Chimaera didierae Kemper 2017
- Dataset
- New species of Chimaera (Chondrichthyes: Holocephali: Chimaeriformes: Chimaeridae) from the Southwestern Indian Ocean
- Rank
- SPECIES
- Published in
- Kemper, Jenny M. (2017): New species of Chimaera (Chondrichthyes: Holocephali: Chimaeriformes: Chimaeridae) from the Southwestern Indian Ocean. Zootaxa 4312 (1): 1-37, DOI: 10.11646/zootaxa.4312.1.1
Classification
- kingdom
- Animalia
- phylum
- Chordata
- class
- Holocephali
- order
- Chimaeriformes
- family
- Chimaeridae
- genus
- Chimaera
- species
- Chimaera didierae
description
(Figs. 14 – 16; Tables 3 – 4)
description
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.
description
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.
description
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, 11.9 ̄ 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.
diagnosis
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 NADH 2 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.
distribution
Distribution. A single specimen was collected from a seamount on the southern part of the Madagascar Ridge, located 34 o 30 ’ S, 43 o 10 ’ 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.
etymology
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.
materials_examined
Holotype. CAS 242334, 825 mm TL, 533 mm BDL, female, Southwestern Indian Ocean, Madagascar Ridge, 34 o 30 ’ S, 43 o 10 ’ E, bottom trawl between 1000 m – 1100 m, collector P. J. Clerkin, 10 March 2012.
Name
- Homonyms
- Chimaera didierae Kemper 2017