Research Article |
Corresponding author: Kevin W. Conway ( kevin.conway@tamu.edu ) Academic editor: David Morgan
© 2018 Kevin W. Conway, Andrew L. Stewart, Adam P. Summers.
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:
Conway KW, Stewart AL, Summers AP (2018) A new genus and species of clingfish from the Rangitāhua Kermadec Islands of New Zealand (Teleostei, Gobiesocidae). ZooKeys 786: 75-104. https://doi.org/10.3897/zookeys.786.28539
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Flexor incus, new genus and species, is described from 15 specimens (14.0–27.2 mm SL) collected from shallow (0–9 meters) intertidal and sub-tidal waters of the Rangitāhua Kermadec Islands, New Zealand. The new taxon is distinguished from all other members of the Gobiesocidae by a combination of characters, including a heterodont dentition comprising both conical and distinct incisiviform teeth that are laterally compressed with a strongly recurved cusp, an oval-shaped opening between premaxillae, a double adhesive disc with a well-developed articulation between basipterygia and ventral postcleithra, and many reductions in the cephalic lateral line canal system. The new taxon is tentatively placed within the subfamily Diplocrepinae but shares a number of characteristics of the oral jaws and the adhesive disc skeleton with certain members of the Aspasminae and Diademichthyinae.
Acanthomorpha , Aspasminae , Diademichthyinae , Diplocrepinae , taxonomy
“The discovery of this and several other new genera in recent years makes it necessary to reconsider the characterization and relationships of various subfamilies within the Gobiesocidae”
The family Gobiesocidae contains over 170 species and 50 genera of predominately small-bodied marine fishes found in coastal areas of the Atlantic and Indo-Pacific oceans (
Clingfishes are considered archetypal crypto-benthic fishes (
Specimens of a reportedly new species of clingfish have been known from the remote Rangitāhua Kermadec Islands (here after Kermadec Islands) of New Zealand since at least 1980s (
Specimens used in this study were obtained from the following museum collections:
Head and body measurements reported follow
Select specimens were cleared and double stained (C&S) for bone and cartilage investigation using the protocol of
A genus of the Gobiesocidae differing from all other genera by a combination of characters, including: head and anteriormost part of body similar in width; a relatively elongate body with a small, double adhesive disc located beneath anteriormost part of body; an oval-shaped gap between premaxillae formed by a semicircular indentation along medial edge of premaxilla; premaxilla with a single row of teeth, comprising 2–3 peg-like, conical teeth anteriorly at, and adjacent to, symphysis and 10–12 strongly laterally compressed, incisiviform teeth with strongly recurved cusp, along outer margin of bone; lower jaw with a single row of 14–16 small, conical teeth with sharply pointed and slightly recurved tip; posterior tip of basipterygium expanded and articulating with anteromedial edge of ventral postcleithrum via a shallow concave facet; mandibular portion of preoperculo-mandibular lateral line canal absent; lachrymal canal with two pores; upper and lower lip simple, uniform in thickness along jaw margin.
New Latin, anatomical term for muscles, from the Latin flexus, past participle of flectere, to bend. In reference to the great flexibility of clingfishes, many of which have the ability to bend the body so that the tail end comes to lie close to the head. Masculine.
Flexor incus, new species
Aspasmogaster
sp.:
All Kermadec Islands.
See generic diagnosis.
General body shape as in Figures
Select morphometric characters obtained from the holotype and six paratypes of Flexor incus. Ranges include value obtained for holotype.
Holotype | Range | Mean | St. Dev. | |
---|---|---|---|---|
Standard Length (SL) | 20.8 | 16.9–27.2 | – | – |
In % of SL | ||||
Head length (HL) | 31.7 | 29.4–34.5 | 31.9 | 1.9 |
Body depth | 14.9 | 10.0–14.9 | 13.6 | 1.9 |
Predorsal length | 75.5 | 73.3–82.2 | 76.3 | 2.9 |
Preanal length | 72.6 | 72.6–77.7 | 74.2 | 1.7 |
Preanus length | 63.0 | 60.7–63.0 | 61.7 | 0.9 |
Anus to disc | 15.9 | 14.1–18.6 | 16.8 | 1.5 |
Anus to anal fin | 8.9 | 8.0–9.7 | 8.6 | 0.8 |
Caudal peduncle length | 10.1 | 8.0–10.1 | 8.9 | 0.9 |
Caudal peduncle depth | 11.1 | 8.2–11.1 | 9.4 | 0.9 |
Disc length | 18.8 | 17.8–26.0 | 20.2 | 3 |
Disc width | 16.3 | 16.3–20.1 | 17.7 | 1.3 |
In % of HL | ||||
Head depth at orbit | 34.8 | 25.9–34.8 | 29.1 | 3.4 |
Head width at orbit | 47.0 | 42.6–51.9 | 47.6 | 3.1 |
Head width at widest point | 60.6 | 52.9–67.3 | 58.3 | 5.4 |
Interorbital width | 21.7 | 19.5–23.1 | 21.4 | 1.5 |
Snout length | 30.3 | 28.1–36.5 | 32.2 | 2.7 |
Eye diameter | 21.2 | 17.2–22.2 | 20.1 | 1.7 |
Flexor incus, Te konui Point, Raoul Island, Kermadec Islands, 28 meters depth, photographed by R. Robinson (www.depth.co.nz) during the 2011 Kermadec Islands Biodiscovery Expedition, a project led by the Auckland Museum. Specimen not retained.
Head of Flexor incus (
Mouth terminal, small; posterior tip of upper jaw reaching imaginary vertical line through anterior nostril when mouth closed. Upper and lower lip narrow; upper lip uniform in thickness along length of jaw; lower lip thicker along lateral margins of lower jaw, narrower at jaw symphysis (Figure
Cephalic lateral-line system with 2 pores in nasal canal; 2 pores in postorbital canal; 2 pores in lachrymal canal; 3 pores in preopercular canal (Figure
Dorsal-fin rays 9 or 10. Anal-fin rays 8 or 9 (first in serial or supernumerary association with anteriormost proximal-middle radial). Principal caudal-fin rays 5+5, dorsal procurrent rays 6 or 7, ventral procurrent rays 6. Pectoral-fin rays 24 or 25; uppermost ray a tiny splint-like element comprised of a single hemitrichium. Pelvic-fin rays I, 4. All fins rays, excluding anteriormost 4–5 procurrent caudal-fin rays, unbranched and segmented; anteriormost 4–5 procurrent caudal-fin rays unsegmented, azygous elements. Caudal fin marginally truncate, tips of principal caudal-fin rays extended beyond fin margin. Caudal-fin skeleton comprised of upper and lower hypural plates; epural triangular, with broad cartilaginous dorsal margin; parhypural absent, parahypural cartilage roughly triangular (Figure
CT scanned anterior skeleton of Flexor incus,
Neurocranium of Flexor incus,
Flexor incus,
Hyoid bar (A–B) and gill arches (C–D) of Flexor incus,
Adhesive disc small (18–26% of SL), double (Figure
Surface features of the adhesive disc (A
Caudal-fin skeleton (left side, lateral view) of Flexor incus,
Colouration. In alcohol, head and body background colour typically uniformly pale cream to yellow (Figure
In life (Figure
Distribution and habitat. Known to date only from intertidal and subtidal waters of the Kermadec Islands (Figure
Etymology. Incus is the Latin word for anvil, in reference to the anvil-like outline of Raoul Island, the largest island in the Kermadec archipelago and type locality of the new species. A noun in apposition.
Gut content. Hard and irregular shaped items ranging in size from 50–300 μm are scattered throughout the stomach of the CT scanned individual (Figure
Gut content of Flexor incus. A Hard gut content of
The Kermadec Islands are a group of tiny remote islands almost 1,000 km from New Zealand, about half way between Tonga and Auckland, and lie between 29°15'S and 31°21'S. The Kermadec-Tonga arc is the longest submarine arc on the planet, running 2,500 km along the boundary of the Pacific and Australian Plates. It is a region of high geothermal activity with 83% of investigated volcanic centres venting (
Specimens of Flexor incus have been referred to previously as Aspasmogaster sp. (
Scanning electron micrographs of the tooth-bearing oral jaw bones of Aspasmogaster costata (
CT scanned anterior skeleton of Aspasmogaster costata,
Based on the characters listed in the key to the subfamilies of the Gobiesocidae (
The characteristic type of incisiviform tooth present on the premaxilla of Flexor (Figure
CT scanned anterior skeleton of Pherallodus indicus, NSMT-P 114703, 25.0 mm SL. A Dorsal view B Lateral view (left side) C Ventral view. Abbreviations: ACh, anterior ceratohyal; Ana, anguloarticular; Apa, autopalatine; Boc, basioccipital; Bp, basipterygium; Br, branchiostegal rays; Cl, cleithrum; DHh, dorsal hypohyal; DPcl, dorsal postcleithrum; Ec, epicentral; Ect, ectopterygoid; Epoc, epiotic; Exoc, exoccipital; Fr, frontal; Hy, hyomandibular; I, pelvic-fin spine; Iop, interopercle; LE, lateral ethmoid; Na, nasal; NS1, 5, neural spine of vertebral centrum 1, 5; Op, opercle; Pa, parietal; PecR, pectoral radial; PecFR, pectoral-fin ray; PelFR1-4, pelvic-fin ray 1–4; Pop, preopercle; Pro, prootic; Psph, parasphenoid; Pt, posttemporal; Pte, pterotic; Q, quadrate; Ra, retroarticular; Ri, rib; Scl, supracleithrum; Soc, supraoccipital; Sph, sphenotic; Ur, urohyal; V1, vertebral centrum 1; Vo, vomer; VPcl, ventral postcleithrum.
CT scanned anterior skeleton of Aspasmichthys ciconiae,
CT scanned anterior skeleton of Lepadichthys bolini,
We consider the aforementioned characters of the oral jaws ([1] characteristic incisiviform teeth and [2] characteristic oval opening between the premaxillae formed by a semicircular indentation along the medial edge of each premaxilla) and the complex articulation between the posterior tip of the basipterygium and the anteromedial edge of the ventral postcleithrum as derived characteristics and putative evidence that the aforementioned members of the Diplocrepinae (Flexor, Pherallodus), Aspasminae (Aspasmichthys and Pherallodichthys), and Diademichthyinae (Diademichthys and Lepadichthys) are potentially more closely related to each other than they are to other members of these subfamilies that do not exhibit these characters. If correct, the relationships of Flexor would lie with Indo-Pacific taxa and not with the members of the endemic New Zealand gobiesocid fauna (
We started our paper with a quote from John C. “Jack” Briggs (1920–2018): “The discovery of this and several other new genera in recent years makes it necessary to reconsider the characterization and relationships of various subfamilies within the Gobiesocidae”
Aspasminae – Aspasma: A. minima –
Diademichthyinae – Diademichthys: D. lineatus –
Diplocrepinae – Aspasmogaster: A. costata –
We would like to thank the clingfish guru J. Briggs (1920–2018) for his support of our recent work on clingfishes; his omelette yellow covered 1955 monograph has and will continue to represent the magnum opus on these wee tenacious fishes and will always have a place on our bookshelves. We would also like to thank T. Trnski, S. Hannam (