Chimaera didierae, 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 : 20-25

Chimaera didierae , sp. nov.

The Falkor Chimaera

( Figs. 14–16 ; Tables 3–4)

Holotype. CAS 242334, 825 mm TL, 533 mm BDL, female, Southwestern Indian Ocean , Madagascar Ridge, 34o30’S, 43o10’E, bottom trawl between 1000 m – 1100 m, collector P.J. Clerkin, 10 March 2012.

Diagnosis. Chimaera didierae , sp. nov., is the seventh species of chimaera known from the Indian Ocean, and is distinguishable from other members of the genus by the following combination of characters: medium-bodied slender species, short trunk, long tail, with moderately sized head, large eyes, without well-defined suborbital ridge; short thin snout; uniform light toffee-tan color, not iridescent, without defined patterning, spots, reticulations, or mottling, dark, sooty brown on snout, white blotching around mouth; pectoral fins long and thin, anterior margin 33.7% BDL, pectoral fin width 16.7% BDL; dorsal spine height>21.6% BDL, equal or subequal to height of first dorsal fin; second dorsal fin very long and low, anterior height 2.7% BDL, not undulating; caudal fin small and slender, dorsal caudal height 1.8% BDL, ventral caudal height 1.1% BDL. Structure of the NADH2 gene. Chimaera didierae , sp. nov. can be distinguished from its morphologically similar congeners, Chimaera obscura Didier et al. 2008 , and Chimaera opalescens Luchetti et al. 2001 , by the combination of characters: relatively short dorsal spine, short first dorsal fin height, short second dorsal fin, small pectoral fin, moderately large eye length, abdomen tapering rapidly into tail, relatively long snout length, and coloration.

Description. Morphometric proportions of holotype are provided in Table 3. A medium-bodied species, moderate sized head length 24.2% BDL, relatively tall head height, 20.5% BDL, suborbital ridge not well-defined; snout moderately long relative to head, 40.3% head length, and thin, width 2.0% BDL and 8.2% head length. Trunk slightly compressed, trunk height 25.7% BDL, tapering slightly to abdomen, height 19.9% BDL, before tapering somewhat rapidly into tail, height 12.4% BDL, continuing into caudal filament. Tail long making up 52.6% precaudal length, short trunk, 33.2% precaudal length, relatively long head, 20.0% precaudal length. Eyes large 8.3% BDL making up one-third (33.9%) of head length, and ovoid, located in posterior half of head, preorbital length 52.4% head length. Interdorsal space moderate, 8.3% BDL, pectoral-anal space 32.1% BDL, a little more than half (60%) pelvic anal space, 53.8% BDL. Pectoral-pelvic space 32.0% BDL, 1.3 times head length, and is shorter than pelvic caudal space. Pelvic-caudal space 57.3% BDL, about 2.3 times head length, and is approXimately equal to snout-vent length 59.4% BDL, 2.5 times head length. Skin smooth without denticles, strongly deciduous.

Pectoral fins relatively narrow, pectoral fin width 16.7%, long anterior margin, 33.7% BDL, about 1.4 times (139.3%) head length; triangular in shape, rounded near base, anterior margin sigmoidal in shape, slightly concave near origin, increasing conveXity about mid-length of anterior margin, increasing curvature distally to an apeX, posterior margin slightly concave, rounded towards base. Pectoral fins, when depressed posteriorly against the body, barely reach the origin of pelvic fins, overlapping by 2.0% BDL. Pectoral fin base fleshy, rounded, asymmetrical in shape. Pelvic fins about half size (59%) of pectoral fins, smaller than (82.3%) head length, anterior margin very conveX, posterior margin straight, rounding sharply into base, tear-drop in shape, tapering to a point distally; fleshy base thin and oval in shape.

Chimaera didierae sp. nov Chimaera buccanigella sp. nov Holotype Holotype n = 1 n = 1 Female Female Body length 532 mm 397 mm Measurement %BDL %BDL Total Length 155.5 192.4 Pre-caudal length 121.1 125.4 Snout to Vent length 59.4 67.3

Tail length 63.7 60.5

Trunk length 40.2 46.2

Head length 24.2 28.3

Pre-first dorsal fin length 25.0 29.5

Pre-second dorsal fin length 46.2 45.0

Pre-pectoral fin length 28.0 32.9

Pre-pelVic fin length 61.1 70.1

Pre-orbital length 12.5 14.8

Pre-orbital distance 12.8 14.8

Pre-narial length 13.6 9.1

Pre-narial distance 9.7 11.8

Pre-oral length 9.0 11.7

Pre-oral distance 13.1 16.7

Snout length 10.3 13.1

Eye Length 8.3 9.6

Eye Height 6.0 6.6

First dorsal to pectoral 16.0 20.1

First dorsal to pelVic 41.6 45.8

Second dorsal to pectoral 24.4 23.9

Second dorsal to pelVic 23.1 29.9

Snout Width at base 2.0 2.0

Snout anterior Width 6.5 7.1

Head Width at suborbital ridge 12.0 14.5

Trunk Width 11.1 12.6

Abdominal Width 6.4 7.5

Tail Width 5.8 7.3

Cauldal peduncle Width 1.5 1.7

Snout height at base 7.5 9.5

Head height 20.5 21.4

Trunk height 25.7 24.9

MaX Trunk height 24.8 24.1

Abdomen height 19.9 24.7

......continued on the next page First dorsal fin very small, height 12.0% BDL, base 14.0% BDL, triangular in shape, and proceeded by relatively tall,>21.4% BDL, robust spine. Spine ridge to origin 2.8% BDL, slightly posteriorly curved spine, curvature occurring evenly throughout spine, spine height equal or subequal to apeX of first dorsal fin. Spine triangular in cross section, keel strongly trenchant along anterior edge, and two closely spaced columns of serrations along distal one-fourth of posterolateral edges. Posterior edge connects to first dorsal fin for approXimately half of spine’s length. Dorsal spine originates just posterior to head, pre-first dorsal length 25.0% BDL, just anterior to pectoral fin origin, and when depressed against the body, barely reaches second dorsal fin origin, overlaps by 2.0% BDL. Second dorsal fin less than one-fourth (23.8%) height of first dorsal fin, elongate, base 77.0% BDL, low, second dorsal fin anterior height 2.7% BDL, and not noticeably undulating. Caudal fin small and slender, dorsal caudal margin 21.4% BDL, nearly equal to ventral caudal margin, 22.7% BDL; with very low dorsal caudal height, 1.8% BDL, nearly equal to ventral caudal height, 1.1% BDL; dorsal and ventral margins of caudal fin originate at roughly the same position horizontally; caudal fin tapers off very gradually and ends in a thin, short filament. Anal fin very thin but long. Edges of fins feathery, jagged, and easily frayed.

Lateral line measurements of holotype are presented in Table 4. Lateral lines of head open, narrow grooves, those on snout with sparse dilations. Preopercular and oral lateral line canals share a common branch connecting to the infraorbital canal on both sides of head. Supratemporal canal not fully connected to dorsal spine. 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. Lateral line canal originating at fork between occipital and optic head canals at level of upper eye margin. Orbital canal length 4.4% BDL, and joins a short supratemporal canal, 4.8% BDL, which curves anteriorly to where it joins at dorsal midline 3.3% BDL anterior of dorsal spine origin. Infraorbital to angular canal short, 3.1% BDL, and directed posteriordorsally to the junction of the oral and angular canal, where it continues to main trunk, preopercular to main truck, 7.9% BDL.

Chimaera didierae sp. nov Chimaera buccanigella sp. nov Holotype Holotype n = 1 n = 1

Female Female Body length 532 mm 397 mm Measurement %BDL %BDL Oronasal to nasal canal 2.3 2.0

Length of the rostral canal 1.8 2.1

Length across nasal canal 4.9 5.1

Infraorbital to angular canal 3.1 8.9

Preopercular to main trunk 7.9 9.4

Orbital canal length 4.4 5.3

Supratemporal canal length 4.8 5.1

Spine to supratemporal canal 3.3 3.9

Dentition. In order to preserve the integrity of the unique specimen, the holotype was not investigated internally.

Coloration. Prior to preservation specimen uniformly light tan, flat with no iridescence; some longitudinal light-dark striations along tail. Snout tip and anterior margin of pre-orbital head a dark, sooty, gray-charcoal, with white marking around mouth, fairly uneven. Dorsal fin spine is a light to whitish color, dark brown along length of grooves of the anterior keel. Fins light gray-tan with a strong wash of light lavender, very anterior margins lighter in color, posterior margins frayed and lacking lavender coloration. Pores present on head along canals, light in color with dark boarders, varying in size. Lateral line canals of head and body darkly shaded. Tooth plates light yellow in color. Preserved specimen maintains similar body color, but lavender hue of fins is dulled.

Etymology. The Latin name is dedicated to Dr. Dominique A. Didier for her outstanding contributions to the systematics of this group of fish. Vernacular: the Falkor Chimaera , derived from the Japanese, fukuryu for “lucky dragon,” and so named for this species uniquely pale, slender body resembling a famous description of luck dragons.

Distribution. A single specimen was collected from a seamount on the southern part of the Madagascar Ridge, located 34o30’S, 43o10’E near Walters Shoal in the Southwestern Indian Ocean. This was the only species of Chimaera encountered on this particular seamount ( Fig. 16 ).

Biological notes. The female holotype was eXternally assessed to be in the early stages of maturity based on the presence of a developing, fleshy postanal pad used during copulation. In order to preserve its integrity, the unique type specimen was not eXamined internally. This species has a recorded depth range between 1000 m ̄ 1100 m. Walters Shoal is the shallowest feature of the Madagascar Ridge and is relatively flat, providing a simple habitat structure.

Comparison. Chimaera didierae is the third species of the genus known from the Southwestern Indian Ocean (Ebert, 2014; Eschmeyer, 2014) and can be distinguished from all other Chimaera species by the following combination of characters: light tan body color, without silver sheen, no defined patterning, spots, reticulations, or mottling; slender body, short trunk, long tail, relatively robust spine, very small unpaired fins, eXtremely deciduous skin.

Chimaera didierae is uniformly colored and lacks strongly defined spots, reticulations, or patterning, easily separating it from 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). Chimaera didierae also lacks iridescent sheen or silvery body coloration usually found in C. argiloba , C. cubana , C. fulva , and C. phantasma ( Jordan and Snyder, 1900; Didier et al., 2002, 2012).

Chimaera didierae is a medium-bodied species with a head of moderate length and height relative to body, without well-defined suborbital ridge, large eyes; thick, but moderately long dorsal spine equal to or subequal to height of first dorsal fin; relatively small paired fins. This combination of characters separates C. didierae from C. macrospina , which has a longer dorsal fin spine, 23.0 % (25.3%–31.2%) BDL vs 21.4% BDL, which eXceeds first dorsal fin apeX; larger fins, pectoral anterior margin longer, 39.5% (37.5%–41.4%) BDL vs 34.0% BDL, greater second dorsal fin anterior height, 5.2% (4.5%–6.2%) BDL vs 2.8% BDL; and smaller eye length to head length ratio, one-fourth (25%) head length vs one-third (34%) head length. Chimaera notafricana is distinct in having a less robust body with tail tapering rapidly after pelvic girdle; pectoral fin anterior margin about 1.8 times head length vs 1.5 times head length; dorsal spine more strongly curved, eXceeding apeX of first dorsal fin; shorter eye length, 6.3̄6.5% BDL vs. 7.9% BDL. Chimaera lignaria is distinguishable by its larger, bulkier body and massively blocky head with blunt, squared snout vs slender body and moderately sized head and short thin snout; second dorsal fin taller, anterior height 4% (4̄7%) BDL vs 2.7% BDL, rubbery in teXture and not easily split vs fins which are feathery, jagged, and easily frayed; pectoral fin rounded, not pointed at leading edge vs tear-drop in shape tapering to a point distally. Chimaera orientalis is separable by its shorter trunk length, 37.0% (35.1̄35.4%) BDL vs 40.2% BDL, longer dorsal spine 31.0% (28.4%) BDL vs 21.6%, overlapping its much taller first dorsal fin, height 26.7% (22.8̄25.0%) BDL vs 12.1% BDL. Chimaera jordani is distinguished from C. didierae by its shorter trunk length, 52.8% BDL vs 59.4% BDL, shorter snout length, 2.6% BDL vs 10.3% BDL, smaller eye length, 6.6% BDL vs 8.3% BDL, and larger spine length, 26.6% BDL vs 21.6%, overlapping apeX of first dorsal fin. Chimaera bahamaensis is distinguishable by its shorter trunk length, 35.0% BDL vs 40.2% BDL, much more pronounced snout, preoral length 12.0% BDL vs 9.0% BDL, prenarial length 15.4% BDL vs 13.6% BDL; shorter eye length, 6.9% BDL vs 8.3% BDL, and eye height 3.5% BDL vs 6.0% BDL. Chimaera carophila is differentiable from C. didierae in having a longer preoral length, 11̄19% BDL vs 9.0% BDL, smaller dorsal spine length, 18̄20% BDL vs 21.6% BDL, which eXceeds apeX of first dorsal fin.

The species most morphologically similar to C. didierae are C. obscura and C. opalescens , all characterized by a slender head, smaller fins, and spine not eXceeding first dorsal fin. Chimaera obscura differs from C. didierae in having a longer dorsal spine, 27.2% BDL vs 21.6% BDL, larger fins, first dorsal fin height 23.0% (23.8%) BDL vs 12.1% BDL, second dorsal fin anterior height 5.0% (4.9%) vs 2.7% BDL, pectoral fin anterior length 38.9% (39.6%) BDL vs 33.7% BDL; and shorter eye length, 7.3% (6.1%) BDL vs 8.3% BDL. Chimaera opalescens is most similar to C. didierae , but is known from the northeastern Atlantic along the British Isles, France, and Greenland. It is similar to C. didierae in color being beige to tan, but is iridescent before preservation. Morphologically, C. opalescens tapers slower after its pelvic girdle into its tail transitioning into a greater tail height, 17.0¯17.3% BDL vs 12.4% BDL; shorter snout length, 4.1¯6.2% BDL vs 10.3% BDL, and shorter preoral length, 5.3¯6.0% BDL vs 9.0% BDL; dorsal spine more curved with thicker ridge to origin, 4.9¯5.9% BDL vs 2.8% BDL, first dorsal fin taller, 11.9̄ 17.1% vs 12.1% BDL, second dorsal fin with taller mid dorsal fin height, 3.5¯4.4% BDL vs 2.1% BDL; lateral line canals on side of head much longer, oronasal to nasal canal, 5.6% BDL vs 2.3% BDL, length of the rostral canal 5.4% BDL vs 1.8% BDL, length across nasal canal, 12.6% BDL vs 4.9% BDL, infraorbital to angular canal 14.4% BDL vs 3.1% BDL; lateral line canals on dorsal portion of head much shorter, preopercular to main trunk, 2.1% BDL vs 7.9% BDL, orbital canal length 3.9% BDL vs 4.4% BDL, supratemporal canal length, 1.1% BDL vs 4.8% BDL, and spine to supratemporal canal, 1.5% BDL vs 3.3% BDL.

Figures

FIGURE 14. Full body lateral Chimaera didierae, sp. nov., holotype CAS 242334, immature female, 890 mm TL, 704 mm BDL, 532 mm PCL a) photograph, b) illustration.

FIGURE 15. Illustration of Chimaera didierae, 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).

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