Sunday, March 4, 2018

[Ichthyology • 2018] Dellichthys trnskii • A New Species of Sea Urchin Associating Clingfish of the Genus Dellichthys (Teleostei, Gobiesocidae) from New Zealand


Dellichthys trnskii 
Conway, Stewart & Summers, 2018


Abstract
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.

Keywords: Taxonomy, marine fishes, Acanthomorpha, sexual dimorphism


Figure 8(A–C)Dellichthys trnskii photographed in an aquarium soon after collection.
AB 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

Figure 1. Dellichthys trnskii, AIM MA73570, holotype, male, 22.8 mm SL; New Zealand: Northland, Pacific Bay, Tutukaka Coast. 

Dellichthys trnskii sp. n.

Diagnosis: 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.

Distribution: 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. 9). Its occurrence further south may be confirmed by further sampling and by a better understanding of the differences between the two species.

Notes on biology: 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 (NMNZ P.028060, 25.0 mm SL; Figs 3, 6). A single ctenoid scale also is lodged in the opercular opening of this individual (Fig. 3). Whether this scale was ingested or entered the opercular opening subsequent to capture is difficult to confirm. The specimen was collected with a large number of associated sub-tidal species including triplefins, some of which could have shed scales in the bag.

Etymology: 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.


Figure 8. Dellichthys trnskii (A–C) and D. morelandi (D–F) photographed in an aquarium soon after collection.
 AB 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 D TCWC 17264.02, male, 33.8 mm SL; Pacific Bay, Tutukaka Coast E TCWC 17264.02, potential female, 29.0 mm SL; Pacific Bay, Tutukaka Coast F TCWC 17269.03, male, 37.1 mm SL; Rawhiti, Taupiri Bay. 

 Kevin W. Conway, Andrew L. Stewart and Adam P. Summers. 2018. A New Species of Sea Urchin Associating Clingfish of the Genus Dellichthys from New Zealand (Teleostei, Gobiesocidae). ZooKeys. 740: 77-95.  DOI: 10.3897/zookeys.740.22712



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