July 2022 Amami Islands

Author: Andrew Baird

Project Phoenix’s hunt for topotypes continued in the magical Amami-Oshima Island in the Ryukyu Archipelago in Japan. 

In 1856, the ships of the Northern Pacific US exploring expedition anchored in the south of ‘Amami-Ousima’ (as written in ships log and associated expedition texts) and collected a number of coral specimens that served as the type material for five species described by Verrill in 1866. The Amami-Oshima Island is also the type location for another four species named by Eguchi and his colleagues.

The human population in the Amami Islands is only a fraction of that in Okinawa, a few hundred kilometers to the south with a similar land area. So, I was expecting a much less developed coastline and undisturbed forest in Amami when compared to Okinawa and I was pleasantly surprised. The road network around the island is quite extra-ordinary considering the size of the population. You can get to almost every point around the coast, which includes some of the nicest beaches I have seen in Japan (Fig. 1). The forest was also amazing. Recently given world heritage status, much is relatively undisturbed and although there are few trails that climb to the high point of the islands, Mt. Yuwan was through some of the best forests I have seen in Japan, full of interesting birds including the endemic Pygmy Woodpecker. The reefs show clear signs of recent disturbance, with many dead corals still in place, possibly remnants of the 1998 bleaching, or a more recent event in 2016. However, the corals are coming back at most sites I visited, and some of the reef was spectacular.

Figure 1. Yadori Beach in Amami Island.
Photo credit: Andrew Baird

Most importantly, I managed to find what I believe are good topotypes for all the species that were accessible on snorkel (without the language, it was too difficult to organize to hire tanks) including one species that has been giving us a lot of grief, Acropora striata. Described by Verrill in 1866, it has been interpreted differently by different authors. Wallace 1999 interprets it as a hispidose tenuis. I have no doubt that A. striata-sensu Wallace 1999 is a good species and have seen it in many locations around the world, but not in Japan, which is the type location of striata. However, I have strong doubts that A. striata-sensu Wallace 1999 is a good match for the holotype. I think the holotype is a fragment of a corymbose colony that has been mounted at a peculiar angle giving it an hispidose appearance. Our working hypothesis is that A. striata (Verrill 1866) is a deeper water morph of what Japanese coral scientists call A. tenuis (Dana 1846). It was therefore with immense relief that I finally came across a specimen on one of my last snorkels on the island. You can see that the image of the collected specimen shares many features of the holotype, including thin braches, the occasional tall axial, and areas of some branches which are bare of radials (Fig. 2). A better test will be to compare the genes between this deep-water morph and the more typical A. tenuis-Japan and finally A. striata-sensu Wallace 1999, which unfortunately we have yet to collect.

Figure 2Acropora striata (Verrill 1866) (a) holotype (b) potential topotype.
Photo credit: Andrew Baird

I thank Takuma Fujii, Hiro Fukami and James Reimer for excellent advice on the reefs of Amami and Dr Takahashi Nakamura for securing the permits to collect corals in Kagoshima Prefecture.

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