Gouania pigra (Nardo 1827)

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 : 77-80

3.1.5 | Gouania pigra (Nardo 1827)

English name: Piglet sucker

Neotype. PMR VP3529 , female, 43.12 + 5.03 mm, Glavotok, Krk, Croatia, 45 05 0 44.9 00 N, 14 26 0 32.4 00 E, coll. M. Wagner, May 16, 2015 (Figure 8).

Additional material examined. ZSM-PIS-047648, male, 37.71 + 4.36 mm, ZSM-PIS-047648, male, 37.2 + 4.31 mm and ZSM-PIS-047648, female, 32.58 + 3.94 mm, all from Stara Baška , Krk, Croatia, 44 56 0 45.3 00 N, 14 42 0 22.2 00 E, coll. M. Wagner, September 16, 2019; PMR VP3531 , male, 39.48 + 4.4 mm, Glavotok , Krk. Croatia, 45 05 0 44.9 00 N, 14 26 0 32.4 00 E, coll. M. Wagner, May 16, 2015; PMR VP4619 , female, 35.86 + 4.14 mm, Stoja , Pula, Croatia, 44 51 0 38.4 00 N, 13 49 0 05.0 00 E, coll. M. Wagner, July 17, 2016 ; ZSM-PIS-047649, female, 35.14 + 4.03 mm and ZSM-PIS-047649, male, 37.07 + 4.51 mm, both from Pecine, Rijeka, Croatia, 45 18 0 52.4 00 N, 14 28 0 11.7 00 E, coll. M. Wagner, July 12, 2019 ; PMR VP4581 , male, 38.67 + 4.91 mm and PMR VP4583 , male, 36.87 + 4.08 mm, Sv. Marina, Istria, Croatia, 45 01 0 42.1 00 N, 14 09 0 17.4 00 E, coll. M. Wagner, July 18, 2015 .

Synonyms. Lepadogaster piger Nardo 1827: 9 (original description; type locality: Rovinj; holotype: unknown); Gouania prototypus Nardo 1833: 548 (original description; type locality: Rovinj?; holotype: unknown), Gouania piger Bonaparte 1846: 64 (original description; type locality: unknown; holotype: unknown); Leptopterygius piger Günther 1861: 515 (original description; type locality: unknown; holotype: unknown).

Diagnosis. Gouania pigra differs from the 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, or close to, vertical line drawn through anterior edge of anterior nostril; (3) infraorbital invagination below anterior half of eye or below mideye; (4) posterior opercular edge with two tips, upper longer or equal to lower; (5) longitudinal infralateral and suborbital transversal rows of superficial neuromasts placed in the well-defined deep groove; (6) body cross-section behind pectoral fin base half oval to pentagonal with straight ventral side; (7) granules on body shallow and inconspicuous; (8) pectoral rays 13 – 16; (9) upper attachment of disc membrane attaching to base of pectoral fin at 12th – 15th pectoral ray; (10) principal caudal rays 10 – 11; (11) head length 19.5 – 22.9% of standard length; (12) pectoral-fin length 5.6 – 7.5% of standard length; (13) prepectoral distance 19.5 – 23.4% of standard length; (14) ventral adhesive disc length, 12.1 – 14.6% of standard length; (15) caudal-fin length 11.1 – 12.7% of standard length; (16) large total number of vertebrae (Supporting Information Table S2; 39 – 40); (17) pharyngeal jaws with elongated ceratobranchial 5, having several larger elongated conical teeth; (18) nasal bones hook-shaped; (19) no star-like pigmentation around eyes, pigmentation generally reduced.

Description. General morphology: Body proportions are given in Table 1. Body very slender and elongated, posteriorly laterally compressed, body depth at pectoral fins 8.5 – 9.4 in SL, body depth at anus 8.8 – 11.8 in SL, body depth in width at pectoral fins 1.0 – 1.2, body depth in width at anus 0.7 – 0.9. Body cross-section behind pectoral fin base half oval to pentagonal with straight ventral side. Granules on body shallow and inconspicuous. Head dorsoventrally compressed, head depth in width at orbit 1.5 – 1.9, and moderately small, head length 4.4 – 5.1 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 2.7 – 3.6 in head length, 0.3 – 0.4 in horizontal eye diameter. Snout wide, not produced, blunt. Internostril space convex to gently convex. Eyes dorsolateral, rounded or drop-like with slightly pointed lower eye edge. Eyes small, 9.1 – 11.2 in head length, vertical diameter of the eye 0.7 – 0.9 in horizontal eye diameter. Infraorbital invagination below anterior half of eye or below mideye. Interorbital distance wide, 0.3 – 0.4 in horizontal eye diameter. Centre of eye much closer to tip of snout than to posterior margin of operculum, preorbital distance in postorbital distance 1.8 – 2.4. 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 of leaf shape at the posterior margin of anterior nostril, longer than nostril. Posterior nostril rim crenate or villose 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 21 – 26, STR 2 – 3, POR 2 – 3, PTR 2, SLR 5, MR 8 – 12, AVR 2, PVR 1, ADR 3, PDR 1 – 2, HR 3, SR1 3, SR2 1 – 2, DLR 6 – 10, VLR 12 – 16. STR and LIR rows of superficial neuromasts placed in the well-defined deep groove. DLR row of superficial neuromasts anteriorly starts above pectoral fin, continuously dorsolateral and ends posteriorly variably: downwards at midlateral level or above it, at vertical from anus, or in front or behind it. VLR anteriorly starts behind pectoral fin base, continuously ventrolateral and ends posteriorly upwards with last papilla nearly at midlateral level at caudal fin base or more distant from it. Mouth terminal, upper and lower lips end about equally, lips fleshy, upper lip larger than the lower lip. Posterior angle of jaws extends to, or close to, a vertical line drawn through the anterior edge of the anterior nostril. Chin with bilobed or single lobed fold at anterior edge covering MR row of superficial neuromasts. Gill membrane is attached to isthmus, gill opening starting at base of pectoral fin, with upper attachment of gill membrane opposite to 3rd to 5th pectoral ray. Posterior opercular edge with two tips, upper longer or equal to lower. No subopercular spine. No fleshy pad present on lower pectoral base. Urogenital papilla present. Preanus length in postanus length 0.7 – 0.9. Anal papillae absent, the area around anus wrinkled.

Fins. Rudimentary dorsal and anal fins located well posteriorly and short, reduced to low ridges with very weak rays, connected to caudal fin. Pectoral rays 13 – 16. Caudal fin rounded, principal caudal rays 10 – 11. Ventral adhesive disc (Figure 4d) of “ double ” type, anterior margin crenate or straight with large invagination on each lateral side and central invagination at midventral; posterior margin crenate or straight. Disc very small, disc length 6.9 – 8.3 in SL, its width slightly larger than its length, width in length 0.8 – 1.0. 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 11 – 23 and in region C one or two rows of papillae with total papillae count 4 – 11. 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 12th – 15th 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 sometimes equal or exceed length of disc region A (Figure 4f).

Colouration. Background colouration of live specimens white to flesh-coloured, slightly transparent (Figures 1b and 8) and no starshaped pigmentation around eyes. In life body almost pigmentless or with very small pigments, leading to an irregular marbled pattern, but never as strong as in other Gouania species (Supporting Information File S1). Formaldehyde fixed specimens white-yellow and without pigments. Ethanol fixed specimens white to skin-coloured pigmentation reduced. For more pictures of life 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 as four large caniniforms of variable size, followed behind by four to five medium-sized caniniforms. Lower jaw with outer row of 10 to 12 (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 six larger caniniforms continuous laterally. Pharyngeal jaws with elongated ceratobranchial 5, having several (about 4 – 5) larger elongated conical teeth (Figure 5d), pharyngobranchial 3 toothplate not visible on 3D models from microcomputed tomography (microCT) images. Number of vertebrae 39 – 40, abdominal 17 and caudal 22 – 23 (Supporting Information Table S2). The first gill arch with hemibranch, the 2nd – 4th gill arches with holobranchs. Six small, pointed rakers on third gill arch. The subopercular element is present/absent as the terminal bone posteriorly. Subopercle indistinguishable from opercle, shaped as its posterior elongated extension, not forming or having subopercular spine. Six branchiostegals. Nasal bones hook-shaped. Maxillary, premaxillary, nasal and ceratobranchial 5 bones shaped as on Figure 5d.

Etymology. The Latin adjective masculine singular nominative “ piger ” in Lepadogaster piger Nardo 1827 , meaning slow-moving, was changed to “ pigra ” in Gouania pigra which is an adjective feminine singular nominative, following the necessity of agreement in gender (Article 31.2, ICZN, 1999).

Ecology and geographical distribution (Figure 1a). Gouania pigra is endemic to the Adriatic Sea and hence the only purely marine endemic fish known for this basin. The southernmost record is from Vlorë (Albany) and it was (so far) not found on Corfu. Quantitative data on ecology is largely lacking. Throughout its distribution range the species occurs in sympatry with G. adriatica sp. nov. Sympatric and syntopic occurrence with both G. adriatica sp. nov. and G. hofrichteri sp. nov. is only known from Pelješac (Figure 1c). The species inhabits intertidal pebble beaches, where it might be found even above the waterline during low tide, and only rarely occurs in fields of larger boulders. See Supporting Information Video S1 for locomotion behaviour.

Remarks. G. pigra (Nardo 1827) differs from all other Gouania species by the posterior angle of jaws extending to, or close to, a vertical line drawn through the anterior edge of the anterior nostril (vs. posterior angle of jaws extending to between a vertical line drawn through the posterior edge of the anterior nostril and a vertical line drawn through the anterior edge of the eye in three other Gouania species or even to below the anterior edge of the eyes to the anterior part of the eye in G. orientalis sp. nov.). G. pigra differs from all other congeneric species also by its overall reduced pigmentation. G. pigra differs from the three stout-bodied Gouania species ( G. adriatica sp. nov., G. orientalis sp. nov. and G. willdenowi ) by dorsal head profile “ S ” curved, concave above eye and convex at nape (vs. dorsal head profile straight between nape above eye and upper lip tip), the absence of star-like pigmentation around eyes (vs. no pigmentation around eyes) and a large number of vertebrae (Supporting Information Table S2; 39 – 40 vs. 35 – 38). Five morphometric characters as percentages of standard length of G. pigra are nonoverlapping in range with all three stout-bodied Gouania : head length, pectoral-fin length, prepectoral distance, ventral adhesive disc length and caudal fin-length (values in the Table 1). There are also morphometric characters nonoverlapping in range with one or two out of three stout-bodied Gouania species (Table 1). In addition, it differs from G. willdenowi by infraorbital invagination below anterior half of eye or below mideye (vs. infraorbital invagination vertical to posterior part of eye); from G. orientalis sp. nov. by pectoral rays 13 – 16 (vs. pectoral rays 17 – 19), upper attachment of disc membrane attaching to base of pectoral fin at 12th – 15th pectoral ray (vs. upper attachment of disc membrane attaching to base of pectoral fin at 16th – 18th pectoral ray), infraorbital invagination below anterior half of eye or below mideye (vs. infraorbital invagination vertical to posterior part of eye); and from G. adriatica sp. nov. by posterior opercular edge with two tips, upper longer or equal to lower (vs. posterior opercular edge with pointed upper tip and rounded lower edge) and principal caudal rays 10 – 11 (vs. principal caudal-fin rays 12 – 13). Gouania pigra differs from another slender-bodied species, G. hofrichteri sp. nov., by posterior opercular edge with two tips, upper longer or equal to lower (vs. posterior opercular edge with pointed upper tip and rounded lower edge), longitudinal infralateral and suborbital transversal rows of superficial neuromasts placed in the well-defined deep groove (vs. longitudinal infralateral and suborbital transversal rows of superficial neuromasts placed in shallow groove disappearing in posterior part of longitudinal infralateral row), body cross-section behind pectoral fin base half oval to pentagonal with straight ventral side (vs. body cross-section behind pectoral fin base triangular with ventral flat and dorsal pointed), and the granules on body shallow and inconspicuous (vs. granules on body, at least on posterior part and nape, large and prominent). It is known from the Adriatic Sea and has a nonoverlapping geographic distribution range with G. orientalis sp. nov., and G. willdenowi . Based on the distributional data presented here, differential morphological and genetic characters as well as the taxonomic positioning of the species G. pigra (see Discussion, Taxonomical and systematic considerations below) and the fact that no original types (holo-, lectotypes) exist we designate a neotype for this species. The designated neotype was collected on the island of Krk, close to the original locus typicus (Rovinj, northern Adriatic Sea) and is accessible at the voucher numbers PMR VP 3529 at the PMR.

Neotype designation. We designated a neotype for G. pigra , fulfilling the qualifying conditions (Article 75.3, ICZN, 1999). We are positive that no name-bearing type specimens exist for G. pigra ( Fricke et al., 2020b; Article 75.3.4, ICZN, 1999). The genus Gouania represents a complex zoological problem (Article 75.2, ICZN, 1999) of morphologically very similar congenerics. The redescription of G. willdenowi , resurrection of G. pigra and description of three new species of Gouania in the hitherto monotypic genus thus represented an exceptional need for designation of a neotype for G. pigra (Article 75.3, ICZN, 1999). The situation could become even more complicated if more Gouania linages were to be found around the Mediterranean. In that case, the name-bearing material of the present species, holotypes and neotypes, should be available for comparison with potential new material. The diagnostic characters are stated in the species redescription (Article 75.3.1, ICZN, 1999), which is sufficient to ensure the recognition of the species (Article 75.3.3, ICZN, 1999). The neotype fits the original species descriptions of G. pigra ( Nardo, 1827a and Nardo, 1827b; Article 75.3.5, ICZN, 1999) and the neotype were collected close to the original type localities (Article 75.3.6, ICZN, 1999). The neotype is stored in a scientific museum collection (Article 75.3.7, ICZN, 1999).