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Chronic outbreaks of the coral eating crown-of-thorns starfish (Acanthaster planci) have devastated coral communities throughout the Ryukyu Islands in the past four decades. Since A. planci has high fecundity and long larval duration, knowledge of reproductive timing and larval dispersal are keys to understanding mechanisms of successive recruitment and consequent outbreaks of adults. As the first step to acquiring this knowledge, we monitored water temperature and peak spawning periods using gonad observation. A total of 379 A. planci specimens were collected from

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Pocillopora acuta Lamarck, 1816, that had long been treated as a junior synonym of Pocillopora damicornis (Linnaeus, 1758), was resurrected in Australia based on differences in the mitochondrial open reading frame (ORF) sequences with 6-8 nucleotide differences in 840 bp (Schmidt-Roach et al. 2014). To investigate whether P. acuta exists in Japan, we collected 73 colonies with P. damicornis-like morph from eight locations that are a maximum of 44.4 km apart around Yaeyama Islands (24°13′-24′ N, 123°41′-124°07′ E), southwestern-most islands of Japan, and analyzed their mitochondrial ORF sequences. We found that the DNA sequences of 72 of the 73 samples were identical to those of Australian P. acuta (e.g. JX985592-6; they are still registered as P. damicornis "type beta SSR-2012"), while the remaining one gave sequences identical to those of Australian P. damicornis (e.g. JX985597-601). Thus, DNA typing revealed that P. acuta exists abundantly at least around Yaeyama Islands. According to Schmidt-Roach et al. (2014), Pocillopora acuta has more elongated, sharper, and thinner branchlets than P. damicornis, and polyp of P. acuta looks like a brown ring. Hence, we propose a Japanese name "hosoeda-hanayasai" for P. acuta after the thinnest branchlets ("hosoeda") among all Pocillopora spp. ("hanayasai"). However, two species from Yaeyama Islands cannot be distinguished by these characteristics (Figure 1). Besides, size of columellae and density of spinular are highly variable even in a single corallum in both two species. Therefore, the ORF sequences appear to be the only measure to distinguish the two species in Yaeyama Islands. This study certainly highlights the importance of identifying P. acuta in Japan because previous studies on "P. damicornis" might have included P. acuta. Further studies may disclose whether these "P. damicornis" morphs are indeed P. damicornis or include P. acuta.

The blue coral (Heliopora coerulea, Pallas 1766) is a reef-building coral, which is recently been classified as a threatened species. Recent population genetic analyses have found two genetically distinct, cryptic lineages of this coral (types A and B). However, the ecological differences between them, as well as the drivers of this speciation, are still unclear. The aim of this study was to examine the possible differentiation in the reproductive timing of the two lineages, as a plausible cause of speciation. We subjected both formalin-and ethanol-preserved samples of the coral, collected from sympatric H. coerulea populations, for tissue and genetic analyses. Samples were collected every one or two months, from June 2014 to September 2017, around Sekisei Lagoon, southwest Okinawa, Japan. We also conducted field observations of the coral's reproductive behavior (larval brooding) in mid-June and July. As a result we could observe larval brooding behavior from mid-to late-July in type B; however no such behavior was observed in type A during the observation and sampling period. After examining a total of 468 histological samples, we found that the diameters of the oocytes and spermaries peaked from May to June in type A, whereas in type B they peaked from June to July, after which the spermaries disappeared or diminished. Our study demonstrates that the two H. coerulea lineages, under the same environmental conditions, exhibit different reproductive timings. This gap in reproductive timing, which possibly stemmed from endogenous differences, might have promoted their genetic differentiation and speciation into two distinct lineages.