Canthigaster caeruleolineata, Fricke & Wickel & Pinault & Nicet & Delrieu-Trottin, 2021

Fricke, Ronald, Wickel, Julien, Pinault, Mathieu, Nicet, Jean-Benoit & Delrieu-Trottin, Erwan, 2021, Canthigaster caeruleolineata, a new species of toby (Teleostei: Tetraodontidae) from La Réunion, southwestern Indian Ocean, Cybium 45 (4), pp. 257-264 : 260-263

Canthigaster caeruleolineata new species

Blue-lined toby

( Figs 2-4; Tab. I)

Material

Holotype: SMNS 27147 , 86 mm SL, southwestern Indi- an Ocean , La Réunion, Anse des Cascades, 21°11’10.68”S 55°50’4.45”E, found dead in boulder habitat with little coral coverage at 17 m depth (probably originating from adjacent deep reef habitat in more than 100 m depth), Geoffrey Bertrand, 1 Apr. 2021.

Diagnosis

Dorsal-fin rays 8; anal-fin rays ca. 7 (may have been damaged); pectoral-fin rays 15; caudal-fin rays (i) 10 (1); dorsal-fin origin anterior to anal-fin origin; dorsal half of body greyish brown with relatively few short, oblique blue streaks which are also present in the region between the occiput and the dorsal-fin base, lower part of caudal peduncle with yellow spots; eye yellow; dorsal and anal fins yellow; pectoral fins translucent; caudal fin yellowish grey, with 7 irregular, vertical, wavy blue lines.

Description

Counts and measurements listed in table I are part of this description.

Characters provided in Diagnosis not repeated here. Body moderately deep and compressed; head length 2.4 in SL; snout moderately long and conical, its length 4.1 in SL; dorsal profile of snout straight; dorsal profile of nape slightly concave; ventral profile of head almost straight; eye diameter 3.3 in HL; interorbital region flat, fleshy interorbital width 2.8 in HL, bony interorbital width 3.0 in HL; postorbital length 6.0 in HL; gill opening small, located at level below ventral margin of eye, its length 9.0 in HL; caudal peduncle slightly tapering posteriorly, its depth 2.6 in HL, caudal peduncle length 2.4 in HL. Predorsal length 1.2 in SL, anal-fin origin behind dorsal-fin origin, preanal-fin length ca. 1.1 in SL. Dorsal and anal fins slightly rounded; longest dorsal-fin ray 2.6 in HL; longest anal-fin ray 3.0 in HL; pectoral fins broad and short, longest pectoral-fin ray 2.6 in HL; caudal fin truncate, its length 4.1 in SL; length of dorsal-fin base 6.0 in HL; length of anal-fin base 9.0 in HL. Tiny spinules scat- tered on head and body before dorsal and anal fins ( Fig. 3 ); a raised skin fold on back extending from above pectoral-fin base to dorsal-fin origin; a tiny nasal organ on each side of snout, surrounded with elevated rim. Upper jaw with 12 pointed bony plates, lower jaw with 19 such plates. Vertebrae 9 + 7 = 16 [damaged].

Colour of preserved holotype ( Figs 3-5 ). Dorsal half of body greyish brown with short, oblique blue streaks, lower part of caudal peduncle with yellow spots; eye yellow; dorsal and anal fins yellow; pectoral fins translucent; caudal fin yellowish grey, with 7 irregular, vertical, wavy lines consisting of irregular blue spots.

Molecular analysis

Molecular data examined here include all the hypothe- sized (based on colour and morphological characters) closest relatives of Canthigaster caeruleolineata . The topology of our maximum-likelihood tree is similar to that of Matsuura et al. (2020) based on COI. Our mtDNA analysis showed a well- supported genetic divergence between C. caeruleolineata and its congeners ( Fig. 5 ). Our molecular analysis revealed that C. caeruleolineata is closely related to C. aziz , a species found so far only in deep reefs of the Red Sea with a type specimen collected at 315 m depth.

Etymology

Caeruleus (Latin) means light blue; lineatus (Latin) means lined. The name means blue-lined; it is an adjective, with the ending caeruleolineata when in the feminine genus Canthigaster . It refers to the numerous short, blue lines on the head and the body of this species.

Distribution

Canthigaster caeruleolineata n. sp. is known only from the type locality; it was collected near Anse des Cascades on the southeast coast of La Réunion ( Fig. 7 ). The species is expected to be distributed in deep reefs .

Comparison

Canthigaster caeruleolineata n. sp. is distinguished from other species in the genus by its characteristic colouration with the dorsal half of body greyish brown with relatively few short, oblique blue streaks which are also present in the region between the occiput and the dorsal-fin base, lower part of caudal peduncle with yellow spots; the dorsal and anal fins yellow; the caudal fin yellowish grey, with 7 irregular, vertical, wavy blue lines. Canthigaster caeruleolineata n. sp. differs from all other species of Canthigaster except C. aziz and C. margaritata from the Red Sea by the combination of lower fin-ray counts, 8 rays in the dorsal and anal fins and 15 rays in the pectoral fins. The molecular analysis confirmed the meristic results, showing that C. caeruleolineata n. sp. and C. aziz were closely related. From C. aziz , the new species is distinguished by the caudal-fin colouration with 7 irregular, vertical, wavy lines consisting of irregular blue spots (versus pale, without lines in C. aziz ), the dorsal-fin origin anterior to anal-fin origin (versus opposite of anal-fin origin in C. aziz ), and the body with relatively few short, oblique blue streaks which are also present in the region between the occiput and the dorsal-fin base (versus pale brown without streaks in C. aziz ). In terms of colouration, C. caeruleolineata n. sp. is most similar to Canthigaster rapaensis Allen & Randall 1977 from the South Pacific, but differs from that species by its 8 dorsal-fin rays (versus 9 dorsal-fin rays in C. rapaensis ), 15 pectoral-fin rays (versus 16-17), the absence of 3 parallel light blue streaks on the ventral part of the snout (versus present), the region between the occiput and the dorsal-fin base with short blue streaks (versus monochromatic dark brown), and the caudal peduncle with irregular short blue streaks (versus regular, round blue spots).

The Red Sea and Gulf of Aden species C. margaritata shares with the new species 8 dorsal-fin rays, and the caudal fin with many blue spots. The new species is distinguished from C. margaritata in having the body with few wavy short lines (versus body with many blue spots and short lines in C. margaritata ), no black blotch below dorsal-fin base (versus a black blotch present below dorsal-fin base), caudal peduncle with irregular, short blue lines (versus longitudinal rows of spots on caudal peduncle less than 10), and dorsal, anal and caudal fins yellow (versus bluish white).

Figures

Figure 3. – Canthigaster caeruleolineata new species, SMNS 27147, holotype 86 mm SL, southwestern Indian Ocean, La Réunion, Anse des Cascades, 21°11’10.68”S 55°50’4.45”E. Photograph by Julien Wickel. Colour pattern after one month of preservation; left side of body.

Figure 5. – Canthigaster caeruleolineata new species, southwestern Indian Ocean, La Réunion, 11.5 km south of Anse des Cascades, ca. 27°17’19”S, 55°49’09”E. Photograph by Aquarium de La Réunion, 2007. Fresh colouration. Specimen not preserved.

Figure 7. – Geographical distribution of species of Canthigaster with short blue lines. A: Canthigaster caeruleolineata n. sp.; B: C. cal- listerna; C: C. flavoreticulata; D: C. rapaensis.