INTRODUCTION

Parapercis Bleeker, 1863 is a species-rich pinguipedid genus that currently comprises approximately 90 valid species (Johnson and Motomura, 2017; Johnson and Wilmer, 2018; Ho, 2015; Fricke et al., 2021) and exhibits a wide distribution extending from the eastern Atlantic to the central Pacific oceans. In the past decade alone, 23 novel species have been formally described (see references in Johnson and Motomura, 2017; Yosuva et al., 2020; Fricke et al., 2021), not including the new species described herein, and several additional novel species are awaiting formal description. Parapercis are commonly known as sandperches and are generally colorful, ornately pigmented elongate fishes that frequently occur over sandflats or rubble on or near coral reefs. Members of the genus are conservative in terms of general body shape and meristic features, tending to overlap considerably, such that the most useful diagnostic features for distinguishing species are frequently pigmentation pattern and coloration.

As Johnson and Wilmer (2018) note, with the increase in deeper reef exploration beyond 40 m using closed circuit rebreathers, and demersal trawling in depths up to 400 m, several novel members of Parapercis from mesophotic/rariphotic reef habitats, and even deeper, have been discovered and described in recent years. Herein we describe a new species of Parapercis collected at rariphotic depths in the Western Province of the Solomon Islands. The new species was observed and collected at a depth of 187 m using a novel ROV-based rotenone fish sampler that our research team designed and successfully deployed for the first time in the Solomon Islands in 2019 (Chaloux et al., 2021; fig. 1A). ROV-based ichthyological sampling of mesophotic and rariphotic reefs adds yet another means of accessing and exploring these vastly understudied habitats.

MATERIALS AND METHODS

The holotype of the new species, along with several other mesophotic/rariphotic species, was collected via a novel ROV-based rotenone fish sampler at 187 m depth just outside of Peava Island lagoon in the Western Province of the Solomon Islands on July 28, 2019. We use the recently defined term, rariphotic, to refer to a faunal zone below the mesophotic and above the aphotic, and ranging from ∼130 to 309 m (Baldwin et al., 2018). Figure 1B shows the new species being imaged via a camera mounted on the ROV just prior to collection. Videos and still images of the new species in its natural habitat were taken via an Insite Pacific HD camera affixed with a 5.1–51 mm 10× mechanical zoom that was mounted to the front of the ROV and that recorded 1080 p (progressive scan) video at 60 frames per second (fps). Still images in aquaria were acquired with a Nikon D800 or D4 DSLR fitted with a Nikon AF-S Micro NIKKOR 105 mm f/2.8 macro lens.

The holotype of the new species was fixed in 10% formalin and preserved in 75% ethanol. Osteological features of the new species and related taxa were examined using radiographs, dry skeletal preparations, and specimens cleared-and-stained (C&S) for bone and cartilage (following the protocol of Taylor and Van Dyke, 1985). Morphometric measurements were recorded to the nearest 0.1 mm using dial calipers. Standard length (SL) is used throughout. Vertebral counts exclude the ural centrum (= last half-centrum). Terminology follows Cantwell (1964), Randall (2008), and Sparks and Baldwin (2012), unless noted otherwise. Following Hubbs and Lagler (1949), the first caudal vertebra is defined here as the first vertebra bearing a definitive hemal spine. Vertebral and fin spine/ray counts were obtained from radiographs. Pored scales in the lateral line are counted in series from the dorsal margin of the gill opening to the caudal flexure; scales posterior of flexure are not included in the count. Institutional abbreviations are as listed in Leviton et al. (1985) and Sabaj Pérez (2019).

RESULTS

Systematic Account

Parapercis rota, new species
Figures 1B, 2, 3; table 1

Holotype: AMNH 277100, 44.3 mm SL; Western Province, Solomon Islands, Peava Island; ROV-based rotenone collection from anchor just offshore and outside of Peava Island lagoon; 187 m depth; 8°47′03.3″S 158°14′08.7″E; JSS-SI19-010; J.S. Sparks, N. Chaloux, and B.T. Phillips, July 28, 2019.

Diagnosis: The new species is readily distinguished from all congeners by a unique pigmentation pattern, comprising four large, rounded, orangish-olive saddles dorsally on the flank, each with a large distinct dorsomedial white spot completely enclosed within the saddles, such that they resemble wheels, plus a much smaller fifth saddle on the caudal peduncle with only a small white dorsomedial spot, 10 discrete broad, dark orangish-olive oval vertical bars below the lateral midline, a single row of dark spots on the soft dorsal fin, the caudal fin is lined dorsally and ventrally with stripes of yellowish-olive pigmentation extending the length of the fin, and two prominent dark brown to black spots at the caudal-fin base.

Description: Selected proportional measurements and meristic data presented in table 1. Body elongate and moderately dorsoventrally depressed anteriorly. Body becoming rounded and tubular in cross section medially, and increasingly laterally compressed posteriorly. Head dorsoventrally depressed, particularly anteriorly, and not elongate. Snout short, weakly pointed in lateral profile. Snout more or less rounded in dorsal view. Predorsal profile mostly straight. Orbits very large. Eyes dorsolaterally oriented and fully visible (= included) in dorsal view. Interorbital width roughly half of orbit diameter. Suborbital distance slightly less than orbit height. Nape broad and flattened. Mouth relatively wide and moderate in size, slightly oblique, and jaws not elongate. Posterior margin of maxilla extending to a vertical approximately at anterior margin of orbit. Upper lip generally broad throughout. Lower lip broader anteromedially, becoming progressively narrow posteriorly. Lower jaw weakly prognathous. Rostral margin of lower jaw protruding slightly anterior to upper jaw. Symphysis of lower jaw rounded in shape in ventral view. Fleshy flap present below lower jaw.

Interorbital series comprised of seven elements, including lacrimal, with posterior, uppermost element firmly attached to neurocranium. Posterior margin of preopercle appears smooth, but with very fine serrations that are barely visible even under magnification. Opercle bearing a single well-developed spine. Midcaudal margin of subopercle bears three prominent serrations that resemble teeth. Operculum extending just anterior of a vertical at origin of spinous dorsal fin. Gill membranes free of isthmus, but with broad and substantial, medial flap of tissue.

Upper jaw with outer row of large, slightly recurved caniniform teeth, and an anteromedial band comprising several rows (four rows anteromedially) of much smaller villiform to small conical teeth. Villiform and small conical teeth in upper jaw restricted medially. Greatly enlarged outer canine teeth in upper jaw number three to four on each side, with the second or third tooth from symphysis of upper jaw largest. Posterolateral to greatly enlarged teeth surrounding symphysis, caniniform outer row teeth becoming progressively smaller posteriorly. Outermost row on lower jaw comprised of three large, recurved canine teeth on each side, with posteriormost, third tooth in series largest. A broad anteromedial band of small villiform to conical teeth present in lower jaw with multiple rows medially (three rows anteromedially), tapering to a single row posteriorly. Posterior teeth becoming caniniform and somewhat larger than those anterior in lower jaw. Vomer with two to three (medially) rows of very stout, slightly recurved conical teeth. Palatine teeth absent.

Lower limb of first gill arch with 10 elongate and triangular rakers, comprising nine denticulate outer ceratobranchial rakers, and one smaller hypobranchial raker of same morphology. Other rakers on arches two to four considerably shorter and more robust. These rakers highly denticulate apically with denticles directed medially. Six branchiostegals present.

Scales on flank and opercle comparatively large and strongly ctenoid. Smaller ctenoid scales present on caudal fin, and extending approximately 1/2 to 2/3 length of fin. Scales on nape reduced in size. Scales on nape cycloid anteriorly and becoming weakly ctenoid posteriorly. Scales on cheek numerous and cycloid, much smaller than those on flank. Ventrum fully scaled. Interpelvic chest scales and scales below pectoral insertion markedly reduced in size, cycloid anteriorly and becoming increasingly ctenoid posteriorly. Lacrimal, snout, and occiput asquamate. Nine or 10 scales in diagonal from dorsal margin of opercle to origin of spinous dorsal fin. Seven scales in diagonal from lateral line to first ray of soft dorsal fin. Nine predorsal scales along dorsal midline. Pored scales in lateral line 58.

Fin spine and soft-ray counts as follows: dorsal V, 21; anal I, 17; pectoral 17; pelvic I, 5; principal caudal rays 9 upper + 7 lower, all branched. Vertebral count 10 precaudal + 19 caudal = 29. Anteriormost three to four vertebral centra noticeably reduced in size when viewed laterally. Dorsal insertion of pectoral fin at about level of vertical through origin of spinous dorsal fin; pectoral fin extending posteriorly to vertical through eighth soft dorsal-fin ray when adducted. Pelvic-fin origin at about level of vertical through posterior margin of opercle and extending to just past third anal-fin ray when adducted. Membrane of fifth dorsal spine attached to first ray of soft dorsal at about 1/2 of length of fifth spine measured from fin base. Anal-fin origin at vertical through fifth ray of soft dorsal fin. Soft dorsal terminating slightly anterior to anal-fin termination. Caudal fin relatively short and weakly emarginate.

Pigmentation in Life: Coloration of the freshly collected holotype is shown in figure 2. Pigmentation pattern on the upper flank comprises four large orangish-olive saddles, each with a distinct dorsomedial white spot comprising multiple scales that is completely surrounded by a wide margin of darker pigmentation, plus a fifth saddle on the caudal peduncle with only a very small dorsomedial white dot. Each saddle is broadly outlined in white. Scales within the flank saddles are outlined in dark olive. Saddles with burgundy pigmentation dorsally, neon green medially, and with dark red stripes along their ventral margin. There are 10 discrete, dark orangish-olive oval vertical bars below the lateral midline, and two prominent dark brown to black spots at the caudal fin base, with the lower spot somewhat smaller and more diffuse than the upper. The chest and belly are white and somewhat iridescent. The dorsal fin is hyaline with a single row of well-defined dark olive spots at about 2/3 length of the dorsal spines and rays spanning the length of the soft dorsal fin, and also with some dark olive pigmentation distally. The caudal fin is hyaline centrally and distally along the posterior margin, somewhat white centrally, and with stripes of yellowish-olive pigmentation dorsally and ventrally extending the length of the fin. There are two black patches distally on the caudal fin central to the bands of yellowish-olive pigmentation. The pectoral fin is mostly hyaline with some yellowish pigmentation dorsally, and the pelvic fin is bright white.

Pigmentation in Preservative: Coloration in alcohol is shown in figure 3. Overall body coloration is tan to light brown with only faint remnants of the dorsal saddles, series of vertical bars below the lateral midline, and spots at the caudal base remaining in preservative. Additionally, a large black blotch is present posterior to the orbit and another smaller black blotch is present dorsally on the preopercle. All remaining faint markings are black or dark brown in coloration. All other former pigmentation has faded in preservation.

Distribution: Known only from a single specimen collected by an ROV-based rotenone fish sampler (fig. 1A) at a depth of 187 m in the Western Province of the Solomon Islands near Peava Island, just outside of Peava Lagoon (8°47′03.3″S 158°14′08.7″E). The specimen was collected on a mostly barren rocky outcropping surrounded by sandy substrate and rubble, where other mesophotic/rariphotic species, were also observed and collected (fig. 1B). Additional individuals of the new species were observed at this locality, but could not be collected.

Etymology: Named in reference to the characteristic pigmentation pattern on the upper flank comprising well-defined dark saddles that are continuous (i.e., connected) ventrally along the lateral midline, and that have a central (= dorsomedial) white spot, such that they resemble wheels (Latin = rota).

FIG. 1.

A, ROV-based fish sampling system utilized to collect new Parapercis species being deployed in the Solomon Islands. The fish sampler can be seen mounted to the bottom of the ROV. B, Parapercis rota, new species, shown in its rariphotic habitat just prior to collection (enclosed by yellow oval) by ROV at 187 m depth in the Western Province, Solomon Islands. The suction intake of the fish sampler can be seen just below the specimen.

FIG. 2.

Parapercis rota, new species, holotype, AMNH 277100, Western Province, Solomon Islands, off Peava Island, 187 m depth. Imaged immediately following collection to illustrate pigmentation pattern in life.

FIG. 3.

Parapercis rota, new species, holotype, AMNH 277100, 44.3 mm SL. Preserved in ethanol.

DISCUSSION AND COMPARISONS

Based on examination of the original descriptions, museum collections, and available images of live, fresh, and preserved Parapercis specimens, the pigmentation pattern of P. rota is unique within the genus. As Allen and Erdmann (2012: 1156) noted, two other species that occur in the general region, P. biordinis Allen, 1976 (endemic to Western Australia), and P. diplospilus Gomon, 1981 (Philippines, Indonesia; Exmouth, Western Australia to Moreton Bay, Queensland; Bray, 2021), in addition to their newly described P. sagma Allen and Erdmann, 2012 (Indonesia, Vanuatu), also have a characteristic pair of dark spots at the base of the caudal fin. To these three species can be added, P. hoi Johnson and Motomura, 2017 (Philippines; Broome, Western Australia), and the new species (Solomon Islands), both of which also have a prominent pair of dark spots at the caudal base.

Of all Parapercis species occurring in the region, those most similar in terms of overall pigmentation pattern to P. rota are P. sagma, P. diplospilus, and P. snyderi (Indo-West Pacific, extending from southern Japan to Queensland and Western Australia; Bray, 2021). However, P. rota is easily distinguished from both P. sagma and P. diplospilus by the presence of only five large saddles in the new species, due to the fact that the darkly pigmented portions of the saddles are conjoined ventrally (above the lateral midline; fig. 2), in contrast to the pattern in P. sagma and P. diplospilus where the saddles are not continuous ventrally, but are interrupted by regions of lighter pigmentation. As a result, in the latter two species there are eight to nine smaller saddles spanning the length of the flank, lending these taxa a more mottled overall appearance.

Parapercis rota can be further distinguished from P. sagma by fewer vertebrae (29 vs. 31 in P. sagma), shorter jaws (maxilla reaching only to about anterior margin of orbit vs. extending through anterior 1/3 of orbit), fewer canine teeth on each side at the front of the lower jaw (3 vs. 4), fewer inner rows of teeth in both the upper (4 vs. 10) and lower (3-4 vs. 5-6) jaws, an increased number of dark vertical bars along the flank below the lateral midline (10 vs. 8–9), a single row of dark spots on the soft dorsal fin (vs. two rows), more caudal fin rays (16 vs. 15), an emarginate caudal fin (vs. weakly rounded), and a higher lateral-line scale count (58 vs. 53).

Although the new species was collected at a depth of 187 m, considerably deeper that the reported range of the type series of P. sagma, which is reported as 60–80 m (Allen and Erdmann, 2012), it is noteworthy that Ho (2015: 269) lists a number of MNHN nontype specimens of P. sagma from Vanuatu that he examined, most of which were collected at significantly deeper depths (up to 439 m) than were the specimens comprising the type series of Allen and Erdmann (2012: 60–80 m), which significantly extends the depth range of that species.

Parapercis rota is further distinguished from P. diplospilus by a nonmottled overall pigmentation pattern, particularly dorsal to the lateral midline (vs. highly mottled in P. diplospilus), more dark vertical bars below the lateral midline (10 vs. 9), a longer snout (9.5 vs. 6.5–7.1% SL), more pectoral-fin rays (17 vs. 14–16), fewer dorsal-fin soft rays (21 vs. 22), fewer anal-fin soft rays (17 vs. 18), a single row of dark spots on the soft dorsal fin (vs. 2–3 rows), and by a the presence of a somewhat diffuse lower dark spot at the caudal base (vs. both spots equally vivid).

Although P. snyderi Jordan and Starks, 1905, also has a similar number of large, rounded saddles on the upper flank as in P. rota, in P. snyderi these saddles have at most a small light dorsomedial dot, or the dot is lacking entirely, in contrast to a conspicuous dorsomedial region of white pigmentation comprising multiple scales in the new species (fig. 2). Parapercis rota can further be distinguished from P. snyderi by the presence of two prominent dark brown to black spots at the caudal-fin base (vs. absence in P. snyderi), absence of a heavily spotted operculum with solid, black pigmentation ventrally (vs. presence), absence of a darkly pigmented spinous dorsal fin (vs. presence), absence of multiple rows of large dark spots on the soft dorsal fin (single vs. 2–4 rows), more pectoral-fin rays (17 vs. 13–15), absence of a series of vertical rows of large dark spots on the caudal fin, lending the fin a striped appearance (vs. presence), and a significantly higher lateral-line scale count (58 vs. 38–43: P. snyderi lateral-line scale count range from Randall, 2003).

The other two species that possess a characteristic pair of dark spots at the base of the caudal fin, P. biordinis and P. hoi, both lack dark saddles on the upper flank. Instead, flank pigmentation in P. biordinis is characterized by two rows of small dark blotches, with each row comprised of four dark spots (Allen, 1976: fig. 3), whereas flank pigmentation in P. hoi is characterized by two rows of irregular dusky colored blotches, with each row comprised of seven blotches (Johnson and Motomura, 2017: fig. 6A, B).

TABLE 1.

Morphometric and meristic data for holotype of Parapercis rota.

Parapercis rota is further distinguished from P. biordinis by the absence of a pair of dark blotches on the medial portion of the caudal fin (vs. presence in P. biordinis), the presence of a series of 10 dark vertical blotches below the lateral midline (vs. four spots), fewer anal-fin rays (17 vs. 18), fewer pectoral-fin rays (17 vs. 18), and a higher lateral-line scale count (58 vs. 49–54: P. biordinis lateral-line scale count range from Allen, 1976, and Johnson and Motomura, 2017). Parapercis rota is further distinguished from P. hoi by a higher lateral-line scale count (58 vs. 49–50 in P. hoi), fewer vertebrae (29 vs. 30), a longer snout (9.5 vs. 6.8%–7.0% SL), the absence of a broad red bar ventral to the orbit and extending across the suborbital region (vs. presence), and the absence of a series of alternating dark and light wavy lines on the caudal fin (vs. presence).

Despite repeated attempts, only a single specimen of the new species could be collected via ROV during our 2019 expedition to the Solomon Islands. However, based on its unique and striking pigmentation pattern, which is quite unlike any described species of Parapercis, as well as the extreme depth (nearly 200 m) that the specimen was collected relative to most other members of the genus in the region except P. sagma, we believe that it is both justified and prudent to formally describe the new species at this time, particularly given the likelihood of obtaining additional specimens in the near future is quite low. However, we anticipate that with intensified collecting efforts focusing on deeper mesophotic/rariphotic reefs in the region via ROV-based ichthyological sampling devices like the one described herein, which are relatively affordable and can be operated by both a small crew and vessel, additional specimens attributable to the new species will be collected.

ACKNOWLEDGMENTS

Research and collecting permits were obtained from the Ministry of Fisheries and Marine Resources (MFMR Ref. F/12/11), and the Ministry of Environment, Climate Change, Disaster Management and Meteorology (MECDM Permits EX 2019/070 and BR/2019/004), Honiara, Solomon Islands. Fishes were collected and handled in accordance with AMNH Institutional Animal Care and Use Committee (IACUC) and American Fisheries Society (AFS) guidelines, as established for the safe and humane care and handling of vertebrate animals. This work was carried out in collaboration with and permitted by the Solomon Islands MFMR and MECDM, and facilitated in the Solomon Islands by the Wildlife Conservation Society (WCS, New York; Munda, Western Province, Solomon Islands). We thank Alec Hughes (WCS) for logistical support and help obtaining permits, Rendhy Sapiie for ROV operations and technical support, and Silentworld Shipping and Logistics, and the crew of the A.R. Ford (Honiara) for considerable support in the field. We are grateful to Hsuan-Ching (Hans) Ho (NMMBA) for helpful discussions regarding Parapercis, and for alerting us to species potentially resembling the new species for comparison. Many thanks to Gerald Allen (WAM) and William Leo Smith (KU) for help in identifying Solomon Islands fishes and for forwarding references and to Paul Loiselle (WCS) for assistance with naming the new species. We are grateful to Dave Casagrande and Todd Gregory/Gregory Designs LLC for their assistance with subsea electronics design, control software, and pressure housing design.

Funding: Field research was funded by a National Science Foundation award to J.S.S. (DEB-1257555) and the American Museum of Natural History (AMNH). The DeepReef ROV was funded via a National Science Foundation award to D.F.G. (MRI-1040321). We are grateful to the Ray and Barbara Dalio Family Foundation and OceanX for funding the design and construction of the ROV-based mesophotic fish sampler that permitted collection of the new species.