Exploring the Phylogeny and Species Diversity of Chelidoperca (Teleostei: Serranidae) From the Western Pacific Ocean by an Integrated Approach in Systematics, With Descriptions of Three New Species and a Redescription of C. lecromi Fourmanoir, 1982

Lee, Szu-Hsuan; Lee, Mao-Ying; Matsunuma, Mizuki; Chen, Wei-Jen

doi:10.3389/fmars.2019.00465

ORIGINAL RESEARCH article

Front. Mar. Sci., 06 August 2019

Sec. Marine Evolutionary Biology, Biogeography and Species Diversity

Volume 6 - 2019 | https://doi.org/10.3389/fmars.2019.00465

Exploring the Phylogeny and Species Diversity of Chelidoperca (Teleostei: Serranidae) From the Western Pacific Ocean by an Integrated Approach in Systematics, With Descriptions of Three New Species and a Redescription of C. lecromi Fourmanoir, 1982

$\nSzu-Hsuan Lee$ Szu-Hsuan Lee¹

Mao-Ying Lee^1,2

Mizuki Matsunuma³

Wei-Jen Chen¹^*

¹Institute of Oceanography, National Taiwan University, Taipei, Taiwan
²Marine Fisheries Division, Fisheries Research Institute, Council of Agriculture, Keelung, Taiwan
³Department of Environmental Management, Faculty of Agriculture, Kindai University, Nara, Japan

With 11 species, the genus Chelidoperca is a small group of teleost fishes belonging to the Serranidae. They are bottom-dwelling fishes living on continental shelves/slopes in offshore areas or on remote seamounts/banks at depths ranging from around 40–400 m mostly in the tropical Indo-West Pacific. Over the past few years, efforts have been made to resolve the taxonomy of Chelidoperca, and subsequently four new species were described. However, these recent advances were made with a traditional approach (i.e., morphology) and limited examinable materials, usually preserved specimens, from ichthyological collections. Further investigations are still needed to address the gaps in our knowledge about their diversity, phylogeny, and biogeography. In this study, we collected 65 new samples, mainly during eight biodiversity expeditions carried out between 2007 and 2016 in the West Pacific under the Tropical Deep-Sea Benthos program. Specimens were photographed after collection to record fresh color patterns, which are essential for species diagnosis. Our analytical approach includes state-of-the-art DNA-based methods for species delimitation. The combined evidence from both molecular and morphological examinations, as well as other information such as geography, is used to test species validity. This reveals 15 species, including six new ones. We formally describe herein C. leucostigmata sp. nov., C. microdon sp. nov., and C. barazeri sp. nov. on the basis of specimens collected on Macclesfield Bank in the South China Sea, on the Chesterfield and Island of Pines plateau of New Caledonia, and off the New Ireland Province of Papua New Guinea, respectively. These new species are morphologically distinct from all other known species of Chelidoperca by body color pattern and combinations of a few identified characters. We also redescribe one of the lesser known species, C. lecromi, from fresh specimens collected close to its type locality and a new site in the Coral Sea. The distributional records for this and other known species are updated accordingly. Genetic references of the species as well as an updated identification key to western Pacific species are also provided.

Life Science Identifier (LSID): urn:lsid:zoobank.org:pub:AB996C2C-1669-41E9-923C-ADB086BC6687.

Introduction

The tropical Indo-West Pacific is the largest marine biogeographic ensemble on Earth (Crandall and Riginos, 2014). Its exceptionally high species diversity is well-known; however, our knowledge is largely limited to shallow water reef ecosystems and associated fauna. The mesophotic coral ecosystems and numerous deep-sea habitats such as seamounts or remote ocean banks are also hotspots of biodiversity, but these have received only limited study due to the technical limitations of comprehensive surveys.

Chelidoperca (Boulenger, 1895) is a genus of small-sized perch-like fishes, commonly known as perchlets, belonging to the family Serranidae. The genus is characterized by relatively slender, rounded, and elongate bodies. They are bottom-dwelling fishes usually collected in benthic trawls (Williams and Carpenter, 2015; Matsunuma, 2016). All members except the eastern Atlantic C. africana are known to be distributed in the Indo-West Pacific at depths of 40–400 m (Matsunuma and Motomura, 2016; Matsunuma et al., 2018; this study). Eleven nominal species are currently recognized in this genus (Bineesh et al., 2013; Williams and Carpenter, 2015; Iwamoto and Wirtz, 2018; Matsunuma et al., 2018; Fricke et al., 2019): C. hirundinacea (Valenciennes in Cuvier and Valenciennes, 1831), C. pleurospilus (Günther, 1880), C. investigatoris (Alcock, 1890), C. margaritifera Weber, 1913, C. africana Cadenat, 1960, C. occipitalis Kotthaus, 1973, C. lecromi Fourmanoir, 1982, C. maculicauda Bineesh and Akhilesh in Bineesh et al., 2013, C. santosi Williams and Carpenter, 2015, C. stella Matsunuma and Motomura, 2016, and C. tosaensis Matsunuma et al., 2018. Among these, C. stella is the only species known to be widespread from the Andaman Sea in the eastern Indian Ocean to the South China Sea in the western Pacific Ocean; others are restricted to single ocean basins or maritime areas (Matsunuma et al., 2018). In addition to C. stella, six other species have been reported in the West Pacific (Williams and Carpenter, 2015; Matsunuma et al., 2018). C. lecromi has only been recorded from off the Chesterfield Islands in the Coral Sea and off American Samoa. C. santosi is currently known from the northwestern Pacific from the Philippines to Japan. C. hirundinacea and C. pleurospilus are distributed from Indonesia to Japan and C. margaritifera is known only from its type locality: the Bird's Head Peninsula region, Indonesia. C. tosaensis was the last described species from the genus, based on the specimens found in waters of Japan and the Philippines.

During a series of biodiversity expeditions carried out between 2007 and 2017, mainly in the West Pacific, under the Tropical Deep-Sea Benthos (TDSB) program (Bouchet et al., 2008) and the cooperative project between Taiwan and France entitled “Taiwan-France marine diversity exploration and evolution of deep-sea fauna (TFDeepEvo; 2013–2016), 58 specimens of Chelidoperca species were collected from waters at depths of 77–338 m off Papua New Guinea, EEZ of New Caledonia, the Philippines, and South China Sea, including several specimens that were unable to be identified as existing known species in the West Pacific but recognizable in several morphotypes. After the detailed examinations carried out in this study, we concluded that they belonged to at least four new species. However, during the course of manuscript preparation, one co-author, Mizuki Matsunuma (MM), and his undergraduate student, Akari Ogino (AO), simultaneously examined other specimens of Chelidoperca collected from New Caledonia and Australia, which were deposited in the ichthyological collection of the National Natural History Museum of Paris (MNHN) and the National Museum of Nature and Science of Tsukuba (NSMT), and also concluded that specimens characterized by orange spots on the pectoral and caudal fin bases are a new species. As a paper by MM and AO describing this new species was already in preparation, all four present co-authors agreed to separately describe the other species. The objective of the present paper is thus to use an integrated approach in systematics (see: Dayrat, 2005; Hung et al., 2017; Lo et al., 2017; Puillandre et al., 2017) to explore the phylogeny and species diversity of the Chelidoperca, especially those occurring in the West Pacific. Our results reveal an even greater species diversity of the genus than previously thought and extend the distribution range of two already known species, C. stella and C. tosaensis. We formally describe herein three of the newly discovered species based on morphological and molecular diagnoses. We also redescribe one of the lesser known species, C. lecromi, using fresh specimens newly collected close to its type locality around the Chesterfield Islands in the Coral Sea. Genetic references of the new species as well as an updated identification key to the West Pacific Chelidoperca species are also provided.

Materials and Methods

Sample Collection, Morphological Measurements, and Species Identification

Most of the Chelidoperca specimens (n = 58) examined in the present study were collected during eight exploratory cruises in the West Pacific (campaigns: AURORA 2007, BIOPAPUA 2010, EXBODI 2011, MADEEP 2014, KAVIENG 2014, ZHONGSHA 2015, KANACONO 2016, and KANADEEP 2017) conducted between 2007 and 2017 under the TDSB and the TFDeepEvo programs with the French research vessel ALIS and the Taiwanese research vessel OR1. A few others (n = 7) were collected at fish landing ports in Taiwan (Dashi, Ilan, on 13 March 2014 and Keziliao, Kaohsiung, on 6 May 2017) and Japan (Saga, Tosa bay, on 31 Jan. 2018) (Figure 1; Supplementary Table 1). A small piece of muscle or fin tissue was excised from each specimen, preserved in 95% ethanol, and stored at −20°C in the Marine Biodiversity and Phylogenomics Laboratory at the Institute of Oceanography, National Taiwan University (NTU), Taipei, for subsequent molecular analyses. Specimens were photographed shortly after collection to record fresh color patterns, preserved in formalin, and deposited in the ichthyological collections of the NTU Museums, Taipei (NTUM), Academia Sinica, Taipei (ASIZP), and National Natural History Museum of Paris (MNHN).

FIGURE 1

Figure 1. Map of the West Pacific region indicating sampling sites (open and color filled circles) for the specimens of Chelidoperca species examined in the present study. Open circles: specimens collected from fish landing ports with unknown collection depths; color-filled circles: specimens collected during exploratory cruises through the TDSB program and its joint TFDeepEvo project.

Collected specimens were identified to species where possible using morphological features in taxonomic references (Williams and Carpenter, 2015; Matsunuma, 2016; Matsunuma and Motomura, 2016; Matsunuma et al., 2018) and then checked against photographs (if available) in the original papers describing each species. If a specimen could not be identified by morphology or if metric counts overlapped with more than one species, it was first identified to genus level and then checked again after molecular analyses. Methods for morphological examination and specimen measurements generally followed (Matsunuma, 2016) and (Matsunuma and Motomura, 2016). Definitions of some specific morphological features, including the identification of the last anal- and dorsal-fin rays, differentiation of segmented procurrent rays and soft segmented caudal rays, counts of scale rows above the lateral line, and counts of preopercular, opercular, interopercular, and subopercular serrae followed (Matsunuma et al., 2018). Examination of the supraneural dorsal-ray and pattern formula of pterygiophore neural spine interdigitation followed (Anderson and Heemstra, 2012). Specimens examined in this study are listed in Supplementary Table 1. Other type materials examined included: MNHN1981-1436 and MNHN1981-1437 (C. lecormi, holotype, and paratype). All measurements were taken in a straight line, made with a dial caliper, and recorded to the nearest 0.1 mm. Internal osteological features of specimens were recorded based on X-ray photographs.

Collection of Molecular Data and Measurements

Total genomic DNA was extracted from the tissue samples of 47 Chelidoperca individuals and one individual from an outgroup taxon, Centropristis philadelphica, using an automatic extractor: LabTurbo 48 Compact System and LGD 480–500 kits (Taigene Biosciences Corp., Taipei) following the manufacturer's protocol. One mitochondrial protein-coding gene (cytochrome oxidase c subunit I [COI]) and one nuclear protein-coding gene (recombination activating protein 1 [RAG1]) were used as genetic markers in this study for their ability to provide species delimitation (Ward et al., 2005; Hung et al., 2017; Lo et al., 2017) and phylogenetic information (López et al., 2004; Chen et al., 2014; Lo et al., 2015, 2017; Hung et al., 2017), respectively. Protocols for collecting molecular data followed Ward et al. (2005) and the previous study of Lo et al. (2015). Gene amplicons were sequenced with the Sanger sequencing technique at Genomics BioSci &Tech (Taipei) and the Center of Biotechnology (National Taiwan University, Taipei). DNA sequences obtained were edited and aligned with sequence assembly and alignment software CodonCode Aligner v. 7.0.1 (CodonCode Corporation, Dedham, MA, USA) and Se–Al v2.0 (Rambaut, 1996). Sequences (usually at both ends) and base pairs of low quality, i.e., below Q (phred quality value) 20, were verified and trimmed manually. In addition to the sequences newly obtained through our laboratory work, 35 COI sequences and one RAG1 sequence of Chelidoperca plus one outgroup taxon, Paralabrax clathratus, were retrieved from GenBank (NCBI, Nation Center for Biotechnology Information) and the BOLD system (The Barcode of Life Data Systems) (n = 3), and three unpublished COI sequences of Chelidoperca stella samples collected from Palikulo Bay, Vanuatu, through the Santo Marine Biodiversity Survey led by the MNHN in 2006, were provided by Dr. Agnès Dettaï (MNHN) (Supplementary Table 1). Sequences were compiled into two separate gene datasets for the molecular analyses described below. The software PAUP^* (Swofford, 2002), MEGA6 (Tamura et al., 2013) and Se–Al were used to obtain the basic statistics of the sequences from the two compiled datasets to compute pairwise genetic distances with the Kimura-2-parameter distance model (K2P) (Kimura, 1980) and to determine and visualize the nucleotides at the COI locus that are apomorphic and unique to the new species.

Phylogenetic Inference

Partitioned maximum likelihood (ML) analysis with the nucleotide substitution model GTR + G (Yang, 1994) was performed on each gene dataset with the software RAxML version 8.0.4 (Stamatakis, 2014) to infer the phylogeny of Chelidoperca species and test the monophyly of recognized species. Partitioning was set by codon position. The final tree with the best likelihood score was selected. Nodal support was assessed by bootstrapping (Felsenstein, 1985) with the ML criterion based on 1,000 pseudo-replicates. Tree topology and bootstrap values were visualized using FigTree v1.4.3 (Rambaut, 2012). According to a previous phylogenetic hypothesis of serranid fishes suggested by Meisler (1987), Chelidoperca appears to be the sister group of all other genera in the serranid subfamily, Serraninae. Here, two taxa belong to the Serraninae, Centropristis philadelphica, and Paralabrax clathratus, were chosen as outgroups and used to root the inferred gene trees.

Species Delimitation Analyses

Two DNA-based species delimitation analyses, the Automatic Barcode Gap Discovery (ABGD) (Puillandre et al., 2012) and Bayesian based Poisson Tree Processes (bPTP) (Zhang et al., 2013), were primarily used to explore the species diversity of the West Pacific Chelidoperca based on the COI dataset. ABGD is a species delimitation method based on pairwise genetic distances. With this tool, sequences are clustered into operational taxonomic units (OTUs) or putative species through the detection of significant differences between intra-specific and inter-specific genetic distances (barcode gap). This analysis was performed at the web interface (http://wwwabi.snv.jussieu.fr/public/abgd/) using a relative gap width (X) value of 1.5 and intraspecific divergence (p) value from 0.001 to 0.1, with 50 steps under K2P pairwise distances.

The bPTP analysis infers OTUs by analyzing branching events on a rooted dendrogram tree. A rooted COI gene tree of Chelidoperca with identical sequences excluded was inferred using RAxML as our input tree. This analysis was performed at the web server available at https://species.h-its.org/ptp/. The default settings used in the analysis were 100,000 MCMC generations, thinning as 100, burn-in as 0.1, and seed as 123. Congruent results (i.e., common OTUs) from ABGD and bPTP were considered primary evidence for considering putative species. Other criteria applied to evaluate the validity of inferred species included an evaluation of the pairwise genetic distances of the taxa, species monophyly found in gene trees, and the results of morphological comparisons. Finally, as suggested in Kekkonen and Hebert (2014) and applied by Lo et al. (2017) and Hung et al. (2017), resulting allopatric sister OTUs from the COI species delimitation analyses were treated as a single OTU rather than separating them into multiple OTUs when no other evidence suggested the reproductive isolation of sister putative species or OTUs.

According to the distribution data of taxa recorded in previous studies (e.g., Matsunuma et al., 2018), most species within Chelidoperca are restricted to a single ocean basin or marine biogeographic realm (as in Costello et al., 2017). Therefore, we defined three western Pacific geographic regions based on the levels of regional endemicity of marine species (notably in Chelidoperca spp.), ocean currents, and other physical barriers (see: Hung et al., 2017): (1) northwestern Pacific (NWP; including East China Sea, Philippines, Southern Japan, South China Sea, and Taiwan); (2) tropical West Pacific (TWP; including West Papua and the Bismarck Sea off northern Papua New Guinea); and (3) tropical Australia and Coral Sea (TA+CS; including New Caledonia, Vanuatu, and the Solomon Sea). The designation of sympatry or allopatry of inferred sister OTUs was based on these defined regions.

Results and Discussion

Molecular Data and Inferred Phylogeny

The COI dataset comprised 50 newly obtained sequences plus 42 published and unpublished sequences from all (10) nominal Chelidoperca species in the Indo-West Pacific, several undetermined species in the West Pacific, and two outgroups (Supplementary Table 1). The length of the aligned sequences of the dataset is 630 bp. The aligned sequences contained no indels or stop codons and included 235 (37.3%) variable sites, 210 of them being parsimony-informative. Most of the variable sites were found from the third codon positions (203/235; 86.4%).

The RAG1 dataset included 12 newly obtained sequences of five nominal and several undetermined species from the West Pacific, and two outgroups (Supplementary Table 1). The length of the aligned sequences of the dataset is 1,449 bp. The aligned sequences contained no indels or stop codons and included 147 (10.1%) variable sites, 66 of them being parsimony-informative. Most of the variable sites were found from the third codon positions (104/147; 70.7%).

Figures 2, 3 show the phylogenetic trees inferred from the partitioned ML analysis based on COI and RAG1 datasets, respectively. The monophyly of the genus Chelidoperca has only moderate support (BS = 63%) from COI gene analysis, but has maximal support (BS = 100%) from RAG1 analysis. All but one (C. stella) of the included nominal species are confirmed to be monophyletic by COI gene analysis. In addition, those samples that cannot be identified by morphology to any existing Chelidoperca species cluster into six independent lineages in the COI gene tree: C. sp. 1 (samples exclusively from the South China Sea), C. sp. 2 (one sample from the Coral Sea and another from southeastern New Caledonia), C. sp. 3 (samples from the Coral Sea and southeastern New Caledonia), C. sp. 4 (two samples from Papua New Guinea), C. sp. 5 (one sample from the Philippines), and C. sp. 6 (two samples from the Philippines) (Figures 1, 2). Further detailed examination on the specimens (when available) revealed that they represented at least four morpho-species (see below).

FIGURE 2

Figure 2. Phylogenetic tree of Chelidoperca species inferred by the partitioned maximum-likelihood method with GTR + G nucleotide substitution model based on the COI gene dataset, species delimitation analyses, and additional criteria (see materials and methods). Branch lengths are proportional to inferred nucleotide substitutions. Numbers at nodes represent bootstrap values in percentages. Values <50% are not shown. Taxa names in bold indicate new or potential new species discovered in this study. *indicates probable misidentified samples. The tree is rooted with two known species from the Serraninae. A summary of determined OTUs (vertical bars) is presented on the right side of the phylogenetic tree.

FIGURE 3

Figure 3. Phylogenetic tree of Chelidoperca species inferred by the partitioned maximum-likelihood method with GTR + G nucleotide substitution model based on the RAG1 gene dataset. Branch lengths are proportional to inferred nucleotide substitutions. Numbers at nodes represent bootstrap values in percentages. Values <50% are not shown. Taxa names in bold indicate new or potential new species discovered in this study. The tree is rooted with two known species from the Serraninae.

For intra-generic relationships, COI gene analysis resolved the following sister-group relationships with strong support (BS > 80%): between C. tosaensis and C. sp. 4, between C. lecromi and C. sp. 3, and between C. pleurospilus and C. maculicauda (Figure 2). The clade comprising the four samples of C. “margaritifera” from the South China Sea is nested within C. stella (Figure 2). RAG1 gene analysis revealed that all the sister-group relationships resolved in the COI tree (except C. pleurospilus/C. maculicauda pair; no sample from C. maculicauda for RAG1 sequencing) were confirmed. In addition, RAG1 gene analysis further resolved C. stella to be the sister group of the clade containing C. tosaensis and C. sp. 4 and the sister-group relationship between C. sp. 1 and C. sp. 5, with strong nodal support (BS = 99 and 86%, respectively) (Figure 3).

Discovery of Hidden Species Diversity of Chelidoperca in the West Pacific

To further explore species diversity, a dataset with COI sequences for 90 Chelidoperca samples including 10 out of 11 nominal species were compiled and analyzed by two species delimitation analyses, ABGD and bPTP. The eastern Atlantic C. africana samples were not included due to a lack of specimens for sequencing. The two analyses presented partially incongruent results, with 15 predicted OTUs (or putative species) from the ABGD and 18 predicted OTUs (or putative species) from bPTP. Regardless of the method used, the number of predicted OTUs (putative species) is much higher than previously recognized. Among them, 12 OTUs are common to both analyses and considered robust support for the inferred species. These are C. investigators, C. lecromi, C. maculicauda, C. occipitalis, C. santosi, C. tosaensis, and the six independent lineages (C. sp. 1–6) discovered during phylogenetic analyses (Figures 2, 3). Incongruent results appeared in two morphologically identified species clades, C. hirundinacea and C. pleurospilus, and in the clade containing the taxa C. “margaritifera” and C. stella (Figure 2). In all of these clades, the ABGD predicted a single OTU (species) whereas the bPTP tended to separate it into two allopatrically distributed entities. By examining the genetic divergence between the sister OTUs within each clade, we found a limited genetic difference of only 1.9% for the C. hirundinacea clade, 2.6% for the C. pleurospilus clade, and 3.1% for the C. stella/C. “margaritifera” clade. When further comparing the morphology from the conspecific and available specimens of each clade, we found only slight coloration differences but no significant difference in morphometrics and meristic counts among conspecific individuals. Here, we followed the criterion of species delimitation suggested by Kekkonen and Hebert (2014); that is, merging allopatric clusters and considering them to be the same species when the results from both species delimitation analyses are in disagreement and when there is no other evidence indicating the presence of reproductive isolation between the compared OTUs. As a result, we validated a total of 15 inferred species in Chelidoperca on the basis of the samples examined in this study (Figure 2).

C. margaritifera is currently known to be distributed only around its type locality, the Bird's Head Peninsula region, West Papua (Matsunuma et al., 2018), and was included in our analyses. However, the C. “margaritifera” samples used for COI gene analysis were from the South China Sea, which is around 1,000 km from the species' type locality. Corresponding sequences were retrieved from the BOLD system, and upon examination we found they were very similar to those from the C. stella samples collected from the Philippines (average K2P distance = 1.1%). We were unable to check the species identification for C. “margaritifera” samples from the South China Sea due to not having access to voucher specimens. However, considering the combined evidence from our species delimitation analyses and the geographic distributions of the two concerned species, we opine that the C. “margaritifera” samples from the South China Sea were misidentified and should be referred to C. stella, which is a widespread species distributed from the Andaman Sea in the eastern Indian Ocean to the South China Sea and to the Coral Sea, including New Caledonia and Vanuatu, according to the new data presented in this study (Figures 1, 2).

Morphological Comparison

Fifty newly collected specimens were used to carry out the morphological examination and comparison. The specimens of C. sp. 5 and C. sp. 6 were not examined because the voucher specimens deposited in the ASIZP were unavailable (specimens were loaned to others). Data from examined specimens are provided in Supplementary Data 1. The comparison of meristic and morphometric data from the specimens of the selected species is summarized in Tables 1–8.

TABLE 1

Table 1. Meristic features of Chelidoperca leucostigmata sp. nov. and C. santosi from references; bold font presents distinguishing characteristics; parentheses in Williams and Carpenter (2015) contains holotype data.

In general appearance, the species of Chelidoperca are small-sized fishes with relatively slender and elongated bodies (Figures 4–7). The species are characterized by the following combined characters: dorsal-fin rays usually X, 10; anal-fin rays usually III, 6; two flattened strong opercular spines; and body coloration mostly pale pink (Matsunuma and Motomura, 2016; Matsunuma et al., 2018; this study). In spite of the similarity in overall appearance, the species occurring in the West Pacific (including the new species discovered in this study) can usually be distinguished from each other by the combination of the following characters: body color pattern, number of pored lateral-line scales, number of scale rows between the lateral line and the middle of the spinous dorsal-fin base, presence of scales on the dentary, and presence of enlarged canines on the upper jaw. In color pattern, C. sp. 1 is characterized by having several predominant white spots lying just above the lateral line on the body, which is unique among recognized species (Figure 5). C. margaritifera (no real samples included in this study), C. lecormi (Figure 4), and Chelidoperca sp. 3 (orange spot) (Figure 4) are characterized by having a yellow stripe [along the lateral line in C. lecromi and Chelidoperca sp. 3 (orange spot); and along ventral potion of body in C. margaritifera], which is absent in other congenic species (Williams and Carpenter, 2015; Matsunuma et al., 2018; this study). Among them, C. margaritifera also presents numerous small white spots below the yellow stripe. C. sp. 3 (orange spots) is characterized by having orange spots on pectoral and caudal fin bases (Figure 4).

FIGURE 4

Figure 4. Chelidoperca lecromi (A–C) from off Chesterfield Island, Coral Sea, and Chelidoperca sp. 3 (orange spot) (D,E) from Kelso Bank, Coral Sea. (A) MNHN1981-1436 (holotype) standard length 125.3 mm (photographed by MM); (B) NTUM13749 (NC1452), collected on 22 Sep 2017; standard length 102.3 mm (photographed by MYL); (C) NTUM13749 (NC1453), collected on 22 Sep 2017; standard length 63.7 mm (photographed by MYL). (D) NTUM13736 (NC1101), collected on 5 Sep 2017; standard length 90.0 mm (photographed by MYL); (E) NTUM13737 (NC1115), collected on 5 Sep 2017; standard length 110.4 mm (photographed by MYL). Bars = 10 mm.

FIGURE 5

Figure 5. Chelidoperca leucostigmata sp. nov. from north Macclesfield bank. (A) NTUM14721 (WJC5843, holotype), collected on 26 Jul 2015; standard length 85.0 mm (photographed by WJC-Lab); (B) NTUM15634 (WJC5911, paratype), collected on 26 Jul 2015; standard length 57.6 mm (photographed by WJC-Lab); (C) same specimen in (A), showing preserved pigmentation (photographed by MYL). Bars = 10 mm.

The number of pored lateral-line scales is different among Chelidoperca spp., and the West Pacific Chelidoperca can be separated into two groups by this character. The low-number group having 33–37 (usually 34–35) pored lateral-line scales consists of C. stella and Chelidoperca sp. 4; the high-number group having 37–46 (usually ≥ 38) pored lateral-line scales contains nine species: C. hirundinacea, C. lecromi, C. margaritifera, C. pleurospilus C. tosaensis, C. santosi, C. sp. 1, C. sp. 2, and C. sp. 3 (orange spot) (Tables 1–4; Supplementary Data 1) (Williams and Carpenter, 2015; Matsunuma and Motomura, 2016; Matsunuma et al., 2018). In terms of the number of scale rows between the lateral line and the middle of the spinous dorsal fin base (Supplementary Figure 1), the six West Pacific species, C. margaritifera, C. stella, C. tosaensis, Chelidoperca sp. 1, Chelidoperca sp. 2, and Chelidoperca sp. 4, have three scales rows whereas the five other species, C. hirundinacea, C. lecromi, C. pleurospilus, C. santosi, and Chelidoperca sp. 3 (orange spot), have four scales rows [(Williams and Carpenter, 2015; Matsunuma et al., 2018); this study]. While examining the scale rows on the dentary (Supplementary Figures 2B,D,F,H), we observed that they are present (at least one scale row) in the six West Pacific species, C. hirundinacea, C. margaritifera, C. pleurospilus, C. santosi, C. stella, and C. sp. 1, but absent in the other five, C. lecromi, C. tosaensis, C. sp. 2, C. sp. 3 (orange spot), and C. sp. 4 (Williams and Carpenter, 2015; Matsunuma et al., 2018; this study). On their upper jaw, enlarged canines (Supplementary Figure 3) are present in eight West-Pacific species, C. lecromi, C. tosaensis, C. pleurospilus, C. santosi, C. stella, C. sp. 1, C. sp. 3 (orange spot), and C. sp. 4, but absent in C. hirundinacea, C. margaritifera, and C. sp. 2 (Williams and Carpenter, 2015; Matsunuma et al., 2018; this study). In addition to these key morphological features, the fresh pigmentation observed and morphometrics from specimens or photographs are also important in distinguishing them, especially in separating new species from similar and/or closely related congenic species. Detailed comparisons are given in the following section on taxonomy.

TABLE 2

Table 2. Meristic features of Chelidoperca microdon sp. nov. and C. tosaensis (including examined specimens and reference data); bold font presents distinguishing characteristics; parentheses in Matsunuma et al. (2018) contains holotype data.

TABLE 3

Table 3. Meristic features of Chelidoperca barazeri sp. nov. and C. stella (including examined specimens and reference data); bold font presents distinguishing characteristics; parentheses in Matsunuma and Motomura (2016) contains holotype data.

TABLE 4

Table 4. Meristic features of Chelidoperca lecromi (including examined specimens and references data) and Chelidoperca sp. 3 (orange spot); bold font presents distinguishing characteristics.

Taxonomy

Below, we formally describe three of the newly discovered species in this study on the basis of available specimens. Subsequent to the original description of C. lecromi, only one holotype (MNHN1981–1436) and one paratype (MNHN1981–1437) have ever been collected. In this study, seven fresh specimens, among which six were collected close to its type locality around the Chesterfield islands in the Coral Sea, were available for examination. Here, and for the first time, we redescribe C. lecromi in detail and provide images of its fresh coloration. Finally, by combining the results of the morphological examination and data from taxonomic references of Chelidoperca, a diagnostic key for the West Pacific Chelidoperca spp. is provided.

Chelidoperca leucostigmata sp. nov. (Figure 5; Supplementary Figures 1B, 2C,D, 3B; Tables 1, 5)

Previously Referred to as Chelidoperca sp. 1

Holotype

NTUM14721 (tissue voucher: WJC5843), 85.5 mm SL, sta. CP4149, 16°07′N, 114°20′E, 162–165 m, north Macclesfield Bank, South China Sea, Ocean Research I, French beam trawl, ZhongSha 2015 expedition, 26 Jul 2015.

TABLE 5

Table 5. Mophometrics expressed as percentages of the standard length for Chelidoperca leucostigmata sp. nov.

Paratypes

Five specimens (52.3–57.6 mm SL): NTUM15632 (tissue voucher: WJC5681), 56.0 mm SL, sta. DW4144, 16°07′S, 114°23′E, 161 m, north Macclesfield Bank, South China Sea, Ocean Research I, Waren Dredge, ZhongSha 2015 expedition, 26 Jul 2015. NTUM15634 (tissue voucher: WJC5910 & 5911), two specimens, 56.1–57.6 mm SL, sta. CP4150, 16°07′N, 114°24′E, 162–163 m, north Macclesfield Bank, South China Sea, Ocean Research I, French beam trawl, ZhongSha 2015 expedition, 26 Jul 2015. NTUM15355 (tissue voucher: WJC5844 & 5845), two specimens, 52.2–55.7 mm SL, sta. CP4149, 16°07′N, 114°20′E, 162–165 m, north Macclesfield Bank, South China Sea, Ocean Research I, French beam trawl, ZhongSha 2015 expedition, 26 Jul 2015.

ZooBank registration

urn:lsid:zoobank.org: act:CF478E5E-3A64-42CA-9CA3-B528287 41EE0.

GenBank registration of the holotype

MK988055 (COI); MK988087 (RAG1).

Diagnosis

Chelidoperca leucostigmata is characterized by the combination of the following morphological characters: 44 pored lateral line scale rows; 3 (dorsal-most scale half-sized) scale rows between the lateral line and middle of spinous dorsal fin base; relatively fewer scale rows 5–6 cheek; scale rows present on ventral side of dentary; scale rows on interorbital area extend beyond the level of the anterior pupil rim, reaching the anterior orbit rim; longitudinal series of clear white spots along lateral line; and elliptical light yellow mark on side of body. Along the COI gene, the following apomorphic sites have unique nucleotides shared by all six specimens of C. leucostigmata examined so far; these nucleotide sites can be used for the diagnosis of the species to other congeners. Nos. 168 (T vs. C), 180 (T vs. A, G or C), 451 (A vs. G), 522 (T vs. A or C), 621 (T vs. C).

Description

Morphometric and selected meristic values are summarized in Tables 1, 5. Dorsal fin rays X, 10; anal-fin rays III, 6; pectoral fin rays 16; pelvic fin rays I, 5. Body fusiform, slightly elongated; snout round; caudal peduncle moderately long. Orbit large, its dorsal margin included in the dorsal contour of the head. Mouth large, slightly oblique; posterior margin of maxilla reaching a vertical through mid-orbit; maxilla expanded posteriorly, with low lateral ridge along dorsal margin; lower jaw slightly protruding beyond upper jaw when mouth closed.

Upper jaw with band of 7 (5–7) rows (in anterior portion) of small, sharp-tipped conical teeth, tooth band becoming narrow posteriorly, outermost row of teeth enlarged, anteriorly projecting antrorse canines (Supplementary Figure 3B); lower jaw with band of about 5 (4–5) rows (in anterior portion) of small, sharp-tipped conical teeth, innermost and outermost rows of teeth enlarged canines, band of small teeth narrowing posteriorly; vomer with V-shaped band of about four rows of small conical teeth; palatine with relatively long band of four rows of small, sharp-tipped conical teeth. Anterior nostrils situated at middle of snout, with small rounded flap rising from posterior rim; posterior nostril with elliptical opening at anterior border of orbit.

Posterior margins of preopercle, interopercle and subopercle finely serrated, serrae on preopercle 39 on both sides (28–39), interopercle 15 (13 on the right side) (6–15); serrae on subopercle about 25 (23 on the right side) (14–25), relatively weaker; number of serrae generally increasing with growth. Opercle with two flat, prominent spines, upper spine slightly longer than lower. Posttemporal with 5 (4) (2–5) serrae tips at beginning of lateral line.

Body covered with ctenoid scales; lateral line slightly arched, gradually descending over pectoral fin, terminating at caudal-fin base. Uppermost row of body scales along dorsal-fin base always about half the size of adjacent lower body scales; tiny and irregularly spaced scales present at bases of spines. Caudal-fin base covered with ctenoid scales, extending onto fin over about half of basal length (depends on specimen condition) of fin. Pectoral fin with ctenoid basal scales, small elongate cycloid scales extending onto fin ventrally. Basal scales absent on either dorsal fin or anal fin. Pelvic-fin base covered with small elongate cycloid scales, but not extending onto fin. Head generally covered with scales, snout and maxilla naked; scales on ventral surface of lower jaw present on angular, and present posteriorly on dentary (Supplementary Figure 2D); opercle, interopercle, and subopercle with both ctenoid and cycloid scales; interorbital region with 1–2 rows of cycloid scales, extending from mid-orbit to around anterior pupil rim (Supplementary Figure 2C). A pair of interorbital canals with numerous small pores along outer margin of interorbital region. Lower jaw with around 4–5 pores anteriorly on each side of dentary symphysis, followed on each side by two pore positions along dentary sensory canal, each position with a single pore, and a fourth slit-like or rounded pore at angular–dentary junction.

Dorsal-fin origin above pectoral-fin base, 5th (or 4th) spine longest, 1st spine shortest; all soft rays branched, subequal in length. Anal-fin origin below base of 1st or 2nd dorsal-fin soft ray, 3rd spine longest; all soft rays branched, 5th ray longest. Posterior tip of dorsal and anal fins reaching a vertical through caudal-fin base when fins adpressed. Pectoral fin with uppermost two rays unbranched, remaining rays branched, 9th longest, its posterior tip being vertical through anal-fin origin. Pelvic-fin origin below pectoral-fin base; spine covered with skin; all soft rays branched, 2nd longest, elongate, slightly expanded distally, its tip reaching anus when adpressed. Caudal fin emarginate; upper lobe with elongate tip, slightly longer than lower lobe; upper lobe with seven unbranched unsegmented procurrent rays, 2–3 unbranched segmented rays, and eight branched segmented rays; lower lobe with 6–7 unbranched unsegmented procurrent rays, 2–3 unbranched segmented rays, and eight branched segmented rays; 19–21 segmented rays in total.

Formula for configuration of supraneural bones, anterior neural spines, and anterior dorsal pterygiophores 0/0/0 + 2/1 + 1/1; vertebrae 10 + 14.

Fresh coloration (based on color photographs of the following specimens when fresh, NTUM14721 [holotype] and NTUM15634) (Figures 5A,B): head pinkish orange, gradually becoming whitish ventrally; tips of upper-jaw and lower-jaw pinkish; snout pinkish; yellow mark extends from suborbital region along dorsal margin of maxilla to ventral corner of cheek, along anteroventral margin of cheek; yellow mark present on suborbital rim; color patterns of cheek and opercle generally the same as that of head. Body pinkish to orange, becoming whitish ventrally; row of clear white spots present dorsally along lateral line (few white spots not in line with the rest sometimes, present ventrally or dorsally), curving upwardly around 7th−8th dorsal-fin ray, descending afterward, terminating at caudal-fin base; row of around 15 poorly defined white spots midlaterally; six irregular, broad orange bands extending from dorsal profile to about ventral profile, distributing from fourth to fifth dorsal-fin spine to caudal fin base; an elliptical light yellow mark below lateral line present at around 5th dorsal-fin spine to 8th dorsal-fin spine. Spinous dorsal-fin membrane translucent white, with two longitudinal rows of yellow spots, one at about a third length of rays, one at about two thirds of length of rays; soft dorsal-fin membrane translucent, with yellow distal margin, and yellow spots scattered over fin in irregularly diagonal rows. Anal fin dusky white, with narrow yellow distal margin and yellow spots scattered over fin in irregularly diagonal rows (sometimes ambiguous). Pectoral fin translucent or with pale yellowish tint, an unclear reddish orange blotch basally on middle rays. Pelvic fin generally pale with yellow tint. Caudal fin generally translucent, with a transverse red to dark brown band on caudal-fin base and irregular diagonal rows of dark spots over fin.

Preserved coloration (based on all examined specimens) (Figure 5C): head and body tan, no melanophore or coloration remain.

Distribution

Chelidoperca leucostigmata is a relatively shallow water perchlet, known only from six specimens collected at depths ranging 161–165 m on Macclesfield Bank (Zhongsha), South China Sea (Figure 1).

Etymology

The name leucostigmata is derived from the Greek, leuco meaning white, and stigmata, meaning spots, in reference to the row of mid-lateral white spots when fresh.

Comparisons

C. leucostigmata can be distinguished from C. hirundinacea, C. lecromi, C. microdon, and C. pleurospilus by having three scale rows between the lateral line and middle of the dorsal-fin base (Matsunuma et al., 2018; this study: Supplementary Figure 1B). Among the species having three scale rows in that region, C. leucostigmata can be distinguished from other congeners except C. santosi by having 43 or more pored lateral-line scales and enlarged canines on the upper jaw. In meristics, C. leucostigmata differs from C. santosi in having more scale rows below the lateral line (12–13 vs. 10–11 in C. santosi), circumpeduncular scale rows (20–24 vs. 19–20 in C. santosi), fewer preopercular serrae (28–39 vs. 40–45 in C. santosi), and fewer total gill rakers (16–19 vs. 20–22 in C. santosi) (Table 1). In pigmentation, C. leucostigmata has a longitudinal series of clear white spots along the lateral line (vs. no white spots along body in C. santosi) and uniformly pigmentation on the snout (vs. two black spots on each side of snout in C. santosi) (this study). C. leucostigmata is phylogenetically close to C. santosi (Figure 2).

Remarks

C. hirundinacea, C. stella, and C. tosaensis sometimes have the row of white spots along the lateral line with different combinations of characters.