Onykia and Identification of Their Paralarvae from Northern Hawaiian Waters
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J. Mar. Biol. Ass. U.K. (2007), 87, 959–965 doi: 10.1017/S0025315407056196 Printed in the United Kingdom Molecular evidence for synonymy of the genera Moroteuthis and Onykia and identification of their paralarvae from northern Hawaiian waters Toshie Wakabayashi*, Tsunemi Kubodera†, Mitsuo Sakai*, Taro Ichii* and Seinen Chow‡∫ *National Research Institute of Far Seas Fisheries, 2-12-4 Fukuura, Kanazawa-ku, Yokohama, Kanagawa 236-8648, Japan. †National Science Museum, Tokyo, 3-23-1 Hyakunin-cho, Shinjuku-ku, Tokyo 169-0073, Japan. ‡National Research Institute of Fisheries Science, 6-31-1 Nagai, Yokosuka, Kanagawa 283-0316, Japan. ∫Corresponding author, e-mail: [email protected] It has been claimed that most squid species in the genus Onykia may be immature stages of species in the genus Moroteuthis. To evaluate the generic status of Moroteuthis and Onykia and to identify paralarvae collected in northern Hawaiian waters, we performed morphological investigation and nucleotide sequence analysis of the mitochondrial cytochrome oxidase I (COI) gene. Of 42 Onykia paralarvae (1.8–8.5 mm dorsal mantle length, DML) examined, 41 had a nucleotide sequence identical to that of M. robusta and one (designated Onykia sp. A) could not be assigned to any known Moroteuthis species. Nucleotide sequence diversity estimates based on Kimura’s two-parameter distances between Onykia sp. A and Moroteuthis spp. (0.109–0.150) fell well within the range of congeneric species, suggesting that Onykia sp. A is a member of the genus Moroteuthis. Molecular data supported the conclusion that the genus Moroteuthis is a junior synonym of the genus Onykia. Morphological investigation revealed that paralarvae of O. robusta (= M. robusta) <4.0 mm DML were distinct from other Onykia paralarvae in the chromatophore pattern on the mantle. The key characters for distinguishing O. robusta paralarvae from Onykia sp. A were the number and arrangement of chromatophores on the funnel. INTRODUCTION fragment length polymorphism (RFLP) and/or direct The squid family Onychoteuthidae presently comprises nucleotide sequencing analyses based on the polymerase five genera (Onychoteuthis, Ancistroteuthis, Onykia, Moroteuthis, chain reaction (PCR) have been used to successfully analyse and Kondakovia; Kubodera et al., 1998), however, the ommastrephid squid paralarvae collected in northern taxonomic status of some genera is controversial. Neither Hawaiian waters (Wakabayashi et al., 2006). paralarvae nor juveniles of the genus Moroteuthis have been In this study, we present molecular evidence for synonymy described, and only one adult form of the genus Onykia (O. of the squid genera Moroteuthis and Onykia and report results rancureli) has been reported (Kubodera et al., 1998). It has of morphological and molecular genetic analyses to identify been suggested that some Onykia species are actually juvenile species of Onykia collected from northern Hawaiian waters. stages of Moroteuthis species (Tsuchiya & Okutani, 1991). We also briefly discuss the Onykia life cycle, which has not Paralarvae of Onykia species are distributed in surface been previously described. waters and are frequently caught by plankton nets. Although paralarvae of this genus have been described (Pfeffer, MATERIALS AND METHODS 1884, 1900, 1912; Okutani, 1968), species identification has not been established. Most oceanic squids have few Squid samples chromatophores on the body during the paralarval stages, Standard specimen whereas Onykia paralarvae are characterized by numerous Adult samples from six onychoteuthid squids were used chromatophores on the mantle, head and arms (Clarke, as standards (Table 1). Moroteuthis robusta was obtained from 1992). The arrangement of chromatophores is often useful the stomach content of a sperm whale caught off Sanriku, in identifying species at the paralarval stage (Okutani & Japan, and M. loennbergii from a bottom trawl off Sanriku, McGowan, 1969; Young & Harman, 1987; Wakabayashi et Japan. Moroteuthis robsoni and M. ingens distributed in the al., 2002). However, the large number of chromatophores southern hemisphere were obtained from squid jigging in characteristic of Onykia paralarvae may hinder species New Zealand waters. Two species of the genus Onychoteuthis identification within this genus. To date, most paralarvae of (O. banksii and O. borealijaponica) were collected by mid-water Onykia species have been identified to only a single species, trawl off Sanriku. The nucleotide sequences for M. robusta, O. carriboea Lesueur, 1821, based on this character, but it is M. knipovitchi, Onychoteuthis compacta and Watasenia scintillans likely that O. carriboea is a species complex considering the (family Enoploteuthidae) were derived from Anderson number of adult species that are. Molecular genetic analyses (2000), Lindgren et al. (2004), Carlini & Graves (1999) and may resolve the problems mentioned above, and restriction Yokobori et al. (2004), respectively. Journal of the Marine Biological Association of the United Kingdom (2007) 960 T. Wakabayashi et al. Molecular DNA analysis for squid genus Onykia Table 1. Sampling localities of adult Onychoteuthid samples used in this study. Species Locality N Vessel Moroteuthis robusta Off Sanriku, Japan 1 ‘Nisshin-Maru’ M. loennbergii Off Sanriku, Japan 1 ‘Wakataka-Maru’ M. robsoni New Zealand 1 – M. ingens New Zealand 1 ‘Hakurei-Maru’ Onychoteuthis banksii Off Sanriku, Japan 1 ‘Marutei-Maru’ O. borealijaponica Off Sanriku, Japan 1 ‘Marutei-Maru’ Paralarvae Onykia paralarvae were collected north of the Hawaiian Archipelago (26°30'–37°N 155°–162°30'W; Figure 1) in 2002 and 2003 by the National Research Institute of Far Seas Fisheries aboard the RV ‘Shunyo-Maru’. In total, 42 paralarvae were collected using a large larva net (2 m mouth diameter; 526-μm mesh) in surface horizontal tows at ship speeds of 1.5 to 2 knots. The sorted paralarval samples were frozen or preserved in 70% ethanol on-board, transferred to the laboratory, and identified based on morphology. All paralarval samples were deposited at the National Science Museum in Tokyo, Japan. Figure 1. Map of the sampling area showing transects surveyed Crude DNA was extracted from the mantle of each during 2002 (solid line) and 2003 (dashed line). Closed and open standard sample and one of the fins of each paralarva circles indicate stations where paralarvae of Onykia were collected using a DNA extraction kit (GenomicPrep Cells and Tissue in 2002 and 2003, respectively. DNA Isolation Kit; Amersham Biosciences, Piscataway, NJ, USA). PCR amplification nucleotide sequences obtained using both forward and We used primers LCO1490 and HCO2198 (Folmer et reverse primers were edited and aligned on GENETYX v. al., 1994) for standard samples and primers LCO1495N 6.1 (GENETYX, Tokyo, Japan), considering their deduced (5'-ACAAAYCATAAAGAYATTGG-3') and COI6785R1 amino acid sequences, and then imported into MEGA v. (5'-GATAATATATGRTGGGCTCA-3') for paralarval 3.1 (Kumar et al., 2004) to calculate sequence divergence samples to amplify a partial segment of the mitochondrial (Kimura’s two-parameter distance: K2P) and to construct a cytochrome oxidase I (COI) gene. neighbour-joining (NJ) phylogenetic tree. Polymerase chain reaction amplification was carried out According to the nucleotide sequence data obtained, we in 10 μl reaction mixtures containing 5 μl of 2×GC buffer, selected an endonuclease (Fok I) for species identification 1 mM of each dNTP, 0.4 μM of each primer, 0.4 units of using RFLP. The PCR products were directly digested by LA Taq polymerase (TaKaRa, Shiga, Japan), and the DNA this enzyme and electrophoresed through a 2.5% agarose gel template. The reaction mixtures were preheated at 95°C for (Biogel, BIO101; Regent Medical, Manchester, UK) for 2 h, 3 min, followed by 30 amplification cycles (95°C for 40 s, stained with ethidium bromide, and photographed. 46°C for 40 s, and 72°C for 1.5 min), with a final extension The nucleotide sequences reported here were deposited at 72°C for 5 min. in DDBJ/EMBL/GenBank under accession numbers AB264116–AB264122. Nucleotide sequence and RFLP analyses Nucleotide sequence analysis was performed on all standard Morphological observations samples and on five paralarval samples (designated Onykia A binocular microscope with a micrometer was used to sp. 16-1, 18-1, 22-1, 46-4 and 50-1) having different dorsal observe and measure the paralarvae. The measurements, mantle lengths (DML; 2.0, 4.0, 6.3, 7.5, and 8.5 mm). The indices, and terminologies used here follow Roper & Voss PCR products were treated with ExoSAP-IT (Amersham (1983). The specimens used for scanning electron microscope Biosciences) to remove the oligonucleotide primers. (SEM) observations were dehydrated in a graded series Sequences were generated on an automated sequencer (ABI of ethanol and t-butyl alcohol, dried using a freeze dryer Prism310; Applied Biosystems, Foster City, CA, USA) using (ES-2030; Hitachi, Ibaraki, Japan), and coated with gold. A the ABI Big-dye Ready Reaction kit (Applied Biosystems) SEM (SM-200; Topcon, Tokyo, Japan) was used to observe following the standard cycle sequencing protocol. The the tentacles, arms and mouthparts. Journal of the Marine Biological Association of the United Kingdom (2007) Molecular DNA analysis for squid genus Onykia T. Wakabayashi et al. 961 Table 2. Estimates of mean nucleotide sequence diversity based on Kimura’s two-parameter distance between species. M.rst M.lbg M.rsn M.igs M.kpv Ok50-1 O.com O.bks O.bjp M.rst M.lbg 0.109 M.rsn 0.106 0.125 M.igs 0.142 0.147 0.140 M.kpv 0.176 0.167 0.205 0.124 Ok50-1 0.120 0.109 0.124 0.138 0.150 O.com 0.194 0.199 0.206 0.157 0.160 0.204 O.bks 0.180 0.199 0.218 0.145 0.160 0.206 0.103 O.bjp 0.193 0.197 0.232 0.164 0.159 0.215 0.138 0.102 Ws 0.224 0.229 0.257 0.192 0.217 0.231 0.225 0.221 0.214 M.rst, Moroteuthis robusta; M.lbg, M.