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 species of sea urchin associating clingfish of the genus Dellichthys from New Zealand (Teleostei, Gobiesocidae). ZooKeys 740: 77-95. https://doi.org/10.3897/zookeys.740.22712
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A new species of clingfish, Dellichthys trnskii sp. n. is described on the basis of 27 specimens, 11.9–46.0 mm SL, collected from intertidal and shallow coastal waters of New Zealand. It is distinguished from its only congener, D. morelandi Briggs, 1955 by characters of the cephalic sensory system and oral jaws, snout shape, and colouration in life. A rediagnosis is provided for D. morelandi, which is shown to exhibit sexual dimorphism in snout shape.
Taxonomy, marine fishes, Acanthomorpha , sexual dimorphism
The family Gobiesocidae contains over 160 species within 50 genera of predominately small-bodied marine fishes found in coastal areas of the Atlantic and Indo-Pacific Oceans (
Many species of clingfishes are reported to live in close association with echinoderms (
Recent ichthyological surveys targeting clingfishes in intertidal and shallow sub-tidal areas along the coast of Northland (New Zealand) produced multiple individuals of Dellichthys from directly beneath or in close proximity to the sea urchin E. chloroticus. Subsequent investigation revealed that these specimens represent two species; one D. morelandi and the other an undescribed species, which is described herein.
Specimens used in this study were obtained from the following museum collections: Australian Museum, Sydney (AMS); Auckland War Memorial Museum, Auckland (AIM); Museum of New Zealand Te Papa Tongarewa, Wellington (
Head and body measurements reported follow
Select specimens were cleared and double stained (C&S) for bone and cartilage investigation using the protocol of
Genomic DNA was extracted from muscle tissue or fin clips (stored in 95% ETOH) using a DNeasy Blood and Tissue Extraction Kit (Qiagen, Inc.) in accordance with the manufacturer’s protocols. A segment of the cytochrome c oxidase subunit I (COI) and the 12s ribosomal RNA (12S) was amplified using the primers LCO1490/ HC02198 (
AIM MA73570, 22.8 mm SL, New Zealand, Northland, Tutukaka, Pacific Bay, 35°37'07.2"S, 174°32'03.8"E, 0–2 meters depth, 8 March 2016, T. Trnski, I. Middleton, K.W. Conway, S. Hannam, & G. Short.
All New Zealand. Auckland:
AMS I.34453-005, 1, 20.0 mm SL; New Zealand: locality unknown.
Dellichthys trnskii is diagnosed by the following combination of characters: snout broad, short (length less than or equal to interorbital distance); upper and lower jaws equal in length or lower jaw only slight shorter than the upper; upper jaw teeth not visible or only few teeth visible in gap between upper and lower lip at tip of jaws when jaws are closed; patch of teeth on lingual surface of premaxilla roughly rectangular, with ~50 small conical teeth; skin fold on surface of snout directly posterior to fold of upper lip; postorbital lateral line canal pore 2 located directly above preopercular lateral line canal pore 3; tip of snout and lower jaw pale pink in life; dorsal and lateral surface of head light yellow to green in life; body pale orange to yellow in life; and median fins transparent and without faint brown reticulate markings in life.
General body shape as in Figure
Select morphometric characters for Dellichthys trnskii (n=7) and D. morelandi (n=12).
Dellichthys trnskii | Dellichthys morelandi | ||||||
---|---|---|---|---|---|---|---|
Holotype | Range | Mean | St. Dev. | Range | Mean | St. Dev. | |
Standard Length (SL) | 22.8 | 20.1–31.7 | 31.0–65.5 | ||||
In % of SL | |||||||
Head length (HL) | 41.6 | 40.4–45.5 | 42.1 | 1.8 | 38.3–43.6 | 41 | 1.6 |
Body depth | 15.3 | 14.2–16.4 | 15.2 | 0.8 | 12.3–15.5 | 13.7 | 1 |
Predorsal length | 72.8 | 72.8–80.1 | 75.4 | 2.6 | 74.3–79.2 | 76.3 | 1.6 |
Preanal length | 75.4 | 73.7–79.1 | 78.5 | 1.8 | 73.8–80.5 | 76.7 | 1.9 |
Preanus length | 62.3 | 62.2–66.3 | 63.6 | 1.8 | 62.2–71.2 | 66.1 | 2.6 |
Anus to disc | 8.8 | 8.8–12.6 | 10.4 | 1.3 | 11.2–15.2 | 13.1 | 1.3 |
Anus to anal fin | 17.5 | 17.3–24.5 | 19.2 | 2.7 | 10.5–15.2 | 12.8 | 1.8 |
Caudal peduncle length | 10.1 | 7.7–10.1 | 9.1 | 0.8 | 7.2–9.4 | 8.2 | 0.7 |
Caudal peduncle depth | 10.1 | 9.7–11.8 | 10.5 | 0.7 | 8.4–10.3 | 9.4 | 0.5 |
Disc length | 24.1 | 22.8–27.8 | 25.9 | 1.9 | 22.6–25.9 | 24.3 | 1 |
Disc width | 24.5 | 22.0–25.9 | 23.8 | 1.3 | 20.4–23.5 | 21.9 | 1.1 |
In % of HL | |||||||
Head depth at orbit | 31.6 | 25.2–31.6 | 28.5 | 2.1 | 21.3–24.6 | 23.4 | 1 |
Head width at orbit | 45.3 | 36.1–45.3 | 40.6 | 3 | 32.5–39.3 | 35.3 | 2.3 |
Head width at widest point | 68.4 | 58.5–68.4 | 62.7 | 4.2 | 51.1–65.3 | 55.9 | 4.3 |
Interorbital width | 26.3 | 20.5–27.7 | 23.9 | 3.3 | 17.9–23.2 | 19.9 | 2 |
Snout length | 28.4 | 23.9–28.8 | 26.7 | 1.8 | 25.6–33.7 | 31.2 | 2.3 |
Eye diameter | 22.1 | 18.8–23.5 | 20.9 | 1.7 | 13.9–19.8 | 16.3 | 1.8 |
Head (in dorsal, lateral and ventral view) in members of Dellichthys highlighting position of cephalic lateral line canal pores (grey circles) and superficial neuromasts (white circles) on the left side of the head, and skin fold on snout. A Dellichthys trnskii, AIM MA73573, paratype, 21.3 mm SLB Dellichthys morelandi, TCWC 17264.02, 34.2 mm SL. Black arrows point to location of postorbital canal pore 2 (upper arrow) and preopercular canal pore 3 (lower arrow). White arrows point to location of posterior margin of upper lip (anterior arrow) and anterior margin of skin fold on snout (posterior arrow). White dashed line follows margin of skin fold on snout in dorsal and lateral view. Superficial neuromasts arranged in rows are connected by a thin black line. Superficial neuromasts on surface of body not highlighted. Abbreviations: AN, anterior nostril; LC1-3, lachrymal canal pores 1–3; MC1–3, mandibular canal pores 1–2; MG, mandibular row of superficial neuromasts; NC1–2, nasal canal pores 1–2; PN, posterior nostril; PO1–2, postorbital canal pores 1–2; POR, postorbital row of superficial neuromasts; PR1–3, preopercular canal pores 1–3; SOR, suborbital row of superficial neuromasts.
Mouth terminal, small; posterior tip of upper jaw reaching imaginary vertical line through anterior margin of orbit when mouth closed. Upper lip narrow; thickest along lateral margin of upper jaw; thinnest at snout tip. Lower lip thin at jaw symphysis; expanded into fleshy lobes adjacent to symphysis. Premaxilla with outer row of larger conical teeth with strongly recurved tips (Figs
CT scanned anterior skeleton, including cranium, paired-fin girdles and abdominal region of vertebral column, of Dellichthys trnskii,
Cephalic lateral-line system with 2 pores in nasal canal; 2 pores in postorbital canal; 3 pores in lachrymal canal; 3 pores in preopercular canal; 2 pores in mandibular canal (Fig.
Dorsal-fin rays 9. Anal-fin rays 7 (1), 8 (2) or 9 (1). Principal caudal-fin rays 5+5, dorsal procurrent rays 6 (2) or 7 (2), ventral procurrent rays 5 (1), 6 (2) or 7 (1). Pectoral-fin rays 22 (3) or 23 (1). Pelvic-fin rays I,4. All fin rays unbranched and segmented. Caudal fin rounded, tips of principal caudal fin rays extended slightly beyond fin margin. Caudal-fin skeleton comprised of upper and lower hypural plates; epural and parhypural poorly ossified, triangular and similar in size (Fig.
Adhesive disc large, double (Fig.
In alcohol, body background colour pale yellow. Median fins pale yellow to white along bases, transitioning to hyaline along distal margins. Paired fins hyaline; papillae on adhesive disc translucent white. In formalin and shortly after initial transfer to alcohol (Fig.
In life, background colour translucent orange to pale yellow (Fig.
Dellichthys trnskii is endemic to New Zealand coastal waters, currently known only from shallow (0–7 meters in depth) waters along the northeastern coast of both the North Island (Auckland, Bay of Plenty, Hawke’s Bay, Northland, and Wellington) and South Island (Marlborough Sounds) (Fig.
At the type locality, D. trnskii was found primarily under rocks or boulders covered with filamentous algae or low macroalgae often in close proximity to the sea urchin Evechinus chloroticus. Small dense objects, possibly sand grains, are visible in the pharyngeal cavity and gut of the CT scanned paratype (
No obvious sexual dimorphism is present in the available material. Potential sexual dichromatism is described above in the section on colouration.
Named for Tom Trnski, who played a key role in the discovery of the new species by collecting in depths beyond the reach of the first author. A noun in the genitive.
The sequences of COI (684bp) obtained from two specimens of D. trnskii (Genbank numbers [GB#] MF621939-40) were identical and differed from sequences obtained from six specimens of D. morelandi (GB# MF621941-44, MF318544-45) by 11.7 % (uncorrected p-distance). Similarly, the sequences of 12S (365bp) obtained from three specimens of D. trnskii (GB# MF621933-35) were identical and differed from sequences obtained from five specimens of D. morelandi (GB# MF318559-60, MF621936-38) by 3.4% (uncorrected p-distance).
Dellichthys trnskii is most easily distinguished from D. morelandi by features of the colour pattern in life (Fig.
Dellichthys trnskii is further distinguished from D. morelandi by features of the oral jaws, including having the upper and lower jaws equal in length or the lower jaw only slight shorter than the upper, with few upper jaw teeth visible in the gap between the upper and lower lip when the jaws are closed (vs. upper jaw notably longer than lower jaw, with many upper jaw teeth visible in the gap between the upper and lower lip when the jaws are closed) (Fig.
Hyopalatine arch and opercular series (right side in lateral view [image reversed]) in members of Dellichthys. A D. trnskii,
CT scanned skeleton of Dellichthys trnskii,
Surface features (A, C) and internal supporting skeleton (B, D) of the adhesive disc in species of Dellichthys in ventral view (anterior to top of page). A D. trnskii, AIM MA4341, 45.8 mm SLB D. trnskii,
Dellichthys trnskii (A–C) and D. morelandi (D–F) photographed in an aquarium soon after collection. A–B AIM MA73570, holotype, male, 22.8 mm SL; Pacific Bay, Tutukaka Coast C AIM MA73571, paratype, female, 20.0 mm SL; Pacific Bay, Tutukaka Coast DTCWC 17264.02, male, 33.8 mm SL; Pacific Bay, Tutukaka Coast ETCWC 17264.02, potential female, 29.0 mm SL; Pacific Bay, Tutukaka Coast FTCWC 17269.03, male, 37.1 mm SL; Rawhiti, Taupiri Bay.
Though
Dellichthys trnskii is sympatric with D. morelandi, at least along the coast of Northland, and specimens of the two species were commonly collected from within close proximity, in some cases from under the same rock.
All New Zealand. Gisborne:
Dellichthys morelandi is diagnosed by the following combination of characters: snout spatulate, long (length greater than interorbital distance); lower jaw shorter than upper jaw; teeth at tip of upper jaw visible in gap between upper and lower lip at tip of jaws when jaws are closed; patch of teeth on lingual surface of premaxilla roughly triangular, with ~90 small conical teeth; skin fold on surface of snout located at approximately one quarter of the distance from snout tip to anterior margin of eye, widely separate from fold of upper lip by a broad band of thin, transparent skin; postorbital lateral line canal pore 2 located anterior to imaginary horizontal line through preopercular lateral line canal pore 3; dorsal and lateral surface of head light brown to bright orange or red in life; body light brown to dark orange, red or purplish in life; faint brown reticulate markings on median fins in life.
We thank T. Trnski, S. Hannam (AIM) and M. McGrouther (AMS) for providing access to material under their care, H. Prestridge (TCWC) for curatorial assistance, C. Duffy and P. Caiger for discussions on New Zealand’s endemic clingfishes, J. Barker (