We describe a new species of goby, Varicus lacerta sp. n., which was collected from a mesophotic reef at Curacao, southern Caribbean. The new species is the tenth species of Varicus, all of which occur below traditional SCUBA depths in the wider Caribbean area. Its placement in the genus Varicus is supported by a molecular phylogenetic analysis of three nuclear genes and the mitochondrial gene cytochrome b. In addition, the new species has one anal-fin pterygiophore inserted anterior to the first haemal spine, which distinguishes Varicus species from most species in the closely related and morphologically similar genus Psilotris. Varicus lacerta sp. n. is distinguished from all other named species of Varicus by the absence of scales, having highly branched, feather-like pelvic-fin rays, and in its live coloration. We provide the cytochrome c oxidase I DNA barcode of the holotype and compare color patterns of all species of Varicus and Psilotris for which color photographs or illustrations are available. This study is one of several recent studies demonstrating the utility of manned submersibles in exploring the diversity of poorly studied but species-rich deep-reef habitats.

Systematics, molecular phylogeny, deep reefs, submersible, Curaçao, Psilotris

Operating out of Substation Curaçao (www.substation-curacao.com), the Smithsonian Institution’s Deep Reef Observation Project (DROP) uses the manned submersible Curasub to capture tropical marine fishes and invertebrates at depths up to 300 m, providing new information on the fauna that inhabits poorly studied deep-reef ecosystems. DROP’s exploratory submersible diving in the southern Caribbean has led to the discovery of a cache of undescribed fish biodiversity, some of which has been recently described (Van Tassell et al. 2012; Baldwin and Johnson 2013; Baldwin and Robertson 2013, 2014, 2015; Tornabene et al. 2016). Many of the new species belong to the Gobiidae, most notably the tribe Gobiosomatini (Van Tassell et al. 2012; Tornabene et al. 2016). This tribe comprises the American seven-spined gobies, a taxonomically and ecologically diverse clade of fishes that is endemic to the western Atlantic and eastern Pacific Oceans. A repeated pattern of rapid speciation via microhabitat specialization in this tribe has resulted in the Gobiosomatini becoming a model group for the study of adaptive radiation in the marine environment (Rüber et al. 2003; Taylor and Hellberg 2005; Tornabene et al. in press). One of the most ecologically and taxonomically diverse clades within the Gobiosomatini is the Nes subgroup, which comprises 39 species in 11 genera that inhabit a wide variety of marine habitats (Tornabene et al. 2016). Within the Nes subgroup, three genera have species described from mesophotic reefs below 50 m: Pinnichthys Gilmore, Van Tassell & Tornabene, 2016, with four species, all from deep reefs; Psilotris Ginsburg, 1953, with six species, one from deep reefs; and Varicus Robins & Böhlke, 1961 with nine species prior to this study, all from deep reefs (Tornabene et al. 2016). Here we describe a tenth deep-reef species of Varicus based on a single specimen that was collected at 129-147 m from Curaçao.

The new species was collected using the Curasub manned submersible. The sub has two hydraulic arms, one equipped with a suction hose and the other with a quinaldine-ejection system used to anaesthetize fishes. Specimens collected with the suction hose are deposited into a vented acrylic cylinder attached to the outside of the sub. The captured holotype was brought to the surface alive, where it was photographed and tissue sampled prior to fixation in 10% buffered formalin and subsequent storage in 75% ethanol.

Tissue from the holotype was stored in saturated salt-DMSO (dimethyl sulfoxide) buffer (Seutin et al. 1991). DNA extraction and cytochrome c oxidase subunit I (COI) DNA barcoding were performed as outlined by Weigt et al. (2012). To confirm the phylogenetic placement of the new species we also sequenced the mitochondrial gene cytochrome b and the nuclear genes Rag1, sreb2, and zic1. Following nomenclature of Chakrabarty et al. (2013), new sequences here constitute genseq-1 COI, cytb, Rag1, sreb2, and zic1. Primers and PCR conditions for amplifying these four loci were identical to those used in Agoretta et al. (2013). Sequences generated here were aligned with Gobiosomatini sequences from Tornabene et al. (2016) in Geneious v. 9 (Biomatters, Ltd., Auckland). Substitution model choice and partitioning scheme were assessed using PartitionFinder (Lanfear et al. 2012). Phylogeny was inferred using Bayesian inference in the program MrBayes ver. 3.2, using two Metropolis-coupled Markov Chain Monte Carlo (MCMC) runs, each with four chains. The analysis was run for 10 million generations sampling trees and parameters every 1000 generations. Burn-in, convergence and mixing were assessed using Tracer (Rambaut and Drummond 2007) and by visually inspecting consensus trees from both runs.

All measurements were taken with digital calipers to the nearest 0.1 mm. Vertebral counts and pterygiophore patterns were taken from digital radiographs. Dorsal pterygiophore formula is that of Birdsong et al. (1988), and head pore terminology follows Akihito et al. (1988). Sensory papillae are described following the terminology of Sanzo (1911), with the exception that the interorbital series follows terminology described by Tornabene et al. (2016). All other morphological characters are as defined by Böhlke and Robins (1968) as modified by Van Tassell et al. (2012), who like many authors, differentiate the unsegmented spine from the segmented rays of the second dorsal, anal, and pelvic fins using the roman numeral ‘I’ for the spine followed by Arabic numbers for the soft rays. The holotype was deposited at the National Museum of Natural History, Smithsonian Institution(USNM).

The molecular phylogeny (Fig. 1) shows the new species nested within the genus Varicus, where it is recovered as sister to an undescribed species Varicus sp. 1 from Curaçao. This undescribed species is represented by a single specimen in poor condition that also lacks body scales, but is readily distinguishable from V. lacerta based on live coloration (see below). Varicus lacerta is easily distinguished from all described congeners by the absence of scales on the body and the presence of highly branched, feather-like pelvic-fin rays 1-4. Varicus decorum Van Tassell, Baldwin & Tornabene, 2016, lacks scales on most of the body, but possesses a pair of small, ctenoid scales on each side of the caudal peduncle near the base of the caudal fin, which are absent in V. lacerta. Live coloration also easily distinguishes V. lacerta from all other species of Varicus for which the live color pattern is known (Fig. 6). While V. lacerta has a color pattern of indistinct broad dark bars on a yellowish body, in five other Varicus species (V. cephalocellatus Gilmore, Van Tassell & Baldwin, 2016, V. decorum, V. nigritus Gilmore Van Tasell & Baldwin, 2016, Varicus sp. 1, and V. veliguttatus Van Tassell, Baldwin & Gilmore, 2016) the color pattern comprises blotches and spots of yellow or black on a white body. Varicus lacerta differs from V. adamsi Gilmore, Van Tassell & Tornabene, 2016, and V. vespa Hastings & Bortone (1981), in having indistinct broad dark bars on a yellowish body and yellow median fins vs narrow yellow bars on a white body and white median fins with black edges in V. adamsi, and narrow brown bars on a white body and white fins with black borders in V. vespa. While V. lacerta has a yellowish body with indistinct broad dark bars, uniformly yellow dorsal and caudal fins, and a yellow anal fin accentuated with dark orange, in V. marilynae Gilmore, 1979 the body is yellow above, reddish orange below, the body bars are narrow, green-edged and dark brown, the dorsal and tail fins have narrow yellow stripes and bars, and the anal fin is red with a black border.

Figure 6. 

Coloration of species of Varicus. All illustrations by R. Grant Gilmore. Photographs by Barry Brown, Ross Robertson and Carole Baldwin (Varicus sp. 1), and the crew of the R/V Bellows (for V. vespa). Photos of V. bucca and V. benthonis not available.

The absence of scales and the presence of highly branched pelvic rays without fleshy tips make this species superficially similar to species of Psilotris. No single morphological character unambiguously distinguishes Varicus from Psilotris, but the most consistent morphological feature thus far is the presence of a single anal-fin pterygiophore inserted before the first haemal spine in Varicus versus two in all but one species of Psilotris. Psilotris laurae Van Tassell, Tornabene & Baldwin, 2016, has a single pterygiophore anterior to the haemal spine, and it is the only known deep-reef species of Psilotris. The relationship between anal-fin pterygiophore pattern and habitat depth warrants further investigation.

Despite the morphological similarities between V. lacerta and species of Psilotris, the new species is easily distinguished by live coloration (Fig. 7). Only three members of Psilotris have discrete body bars: P. alepis Ginsburg, 1953, with irregular grey bars on a white body speckled with black and brown; P. celsa Böhlke, 1963, with irregular narrow orange bars on a white body and head; and P. laurae, with narrow, strongly defined dark-yellow bars on a white head and body. Psilotris boehlkei Greenfield, 1993, P. kaufmani Greenfield, Findley & Johnson, 1993, and P. laetarii Van Tassell & Young, 2016, lack bars. Varicus lacerta can also be distinguished from P. boehlkei, P. celsa, P. kaufmani and P. laurae by having I,7 anal-fin rays (vs. > I,7; Table 1), and from P. alepis, P. celsa, and P. laetarii in having 18 pectoral-fin rays (vs. <18; Table 1). The connection of papillae rows 5i and 5s further distinguishes V. lacerta from P. alepis and P. boehlkei, in which rows 5i and 5s are separate.

Figure 7. 

Coloration of species of Psilotris. Photos by Luiz Rocha, Jeffrey Williams, Ross Robertson, Barry Brown, and James Van Tassell.

We thank Thomas Devine for assistance in the field and with DNA barcoding the holotype specimen; Matthew DeSaix for his help with molecular work; Jeffrey T. Williams and Diane Pitassy for cataloging material, and Sandra Raredon for photographing the preserved holotype and assisting with radiographs. We are grateful for the help of Cristina Castillo, Adriaan ‘Dutch’ Schrier, Barry Brown, Bruce Brandt, and the rest of the staff of Substation Curacao for their assistance in the field. The project was funded in part by the Smithsonian Peter Buck Fellowship to LT. Funding for the Smithsonian Institution’s Deep Reef Observation Project was provided internally by the Consortium for Understanding and Sustaining a Biodiverse Planet to CCB, the Competitive Grants for the Promotion of Science program to CCB and DRR, the Herbert R. and Evelyn Axelrod Endowment Fund for systematic ichthyology to CCB, and externally by the Prince Albert II of Monaco Foundation. This study is Ocean Heritage Foundation/Curacao Sea Aquarium/Substation Curacao contribution number OHF/CSA/SC#24.