Hetereleotris nasoramosa, Kovačić & Bogorodsky & Zajonz & Tornabene, 2021

Kovačić, Marcelo, Bogorodsky, Sergey V., Zajonz, Uwe & Tornabene, Luke, 2021, A new species of Hetereleotris (Teleostei: Gobiidae) from the Socotra Archipelago (north-western Indian Ocean), a rare case of a hole-associated adaptation in gobiid fishes, Zootaxa 4996 (2), pp. 284-300 : 287-294

Hetereleotris nasoramosa sp. nov.

Socotra hole-hiding goby

Figs. 2–5 , Table 1

Holotype. SMF 39500 [sample tissue SOC18-191], female, 20.9+ 4.8 mm, Socotra Island, Delisha , 12°40.312’ N, 54°09.212’ E, a small stone on sand flat, depth 11–12 m, coll. S. V. Bogorodsky & F.N. Saeed, 05 May 2018 ( Fig. 4A & B ).

Paratypes (5 specimens, 18.6–24.9 mm SL). PMR VP4890 [sample tissue SOC19-355], male, 22.3+ 5.1 mm, Socotra Island, Di Hamri , 12°40.046’ N, 54°10.758’ E, a small rock, depth 8–10 m, coll. S . V. Bogorodsky , 02 April 2019 ; PMR VP4891 [sample tissue SOC19-358], female, 18.6+ 4.3 mm, Socotra Island, Di Hamri , 12°40.046’ N, 54°10.758’ E, a small rock, depth 8–10 m, coll. S . V. Bogorodsky , 02 April 2019 ; SMF 39501, female, 24.9+ 5.3 mm, Socotra Island, Di Hamri , 12°40.046’ N, 54°10.758’ E, a small rock, depth 8–10 m, coll. S . V. Bogorodsky , 02 April 2019 ( Fig. 5A & B ) ; SMF 39502, presumably male, 20.7+ 4.6 mm, Socotra Island, Di Hamri , 12°40.046’ N, 54°10.758’ E, a small rock, depth 8–10 m, coll. S . V. Bogorodsky , 02 April 2019 ; SMF 39503, male, 21.1+ 4.5 mm, Socotra Island, Di Timri , 12°37.215’ N, 54°17.202’ E, rocky ridge with large stones, depth 10 m, coll. S . V. Bogorodsky , 08 April 2019 ( Fig. 5C ).

Diagnosis. Dorsal-fin rays VI+I,12; anal-fin rays I,11; pectoral-fin rays 15–16, all rays branched; pelvic-fin rays I,5, fins separated and without frenum, fifth ray unbranched; anterior nostril a moderately long tube with the process extending from median side of rim (as tentacle longer than tube) or as a slender flap slightly shorter than tube; posterior nostril a long tube with two tentacles, anterior long and posterior shorter; no tentacle above eye; mouth moderately large, posterior angle of jaws behind vertical through posterior edge of eye; no opercular spine; small mental frenum present; pelvic fins ending distantly well in front of anus; head and body mainly naked except for several ctenoid scales on caudal peduncle at caudal-fin base; head with anterior oculoscapular canal and preopercular canal, posterior oculoscapular canal absent; anterior oculoscapular canal pores with erected rim; suborbital rows of papillae in five transverse rows; nearly rounded dark blue or blackish spot as large as pupil above opercle; a large irregular white blotch on postorbital head, cheek and lower preopercle.

Description (The morphometric values in the text are presented first for the holotype followed by ranges for paratypes; meristic values, if variable, the same). Body elongate, depth at anal-fin origin 5.6 (6.0–6.3) in SL, laterally compressed posteriorly, caudal peduncle deep and short, caudal peduncle depth 1.4 (1.3–1.4 female paratypes, 1.5–1.6 male paratypes) of body depth at anal-fin origin, caudal peduncle depth 0.9 (0.9 female paratypes, 1.1 male paratypes) of caudal peduncle length ( Fig. 4 ). Head of moderate size, its length 3.4 (3.2–3.4) in SL, width 4.7 (4.8– 5.0) in SL, depth 5.1 (5.1–5.2) in SL, not depressed, its depth 1.1 (1.0–1.1) of width. Snout very steep in profile from lateral view, and short, length 0.5 (0.5) of eye diameter, 7.7 (7.7–8.1) in head length, no unpaired horn-like tentacle at the level of nostrils on snout midline. Anterior nostril a moderately long tube set over tip of upper lip with process extending from median side of rim (as tentacle longer than tube) or as slender flap slightly shorter than tube. Posterior nostril long tube, with tentacle longer than tube extending from anterior side of rim and tentacle shorter than tube extending from posterior side of rim ( Fig. 2A ). Eyes dorsolateral, moderately large, eye diameter 4.0 (3.7–4.0) in head length, orbit projecting forward and slightly elevated above dorsal profile of head. Interorbital narrow, 4.4 (4.1–5.3) of eye diameter. No tentacle above eye. Nape straight and flat. Mouth slightly subterminal, oblique, jaws ending anteriorly unequally, lower jaw slightly retracted anteriorly. Mouth moderately large, posterior angle of jaws behind vertical through posterior edge of eye. Upper lip wider than cheek, slightly inflated, in preserved specimens flattened and extending upwards on cheek. Cheek very narrow, suborbital depth less than upper lip width. Each side at front of upper jaw with outer row of 4–5 large recurved caniniform teeth, followed by irregularly scattered band of small conical inner teeth. Side of jaw with a single lateral row of about 10 medium-sized caniniform teeth. Sides of front of lower jaw with outer row of 4–5 large caniniform teeth, followed by irregularly scattered band of small conical median teeth and inner row of 5–6 large widely-spaced caniniform teeth. Single row of about ten mediumsized caniniform teeth continuous laterally on side of jaw. Small mental frenum midventrally behind lower lip. Branchiostegal membranes fused from isthmus to below pectoral-fin base, gill openings restricted to pectoral-fin base. Most of lower limb of first gill arch joined to gill cover by membrane. No spines on preopercle.

Fins. First dorsal fin with VI spines, second dorsal fin I,12; anal fin I,11; branched caudal-fin rays 15, segmented 17 (16:1, 17:3). Pectoral-fin rays left 16 and right cut (15:4, 16:2, right side cut in two paratypes), all rays branched, not free at tips. Pectoral girdle without flaps on anterior edge. Pelvic fins I,5+5,I, left and right fin completely separated, distant and without frenum ( Fig. 2B ). Pelvic-fin rays branched, except fifth ray, fourth ray the longest, rays progressively shorter towards the first ray and pelvic spine. Spines of first dorsal fin not elongate or filamentous, first to fifth spine of first dorsal fin about equal in length, third always slightly longer than others, sixth spine short; fourth or fifth to sixth spine of first dorsal fin barely reaching origin of second dorsal fin when folded down. Origin of first dorsal fin behind vertical at pectoral-fin base. Origin of anal fin posterior to vertical at origin of second dorsal fin, i.e. opposite about first segmented ray of second dorsal fin. Pectoral fins not reaching posteriorly to below origin of second dorsal fin or just reaching to vertical at the second dorsal-fin spine. Pelvic fins short, ending well in front of anus in both sexes, 0.6 (0.6–0.7) of distance between origin of fins and anus, shorter than pectoral fins, 0.9 (0.9) of pectoral-fin length. Caudal fin rounded, shorter than head, 1.3 (1.3–1.4) in head length.

Squamation. Head and body naked except for several ctenoid scales on caudal peduncle at caudal-fin base: four to eight scales ventrally on lateral side and one scale on the dorsal lateral side, most specimens with one more scale midlaterally ( Fig. 2C ).

Cephalic sensory systems ( Figs. 2D & 3 ). Head with anterior oculoscapular canal and preopercular canal with pores σ, λ, κ, ω, α, ρ, and δ, ε respectively. Pores in anterior oculoscapular canal with erected rim, nearly short tubes in some specimens (e.g. holotype) ( Fig. 2D ). Pore ω distant from eye, pore ρ positioned quite dorsally close to the level of pore ω, pore β absent. Posterior oculoscapular canal absent. Rows of head sensory papillae counted on all types, at least one side was in sufficient condition to count (holotype with better right side used for Fig. 3 ). Preorbital rows: snout with four median preorbital series, upper row r (1–2) middorsally between eyes above pore σ and posterior nostrils, row s 1 (1) at posterior nostril, row s 2 (1) below posterior nostril and row s 3 (2–3) above upper lip (rows s 1 and s 2 on Fig. 3 hidden by nostrils and tentacles). Lateral series c on snout in four parts, superior rows: upper row c 2 (2) between anterior and posterior nostrils, lower row c 1 (2–3) at anterior nostril; inferior rows: upper horizontal c 2 (3) anteriorly, and lower horizontal c 1 (1–2) posteriorly above upper lip. Suborbital rows: row a absent; row b short, behind vertical of posterior edge of eye and anteriorly close to suborbital row 4; five transverse suborbital rows of sensory papillae (1–5) present, row 1 oblique, reaching upper lip, rows 2 and 3 short and distant from eye, close to row d, row 4 long, curved, from posterior edge of eye slanting to posterior end of row d or slightly below it, row 5 close to pore α (1: 6–9, 2: 4–5, 3: 5–7, 4: 13–19, 5: 4); row d (6+10 – 7+13) long, above posterior part of upper lip, and continuing on lower cheek to meet suborbital row 4. Preoperculo-mandibular rows: external row e (14+10 – 18+18) longitudinal and uniserial, divided into anterior and posterior sections; internal row i (7+8 – 10+8) longitudinal and uniserial, divided into anterior and posterior sections, mental row f (4) behind frenum. Oculoscapular rows: three larger papillae longitudinally arranged on position of missing posterior oculoscapular canal above opercle, marked poc. Anterior longitudinal row x 1 (3+1 – 4+3) above level and behind pore ρ, divided in two parts, posterior longitudinal row x 2 (3) above posterior opercular edge, transverse row z (7–10) below and anterior to pore ρ, row y (1) below and behind row x 2. Transverse axillary rows as 1 (3) and as 2 (2–3) and as 3 (1–2) present, row la 1 (2) above between rows as 1 and as 2 not visible in all specimens and la 2 not present (row as 3 on Fig. 3 hidden by pectoral fin). Opercular rows: single papilla at location of missing pore γ, marked pc. Transverse row ot (11–13); superior longitudinal row os (4–5); and inferior longitudinal row oi (3) not visible in every specimen. Anterior dorsal rows: transverse row n (3–4) behind pore ω, rows o and m absent; row g longitudinal (6–8); row h (3–5) in front of the first dorsal-fin base.

Osteology. There are 10 precaudal vertebrae and 17 caudal vertebrae. The dorsal-fin pterygiophore pattern is 3-22110.

Color of fresh and live female ( Fig. 4A , holotype, SMF 39500; Fig. 5A & B , SMF 39501). Body in life transparent, with numerous yellow-brown or brown dots, a series of six or seven short, double, saddle-like dark brown marks along back, four series of 2–5 irregular iridescent white marks alternating with dark brown dashes along vertebral column, and five series of reflected white spots ventrally on body visible in alive specimens, the first series as 4–5 spots on abdomen, the last, fifth series as 1–2 very small spots above posterior part of anal fin; two obscure dusky blotches on abdomen, first beneath the pectoral fin, the second just behind it. An obvious nearly rounded dark blue to blackish spot as large as pupil above opercle over posterior opercular edge at the level of the pupil is most striking coloration pattern. Head brown, darker anteriorly, with a large oblique, irregular, white blotch on postorbital head and most of cheek, with ventroposterior extension ending at lower edge of preopercle; behind large blotch several smaller whitish spots of various size and shape present over preopercle and opercle and on nape and predorsal area, and a small white spot at angle of jaws; head covered with dark brown to blackish dots, becoming black and more dense on cheek and preopercle. First dorsal fin with two brown oblique bands, one in outer part, another short in the middle of fin from first to fourth spine, with white rectangular mark at base of first two spines and oblique white band between two brown bands, tips from fourth to sixth spines white. The second dorsal fin with transparent membranes and greenish brown spine and rays, with white dots on rays forming three irregular oblique rows. Anal fin mostly transparent with widely scattered small melanophores, mostly at base. Caudal fin transparent, with greenish rays, clearly visible in freshly dead specimens, and melanophores mostly at the fin base. Pectoral-fin base within a large white blotch, extending on base of fin except between sixth to eighth rays, rest of fin transparent, yellow in freshly dead specimens. Pelvic fins dark brown, densely dotted with melanophores.

The overall live surface coloration pattern is retained in freshly dead specimens, with white marks on body less obvious and brown dotted coloration more obvious than in live specimens. Iris mottled brown with four faint radiating orange-red bars, pupil green-black. Body opaque white, with scattered melanophores concentrated in six double, short, brown bars along dorsal-fin bases, two below the first dorsal fin and four below the second dorsal fin.

Color of live male ( Fig. 5C , paratype, SMF 39503, Fig. 5D ). Material is limited, hence sexual dichromatism cannot be confirmed. Based on photograph of a male ( Fig. 5C ), head is not darker anteriorly than rest of the head as in the female, black spot above posterior edge of opercle is faint, a single white blotch on abdomen (vs. series of clusters of reflected white spots ventrally on body in females), and two dark bands on first dorsal fin are indistinct.

Color of preserved specimens ( Fig. 4B ): Coloration lost in preservation, body yellowish white, with dark brown dots from melanophores. No sexual dichromatism observed. Head dotted brown. Ventral side and mouth darker than rest of head. Large oblique irregular whitish marking behind and below eye. Smaller whitish spots of various size and shape on head opercle, preopercle, dorsal and ventral side, not prominent, formed by less dense pattern of melanophores compared to darker parts. Eye with dark iris and white pupil. Body with scattered melanophores more concentrated in dorsal part, six marks along both dorsal-fin bases and ill-defined marks along lateral midline recognizable in some specimens. Intensive dark brown rounded mark above posterior opercular edge and pectoral fin is most conspicuous coloration pattern. Breast brown with many melanophores, rest of ventral side of body with more broadly spaced melanophores. First dorsal fin with two dark oblique bands, one in upper part, one in the middle of fin, alternating with whitish mark at anterior corner of fin base and oblique white band between two brown bands. Second dorsal fin marbled with dark and white spots. Anal fin transparent with rarely scattered small melanophores mostly at base. Caudal fin transparent, with melanophores at the fin base. Pectoral fins with few scattered melanophores, the rest of fin transparent. Pelvic fins dark dotted with melanophores.

Etymology. The specific name nasoramosa is formed from the combination of two Latin words naso (nose), and ramosa (branched) in reference to the well-developed, branched process extending from the rim of the anterior and posterior nostril, respectively.

Habitat and Distribution. Specimens of H. nasoramosa were collected on rubble-sand patches in sandy areas and in areas with mixed corals and stones or rocks at several localities from the north-eastern part of the Socotra Island. The holotype and paratypes were found living inside small holes in moderately large pieces of coral rock covered with short algae at depths of 8–11 m. The species has not yet been recognized from elsewhere and appears to be endemic to the Socotra Archipelago .

Remarks. Based on the molecular phylogeny and several diagnostic morphological characters (see Generic identification above), the new species was assigned to Hetereleotris . It is unique though among Hetereleotris species in having a simple tentacle or slender flap extending from the anterior nostril and anterior and posterior tentacles extending from the posterior nostril, and by having five suborbital transverse papillae rows. An obvious large (as large as pupil), dark spot above the opercle is shared only with H. bipunctata Tortonese, 1976 and H. margaretae Hoese, 1986 . However, both latter species have coloration patterns distinguishing them from the new species. Among twenty Hetereleotris species presently recognized, only the new species and H. tentaculata ( Smith, 1958) share forward-set elevated eyes, a very short snout, and the posterior angle of the jaws behind vertical through the posterior edge of eye. The combination of head canals and pores seen in the new species is present otherwise only in H. caminata ( Smith, 1958) , H. tentaculata and H. vulgaris . The ctenoid scales, restricted to caudal peduncle only as a ventral patch and one or two individual scales dorsally, was reported among Hetereleotris species only in some specimens of H. tentaculata by Hoese (1986), in which it is variably present. The extreme reduction to a few scales is also present in H. aurantiaca Kovačić & Bogorodsky, 2019 , but with a different pattern. All other Hetereleotris species are more extensively scaled, at least on the caudal peduncle, or the body is completely scaleless. Hetereleotris nasoramosa is morphologically most similar to H. tentaculata , sharing the following combination of characters: dorsal-fin rays VI+I,12, anal fin rays I+I,11, presence of some kind of tentacles on the head, eyes forward-set and elevated, a very short snout, posterior angle of jaws behind vertical through posterior edge of eye, scales restricted to caudal peduncle in a similar pattern (at least in some H. tentaculata specimens), and the same pattern of head canals and pores. However, H. tentaculata has a tentacle over the eye, no tentacles on the nostrils and a different coloration, e.g. presence of a dark bar below first dorsal fin and absence of a dark humeral spot. The putatively close relationship of these two species based on morphology should be confirmed once H. tentaculata material is available for molecular analysis.

Cerogobius petrophilus was described in its own genus based on the presumed distinctive presence of a single tentacle on the snout midline between nostrils, with no other tentacles on the head. Compared to the new species, C. petrophilus is scaleless, with head canals and pores absent, with four suborbital transverse papillae rows and a different coloration (see Kovačić et al. 2019b). Its generic assignment is pending further investigation, as elaborated below.

Figures

FIGURE 2. Hetereleotris nasoramosa sp. nov., holotype, SMF 39500 [sample tissue SOC18-191], female, 20.9 mm SL, Di Hamri, Socotra Island: A: head with AN - anterior nostril as a short tube with tentacle from the rim, PN - posterior nostril a long tube with very long anterior tentacle and shorter posterior tentacle extending from the rim, PAJ - posterior angle of jaws extends behind vertical through posterior edge of eye; B: pelvic fins completely separated and without frenum; C: caudal peduncle stained, with visible scales; D: nape stained, erected pores of anterior oculoscapular canal, terminology in text. Photos by S.V. Bogorodsky (A) and M. Kovačić (B-D).

FIGURE 3. Hetereleotris nasoramosa sp. nov. Cephalic sensory papillae, paratype, PMR VP4890, male, 22.3 mm SL, Di Hamri, Socotra Island. The right side illustrated, as it is in better condition, terminology in text. Drawing by M. Kovačić.

FIGURE 4. Hetereleotris nasoramosa sp. nov., holotype, SMF 39500, female, 20.9 mm SL, Di Hamri, Socotra Island: A: freshly collected specimen; B: preserved specimen. Photos by S.V. Bogorodsky (A) and M. Kovačić (B).

FIGURE 5. Hetereleotris nasoramosa sp. nov.; A: SMF 39501, paratype, female, 24.9 mm SL, alive specimen, Di Hamri, Socotra Island; B: the same specimen, freshly collected; C: paratype, SMF 39503, male, 21.1 mm SL, alive specimen, Di Timri, Socotra Island; D: presumably male, alive specimen, not collected, Di Timri, Socotra Island. Photos by S.V. Bogorodsky.