Sueviota aethon Nunes Peinemann, Pombo-Ayora & Tornabene 2024, sp. nov.

Sueviota aethon Nunes Peinemann, Pombo-Ayora & Tornabene sp. nov.

Figs 1, 2, 3, 4 Grumpy dwarfgoby

Type material.

Holotype. UW 203365, CRF 186, female, 13.3 mm SL, Shark Reef 22.4283 ° N, 38.9932 ° E, central Red Sea, Thuwal, Makkah Province, Saudi Arabia, collected at 14 m from crustose coralline algae (CCA) covered overhang with lots of holes, clove oil and hand net, Viktor Nunes Peinemann, 22 June 2022. GenBank accession numbers: PP 955452 (COI); PP 955326 (16 S). Paratypes. • UW 203366, CRF 114, male 13.3 mm SL, 19.8375 ° N, 39.9296 ° E, central Red Sea, Al Lith, Makkah Province, Saudi Arabia, collected at 30 m from the roof of a cave, clove oil and hand net, Viktor Nunes Peinemann, 19 May 2022. GenBank accession numbers: PP 955451 (COI); PP 955325 (16 S). • UW 203367, CRF 379, female, 12.4 mm SL, 22.2948 ° N, 39.0688 ° E, central Red Sea, Thuwal, Makkah Province, Saudi Arabia, collected at 10 m from a cave with a sandy bottom, collected as a mass sample, rotenone, Darren Coker, 7 August 2023. GenBank accession number: PP 955453 (COI). • CAS -ICH 248441, CRF 454, female, 9.2 mm SL, 18.8582 ° N, 40.3779 ° E, central Red Sea, Maras Reef, Makkah Province, Saudi Arabia, collected at 30 m from a CCA-covered overhang, clove oil and hand net, Viktor Nunes Peinemann, 6 June 2024. • CAS -ICH 248442, 6 specimens, 11.2 – 16.7 mm SL, 18.8582 ° N, 40.3779 ° E, central Red Sea, Maras Reef, Makkah Province, Saudi Arabia, collected at 20 m as a mass sample, rotenone, Viktor Nunes Peinemann, 6 June 2024.

Generic placement.

This species is placed in the genus Sueviota due to the presence of several key characteristics that differentiate Sueviota from the genus Eviota: a well-developed membrane between the fifth pelvic fin rays (extending entire length of ray) and the fifth pelvic rays elongate (77 – 88 % of fourth ray), sometimes branched.

Diagnosis.

This is a species of Sueviota characterized by the following combination of characters: no cephalic sensory-canal pores; dorsal fin VI-I, 8, or I, 9, without filamentous spines; anal fin I, 7 or I, 8; pelvic fin I, 5, rays 1 – 4 branched, fifth ray unbranched or with two branches, elongate (77–88 % of fourth) and flattened towards the tips if unbranched, fourth ray longest; well-developed pelvic fin membrane fully joining fifth pelvic fin rays, frenum absent; 14 or 15 pectoral fin rays, some branched; body robust and deep, anterior slope of snout nearly vertical giving the head a blunt profile, terminal mouth inclined vertically forming a 72 ° angle to horizontal body axis.

Description.

Dorsal fin elements VI-I, 9 (I, 8), first dorsal fin rounded to square shaped, second and third spines slightly longer than the first spine; no elongate filaments on first dorsal fin; some or all soft rays of second dorsal fin branched, final ray branched to base; anal fin I, 8 (one paratype I, 7); pectoral fin rays 14 (14 – 15), 6 – 7 lower rays branched; pelvic fin I, 5; fifth ray 77 – 88 % of fourth ray; fourth pelvic fin ray with 4 branches, fifth pelvic fin ray unbranched or with 2 branches; 3-2 - 2 segments between consecutive branches of fourth pelvic fin ray; membrane connecting pelvic 5 th fin rays well developed extending out towards the tip, no frenum (Fig. 2 B); 17 (15 – 17) segmented and 13 (12 – 13) branched caudal fin rays; lateral scale rows 25 (24 – 25); transverse scale rows 7 (6 – 7); ctenoid scales on body, no scales on head and breast; anterior extent of scales does not reach the base of the pectoral fin, no scales on the base of the first dorsal fin, but present on the base of the second dorsal fin; scales on the trunk extend ventrally onto the abdomen to beneath the pelvic fin rays with a small naked section on the ventral midline of the abdomen; front of the head distinctively blunt; mouth inclined vertically forming an angle of 72 ° to horizontal body axis, lower jaw projecting; upper jaw extending posteriorly to a vertical reaching the middle of the pupil; anterior tubular nares about 50 % of the pupil diameter, posterior nares enlarged with an elevated rim adjacent to the eye; prominent canines; gill opening extending forward reaching the anterior edge of the operculum; lacking entire cephalic sensory canals and corresponding pores, but papillae (free neuromasts) are present where canal pores would be located (Fig. 2 A); female urogenital papilla short and bulbous (Fig. 3 B); male urogenital papilla elongated, smooth and bulbous with weakly fimbriate margin resembling type e (Fig. 3 A); vertebral count 10 + 15 = 25 (Fig. 4 C).

Measurements (percentage of SL; based on holotype and nine paratypes, 9.2 – 16.7): head length 27.1 (22.8 – 27.1); origin of first dorsal fin 33.8 (33.5 – 37.9), slightly behind pectoral fin base and pelvic fin origin; origin of second dorsal fin 55.6 (53.2 – 59.8); origin of anal fin 58.6 (56.2 – 60.9); caudal peduncle length 20.3 (19.5 – 23.8); caudal peduncle depth 15.0 (14.9 – 17.5); body depth at origin of first dorsal fin 22.6 (19.5 – 25.2), body relatively slender; pectoral fin length 16.5 (17.3 – 19.9); pelvic fin length 19.3 (15.0 – 21.3). As a percentage of HL: eye diameter 25.8 (22.2 – 30.8); snout length 15 (15.8 – 21.3); upper-jaw length 52.8 (46.9 – 59.3).

Teeth: Sueviota aethon has two irregular rows of conical teeth in both its upper and lower jaws. As described by Winterbottom and Hoese (1988) in the initial description of the Sueviota genus, S. aethon has enlarged conical canines in both the upper and lower jaws. A closer examination of the head osteology through a micro-CT scan (Fig. 4) shows this detail with one enlarged curved canine situated on each side of the premaxilla, as well as one enlarged curved canine on each side of the innermost row of teeth on the dentary.

Fresh coloration.

The following description is based on ten specimens. Nine of these are dark red (Fig. 1 A), while one is yellow-orange with several minor differences (Fig. 1 B). Additional specimens are needed to determine the breadth of this intraspecific variation. Background of head and body bright red or yellow-orange; head and base of the pectoral fin heavily peppered with melanophores, giving the appearance of a burnt-red or peppered yellow coloration which intensifies towards nape and pre-dorsal area, melanophores concentrated on scale margins in yellowish specimen; cheeks heavily covered with melanophores with sparse marbling of white; no distinct spots on the pectoral fin base; breast, posterior margin of opercle, and branchiostegal areas light red in two specimens, white in a third; seven broad, faint, dark vertical bars on trunk starting from origin of first dorsal fin to base of caudal fin; two preanal bars poorly defined, five post-anal bars well defined and characterized by heavily pigmented subdermal melanophores; dark pigmentation of third and fourth bars extend to base of anal fin and give an appearance of two bright red spots on base of anal fin; no distinctive bars on head or radiating from the eye; fin elements on both dorsal and anal fins with alternating broad red and narrow white bands; pink band formed by tightly clustered chromatophores covers approximately one-third of dorsal and anal fins; dark red mottled pattern covering the remaining dorsal and anal fins; caudal fin primarily translucent except for relatively narrow pink bar of tightly clustered chromatophores on base of fin; pelvic fin translucent with small uniform light red chromatophores scattered along membrane but slightly condensed closer to the rays; pectoral fins translucent with no evident coloration; pupil of the eye black, and iris identical to the head coloration, with narrow iridescent gold ring surrounding pupil.

Color in preservative ethanol.

Background color of body and head pale whitish, covered by dark melanophores. Head, nape, and pre-dorsal areas heavily pigmented by tiny condensed melanophores extending along the dorsal region, melanophores more densely concentrated on scale margins; breast and branchiostegal areas brighter with fewer subdermal melanophores; seven dark bars along the trunk only barely distinguishable, the first six bars only slightly visible at dorsalmost and ventralmost edges, seventh bar located at base of caudal fin most apparent; fins generally translucent; membrane on external edge of first dorsal fin covered by tiny melanophores; some scattered melanophores on membranes of second dorsal fin and anal fin; no coloration on the pectoral, pelvic, and caudal fins (Fig. 1 C)

Etymology.

The specific epithet stems from the ancient Greek Aethon, one of the four horses of the sun god Helios. The most similar species to S. aethon, Sueviota pyrios Greenfield & Randall, 2017, is named after a different horse of Helios. The specific name is a noun in apposition. The common name, Grumpy dwarfgoby, refers to the fish’s apparent grumpy and rather unhappy appearance, primarily due to the extremely upturned mouth position.

Distribution and habitat.

Sueviota aethon is a rare species, with only ten specimens found during extensive rotenone and clove oil collections along the Saudi Arabian Red Sea coast. These specimens were collected at depths between 10 and 30 meters. A sample from another expedition (not presented here) was confirmed from 53 meters depth. The species may be more common at similar mesophotic depths, but further collections are needed to confirm this. The specimens collected with clove oil were found on CCA-covered roofs of small caves. Six specimens were collected from a single mass sampling at a CCA-covered wall with small crevices and holes. All but one of the specimens analyzed in this study were collected from exposed offshore reefs.

Sueviota aethon is presumably a Red Sea endemic. Our records range from Al Qunfudhah (18.9922 ° N, 40.6145 ° E) to Thuwal (22.4283 ° N, 38.9932 ° E), but it is likely that the species is more widely distributed throughout the main basin of the Red Sea (Fig. 5).

Comparisons.

A summary of key comparative characters in Sueviota spp. is provided in Table 1. Sueviota aethon is distinguished from all other Sueviota spp. by its complete lack of cephalic sensory pores. The most similar species to S. aethon is Sueviota pyrios, which has a close and potentially overlapping geographic range, as well as a similar body shape, and coloration (Greenfield and Randall 2017). Besides the lack of cephalic sensory pores, S. aethon differs from S. pyrios by having no large red spots on dorsal and caudal fin elements, no elongate spines in the first dorsal fin, a shorter pelvic fin that does not reach the anus, branched pectoral fin rays, and a projecting lower jaw. Sueviota pyrios is currently known from only one specimen collected in the Gulf of Aqaba.

* single interporbital pore, unclear as to whether it represents AITO or PITO; ** description says unbranched but photos of holoptype show branching.

Another superficially similar species is Sueviota tubicola Allen & Erdmann, 2017. Sueviota aethon differs from S. tubicola by having no spots at the base of the pectoral fin, no cephalic sensory pores, no elongate dorsal spines, 14 – 15 pectoral rays (vs. 19 in S. tubicola), 5 th pelvic ray subequal in length to 4 th (vs. equal in S. tubicola), and no pelvic frenum (Allen and Erdmann 2017).