Corals at Green Island were suspected to be infected by Terpios hoshinota in 2006, and field investigations indicated there was massive propagation of the species in both Green Island (Lyudao) and Orchid Island (Lanyu) in 2008 to 2010. We propose two hypotheses, either by Self-Seeding or by Long-Range Dispersal, that explain the fast propagation of Terpios hoshinota in the islands offshore of southeastern of Taiwan. We use ribosomal DNA and mitochondria DNA as molecular markers to investigate how the sponge disperses locally and in a greater geographic scale. A total of 110 samples, from Taiwan: Green Island, Orchid Island, and Kenting (Wanlitong). Japan: Okinawa, Nakijin, Miyako, Bise, Shiraho, Arahama Kumeshima, Yakomo (Okinoerabu), San (Takunoshima), and Xisha Island of China, were collected. Internal Transcribed Spacer 2 (ITS2) from ribosomal DNA and cytochrome oxidase I (COI) from mitochondria DNA are used as markers to infer population structure of Terpios hoshinota. No genetic variation within COI sequence over all sponges from Taiwan to Japan and China was found, although the only sponge sample from Wanlitong in Kenting had three variable sites, which suggest different species of Terpios hoshinota. Based on ITS2 analysis, haplotype diversity (h) is commonly high among most populations, but with different single haplotype found at Green Island and Arahama (Japan). Pairwise population differentiations (FST) are usually high and significant among populations supporting self-seeding, although Bise, Shiraho and Lanyu populations showed no significant differentiation that supports long-range dispersal. Analysis of Molecular Variance (AMOVA) shows no population subdivision; however, genetic differentiations among populations are significantly greater than within populations. TCS analysis indicates that single haplotype in Green Island is originated from Lanyu, and populations in Bise are widely dispersed over other sponge populations in Taiwan and Japan regions. By evidence of TCS analysis with nucleotide diversity, haplotype diversity and field investigation, Bise is the origin of Terpios hoshinota among populations within this study. Frequency of sequence haplotypes indicates one dominant haplotype is shared among most of the sponge populations, and the dominated sponge haplotype takes highest proportions of local populations. The existence of dominant haplotype may result from better dispersal or reproduction ability than other haplotype in populations. Nested clade analysis shows that populations mainly have restricted gene flow with some clade have contiguous range expansion. We suggest that populations of Terpios hoshinota propagate mainly by self-seeding method with occasional long-range dispersal event that leading to genetic connection among populations and obscuring evidence of isolation by distance in these populations. In Green Island, we consider local populations as undergoing explosion within past several years and propagate by self-seeding method coming from single lineage of Lanyu. Populations in Lanyu may come from Bise, Shiraho, and Yakomo, yet may still in status of population explosion. Populations in Japan may underwent founder effect with rapid population growth, while most populations are rarely interact with each other showing deep genetic differentiation among islands, and Bise is the origin of Terpios hoshinota in this study. Not all of the sponge individuals have ability to dominate local populations, expect for one special haplotype of Terpios hoshinota is capable of dominating local population in both range and quantity, which also has capability of spreading across islands as larger distances than its habitats range in Taiwan and Japan.