Schindleria macrodentata, Ahnelt & Sauberer, 2018

Ahnelt, Harald & Sauberer, Michael, 2018, A new species of Schindler's fish (Teleostei: Gobiidae: Schindleria) from the Malay Archipelago (Southeast Asia), with notes on the caudal fin complex of Schindleria, Zootaxa 4531 (1), pp. 95-108 : 96-99

Schindleria macrodentata sp. nov.

( Figures 1–6 ; Tables 1, 2)

Holotype. ZMUC 77624 . Female, 16.5 mm SL, 17.7 mm total length (TL) ( Fig. 2 ). Molucca Sea, Indonesia, between the islands Sulawesi and Halmahera , 00°29′N, 125°54′E, more than 100 km offshore ( Fig. 1 ). Station 3681 (bottom depth 2315 m), haul 4, wire out 100 m, actual sampling depth approximately 30 m, gear Stamin-net (S 150). 28 March 1929. Dana Expedition 1928–1930.

Paratype. ZMUC 77617 . Female , 18.7 mm SL ( Fig. 3 ); caudal fin damaged. Sulu Sea , Philippines, northwest of the northern tip of Panay Island , 11°43′N, 121°43′E, about 20 km offshore ( Fig. 1 ). Station 3734 (bottom depth 1170 m), haul 4, wire out 100 m, actual sampling depth approximately 30 m, gear Stamin-net (S 200). 27 June 1929 . Dana Expedition 1928–1930 .

Diagnosis. A slender, elongated, unpigmented species of Schindleria , body depth at pectoral fin base 3.6–3.7 % of SL and at anal fin origin 3.9–4.8 % of SL; largest specimen 16.5 mm SL, 17.7 mm TL; dorsal fin exceeding anal fin origin distinctly, predorsal length 61.8–65.2 % of SL and preanal length 71.7–75.8 % of SL; dorsal fin rays 19–20, anal fin rays 10; first anal-fin ray positioned below 9 th dorsal-fin ray; few large teeth in the upper and the lower jaws, 7 on the premaxilla, 6 on the dentary; pectoral radial plate long, length 3.7–4.5 % of SL; number of myomeres 42 (30 + 11); first dorsal fin ray at myomere 20–21.

Description. Morphometrics ( Table 1) and meristics ( Table 2) are given separately for the holotype and the paratype, respectively. The data of the paratype are in parentheses. First dorsal fin absent, second dorsal fin rays 19 (20), anal fin rays 10 (10), pectoral fin rays 15 (16), pelvic fin absent; caudal fin rays 13 (7 + 6) with 5 ventral and 6 dorsal procurrent rays; the posterior-most procurrent rays elongated, about 25 % of the length of the first principal caudal-fin ray and with an additional process laterally; first dorsal-fin ray at myomere 21 (20), the last at myomere 40 (40); first anal-fin ray at myomere 31 (30), last opposite last dorsal-fin ray; all fin rays, except those of the caudal fin, unbranched and unsegmented; myomeres 42 (42), precaudal 31 (30) + 11 (12); due to preservation vertebrae are not visible but the myomeres are associated 1:1 with the vertebrae; branchiostegal rays 5; upper and lower jaws with few, widely spaced, large teeth ( Figs. 4A, B, D and 5 ), seven on each praemaxilla and six on each dentary; in the upper jaw the maxilla is distinctly longer than the praemaxilla; the lower jaws form a pointed arch. The body is slender, abdomen and tail of about equal height; the head is short with large, nearly round eyes and a long postorbital area; the snout is short, narrowing rapidly, of triangular shape from dorsal view; the pectoral radial plate is distinctly longer than wide ( Table 1). No conspicuous urogenital papilla developed; ovaries are partly filled with numerous small eggs arranged in a single row [we counted about 80 (70) eggs but because of preservation not all eggs were visible, possibly their number exceeds 100] ( Fig. 4C ). Because of preservation the fish is not translucent. Therefore, it was not possible to detect the exact position of the gas bladder.

Coloration in preserved specimens. Because of the dark muscles showing through the transparent skin, both specimens appear dark brown; urostylar part of caudal peduncle brownish; pectoral radial plate light brown; head translucent; eyes black.

Coloration in life specimens. Not known.

Distribution. Known only from Molucca Sea between the islands Sulawesi and Halmahera ( Indonesia) (00°29′N, 125°54′E) and the Sulu Sea northwest of the north tip of Panay Island ( Philippines) (11°43’N, 121°43′E) ( Fig. 1 ). The specimen from the Molucca Sea was collected about 100 km offshore and represents the first offshore record of a Schindleria species.

Etymology. The name macrodentata refers to the large teeth on the upper and lower jaws. “ macrodentata ” derived from the Greek prefix macro = large, and the Latin adjective dentatus = toothed. The name agrees in gender with the (feminine) generic name. The suggested common name is “Schindler’s large-toothed goby”.

Comparisons. Schindleria macrodentata sp. nov. differs from S. brevipinguis , S. elongata , S. nigropunctata and S. pietschmanni very conspicuously in the combination of large teeth, a short tail and a dorsal fin distinctly exceeding the origin of the anal fin anteriorly. The only species also with a short tail and the dorsal fin distinctly exceeding the origin of the anal fin is S. praematura . In the following we compare S. macrodentata sp. nov. with S. praematura :

S. macrodentata differs from S. praematura (values in parentheses) in (i) few, widely spaced and large teeth (many, closely spaced and tiny); (ii) an elongate, distinctly longer than wider, pectoral radial plate (paddle shaped, nearly as wide as long); (iii) most posterior procurrent ray in the caudal fin skeleton with an additional spiny process at its base (simple); (iv) snout in dorsal view triangular (roundish); (v) a shorter tail 22.1 % of SL (28.9 %); (vi) a longer predorsal 62–65 % (54 %) and preanal length 72–76 % of SL (53 %); (vii) a more slender body with body depth at pectoral fin origin 4 % (6 %) of SL and at anal fin origin 4–5 % of SL (6 %); (viii) a shorter head with a head length 11 % of SL (13–16 %); (ix) larger eyes with an eye diameter 28–29 % of head length (25 %) and (x) females with more than 80 small eggs (~30 large eggs). The traits (i)–(iii) are unique for S. macrodentata sp. nov. and separate this species from all other nominal species. A short tail like S. praematura is also present in the holotype of S. brevipinguis , a female (about 29 % of SL). But males of this species have a distinctly longer tail (mean about 37 % SL) (calculated from Watson and Walker 2004, Table 1).

A possible important morphological character is the shape of the lower jaw (a pointed arch in S. macrodentata sp. nov., a rounded arch in S. pietschmanni and S. praematura ( Figs. 4B and 4D ) and in S. brevipinguis , S. elongata or S. nigropunctata (latter three from photographs). It was not possible to distinguish S. macrodentata sp. nov. unambiguously from S. praematura by the morphological characters for Schindleria addressed by Kon et al. (2007), i.e., by the number of fin rays (values of S. praematura in parenthesis): dorsal fin rays 20–22 (16–21), number of anal fin rays 10 (11–14) and by Fricke and El Regal (2017b), i.e., by the position of the first anal fin ray in relation to the dorsal fin rays: first anal fin ray ventral to dorsal fin ray 9–11 (7–10).

Figures

FIGURE 1. Map of the Indo-Pacific with type localities (1–5) and sampling stations (asterisks) of various Schindleria species 1—Schindleria pietschmanni, 2—S. praematura, 3—S. brevipinguis, 4—S. macrodentata sp. nov., 5—S. elongata and S. nigropunctata. Asterisks—various sampling stations of Schindleria sp. (from Bruun, 1940; Fricke and El-Regal, 2017b). The Easter Islands are not shown.

FIGURE 2. Schindleria macrodentata sp. nov. Holotype, ZMUC 77624, female, SL 16.5 mm; Indonesia, Molucca Sea, 00°29′N, 125°54′E; 28 March 1929. Scale bar = 2 mm.

FIGURE 3. Schindleria macrodentata sp. nov. Paratype, ZMUC 77617, female, SL 18.7 mm; Philippines, Sulu Sea, 11°43′N, 121°43′E; 27 June 1929. Scale bar = 2 mm.

FIGURE 4. Schindleria macrodentata sp. nov. A—Holotype. Head in lateral view; note the large teeth on the upper (premaxilla) and lower (dentary) jaws; arrow points to the damaged branchiostegal area; the maxillary is broken (position of star). B—Paratype. Head in ventral view. Note that the lower jaw forms a narrow and pointed arch; the arrow points to two detached branchiostegal rays. C—Holotype. Lateral view of the transition from the abdominal area (right) to the tail (left). Note row of small eggs (highlighted in dark brown). Arrow points to urogenital opening. Transparent skin ventral to the gut is detached due to preservation. D—Paratype. Head in ventral view. Crystals are artifacts and remnants of the original preservation liquid (formaldehyde). Scale bar = 0.5 mm.

FIGURE 5. Schindleria macrodentata sp. nov. Holotype. Head in dorsal view. Note the large teeth on the upper (premaxilla) and lower (dentary) jaws. White arrow points to the elongated and narrow pectoral fin base. Scale bar = 0.5 mm.

FIGURE 6. Schindleria macrodentata sp. nov. Holotype. Caudal fin complex in lateral view. Dorsal and ventral muscle/ tendon strains (white stars) extending rearwards onto the triangular hypural plate (black arrow). White arrows point to the elongated posterior-most procurrent rays with an additional spine at their bases. Note segmentation and branching (a postlarval character) of the caudal fin rays (lepidotrichia). Insert: schema of the caudal peduncle region of a tuna. Muscle (white arrow) and tendon (gray arrow) strains insert on the hypural plate (black arrow) (after Westneat and Wainwright 2001, Fig. 10B). Scale bar = 0.5 mm.