Burmoniscus kitadaitoensis Nunomura, 2009 (Crustacea, Isopoda, Oniscidea) from southern Japan, a junior synonym of B. meeusei (Holthuis, 1947)

Abstract Re-examination of the holotype of Burmoniscus kitadaitoensis Nunomura, 2009 from Kitadaitojima Island, southern Japan reveals that this species is a junior synonym of B. meeusei (Holthuis, 1947). Partial regions of mitochondrial COI, 12S and 16S rRNA genes, and nuclear 18S and 28S rRNA genes were detected for species identification in the future.


Introduction
Burmoniscus Collinge, 1914 can be dominant in terrestrial isopod communities in subtropical forests of East Asia (Ma et al. 1991). Therefore clarifying the taxonomic status of Burmoniscus species is important to understanding species diversity of isopod communities in these habitats. Thirteen species in the genus Burmoniscus were reported from Japan (Nunomura 2011), but their taxonomic status is still confused (Karasawa and Honda 2012).
Burmoniscus meeusei (Holthuis, 1947) was first described as Chaetophiloscia meeusei Holthuis, 1947, based on specimens found from a greenhouse at the Royal Botanic Gardens, Kew, United Kingdom. Later, Taiti and Ferrara (1991) found this species in Hawaii and transferred it to the genus Burmoniscus. Since then this species has been found in Taiwan and Brazil (Kwon and Jeon 1993;Araujo et al. 1996). Burmoniscus meeusei can be distinguished from congeneric species by a small lobe on the inner margin of the apical part of the male pleopod 1 endopodite, a triangular distal part on the male pleopod 1 exopodite, and the round apex of the pleotelson (see Holthuis 1947). Burmoniscus kitadaitoensis Nunomura, 2009 was described from specimens collected on Kitaditojima Island, southern Japan, where it was supposed to be endemic because it was never reported from other areas (Nunomura 2011). In the original description, Nunomura (2009) compared the morphological features of B. kitadaitoensis to those of B. okinawaensis (Nunomura, 1986) and B. daitoensis (Nunomura, 1986), and he concluded that B. kitadaitoensis was an undescribed species. The figures of Nunomura (2009), however, show that the male pleopod 1 exopodite of B. kitadaitoesis has a similar shape to that of B. meeusei (e.g., Holthuis 1947). However, the small lobe of the male pleopod 1 endopodite is not illustrated in the figures.
The aim of this study is to examine the holotype of B. kitadaitoensis and clarify its taxonomic status. Moreover, partial sequences of the mitochondrial COI, 12S and 16S rRNA genes, and nuclear 18S and 28S rRNA genes are detected for DNA markers of species identification.

Sample collection
The holotype of B. kitadaitoensis was deposited in Toyama Science Museum (male, TOYA-Cr 14899). We examined the holotype, but the specimen was dissected and in bad condition. However, we were able to observe some parts as follows: male pleopod 1 endo-and exopodites, pleopod 2 endo-and exopodites, male pereiopods 1 and 7, genital papilla, epimera of pereionite 7, and pleotelson. Four specimens were also collected from Kitadaitojima Island (type locality) and Amamioshima Island and were used for measurements of the co-ordinate of the noduli laterales and molecular analysis. The voucher specimens are deposited in the collection of Kitakyushu Museum of Natural History and Human History (KMNH-IvR), Kitakyushu, Fukuoka Prefecture, Japan.

Morphology
The male pleopods 1 and 2, genital papilla, and male pereiopods 1 and 7 of the holotype, and the position of noduli laterales of specimens collected from Kitadaitojima Island were examined using a Nikon Eclipse E400 microscope (magnification of 40-400×). The epimera of pereionite 7 and pleotelson of the holotype were examined using an Olympus SZH-10 microscope (magnification of 7-64×). A color image was produced from multi-focused montage images using a digital microscope VHX-2000 (KEYENCE Corporation).

Molecular analysis
The partial sequences of mitochondrial cytochrome oxidase subunit I (COI), mitochondrial 12S and 16S ribosomal RNA (rRNA) genes, and nuclear 18S and 28S rRNA genes were determined for identifying this species in the future. DNA extraction and PCR amplification are described in Karasawa and Honda (2012). The primers and the accession numbers are shown in Tables 1 and 2, respectively.
On the holotype of B. kitadaitoensis, a small lobe was found on the inner margin of the male pleopod 1 endopodite, although this character was not shown in the original description (Fig. 3P in Nunomura 2009). Moreover, the other morphological characters including the co-ordinate of the noduli laterales (Fig. 4) are consistent with those of B. meeusei (see Figs 1 and 2 in Holthuis 1947; Figs 7 and 8 in Taiti and Ferrara 1991;Fig. 7 in Kwon and Jeon 1993;Figs 15-21 in Araujo et al. 1996). Thus the present study considers B. kitadaitoensis as a junior synonym of B. meeusei.
Distribution. Burmoniscus meeusei was previously reported from the United Kingdom (greenhouses), Hawaii, Brazil, Taiwan (Schmalfuss 2004) and Japan. In Japan this species has been collected from Kitadaitojima Island only (Nunomura 2009(Nunomura , 2011, but the present study found the species on Amamioshima Island, which is about 300 km from Kitadaitojima Island.   DNA sequences. The COI, 12S rRNA, 16S rRNA, 18S rRNA and 28S rRNA alignments comprised 653, 354, 453, 675 and 635 bp, respectively. With the exception of the 12S rRNA gene, there is no difference in the four genes among the specimens collected from Kitadaitojima and Amamioshima Islands. Only one 12S rRNA gene base varied between the specimens collected from the two islands.