Pseudobranchiomma pallida, Capa, Maria & Murray, Anna, 2016

Capa, Maria & Murray, Anna, 2016, Combined morphological and molecular data unveils relationships of Pseudobranchiomma (Sabellidae, Annelida) and reveals higher diversity of this intriguing group of fan worms in Australia, including potentially introduced species, ZooKeys 622, pp. 1-36 : 15-16

Taxon classification Animalia Sabellida Sabellidae

Pseudobranchiomma pallida sp. n. Figures 3 M–T, 7

Type material.

Australia, Queensland. Holotype AM W.36366, Heron Island, First Point, North Heron Reef, 23°25'48"S, 151°55'48"E, coral rubble, 13 m, 12 Nov 2009.

Diagnosis.

Approximately six pairs of low serrations evenly distributed along radiolar flanges. Radiolar eyes absent. Thoracic ventral shield separated from uncinal tori. Uncini with three transverse rows of teeth over main fang. Radiolar crown with broad purple band at base and distal third with wide yellow band, rest colourless white bands; body pale with distinct interramal eyespots.

Description.

Specimen incomplete; body measuring 10 mm long (including crown) and 1 mm wide, with six thoracic and more than 18 abdominal segments (Fig. 7A, B). Crown 4 mm long, slightly involuted at base ventrally, with nine radioles on each side, connected by inconspicuous membrane extending 1/7 th– 1/8th of radiolar length, or length of one thoracic segment (Fig. 7D). Radiolar flanges present, with about six low serrations along entire length of radioles (Fig. 7C). Radiolar eyes absent (Fig. 7 A–C). Radioles supported basally by four rows of vacuolated cells. Radiolar pinnules similar in length, shorter distally; tips of radioles as long as pinnules or shorter (Fig. 7C). Dorsal lips with tapered dorsal radiolar appendages, about as long as two thoracic segments, with dorsal lamella attached to base of adjacent radiole. Dorsal pinnular appendages absent. Ventral lips and parallel lamellae present with prominent ventral sacs directed outside of radiolar crown (Fig. 7A, B, D). Collar margins separated dorsally by wide gap, with dorsal margins fused to end of first chaetiger (Fig. 7F), lateral collar margins smooth, just reaching junction of crown and thorax (Fig. 7E). Ventral lappets, sub-triangular and non-overlapping (Fig. 7D). Ventral shields of first two segments slightly shorter than other thoracic segments (Fig. 7E). First shield trapezoidal in shape, but appearing as anterior Y-shape and posterior W-shaped segment when stained with methyl green. Ventral shields not in contact with or indented by tori (Fig. 7E). Interramal eyespots conspicuous (Fig. 7D, E). First chaetiger with narrowly hooded chaetae arranged in two rows. Rest of thoracic chaetigers with about five superior narrowly hooded chaetae and 8-10 shorter inferior spine-like thoracic chaetae with hood similar width to shaft (Fig. 3R) appearing in some cases as broadly hooded (Fig. 3P, Q). Neuropodial uncini with three rows of teeth above main fang, well-developed breast and short handle (Fig. 3M, N). Abdominal chaetigers with narrowly hooded superior chaetae (Fig. 3S) and spine-like inferior chaetae (Fig. 3T). Notopodial uncini similar to thoracic ones (Fig. 3O). Pygidium missing.

Colour pattern.

Body pale with distinct interramal eyespots (Fig. 7B, D, E) and pigment on dorsal margins of collar (Fig. 7F). Crown with broad purple band at base and distal third with wide yellow band, rest colourless (Fig. 7 A–C). Ventral sacs and lappets colourless (Fig. 7D).

Remarks.

Pseudobranchiomma pallida sp. n. is characterised by the remarkable colour pattern of the radiolar crown with a purple basal band and yellow radiolar tips, instead of the characteristic bands, as well as the absence of pigment spots on the body. This species belongs to the artificial Group A of Knight-Jones and Giangrande (2003), members of which possess serrations along the radiolar flanges (Table 3). The number of serrations (4-6) resembles that of Pseudobranchiomma paraemersoni and Pseudobranchiomma schizogenica (with 3-4 and 6-11 respectively), while other larger species bear nine or more (Table 1 of Tovar-Hernández and Dean 2014). The new species differs from Pseudobranchiomma paraemersoni and Pseudobranchiomma schizogenica in the morphology of the uncini, with three transverse rows of teeth over the main fang (4-5 and four rows respectively, for Pseudobranchiomma paraemersoni and Pseudobranchiomma schizogenica ; Tovar-Hernández and Dean 2014).

Distribution.

Australia (Queensland, Heron Island).

Etymology.

This species is named after its colour pigmentation, pale compared with other Pseudobranchiomma species, and completely lacking pigment spots on the body.