Bellottia robusta, Nielsen, Jørgen G., Ross, Steve W. & Cohen, Daniel M., 2009

Nielsen, Jørgen G., Ross, Steve W. & Cohen, Daniel M., 2009, Atlantic occurrence of the genus Bellottia (Teleostei, Bythitidae) with two new species from the Western North Atlantic, Zootaxa 2018, pp. 45-57 : 47-51

Bellottia robusta , new species

( Figs.1–4 )

Bellottia apoda: McEachran & Fechhelm (2005: 18) Bellotia sp.: Cordes et al. (2008: 783)

Material examined (12 specimens, SL 43–82): Holotype: USNM 394117, SL 62, male, Gulf of Mexico, Green Canyon 234, 27°45’N, 91°13’W, st. JSL- 4712, 535 m, coll. C. Fisher, 10 July 2004.

Paratypes: TCWC 10956.01, SL 64, female, Gulf of Mexico, 27°46.96’N, 91°30.46’W, st: BH AT 1, 98 GOM JSL 4035, 540– 580 m, coll. Tracy Ward, 7 Aug.1998. - TCWC 10957.01, SL 53, female, Gulf of Mexico, 27°44.7’N, 91°13.3’W, st: GC AT 1, 98 GOM JSL 4033, 540 m, coll. Tracy Ward, 7 Aug. 1998. – USNM 394118, SL 34, male,Gulf of Mexico, Green Canyon 232, 27°44.49’N, 91°19.07’W, st. JSL- 4437, 569 m, coll. C. Fisher, 24 June 2002. – USNM 394119, SL 35, male, Gulf of Mexico, Green Canyon 234, 27°44.78’N, 91°13.30’W, st. JSL- 4569, 538 m, coll. C. Fisher, 26 Aug. 2003. – USNM 394120, SL 49, male, Gulf of Mexico, Garden Banks 543, 27°27.32’N, 93°11.29’W, st. JSL- 4582, 546 m, coll. S. Hourdez, 3 Sep. 2003. – USNM 394121, SL 82, female, and ZMUC P771652, female, Gulf of Mexico, same data as for holotype. – USNM 394122, SL 77, female, and ZMUC P771653, SL 72, male, Gulf of Mexico, Green Canyon 234, 27°45.80'N, 91°13.30’W, st. JSL- 4713, 532 m, coll. C. Fisher, 10 July 2004. – USNM 394123, SL 50, male, Gulf of Mexico, Green Canyon 234, 27°44.76’N, 91°13.46’W, st. JSL- 4720, 506 m, coll. K. Zelnio, 13 July 2004. – USNM 394124, SL 51, male, Gulf of Mexico, Green Canyon 234, 27°44.76’N, 91°13.46’W, st. JSL- 4721, 506 m, coll. C. Fisher, 14 July 2004.

Condition of material. In most specimens the body is much curled up and the mouth wide open making precise measurements difficult to obtain.

Diagnosis. Bellottia robusta differs from its congeners by the following combination of characters: depth at origin of anal fin 17.5–23.0 % SL, small teeth blunt or pointed, four spines on hind margin and one on crest of preopercle, distinct spine on cleithrum above base of pectoral fin, anterior gill arch with 5–6 long rakers, predorsal 44.0–49.5 % SL and precaudal vertebrae 12.

Similarity. Bellottia robusta is most similar to B. cryptica , in e. g. presence of a spine on cleithrum and in fin ray and total vertebral counts, but differs by the heavier body (17.5–23.0 vs 17.0 % SL at origin of anal fin), origin of anal fin below dorsal fin ray 10–15 vs 8, precaudal vertebrae 12 vs 10 and spine on preopercular crest vs no spine in B. cryptica . It differs from B. apoda by the deeper (17.0–23.0 vs 13.0–16.0 % SL) and darker body, more caudal fin rays (7 vs 6), poorly developed fangs (vs distinct, retrorse fangs), more long rakers on anterior gill arch (5–6 vs 3–4) and longer predorsal (44.0–49.5 vs 35.5–40.0 % SL). From B. galatheae it differs e. g. by the higher number of rays in dorsal (85–83 vs 70–72), caudal (7 vs 6), anal (75–88 vs 61) and pectoral (23–25 vs 19–20) fins. From B. armiger it differs by having more precaudal vertebrae (12 vs 10), more caudal fin rays (7 vs 6) and a larger predorsal length (44.0–49.5 vs 41.5 % SL).

Description. The principal meristic and morphometric characters are shown in Table 1 . The description is based mainly on the holotype. Differences of paratypes are given in brackets and in Table 1 .

B. robusta B. cryptica B. apoda

Gulf of Mexico West. Atl. East. Atl. + Med. HT HT+11 paratypes Holotype n=16 including LT Body robust, highest near base of pectoral fin, completely covered with oval, ca. 1.5 mm, cycloid scales. Anterior segment of lateral line extending close to dorsal margin of body and from above anus along midline of body. Head profile convex, cheek and gill-cover scaled, while rest of head naked. Mouth slightly oblique with posterior margin of maxillary vertically expanded ending well behind eye. Anterior nostril closer to upper lip than to posterior nostril, both with low rim. Small opercular spine strong and pointed, almost completely covered by skin, and not reaching posterior margin of opercle (a few specimens with spine reaching just beyond hind margin of opercle). Ventral margin of preopercle with four distinct spines and one spine on preopercular crest ( Fig. 3 ) (spine often covered by skin; one specimen with two spines on crest). Origin of dorsal fin above tip of pectoral fin, anal fin origin just behind midpoint of fish (some specimens with preanal up to 59 % SL). Pectoral fin placed on mid-body level with peduncle higher than long. A distinct spine on cleithrum just above base of pectoral fin (one specimen with spine ending in a blunt tip). Anterior gill arch with 2–3 (2–4) plate-like rakers on upper branch, one long raker in the angle between the two branches and lower branch with 4–5 long rakers, followed by seven (6–9) plate-like rakers. Longest gill filament slightly shorter than longest raker. Two minute pseudobranchial filaments.

Head pores: Because of thin, often torn skin, pores are difficult to observe. A few, large pores, with three (2–3) in a vertical row behind eye, three below eye and four pores on mandible. Small whitish papillae spread over head.

Dentition: Most teeth are small and blunt. Head of vomer slightly curved with one tooth row of ca. ten small, blunt teeth. Posterior half of palatines edentate, and anterior half with one row of small, blunt teeth. Dentaries with posterior fifth edentate and dentigerous part with one tooth row increasing to 2–3 rows at symphysis; outer row with retrorse fangs. Premaxillaries with posterior third edentate and dentigerous part with one tooth row increasing to 4–5 rows at symphysis; outer row with larger, pointed teeth (three specimens with larger, pointed teeth on all dentigerous bones).

Axial skeleton (based on radiographs): Tips of neural and haemal spines thin and pointed. Anterior neural spine one third the length of second spine. Neural spines 3–7 (2–7) slightly depressed. Bases of neural spines 4–7 (4–8) enlarged. Parapophyses present on vertebrae 8–12 (7–12) and pleural ribs on 4–10 (3–11). Epipleural ribs indistinct.

Otolith ( Fig. 2 ): The 3.5 mm elongate sagittal otolith (from a 64 mm SL paratype, TCWC 10956.01) is twice as long as high and twice as high as thick. Dorsal and ventral rim roundish, vaguely pointed posteriorly. Sulcus undivided, 1/3–1/4 the length of the otolith. No osteal channel.

Coloration: Fig. 1 shows the holotype after four years of preservation. The body is brownish with light vertical fins. The abdomen, operculum and eye-surroundings dark blue and the rest of the head colored like the body. The body of some of the smaller paratypes is dark brown.

Biology. This species appears to be very closely associated with complex habitat, provided by tubeworms or deep-sea corals (e.g., Lophelia pertusa ). Rocky substrata are also likely habitats for B. robusta , even though it has not yet been collected there. This species is well concealed within crevices provided by these habitats, and specimens were not observed prior to collection. Because of its cryptic nature there are no more data on the biology or ecology of this species. A 53 mm specimen (TCWC 10957.01) contained eggs up to 0.7 mm in diameter; embryos were not observed.

Etymology. The specific name, robusta , refers to the short, deep body.

Distribution ( Fig.4 ). Known from nine localities in a restricted area of the northern Gulf of Mexico all caught by JSL at depths of 506– 580 m.

Figures

FIGURE 1. Bellottia robusta. Holotype. USNM 394117. SL 62.

FIGURE 2. Bellottia robusta. Paratype. TCWC 10956.01. SL 64. Right sagitta: A—median view, B—ventral view.

FIGURE 3. Bellottia robusta. Paratype. USNM 394118. SL 34. Head spines: 1 — spine on cleithrum, 2 — opercular spine, 3 — preopercular spines, 4 - spine on preopercular crest.

FIGURE 4. Records of Bellottia robusta () and Bellottia cryptica (●). The number indicates the number of neighbouring stations.

Tables

TABLE 1. Meristic and morphometric characters of Atlantic Bellottia spp. (n = number of specimens examined).

Standard length	62	34–82	n	42	26–65	n
Meristic characters
Dorsal fin rays	87	85(88.8)93	10	92	83(89.0)94	14
Caudal fin rays	7	7	10	7	6	14
Anal fin rays	81	75(81.2)88	12	84	68(74.0)82	15
Pectoral fin rays	24	23(23.9)25	11	23	21(22.9)26	12
Precaudal vertebrae	12	12	11	10	12(12.6)13	15
Caudal vertebrae	38	36(37.6)39	11	39	33(36.0)37	15
Total vertebrae	50	48(49.3)51	11	49	46(48.5)50	15
Pseudobranchial filaments	2	2	12	2	0(1.2)2	15
Anterior dorsal ray above vertebra no.	10	10(10.4)11	10	11	8(8.9)10	15
Anterior anal ray below dorsal ray no.	10	10(12.6)15	10	8	17(18.2)19	13
Anterior anal ray below vertebra no.	14	14(15.3)16	11	14	15(15.7)17	15
Long gill rakers	5–6	5(5.3)6	12	5–6	3(4.0)4	16
Total gill rakers	15	14(15.7)18	11	17	11(13.5)16	15
Spines on preopercle m margin	4	4	12	4	3(4.1)5	16
Spines on preopercle crest	1	1–2	12	0	1	16
Morphometric characters in % of SL
Head length	31.0	27.5(30.0)32.0	11	32.0	26.5(28.4)30.5	15
Depth at anal fin origin	22.0	17.5(20.0)23.0	11	17.0	13.0(14.5)16.0	12
Upper jaw length	15.0	14.0(15.0)16.0	11	14.5	13.5(15.0)16.0	15
Depth of posterior maxillare	5.3	4.3(4.9)5.6	11	5.1	4.2(4.8)5.3	13
Dia. eye window	5.3	4.7(5.2)5.5	11	5.5	3.5(4.6)5.8	15
Postorbital length	19.5	16.5(18.2)20.0	11	18.5	15.5(16.8)18.0	13
Preanal length	52	52(55.9)59	11	51	51(53.0)56	14
Predorsal length	49.5	44.0(46.2)49.5	10	46.5	35.5(37.8)40.0	12
Length of long gill raker	2.3	1.9(2.3)2.6	10	2.2	1.1(1.7)2.3	11