First record of the rare Wide-mouth flounder Kamoharaia megastoma (Kamohara, 1936) (Pleuronectiformes, Bothidae) from the western Indian Ocean collected during the ATIMO VATAE expedition to Madagascar “Deep South”

ABSTRACT Four specimens of Kamoharaia megastoma (Kamohara, 1936) were collected during the Atimo Vatae expedition to the “Deep South” region of Madagascar for the exploration of fauna and flora, representing the first record of this species from the western Indian Ocean. Kamoharaia megastoma has been known to occur exclusively in the southeastern Indian and Western Pacific Oceans. Morphometric and meristic characters of these specimens are congruent with those described for K. megastoma. A description of the morphology and morphometrics are provided along with photographs. These records constitute a considerable range extension for the species.


INTRODUCTION
In 2010 the Muséum national d'Histoire naturelle (MNHN, Paris), the Institut d'Halieutique et des Sciences Marines, University of Toliara (IH.SM), and the Wildlife Conservation Society (WCS) Madagascar Programme united to undertake an expedition to explore the fauna and flora of the "Deep South" region of Madagascar. The expedition took place between April and June 2010 under the name ATIMO VATAE meaning "Deep South" in the regional Antandroy language. During this expedition, four specimens of Kamoharaia megastoma (Kamohara, 1936) described herein were collected between 10 and 11 May 2010.
The monotypic genus Kamoharaia Kuronuma, 1940 comprises a species of flounder that is characterized by having enlarged canine teeth on the anterior tip of the lower jaw, upper jaw protruding past tip of snout, and tip of vomer protruding into mouth cavity. Kamoharaia megastoma (Kamohara, 1936) is a rare species, originally described as a species of Chascanopsetta Alcock, 1894 based on a single specimen from Mimase, Kochi Prefecture, Japan. Nine years after its discovery, in 1945, the holotype of K. megastoma was destroyed in a war-caused fire (Kamohara 1961). T. Kamohara thus set out to collect and replace all the lost types within his laboratory, and in 1961 published an article in which he designated neotypes for many of the types destroyed in the 1945 fire. In this report he designated a neotype for K. megastoma based on a 207 mm standard length (SL) specimen collected from Mimase, Kochi Prefecture, Japan on 20 April 1951 and lodged in the Kochi University, Department of Natural Science collection with the catalog number BSKU 9592. Unfortunately, this new type designation was not done in a revisory work and is considered invalid under the code of nomenclature (Fricke et al. 2019).
K. megastoma has been sporadically reported from several locations within the Western Pacific and southeastern Indian Oceans at depths of up to 800 meters (Hensley & Amaoka 2001). Known geographical distributions include Japan, southern Taiwan, Korea, Philippines, New Caledonia, northwestern Australia and Kyushu-Palau Ridge (Kamohara 1936;Kuronuma 1940;Kamohara 1961;Matsunuma 2016;Voronina et al. 2016;Jang et al. 2018). The four specimens identified herein as K. megastoma based on morphometric and meristic characters were collected during a benthic trawl and represent the first record from the southwestern Indian Ocean. The present study provides a morphological description and external morphometrics of four specimens of K. megastoma from this region and comparative analysis with specimens from the Western Pacific and southeastern Indian Oceans.

MATERIAL AND METHODS
All the specimens analyzed within this study were collected during the ATIMO VATAE expedition. Upon collection specimens where labeled, photographed and placed in a 10% formaldehyde solution. Specimens were later lodged in the South African Institute for Aquatic Biodiversity National Fish Collection (SAIAB) where they underwent curation and preservation in 70% ethanol. A single specimen was deposited into the ichthyological collection of the Muséum national d'Histoire naturelle (MNHN).
External measurements were obtained from specimens preserved in 70% ethanol by means of a digital caliper (with a precision of 0.1 mm). Measurements follow Hubbs & Lagler (1958) and are expressed as percentage of standard length (% SL), in standard length (In SL), percentage of head length (% HL), and in head length (In HL) ( Table 1). Morphometric  and meristic data for K. megastoma from the Pacific and eastern Indian Oceans where extracted from Amaoka (1969Amaoka ( , 1982, Chen & Weng (1965), Fourmanoir (1985, Jang et al. (2018), Kamohara (1936Kamohara ( , 1961, Kuronuma (1940), Matsunuma (2016) and Voronina et al. (2016) for comparison. Terminology of general external morphology and colouration follows Kuronuma (1940). Fresh colouration is based on photographs taken upon collection of the specimens, and preserved colouration is based on specimens preserved in 70% ethanol. Specimens were photographed in ocular and blind side views, as well as individual body parts (e.g. mouth) using a Panasonic Lumix DMC-TZ27 digital camera with a Leica lens. Scales were imaged using scanning electron microscopy (SEM). Scale terminology and morphology of body scales follows Bräger & Moritz (2016) and lateral line scales follows Voronina (2007Voronina ( , 2009. A map of collecting localities of specimens ( Fig. 1) (Fig. 3). Pelvic fins short on both ocular and blind sides, origin of blind side at level of 3 rd ray of ocular side; 6 rays on both ocular and blind sides. Caudal fin of moderate length (13.6-16.3% SL), its posterior margin somewhat rounded. Body scales on both ocular and blind sides cycloid; circular shape, uniform throughout both ocular and blind sides. Lateral line scales oval to rounded shape; circuli distinct on anterior and lateral fields; radii present in anterior field; tubular wide (32.98% scale width) and extending 69.95% of the scale length (Fig. 4).

Fresh colouration
Ocular side of body greyish throughout with darker grey blotches. Blind side of body whitish. Dorsal and anal fins greyish with distal half darker grey to blackish. Ocular side pectoral fin black; blind side pectoral fin translucent. Pelvic fins whitish. Caudal fin greyish with central rays darker grey to blackish ( Fig. 2A).

Preserved colouration
Ocular side of body light brown throughout, with dark blotches scattered throughout body; blind side light brown throughout. Ocular side pectoral fin black; blind side pectoral fin translucent. Pelvic fins whitish. Dorsal and anal fins light brown with distal half greyish. Caudal fin light brown with central rays greyish, and posterior third greyish (Fig. 2B, C).

DISCUSSION
The specimens collected off Madagascar were identified as K. megastoma based on the following combination of characters as described in Kuronuma (1940): canine teeth well developed on anterior tip of lower jaw; tip of vomer protruding into mouth cavity; lateral line absent on blind side; ocular side pelvic fin far in advance of right pelvic fin; length of maxilla longer than head; upper jaw projecting beyond snout; 83-85 anal fin rays; and 10-12 pectoral fin rays. Several morphological variations where noticed when comparing specimens from the western Indian Ocean in the present study to those from the southeastern Indian and Western Pacific Oceans, including (main differences in bold in Table 1 K. megastoma is a rare species which inhabits sandy-mud bottoms at depths of 300-500 m, and feeds on small benthic organisms (Amaoka 2016). Amaoka (2016) reported a juvenile (102 mm) and a young adult (120 mm), and noted they have a shorter lower jaw than adults. There has been very little genetic work done with one and four sequences available respectively in the Barcode of Life BOLD System (Ratnasingham & Hebert 2007) and GenBank (NCBI 2019). Although some genetic sequences are available, they could not be used within this study as the specimens described herein did not have tissue samples taken prior to being fixed in formaldehyde. The status of K. megastoma has not yet been assessed on the IUCN Red List of Threatened Species. This may be due to its rarity, deficiency of biological knowledge and lack of economic interest to fisheries due to its small size.

Acknowledgements
This study was facilitated by the work of ATIMO VATAE Principal Investigator P. Bouchet (MNHN), who organized the Madagascar expedition and arranged for the donation of fish specimens to the South African Institute for Aquatic Biodiversity. The ATIMO VATAE expedition was part of  would also like to thank M. Dwani and R. Bills (SAIAB) for providing technical and curatorial assistance. M. Meltaf and S. Schramm (Margaret Smith Library -SAIAB), and M. Matsunuma (Kochi University) for assisting with literature. M. Randall and S. Pinchuck (Rhodes University) for providing assistance and access to scanning electron microscopy, and E. Voronina and an anonymous reviewer for their valuable suggestions and comments related to this manuscript. A. Paterson and O. Weyl (SAIAB) for institutional support. We acknowledge that opinions, findings and conclusions or recommendations expressed in this publication, partly supported by NRF funds, are those of the authors, and that the NRF accepts no liability whatsoever in this regard.