Gouania hofrichteri, Wagner & Kovac & Koblmüller, 2021

Wagner, Maximilian, Kovac, Marcelo & Koblmüller, Stephan, 2021, Unravelling the taxonomy of an interstitial fish radiation: Three new species of Gouania (Teleostei: Gobiesocidae) from the Mediterranean Sea and redescriptions of G. willdenowi and G. pigra, Journal of Fish Biology 98 (1), pp. 64-88 : 75-77

3.1.4 | Gouania hofrichteri sp. nov.

English name: Hofrichter's clingfish

ZooBank LSID: urn:lsid:zoobank.org:act:3894FA6B-E67C-4905-A31C-F6FD1EF4F2A8

Holotype. PMR VP4595 , male, 30.35 + 3.67 mm, Souda Beach, Plakias, Crete, Greece, 35 11 0 32.1 00 N, 24 22 0 04.9 00 E, coll. M. Wagner, August 17, 2016 (Figure 7).

Paratypes. PMR VP4591 , female, 21.42 + 2.62 mm, Mades , Crete, Greece, 35 24 0 01.1 00 N, 25 02 0 01.6 00 E, coll. M. Wagner, August 15, 2016 ; PMR VP4599 , female, 26.8 + 3.23 mm and PMR VP4600 , male, 29.75 + 3.49 mm, both from Souda Beach , Plakias, Crete, Greece, 35 11 0 32.1 00 N, 24 22 0 04.9 00 E, coll. M. Wagner, August 17, 2016 ; PMR VP4605 , juvenile of unidentified sex, 20.62 + 2.63 mm, Saronida , Greece, 37 43 0 12.2 00 N, 23 55 0 41.0 00 E, coll. M. Wagner, August 2, 2016 ; PMR VP4606 , female, 29.47 + 3.41 mm, ZSM-PIS-047656, female, 35.86 + 4.49 mm and PMR VP4608 , female, 26.69 + 3.32 mm, all from Chamolia , Greece, 37 54 0 58.5 00 N, 24 02 0 08.7 00 E, coll. M. Wagner, August 4, 2016 ; ZSM-PIS-047657, male, 36.91 + 4.24 mm and ZSM-PIS-047657, male, 33.27 + 4.31, mm, both from Chamolia , Greece, 37 54 0 58.5 00 N, 24 02 0 08.7 00 E, coll. M. Wagner, August 16, 2018.

Diagnosis. Gouania hofrichteri sp. nov. differs from congeneric species by the combination of the following characters: (1) dorsal head profile in lateral view “ S ” curved, concave above eye and convex at nape; (2) posterior angle of jaws extends to between vertical line drawn through posterior edge of anterior nostril and vertical line drawn through anterior edge of eye; (3) infraorbital invagination below anterior half of eye or below mideye; (4) posterior opercular edge with pointed upper tip and rounded lower edge; (5) longitudinal infralateral and suborbital transversal rows of superficial neuromasts placed in shallow groove disappearing in posterior part of longitudinal infralateral row; (6) body cross-section behind pectoral fin base triangular with ventral flat and dorsal pointed; (7) granules on body, at least on posterior part and nape, large and prominent; (8) upper attachment of gill membrane opposite to 3rd – 4th pectoral ray; (9) vertical eye diameter 2.0 – 2.7% of standard length; (10) head length 18.9 – 23.4% of standard length; (11) pectoral-fin length 5.4 – 6.4% of standard length; (12) prepectoral distance 19.5 – 23.7% of standard length; (13) ventral adhesive disc length 10.2 – 13.4% of standard length; (14) caudal-fin length 11.5 – 13.4% of standard length; (15) high total number of vertebrae (Supporting Information Table S2; 38 – 40); (16) pharyngeal jaws with ceratobranchial 5 elongated, having several larger elongated conical teeth; (17) nasal bones hook-shaped; (18) star-like pigmentation around eyes absent, body pigmentation striped or marbled, small iridophores visible.

Description. General morphology: Body proportions are given in Table 1. Body very slender and elongated, posteriorly laterally compressed, body depth at pectoral fins 9.2 – 10.5 in SL, body depth at anus 11.0 – 13.5 in SL, body depth in width at pectoral fins 1.0 – 1.0, body depth in width at anus 0.7 – 0.9. Body cross-section behind pectoral fin base triangular with ventral flat and dorsal pointed. Granules on body, at least on posterior part and nape, large and prominent. Head dorsoventrally compressed, head depth in width at orbit 1.5 – 1.8, and moderately small, head length 4.3 – 5.3 in SL, head wider than body width maximum, head width at anterior sucking disc edge 0.7 – 0.8 in body width at pectoral fins. Dorsal head profile “ S ” curved, concave above eye and convex at nape. Head rounded in dorsal view. Snout large compared to eyes, preorbital distance 2.8 – 3.7 in head length, 0.3 – 0.5 in horizontal eye diameter. Snout wide, not produced, blunt. Internostril space almost triangular in cross-section, with ridge top, conspicuously convex. Eyes dorsolateral, with lower eye edge rounded. Eyes small, 7.7 – 10.7 in head length, vertical diameter of the eye 0.8 – 1.1 in horizontal eye diameter. Infraorbital invagination below anterior half of eye or below mideye. Interorbital distance wide, 0.3 – 0.5 in horizontal eye diameter. Centre of eye much closer to tip of snout than to posterior margin of operculum, preorbital distance in postorbital distance 1.7 – 2.3. Anterior and posterior nostrils long tubes of about equal length. Nostrils well separated and posterior nostril located behind and dorsally to the anterior edge of eyes. Single large dermal flap at the posterior margin of anterior nostril leaf shaped, longer than nostril. Posterior nostril rim crenate with no extension. Head lateral line system with canals with pores and with superficial neuromasts arranged in rows. Head canals reduced and pores small. Single pore in nasal canal near posterior nostril. Single pore in postorbital canal close to posterior eye edge. Two pores in mandibular canal, anterior one close to anteriolateral angle of mouth, posterior pore slightly in front of vertical of posterior angle of jaws, posterior pore usually more prominent. Lachrymal as well as preopercular canals and pores absent. Rows of superficial neuromasts as follows: SR 2, NR 3, LIR 22 – 29, STR 2 – 4, POR 3, PTR 2, SLR 4 – 5, MR 9 – 11, AVR 2, PVR 1, ADR 2 – 3, PDR 1, HR 3 – 4, SR1 3 – 4, SR2 1 – 2, DLR 5 – 8, VLR 10 – 13. STR and LIR rows of superficial neuromasts placed in shallow groove disappearing in posterior part of LIR. DLR row of superficial neuromasts anteriorly starts above pectoral fin, continuously dorsolateral and ends posteriorly downwards at or above midlateral level vertical to anus. VLR anteriorly starts behind pectoral fin base, continuous ventrolaterally and ends posteriorly upwards with last papilla near or at midlateral level at or close to caudal-fin base. Mouth terminal, upper and lower lips ends about equally, lips fleshy, upper lip larger than the lower lip. Posterior angle of jaws extends to between vertical line drawn through posterior edge of anterior nostril and vertical line drawn through anterior edge of eye. Chin with bilobed or single lobe fold at anterior edge not covering MR row of superficial neuromasts. The gill membrane is attached to isthmus, gill opening starting at the base of pectoral fin, with the upper attachment of the gill membrane is opposite to 3rd – 4th pectoral ray. Posterior opercular edge with pointed upper tip and rounded lower edge. No subopercular spine. No fleshy pad present on lower pectoral base. Urogenital papilla present. Preanus length in postanus length 0.7 – 1.0. Anal papillae absent, the area around anus wrinkled.

Fins. Rudimentary dorsal and anal fins located well posteriorly and short, reduced to low ridges with the very weak rays, connected to the caudal fin. Pectoral rays 14 – 16. Caudal fin rounded, principal caudal rays 10 – 12. Ventral adhesive disc (Figure 4c) of “ double ” type, anterior margin crenate with large invagination on each lateral side and central invagination at midventral; posterior margin crenate. Disc very small, disc length 7.5 – 9.8 in SL, its width slightly larger than its length, width in length 0.8 – 0.9. No papillae in region A and flattened papillae in regions B and C. In region B one or two rows of papillae with total papillae count 12 – 30 and in region C one or two rows of papillae with total papillae count 4 – 14. No inner row of papillae on lateral sides of the central part of the anterior disc. Upper attachment of disc membrane attaching to base of pectoral fin at 14th – 16th pectoral ray (i.e., at ultimate or penultimate ray). Males can have two prominent seemingly perfused finger-like extensions on each site of sucking disc that are of equal size or exceeding length of disc region A (Figure 4f).

Colouration. Background colour of live specimens bright to skin-coloured (Figure 7). Pigmentation behind head region sometimes with a clearly visible striped or marbled (i.e., irregularly distributed patches of pigments) pattern. Sometimes small evenly distributed iridophores visible in lateral view (Figure 7) in life. No star-like pigmentation around the eyes visible. Formaldehyde fixed specimens white-yellow and without pigments. Ethanol fixed specimens white to skin coloured, striped or marbled pigmentation visible. For more pictures of live colouration see Supporting Information File S1.

Dentition and osteology. Upper jaw with outer row of about eight (one side) medium-sized caniniforms frontally. Behind them inner small conical teeth irregularly scattered in two separate (left and right) drop-like patches medially wide about 5 – 6 teeth, becoming narrowed to a single row of teeth laterally. Outer row continues laterally laterally as four large caniniforms of variable size, followed behind by about six medium-sized caniniforms. Lower jaw with outer row of eight to 10 (one side) medium-sized caniniforms frontally. Behind them single broad patch of small conical inner teeth medially wide about 5 – 6 teeth, becoming narrowed to a single row of teeth laterally. The single row of about five larger caniniforms continuous laterally. Pharyngeal jaws with elongated ceratobranchial 5, having several (about 5) larger elongated conical teeth (Figure 5c), pharyngobranchial 3 toothplate not visible on 3D models from micro-computed tomography (microCT) images. Number of vertebrae 38 – 40, abdominal 17 and caudal 21 – 22 (Supporting Information Table S2). The first gill arch with hemibranch, the 2nd to 4th gill arches with holobranchs. Subopercle indistinguishable from opercle, shaped as its posterior elongated extension, not forming or having subopercular spine. Six branchiostegals. Hook-shaped nasal bones. Maxillary and premaxillary bones shaped as on Figure 5c.

Etymology. Named hofrichteri , in honour of Robert Hofrichter, whose work on European clingfishes sparked our interest in these enigmatic fishes. The species epithet was formed from the personal name, as the noun in the genitive case, with “ i ” added to the stem of the name (Article 31.1.2., ICZN, 1999).

Ecology and geographical distribution (Figure 1a). Species widespread in the eastern Mediterranean Sea with a single record from the Adriatic Sea (Pelješac; Figure 1c). G. hofrichteri sp. nov. is very abundant in the northern and southern Ionian Sea (Corfu, Stomio), the Gulf of Corinth, the islands of Kythira and Crete and the Aegean Sea (Attica). Quantitative data on ecology is largely lacking. The species inhabits intertidal pebble beaches and probably shows passive emergence behaviour (compare with Bilecenoglu, 2015). Throughout its distribution range this species occurs in sympatry with G. orientalis sp. nov. and on the island Corfu with G. adriatica sp. nov. There is a single record of the species inside the Adriatic basin from Pelješac, where it occurs in low densities together with G. pigra and G. adriatica sp. nov.

Remarks. Gouania hofrichteri sp. nov. differs from all other Gouania species by longitudinal infralateral and suborbital transversal rows of superficial neuromasts placed in shallow groove disappearing in posterior part of longitudinal infralateral row (vs. longitudinal infralateral and suborbital transversal rows of superficial neuromasts placed in the well-defined deep groove in all other Gouania species); body cross-section behind pectoral fin base triangular with ventral flat and dorsal pointed (vs. body cross-section behind pectoral fin base half oval to pentagonal (pentagonal only in G. pigra ) with straight ventral side in all other Gouania species); granules on body, at least on posterior part and nape, large and prominent (vs. the granules on body shallow and inconspicuous in all other Gouania species) and hook-like nasal bones. G. hofrichteri sp. nov. differs from three stout-bodied Gouania species ( G. adriatica sp. nov., G. orientalis sp. nov. and G. willdenowi ) by dorsal head profile in lateral view “ S ” curved, concave above eye and convex at nape (vs. dorsal head profile straight between nape above eye and upper lip tip), absence of star-like pigmentation around eyes and large number of vertebrae (Supporting Information Table S2; 38 – 40 vs. 35 – 38). Eleven morphometric characters as percentages of standard length of G. hofrichteri sp. nov. are nonoverlapping in range with all three stout-bodied Gouania : vertical eye diameter, head length, postorbital distance, all three head widths, body width at pectoral fins, pectoral-fin length, prepectoral distance, ventral adhesive disc length and caudal-fin length (values in the Table 1). In addition, there are numerous morphometric characters nonoverlapping in range with one or two out of three stout-bodied Gouania species (Table 1). G. hofrichteri sp. nov. differs from G. adriatica sp. nov. and G. orientalis sp. nov. by the upper attachment of the gill membrane opposite to 3rd – 4th pectoral ray (vs. upper attachment of the gill membrane opposite to 5th – 6th pectoral ray) and from G. orientalis sp. nov. and G. willdenowi by the infraorbital invagination below anterior half of eye or below mideye (vs. infraorbital invagination vertical to posterior part of eye) and by posterior opercular edge with pointed upper tip and rounded lower edge (vs. posterior opercular edge w-shaped with two equally long tips). G. hofrichteri sp. nov. differs from other slender-bodied species, G. pigra , by the posterior angle of jaws extending to between vertical line drawn through posterior edge of anterior nostril and vertical line drawn through anterior edge of eye (vs. posterior angle of jaws extending to, or close to, vertical line drawn through anterior edge of anterior nostril) and by posterior opercular edge with pointed upper tip and rounded lower edge (vs. posterior opercular edge with two tips, upper longer or equal to lower). G. hofrichteri sp. nov. is known from the Adriatic (single findings from Pelješac), Aegean and Ionian Sea and has nonoverlapping geographic distribution only with G. willdenowi .