Paracheilinus filamentosus Allen, 1974

Tea, Yi-Kai & Walsh, Fenton, 2023, Review of Australian Species of Paracheilinus Fourmanoir (Teleostei: Labridae), with Description of a New Species from the Great Barrier Reef and Coral Sea, Ichthyology & Herpetology 111 (3), pp. 397-415 : 409-411

Paracheilinus filamentosus Allen, 1974

Filamentous Flasher Wrasse

Figures 10 , 11A–E

Paracheilinus filamentosus Allen, 1974: 452 (holotype AMS I.16994-001, Kranket Island, Madang, Papua New Guinea); Randall and Lubbock, 1981: 26, pl. 2C (generic revision, specimens from Papua New Guinea and the Solomon Islands [BPBM 16007], but not those from Indonesia and the Philippines); Kuiter and Tonozuka, 2004: 494 (field guide, Papua New Guinea and the Solomon Islands, but not those from Indonesia and Palau); Michael, 2009: 284 (field guide, underwater photograph from Papua New Guinea, but not those from Indonesia, Palau, the Philippines); Kuiter, 2010: 106, figs. B, C (underwater photographs from Papua New Guinea and the Solomon Islands, but not those from Indonesia); Allen and Erdmann, 2012: 706 (field guide, Papua New Guinea and the Solomon Islands, but not those from Brunei, Indonesia, Palau, the Philippines, and West Papua).

Diagnosis.— Dorsal-fin rays IX,11 (holotype VIII,11); anal-fin rays III,9; pectoral-fin rays 14; pelvic-fin rays I,5; pored lateral-line scales 14–17 þ 5–10 ¼ 19–27; gill rakers 5–6 þ 7–10 ¼ 12–16; body depth 3.0– 3.5 in SL; head length 2.9– 3.5 in SL; snout length 3.7–4.8 in HL; orbit diameter 3.1– 4.9 in HL; interorbital width 3.4–4.6 in HL; least depth of caudal peduncle 1.9–2.5 in HL; caudal peduncle length 1.6–2.8 in HL; TP males with 4–7 elongate filamentous dorsal-fin rays, longest dorsal-fin soft ray 1.7–2.0 in SL; pelvic fin length 1.9–2.1 in HL; caudal fin of TP males with pronounced filamentous lobes; caudal-fin length 3.7–5.0 in SL; caudal concavity 2.3–6.4 in SL; body with stripe pattern A; dorsal fin reddish orange at rest, richly yellow when in display; ground color of body red to maroon in life; central portion of caudal fin with triangular hyaline region, upper and lower lobes red with metallic blue margins dorsally and ventrally (in life); spines and rays of median fins purple in preservation.

Remarks.— Allen (1979) described P. filamentosus on the basis of 23 specimens collected from Papua New Guinea and the Solomon Islands. He noted the holotype as having VIII,11 dorsal-fin rays (versus the usual IX,11) for the genus. An additional seven specimens from Saparua, Moluccas, Indonesia, were designated as paratypes (USNM 209923) in an addendum published at the end of the original description. Subsequent work published by other authors expanded the known distribution of P. filamentosus to include Brunei, various localities across Indonesia, Palau, and the Philippines. In the most recent revision of the genus, Allen et al. (2016) restricted P. filamentosus to Papua New Guinea and the Solomon Islands and recognized those from central Indonesia (from Java east to Komodo and Sulawesi) as P. paineorum , and those from southeastern South China Sea (the Anambas Islands and Brunei) as P. xanthocirritus . The distinction of P. filamentosus from P. paineorum and P. xanthocirritus is supported by differences in TP male coloration pattern and mitochondrial COI sequence data ( Allen et al., 2016). Based on the collection locality of the USNM 209923 paratypes, the identity of the specimens should be P. paineorum , and not P. filamentosus .

In addition to Papua New Guinea and the Solomon Islands, Allen et al. (2016) reported on the occurrence of P. filamentosus in the far northern Great Barrier Reef of Australia. The record appears to be spurious, as no photographs or examined material from Australia were included in their study. The Australian distribution record was also omitted from the distribution map (fig. 18 in Allen et al., 2016). An extensive search of Australian museum fish collections conducted by the first author of the present study yielded only a single, previously unexamined specimen of P. filamentosus from Australia. The specimen was collected from Lizard Island, in the northern Great Barrier Reef. The Lizard Island specimen ( Fig. 10 ; AMS I.40666-022) agrees well with P. filamentosus in meristic data, morphometrics, dorsal- and caudal-fin morphology, and aspects of live and preserved coloration details ( Fig. 11 ). The Lizard Island specimen was compared with 12 paratypes and four non-type specimens housed at the Australian Museum (see list of examined material below). Unfortunately, the holotype (AMS I.16994-001) and four paratypes (AMS I.16995- 001) of P. filamentosus could not be located. An ongoing effort to locate the missing types is currently being conducted by the authors.

One record of P. filamentosus from the Gulf of Carpentaria is listed on the Atlas of Living Australia, based on observations taken on the 2005 FRV Southern Surveyor expedition. The specimen that the observation was based off could not be located, and was likely unretained (J. Pogonoski, pers. comm.). Unpublished data indicated that the specimen weighed 19.5 g, which appears unlikely for a Paracheilinus . We do not consider this record as verifiable. At this time, P. filamentosus is known from Australia based solely on the Lizard Island specimen. Given the specific habitat of Paracheilinus , it is likely that this species occurs more widely across the northern Great Barrier Reef and the Coral Sea but has evaded detection due to observation and sampling bias. Indeed, the Lizard Island specimen was collected in Halimeda fields growing in coral rubble on outer reef slopes, a habitat not frequented by divers and fish collectors.

Etymology.— Named after the long filamentous segmented dorsal-fin rays. Although this character is not diagnostic of the species, it was at the time of its description. The only other species of Paracheilinus known at the time was P. octotaenia , a species lacking filaments completely.

Figures

FIG. 10. Paracheilinus filamentosus, AMS I.40666-002, 46.6 mm SL, freshly euthanized male, Lizard Island, northern Great Barrier Reef, Australia. Photograph by J. Leis.

FIG. 11. Paracheilinus filamentosus, images of live and preserved specimens. (A) Male in resting colors, underwater photograph from Guadalcanal, Solomon Islands; (B) flashing male in nuptial colors, underwater photograph from Nggatokae, western Solomon Islands; (C) flashing male in nuptial colors, underwater photograph from the Solomon Islands; (D) AMS I.17479-001, 51.7 mm SL, male paratype, Tassafaronga Point, Guadalcanal, Solomon Islands. Note purple spines and rays in preservation; (E) harem comprising one TP male (middle) and several females and immature males, underwater photograph from Lovukol, central Solomon Islands. Photographs by M. Rosenstein (A–C, E) and Y. K. Tea (D).