Chimaera buccanigella, Kemper, 2017

Kemper, Jenny M., 2017, New species of Chimaera (Chondrichthyes: Holocephali: Chimaeriformes: Chimaeridae) from the Southwestern Indian Ocean, Zootaxa 4312 (1), pp. 1-37 : 26-31

Chimaera buccanigella , sp. nov.

English vernacular name: Dark-mouth Chimaera French vernacular name: Chimère bouche-foncée ( Figs. 17–18 ; Tables 3–4)

Holotype. CAS 242335, 765 mm TL, 401 mm BDL, female, Southwestern Indian Ocean , Walters Shoal, 33o49’S, 42o22’E, bottom trawl between 495–960 m, collector P.J. Clerkin, 3 March 2012.

Non-Type specimens. MNHN 2004-0819 ( BPS0693 ), 729 mm TL, 346 mm BDL, immature male, Madagascar Ridge, Southwestern Indian Ocean , 33°21’S – 44°37’E to 33°28, 317’S–44°50, 525’E, 890 m – 910 m depth, collected by the F/ V Kerguelen de Tremarec, 31 July 2002;

MNHN 2004-0818 ( BPS0692 ), 861 mm TL, 338 mm BDL, immature male, Madagascar Ridge, Southwestern Indian Ocean , 33°21’S – 44°37’E to 33°28’S – 44°50’E, 890m – 910 m depth, collected by the F/ V Kerguelen de Tremarec, 31 July 2002.

Diagnosis. Chimaera buccanigella , sp. nov. is distinguishable from other members of the genus by the following combination of characters: medium-sized species with moderate head length, 28.3% BDL, eyes very large, 9.6% BDL, with defined suborbital ridge, relatively long snout measuring 13.1% BDL; trunk tapering rapidly into long tail, 60.4% BDL; uniform light tan color, not iridescent, no defined patterning, spots, reticulations, or mottling, dark sooty brown on snout, dark markings in and around mouth ( Fig. 17 c); pectoral fins with short anterior margin, 36.6% BDL, pelvic fins broad, pointed distally, tear-drop shaped, with short anterior margin, 22.1% BDL; dorsal spine long, thin, and very straight, height of spine not eXceeding height of first dorsal fin, when depressed just reaches origin of second dorsal fin; second dorsal fin not undulating, fins feathery, jagged, and easily frayed. Structure of the NADH2 gene. Chimaera buccanigella , sp. nov. is distinguishable from its closest congeners, Chimaera obscura Didier et al. 2008 , and Chimaera opalescens Luchetti et al. 2001 , by a combination of characters: small dorsal spine, generally small fins, small first dorsal fin height, small second dorsal fin anterior height, moderately large eyes, generally elongate head, body, and snout, and coloration.

Description. Morphometric proportions of the holotype and two paratypes are presented in Table 3. A medium-bodied species, head relatively large, head length 28.3% BDL, and thick, head width at suborbital ridge 14.4% BDL, and about half (51.5%) head length, suborbital ridge prominent and well-defined; snout length moderately long, 13.1% BDL making up almost one-half (46.2%) head length; snout width at base small, 7% head length. Trunk slightly compressed, length moderately short, 46.2% BDL, height 24.5% BDL, abdomen height 24.7% BDL, tapers rapidly into long, whip-like tail, tail height 14.6% BDL, tail length 60.5% BDL, with short caudal filament. Eyes large, length 9.6% BDL, about one-third (34.0%) head length, and ovoid, located in posterior half of head, pre-orbital length 52.2% head length. Interdorsal space small, 2.7% BDL, pelvic-anal space large, 45.8% BDL. Pectoral-pelvic space 34.8% BDL, 1.2 times head length, and is shorter than pelvic caudal space. Pelvic-caudal space 46.6% BDL, 1.6 times head length, and is shorter than snout-vent length 67.3% BDL, 2.4 times head length. Skin smooth without denticles and not deciduous.

Pectoral fins relatively broad, pectoral fin width 18.5% BDL, and long, anterior margin 36.6% BDL (1.3 times head length), triangular in shape, rounded near base; anterior margin increasing curvature distally to an acute apeX, posterior margin slightly sigmoidal; pectoral fin base fleshy, asymmetrical in shape. Pectoral fins, when depressed posteriorly against the body, barely reach the origin of pelvic fins. Pelvic fins about half (60%) size of pectoral fins, smaller than head length (78.0% head length), anterior and posterior margins fairly straight, rounding sharply into base, tear-drop in shape, tapering to a point distally; fleshy base thick and oval in shape.

First dorsal fin small, height 15.5% BDL, base 16.1% BDL, triangular in shape; proceeded by moderately long (23.4% BDL), thin (3.4% BDL) spine; dorsal spine straight, triangular in cross section, keel strongly trenchant along anterior edge, and two closely spaced columns of serrations along distal half of posterolateral edges; spine length not reaching height of first dorsal fin, but reaching origin of second dorsal fin when depressed against the body. Second dorsal fin about one-fifth (22.2%) height of first dorsal fin, elongate, 81.9% BDL, moderate in height and fairly straight, second dorsal fin anterior height 3.4% BDL, second dorsal fin posterior height 3.5% BDL, second dorsal fin mid height 3.5% BDL. Caudal fin small, dorsal caudal margin 20.1% BDL, ventral caudal margin 28.2% BDL, small dorsal caudal height 2.4% BDL, ventral caudal height 2.6% BDL, and symmetrical in shape; caudal fin tapers off very gradually and ends in a thin, short filament. Anal fin very thin and small. Edges of all fins fairly straight, feathery, jagged, and easily frayed.

Lateral line canals on head open, narrow grooves, those on snout with dilations fairly consistent in size and spacing ( Table 4). Preopercular and oral lateral line canals share a common branch connecting to the infraorbital canal. Anterior origin of trunk lateral lines branches from junction of occipital and optic canals. Lateral line dips sharply ventrally then dorsally in a sigmoidal curve before returning to a relatively stable line at origin of dorsal spine and continuing posteriorly relatively non-undulating. Occipital canal short, 5.3% BDL, directed semivertically to where it joins supratemporal and supraorbital canals, supratemporal canal short, 5.1% BDL, and strongly curved. Supraorbital canal eXtending anteriorly from supratemporal junction, roughly sloping around dorsal eye margin. Infraorbital to angular canal relatively long, 8.9% BDL, eXtending anteroventrally into mandibular and angular canals posterior of mid-eye. Angular canal horizontal before sensory pores and then continues anteroventrally.

Dentition. Tooth plates are smoky-gray in color, and lower tooth plates appear to lack visible rods. The type specimens were not dissected for detailed internal eXamination.

Coloration. Prior to preservation specimens uniformly light tan, flat with no iridescence; some longitudinal light-dark striations along tail. Dark, gray-brown on tip of snout, and dark marking directly around mouth with light blotted labials. Lines of head and body darkly shaded. Dorsal fin spine light white in color, dark brown along length of grooves of the anterior keel. Unpaired fins smoky black-gray in color, with white margin on anterior half of second dorsal fin. Pectoral and pelvic fins light blue with many brown speckles. Pores present on head along canals, light in color. Tooth plates dark smoky-gray in color. Specimens after preservation mostly retain body coloration.

Etymology. The Latin names bucca and nigella means respectively "mouth" and "dark," referring to the characteristic coloration of this species. The vernacular name, dark-mouth Chimaera , is based on the consistent dark coloration of this species’ mouth.

Size. The two immature males measured 729 mm TL, 346 mm BDL, and 861 mm TL, 338 mm BDL, and the immature female measured 401 mm BDL, 765 mm TL.

Distribution. Known only from the deep waters of the Madagascar Ridge, in the Southwestern Indian Ocean (33°21'S – 42°22'E to 33°49'S – 44°50'E) and southern part of the Madagascar Ridge on a seamount (33o49’S, 42o22’E) associated with Walters Shoal in the Southwestern Indian Ocean ( Fig. 16 ).

Biological notes. Males were immature at 861 mm TL, 338 mm BDL. The female was eXternally assessed to be an immature based on the absence of a developing, fleshy postanal pad used during copulation. In order to preserve its integrity, the specimen was not eXamined internally. This species was recorded from a depth range of 495 m ̄ 960 m. Walters Shoal is the shallowest area of the Madagascar Ridge, which divides the Mozambique Basin and Madagascar Basin. Flat-topped seamounts and shallow plateaus characterized the area.

Comparison. Chimaera buccanigella is the fourth Chimaera species known from the Southwestern Indian Ocean (Ebert, 2014) and can be distinguished from other Chimaera species by the following combination of characters: light tan body color, without silver, no defined patterning, spots, reticulations, or mottling; stocky body, short trunk, tapering rapidly into a long tail; long, straight spine, skin not deciduous.

Chimaera buccanigella is uniformly colored, lacking any distinct patterning of spots, mottling or reticulations, such as found on C. monstrosa , C. owstoni and C. panthera that, depending on the species may have distinct spot patterns, usually brownish in color, mottling and or reticulations ( Tanaka, 1905; Didier, 1998; Didier, et al., 2012; Ebert et al., 2013; Kemper et al., 2015). Furthermore, C. buccanigella lacks an iridescent sheen or silvery pink, grayish, or pale brown body coloration, some with faint stripes, usually found in C. argiloba , C. cubana , C. fulva , and C. phantasma ( Jordan and Snyder, 1900; Didier et al., 2002, 2012).

Chimaera buccanigella is a medium-sized species with relatively long, conical snout, moderately sized head, defined suborbital ridge, large eyes, moderately long trunk length tapering rapidly into long tail, with long spine, very straight and not eXceeding the height of first dorsal fin. This combination of characters separates C. buccanigella from C. macrospina , which has a shorter snout to vent length, 58.7% (55.1̄61.3%) BDL vs 67.3% BDL, short trunk length, 39.8% (37.3̄40.5%) BDL vs 46.2% BDL, very weak suborbital ridge vs well defined, shorter eye length, 6.6% (5.7̄8.3%) BDL vs 9.6% BDL, greatly eXceeding apeX of taller first dorsal fin, 19.7% (19.4̄24.4%) BDL vs 15.5% BDL. Chimaera notafricana is distinct from C. buccanigella in having a dorsal spine more strongly curved and shorter in length, 22.1% (15.9̄18.5%) BDL vs 23.4% BDL, and smaller eye length 6.3%–6.5% BDL vs. 9.6% BDL. Chimaera lignaria is distinguishable from C. buccanigella by its larger body, bulkier head, and squared snout. Chimaera orientalis has a much longer spine, 31.0% (28.4%) BDL vs 23.4% BDL, which eXceeds the apeX of a taller first dorsal fin, height 26.7% (22.8̄25.0%) BDL vs 15.5% BDL. Chimaera jordani is distinguished from C. buccanigella by its shorter snout length 2.6% BDL vs 13.1% BDL, smaller eye length 6.6% BDL vs 9.6% BDL, and larger spine length, 26.6% BDL vs 23.4%, which overlaps apeX of first dorsal fin. Chimaera bahamaensis is distinguishable by its smaller trunk length, 35.0% BDL vs 42.2% BDL, smaller eye length 6.9% BDL vs 9.6% BDL, and dorsal spine eXceeding apeX of first dorsal fin. Chimaera carophila is differentiable from C. buccanigella in having a smaller head length, 22̄24% BDL vs 28.3% BDL, shorter eye length, 8% BDL vs 9.6% BDL, shorter dorsal spine length, 18̄20% BDL vs 23.4% BDL, spine usually eXceeding apeX of first dorsal fin.

The species most similar to C. buccanigella , with a conical snout, defined suborbital ridge, large eyes, and long spine not eXceeding first dorsal fin, are C. obscura and C. opalescens . Chimaera obscura differs from C. buccanigella in having a longer dorsal spine, 27.2% BDL vs 23.4% BDL; larger fins, first dorsal fin 23.0% (23.8%) BDL vs 15.5% BDL, second dorsal fin anterior height 5.0% (4.9%) vs 3.4% BDL; and smaller eye length 7.3% (6.1%) BDL vs 9.6% BDL. Chimaera opalescens is similar to C. buccanigella in color being beige to tan, but is iridescent before preservation; all around less elongate, trunk length 33.7¯41.1% BDL vs 46.2% BDL, head length 20.1¯23.8% BDL vs 28.3% BDL; features of head less elongate with shorter pre-oral length, 8.1¯11.5% BDL vs 14.8% BDL, prenarial length 2.8¯4.1% BDL vs 9.1% BDL, snout length 4.1¯6.3% BDL vs 13.1% BDL; spine not as robust with ridge to origin 4.9̄5.9% BDL vs 3.1% BDL.

Comparison of new Southwestern Indian Ocean Chimaera species. The three new Chimaera species can be separated from each other by a combination of eXternal characteristics. Chimaera willwatchi is large-bodied and distinct in its darker, heavily mottled body coloration, and white fin margins. Chimaera willwatchi is a more robust species, distinguishable from C. didierae by its larger, blockier head and trunk, squared snout; larger paired fins, pectoral fin width 22.1% (19.6̄23.2%) BDL vs 16.7% BDL, pelvic fin anterior margin 25.0% (22.9̄26.8%) BDL vs 19.9% BDL; dorsal fin spine longer, 27.3% (22.9¯24.9%) BDL vs 21.6% BDL, exceeding apex of first dorsal fin, longer first dorsal fin base length 17.6% (14.2̄17.9%) BDL vs 13.2% BDL, first dorsal fin height 20.3% (16.2̄19.1%) BDL vs 12.1% BDL, second dorsal fin taller anterior margin, 6.6% (3.8̄7.2%) BDL vs 2.7% BDL.

Chimaera willwatchi can be distinguished from C. buccanigella by its blockier body shape, and by a shorter trunk length, 43.1% (36.4¯44.4%) BDL vs 46.2% BDL; taller head height, 26.6% (23.0¯26.7%) BDL vs 21.4% BDL; exceeding apex of first dorsal fin, first dorsal fin taller, 20.3% (16.2¯19.1%) BDL vs 15.5% BDL, second dorsal fin with taller anterior margin, 6.6% (3.8̄7.2%) BDL vs 3.4% BDL, but not as long 74.8% (70.1̄77.5%) BDL vs 81.8% BDL.

Morphometrically C. buccanigella and C. didierae are the closest congers with both species being light tan in color with dark snouts, blue or purplish fins, and proportionally smaller unpaired fins. However, C. didierae is distinguishable by its shorter snout to vent length, 59.4% BDL vs 67.3% BDL, while having a longer tail length 63.7% BDL vs 60.5% BDL; more slender overall with snout height 7.5% BDL vs 9.5% BDL; shorter snout, 10.3% BDL vs 13.1% BDL, smaller eyes 8.3% BDL vs 9.6% BDL, less blocky head with less defined suborbital ridge, head width at suborbital ridge 12.0% BDL vs 14.5% BDL; fins smaller overall, pectoral fin anterior margin more strongly curved and shorter, 33.7% BDL vs 36.6% BDL, pelvic fin anterior margin 19.9% BDL vs 22.1% BDL, first dorsal fin height 12.1% BDL vs 15.5% BDL, first dorsal fin base 13.2% BDL vs 16.2% BDL, second dorsal fin base 77.1% BDL vs 81.9% BDL, second dorsal fin anterior margin 2.7% BDL vs 3.4% BDL, ventral caudal height 1.1% BDL vs 2.6% BDL.

The maXimum likelihood tree topology at the NADH2 locus for SWIO chimaeras indicates that C. willwatchi , C. didierae and C. buccanigella form three distinct lineages, different from morphologically similar Chimaera species, as well as known South African species (i.e. C. notafricana , H. africanus ) ( Fig. 13 ). Chimaera buccanigella is clearly distict from all species incorporated in this analysis, including the morphologically similar C. opalescens and C. obscura , with 100% bootstrap support. Chimaera didierae also is distinguishable from the other species, recovered as a sister species to C. notafricana , known from South Africa, in this analysis. The morphologically similar C. opalescens , C. obscura , and C. buccanigella are clearly also distinct from C. didierae based on the NADH2 molecular data. Chimaera willwatchi is recovered as a single, distinct species (100% bootstrap support), with 4 sub-clades. These sub-clades are based on the location of collection within the SWIO. There are two clades of SWIO Ridge individuals, however, this encompasses a very large area. All but one of the individuals ( KX761206 ) in the SWIO Ridge clade, sister to the Walter’s Shoal clade, with detailed locality information, was collected from the western region of the SWIO Ridge (see map, Fig. 9 ). The other SWIO Ridge clade indviduals were all collected from a more eastern region of the SWIO Ridge. The individual C. willwatchi , KX761206 , was collected from the eastern region of the SWIO Ridge. The eXact location of two individuals that fall within these sub-clades, KX761197 and KX761216 , were not recorded, but are known to be within the SWIO. The NADH2 locus suggests that C. willwatchi , C. diderae , and C. buccanigella are distinct species from other morphologically similar species and those near by in locality. However, we caution that this tree topology is based on only a single gene with limited species sampling, and may not be congruent with the true species tree based on multiple markers and denser taXon sampling.

Figures

FIGURE 9. Map of study area denoting Where Chimaera willwatchi, sp. nov., specimens Were collected, With subpopulations represented by circles (morph A), star (morph B), and triangles (morph C).

FIGURE 13. MaXimum likelihood tree topology based on a general-time reVersible (GTR) substitution model + gamma distribution for Chimaera willwatchi, sp. nov., Chimaera didierae, sp. nov., Chimaera buccanigella, sp. nov., and comparartiVe species based on aligned NADH 2 DNA sequences. GenBank accession numbers folloW species (see AppendiX 2). Bootstrap support Values of main clades shoWn on tree. Specimens indicated in bold are designated holotypes.

FIGURE 16. Map of study area denoting collection sites of Chimaera didierae, sp. nov., (yelloW triangle), and Chimaera buccanigella, sp. nov., (red circle).

FIGURE 17. Full body lateral photograph of Chimaera buccanigella, sp. nov., a) Holotype CAS 242335, immature female, 830 mm TL, 397 mm BDL b) Illustration of holotype c) Anterior VieW of holotype highlighting dusky mouth.

FIGURE 18. Illustration of Chimaera buccanigella, sp. nov., lateral lines of head shoWing: infraorbital to angular canal (IOA), junction of the oral-infraorbital canal to junction of the oral and angular canal, preopercular to main trunk (OTM), preopercular canal (POP), and oral canal (O).