Research Article |
Corresponding author: Harald Ahnelt ( harald.ahnelt@univie.ac.at ) Academic editor: Ralf Britz
© 2022 Harald Ahnelt, Vanessa Robitzch, Mohamed Abu El-Regal.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Ahnelt H, Robitzch V, El-Regal MA (2022) A new species of toothless, short dorsal-fin Schindleria (Gobiiformes: Gobiidae) from the Red Sea (Egypt). Vertebrate Zoology 72: 551-559. https://doi.org/10.3897/vz.72.e79401
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Abstract
We describe a new, tiny species of Schindleria from a reef lagoon in the Red Sea off the coast of Hurghada, Egypt. Schindleria edentata, new species, belongs to the short dorsal-fin type of Schindleria, with the dorsal and anal fins of about equal length. Schindleria edentata is characterized by an elongated but relatively deep body (body depth at anal-fin origin 10.8% of SL and at 4th anal-fin ray 10.9 % of SL); a short dorsal fin originating just slightly anterior to the anal fin (predorsal-fin length 60.9% of SL, pre-anal fin length 64.8% of SL); a stubby head with a steep frontal profile, a short snout (i.e., 23.1% of head length), and large eye (i.e., 27.7% of the head’s length); a long pectoral radial plate (length 7.6% of SL); four dorsal and four ventral procurrent caudal-fin rays increasing in length posteriorly; last procurrent ray simple without additional spine and, although the longest, not distinctly elongate; 15 dorsal-fin rays; 13 anal-fin rays; the base of the first anal-fin ray positioned below the base of the third dorsal-fin ray; upper and lower jaws toothless; in vivo with translucent body; eye black; swim bladder capped by a melanophore blotch; no pigmentation externally on body after preservation.
Gobiiformes, morphology, new species, paedomorphosis, progenesis
The genus Schindleria (Giltay, 1934) (Schindler’s fishes or infant fishes) has a large biogeographic range spanning the entire Indo-Pacific from remote South American islands to East and South African coasts, and from the Red Sea to Japan (summarized in
Although individuals of Schindleria are likely among the most numerous fishes associated with coral reefs (
Eight nominal species of Schindleria have been described so far: S. brevipinguis
Schindleria are extremely progenetic (
In an attempt to group Schindleria specimens morphologically (
The holotype of Schindleria edentata is deposited in the Natural History Museum in London, Great Britain, and registered as
Morphometric and meristic differences between S. edentata, S. brevipinguis and S. parva, the only three species lacking teeth in one or both jaws, are highlighted in grey in Table
Body proportions in % of standard length of holotype of Schindleria edentata sp. nov.,
Species | S. edentata | S. brevipinguis | S. parva |
Specimen | Holotype | Paratype | Paratype |
Sex | male | male | male |
Total length (TL) in mm | 10.0* | 7.3 | 10.1 |
Standard length (SL) in mm | 9.0 | 6.6 | 9 |
% Standard length | |||
Predorsal-fin length | 60.9 | 63.0 | 65 |
Preanal-fin length | 64.8 | 66.7 | 72 |
Preanus length | 56.1 | 61.2 | – |
Gut length | 41.4 | 42.4 | – |
Base of dorsal fin | 29.8 | 28.5 | – |
Base of anal fin | 24.3 | 23.0 | – |
Tail length (excluding caudal fin) | 36.2 | 39.4 | – |
Head length | 14.9 | 18.4 | 22 |
Head width | 11.6 | 10.6 | – |
Caudal-fin length | damaged | 10.6 | 12 |
Body depth at pectoral-fin base | 7.3 | 10.3 | 5 |
Body depth at anus | 9.6 | 13.3 | – |
Body depth at origin of anal-fin | 10.8 | 13.3 | 8 |
Body depth at base of 4th anal-fin ray | 10.9 | 11.5 | – |
Position of swim bladder along body | 44.6 | 45.5 | – |
Caudal peduncle length | 8.2 | 11.5 | – |
Caudal peduncle depth (min.) | 2.1 | 2.8 | – |
Pectoral radial plate length | 7.6 | 5.8 | – |
Pectoral radial plate width (at origin) | 2.7 | 3.6 | – |
Pectoral radial plate width (max.) | 3.4 | 5.6 | – |
Snout length | 3.4 | 4.3 | – |
Eye diameter horizontal | 4.1 | 5.7 | 5 |
Eye diameter vertical | 4.1 | 6.1 | – |
Postorbital length | 6.9 | 8.5 | – |
Interorbital width | 4.6 | 6.7 | – |
Urogenital papilla length | 4.8 | 7.6 | 3 |
% of caudal peduncle length | |||
Caudal peduncle depth | 25.6 | 25.0 | – |
% of head length | |||
Snout length | 23.1 | 23.0 | 23 |
Eye diameter horizontal | 27.7 | 31.1 | 20 |
Eye diameter vertical | 27.7 | 32.8 | – |
Postorbital length | 46.2 | 45.9 | – |
Interorbital width | 30.8 | 35.2 | – |
Head width | 35.9 | 55.7 | – |
% of eye diameter horizontal/vertical | |||
Interorbital width | 111.1 | 112.0 | – |
% of pectoral radial plate length | |||
Pectoral radial plate width (at origin) | 36.4 | 53.7 | – |
Pectoral radial plate width (max.) | 45.5 | 97.9 | – |
Meristic information for holotype of Schindleria edentata sp. nov.,
Species | S. edentata | S. brevipinguis | S. parva |
Specimen | holotype | paratype | paratype |
Sex | male | male | male |
Total length (TL) in mm | 10.0* | 7.3 | 10.1 |
Standard length (SL) in mm | 9.0 | 6.6 | 9.0 |
Dorsal fin rays | 15 | 13 | 9 |
Anal fin rays | 13 | 11 | 7 |
Pectoral fin rays (left/right) | 14/d | 14 | 13 |
Caudal fin rays (dorsal/ventral) | 13 (7/6) | 13 (7/6) | 13 |
Procurrent rays (dorsal/ventral) | 4/4 | 6/6 | – |
1st anal fin ray ventral to dorsal fin ray x | 3 | 3 | 4 |
Gut ends ventral to dorsal fin ray x | 1 | 1 | – |
Total number of myomeres | 36 | 36 | 39 |
Number of abdominal myomeres | 21 | 20 | 23 |
Number of caudal myomeres | 15 | 15 | 16 |
Number of vertebrae | 37 | 35 | – |
Position of swim-bladder at myomere x | 13 | 12–13 | – |
Position of first dorsal fin ray at myomere x | 21 | 20 | 24 |
Position of last dorsal fin ray at myomere x | 35 | 33 | 36 |
Position of first anal fin ray at myomere x | 23 | 23 | 26 |
Position of last anal fin ray at myomere x | 35 | 33 | 36 |
Teeth on premaxillary | no | no | small |
Teeth on dentary | no | no | no |
Pigmentation preserved (except eyes) | no | no | no |
Due to its subsequent preservation, the specimen has now a dark brown to blackish color (Fig.
A Holotype of Schindleria edentata (
We follow
Schindleria brevipinguis: Paratype (
Schindleria elongata: Photographs of the holotype (
Schindleria macrodentata: Holotype (
Schindleria nigropunctata: Holotype (
Magawish Island, 23 April 2016. Paratype (
Schindleria parva: Holotype (
Schindleria pietschmanni: 42 syntypes (
Schindleria praematura: 49 syntypes (
Schindleria sp. Abu El-Regal & Kon (2008).
Schindleria sp. Fricke & Abu El-Regal (2017a, b).
Schindleria sp. Abu El-Regal & Kon (2019).
Diagnosis. A member of the SDF group of Schindleria, which can be distinguished from all members of the LDF group by the combination of following characters (i) length of dorsal fin nearly equal to that of anal fin (vs. dorsal fin significantly longer than anal fin); (ii) body deeper (10.8% in SL vs. 4.5–5.4% in SL); (iii) body depth significantly increasing from pectoral-fin base to 4th anal-fin ray (vs. not or only slightly increasing); (iv) head short and wide with steep profile (vs. elongated and narrow with flat profile) and (v) both jaws toothless (vs. both jaws with teeth).
From the other species of the SDF group, Schindleria edentata can be distinguished as follows 15 dorsal-fin rays (vs. 9–13 in S. parva and S. brevipinguis, 16–18 in S. pietschmanni), 13 anal-fin rays (vs. 7–11 in S. parva and S. brevipinguis, 19–21 in S. pietschmanni), preanal-fin length 64.8 % SL (vs. 72% in S. parva, 66.7% in S. brevipinguis, 54% in S. pietschmanni), predorsal-fin length 60.9% SL (vs. 65.0% in S. parva, 63.0% in S. brevipinguis, 58.3% in S. pietschmanni); length of tail excluding caudal fin 36.2% SL (vs. 28.2% in S. parva, 39.4% in S. brevipinguis, 42.1% in S. pietschmanni), length of urogenital papilla 4.8% SL (vs. 3.0% in S. parva, 7.6% in S. brevipinguis and < 0.5% in S. pietschmanni), eye diameter 27.7% HL vs. 20.0% in S. parva, 31.1% in S. brevipinguis, 23.1% in S. pietschmanni), mouth terminal (vs. superior in S. parva, S. pietschmanni, S. brevipinguis).
Schindleria edentata can be further distinguished from S. brevipinguis and S. pietschmanni by a wider head (35.9% HL vs. 55.7% in S. brevipinguis, 43.2% in S. pietschmanni) and a lower number of caudal procurrent rays (4/4 vs. 6/6 in S. brevipinguis and S. pietschmanni).
Schindleria edentata can be further distinguished from S. parva and S. pietschmanni by its toothless jaws (vs. upper jaw toothed in S. parvaboth jaws toothed in S. pietschmanni), and head shape (stubby, oval with steep profile vs. elongated, narrow with flat profile in S. parva and S. pietschmanni).
Schindleria edentata can be further distinguished from S. parva by fewer myomeres (36 vs. 39), the first dorsal-fin inserted at myomere 21 (vs. myomere 24), the first anal-fin ray at myomere 23 (vs. myomere 26) and a greater body depth at pectoral-fin base (7.3% SL vs. 5%).
Schindleria edentata can be further distinguished from S. brevipinguis by a shorter caudal peduncle (8.2% SL vs. 11.5%), pectoral-radial plate longer than wide (vs. nearly as long as wide) and a pigmented swim bladder (vs. unpigmented swim-bladder).
Morphometric information for the holotype is given in Table
First dorsal fin and pelvic fin absent; dorsal-fin rays 15; anal-fin rays 13; pectoral-fin rays 14; principle caudal-fin rays 7+6=13; caudal fin truncated; procurrent rays 4 dorsal and 4 ventral; procurrent rays gradually increasing in length, last procurrent ray simple, with no additional spine, not distinctly elongated; base of first dorsal-fin ray at myomere 21, that of last dorsal-fin ray at myomere 35; base of first anal-fin ray at myomere 22, that of last anal-fin ray at myomere 35; total number of myomeres 36 with 21 abdominal and 15 caudal; vertebrae 37,with 21 abdominal and 16 caudal (incl. urostyle); Branchiostegal rays 5; pectoral-radial plate longer than wide, of paddle-like shape, narrow at origin and wide distally; gut straight; male urogenital papilla elongated, tubular, tapering towards posteriorly curved tip, tip without distinct lobes at opening; swim bladder small, inconspicuous, pigmented dorsally, located at myomere 13, in posterior half of abdomen, .
Transparent; the only pigment is a melanophore cap on top of the swim bladder and the black pigmentation of the eye (see also
Due to subsequent preservation artifacts, the entire specimen is now dark brown to blackish (Fig.
Schindleria edentata is only known from a shallow (7 m) reef lagoon near Hurghada (Egypt), Red Sea (27.285°N, 33.772778°E) (Fig.
Records of Schindleria in the Red Sea. Circle = S. elongata, S. nigropunctata, Hurghada (Fricke & Abu El-Regal, 2017a, b) and S. praematura, Hurghada (
The bottom of the lagoon was sandy and covered with algae and seagrass. The specimen was sampled at a depth of 1 m.
The name edentata, derived from the Latin e = without, and dentatus = toothed, refers to the absence of teeth in both jaws, an adjective.
The new species Schindleria edentata from the Red Sea is the ninth in the genus and the fourth species endemic to the Red Sea. Six of nine species of Schindleria are known from the margins of the distributional range of the genus: S. edentata, S. elongata, S. nigropunctata, and S. parva from the Red Sea and S. pietschmanni and S. praematura from the Hawaiian Islands (Northern Central Pacific). The three other species are known from the Society Islands (S. multidentata), from Queensland, Australia (S. brevipinguis) and from the Malayan Archipelago (S. macrodentata) (Ahnelt, 2020). The recent discoveries of three new species endemic to a relatively small area in the extreme north of the Red Sea (
Adults of Schindleria are characterized in life by a translucent body with blackish eyes and a black-capped swim bladder, features otherwise common among many larval fishes (
A reliable character to group species of Schindleria is the relative length of their dorsal and anal fins. Already the first two described species, S. praematura and S. pietschmanni, are easily distinguished by this feature (
An important morphological character system to distinguish species is the diverse dentition pattern. Schindleria can be separated into species with jaw teeth and those that lack teeth in one or both jaws (
The generation time and the developmental time for the two toothless species are unknown but it is conceivable that the smaller species may have an even shorter lifespan and faster development. For instance, the specimens of the “S. praematura”–type (LDF) from Ogasawara (Japan) reach a size of 16 mm – 18 mm SL after an average of just 31 days (Kon and Yoshino 2002). During development of many gobiid fishes teeth appear first in larvae of 4 mm – 9 mm TL (e.g.,
H.A. and M.A.E-R. conceived the idea. M.A.E.-R. sampled the material. H.A., V.R. and M.A.E.-R. analyzed, interpreted, and discussed the data, contributing significantly to the final version of the manuscript.
The authors declare no competing interests.
For the loan of the material we are indebted to James Maclaine, Natural History Museum, London, GB. The constructive comments of one anonymous reviewer and the associate editor are gratefully acknowledged.