Thursday, December 14, 2017

[Ichthyology • 2017] Neopomacentrus aktites • A New Species of Damselfish (Pisces: Pomacentridae) from Western Australia


Neopomacentrus aktites
Allen, Moore & Allen, 2017


Abstract

A new species of damselfish, Neopomacentrus aktites n. sp., is described on the basis of 50 specimens, 17.8–54.1 mm SL, collected from Western Australia. The new species was formerly confused with Neopomacentrus filamentosus, an Indo-Malayan species that appears morphologically indistinguishable and has a mostly similar color pattern. However, the new species lacks several markings characteristic of N. filamentosus, i.e. a large black spot on the pectoral-fin axil, a large dark marking at the lateral-line origin, and yellow or gold color on the upper edge of the rear opercle. The two species differ by 7.55% (K2P) in the sequence of the mtDNA-barcode marker COI. The new species is only 2.19% divergent from an undescribed damselfish species from eastern Australia and southern New Guinea, but differs from that species by having dark margins on the proximal half of the caudal fin and lacking a bright yellow caudal fin, caudal peduncle, and posterior parts of the dorsal and anal fins.

Key words: taxonomy, systematics, ichthyology, coral-reef fishes, Indo-Pacific Ocean, DNA barcoding. 


Neopomacentrus aktites  n. sp.
Figure 2.  
aquarium photograph of freshly collected adult, approx. 45 mm SL, Dampier Archipelago, Western Australia.
Figure 3.  underwater photograph of juvenile, approx. 25 mm SL, Cassini Island, Kimberley District, Western Australia.

photos: G. R. Allen

Neopomacentrus aktites, n. sp. 
Western Australian Demoiselle

Diagnosis. Dorsal-fin elements XIII,10–12 (usually 11); anal-fin elements II,10–12 (usually 11); pectoralfin rays 17–19 (rarely 19); tubed lateral-line scales 16–19 (usually 17–18); total gill rakers on first arch 21–23 (usually 21–22); body depth 2.2–2.4 in SL; ventral margin of suborbital exposed (i.e. not hidden by scales); middle fin rays of dorsal and anal fins filamentous; dorsal and ventral margins of caudal fin filamentous; mainly dark brown in life except pale posteriormost parts of dorsal and anal fins and pale central portion of caudal fin; dark margins of caudal fin restricted to proximal half of fin; small dark spot at upper pectoral-fin base, but not extending into axil of fin.

Etymology. The species is named aktites (Greek: shore dweller) with reference to its relatively shallow-water habitat. The specific epithet is treated as a noun in apposition. 

Distribution and habitat. The new species is currently known only from Western Australia, ranging from Shark Bay northward to the Kimberley coast in the far northern portion of the state. The species is generally associated with rocky substrates with ample crevices and coral formations, which are utilized for shelter. Capture depths range from about 1–10 m, but there is considerable tidal fluctuation (10+ m), especially along the Kimberley coast. They frequently occur in large aggregations, which feed well above the bottom on zooplankton

  
Gerald R. Allen, Glenn I. Moore and Mark G. Allen. 2017. Neopomacentrus aktites, A New Species of Damselfish (Pisces: Pomacentridae) from Western Australia. Journal of the Ocean Science Foundation. 29, 1–10.  oceansciencefoundation.org/josf29a.html

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