Megalomma cf. acrophthalmos ( Grube, 1878 ), Grube, 1878

Capa, María & Murray, Anna, 2015, A taxonomic guide to the fanworms (Sabellidae, Annelida) of Lizard Island, Great Barrier Reef, Australia, including new species and new records, Zootaxa 4019 (1), pp. 98-167: 125-126

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Megalomma cf. acrophthalmos ( Grube, 1878 )


Megalomma cf. acrophthalmos ( Grube, 1878)  

( Fig. 11 View FIGURE 11 A–C)

Sabella acrophthalmos Grube, 1878: 258   –259.

Megalomma acrophthalmos   .— Knight-Jones 1997: 316, fig 2 A–L; Tovar-Hernández & Carrera-Parra 2011: 15 View Cited Treatment –17, fig 2 A–L. Non Megalomma cf. acrophthalmos   .— Capa & Murray 2009: 208 View Cited Treatment , figs 4 C–D, 5 B, 6.

Material examined. AM W. 44206, MI QLD 2370.

Description of material examined. Incomplete specimen; eight thoracic and numerous abdominal chaetigers. Live specimens not studied. Preserved specimens with a few reddish spots on the radiolar crown ( Fig. 11 View FIGURE 11 A), body without pigment, white. Radiolar crown with semicircular basal lobes. Dorsal and ventral basal flanges absent. Basal membrane absent. Radioles with smooth outer margins. Six to eight rows of vacuolated cells supporting radioles basally. Radiolar eyes apparently absent; two dorsal most radioles with unpigmented subdistal expansions. Dorsal lips with long radiolar appendages, one pair of pinnular appendages. Ventral lips and parallel lamellae present, ventral sacs absent. Caruncle present, rounded and with transverse rows of cilia. Posterior peristomial ring collar up to the base or radiolar crown, with dorsal margins fused to faecal groove, and forming two flanking spatulate dorsal flaps ( Fig. 11 View FIGURE 11 C); ventral lappets separated by a midventral incision ( Fig. 11 View FIGURE 11 B). Thoracic ventral shields separated from thoracic tori by a small gap ( Fig. 11 View FIGURE 11 B). Interramal eyes absent. Collar chaetae elongate, narrowly-hooded, in two oblique rows. Following thoracic chaetiger with conical notopodia; superior thoracic chaetae elongate narrowly-hooded; inferior broadly-hooded (type B). Thoracic uncini with several rows of similarsized teeth over main fang, covering slightly over half its length, with well developed breast and medium-sized handle. Companion chaetae with dentate appearance on proximal half of hood, distally asymmetrical. Abdominal neuropodia as low elevations with elongate, broadly-hooded chaetae arranged in rows. Notopodial abdominal uncini similar to the thoracic but with shorter handle. Pygidium not studied. Tube unknown.

Remarks. This specimen is characterised by having ventral shields separated from neuropodial tori by a narrow gap, long and slender inferior thoracic chaetae (type B), thoracic uncini with medium-length handles, a collar with dorsal margins fused to faecal groove, conspicuous and spatulate dorsal lappets, and a ciliated caruncle.

All these features agree with the recent description of Megalomma acrophthalmos ( Grube, 1878)   by Tovar- Hernández & Carrera-Parra (2011), except that M. acrophthalmos   typically possesses subdistal compound eyes on most radioles, apparently absent in this specimen. Regeneration of the distal end of radioles is speculated, supported by the observation of enlarged knobby structures on both dorsalmost radioles. It is also different, however, to the specimens from Western Australia reported by Capa & Murray (2009) as M. cf. acrophthalmos   , which have a short keel-like structure between the dorsal lips, unlike the ciliated caruncle present on this specimen and M. acrophthalmos   . Thus we are tentatively assigning the specimen to M. acrophthalmos   until more undamaged material is found. If this identification is confirmed it would represent the first record for the species in Australia. Megalomma acrophthalmos   was grouped together with other species sharing the presence of a collar with dorsal margins fused to faecal groove, pockets present and eyes in most radioles, into "Group 1 A" of Knight-Jones (1997) ( Capa & Murray 2009), a group recovered as a monophyletic clade by Capa & Murray (2009) but not by Tovar- Hernández & Carrera-Parra (2011).

Habitat. Dead coral rubble, in shallow subtidal depths (6–9 m).

Type locality. Philippines.

Distribution. Philippines, Australia (Queensland: Lizard Island).














Megalomma cf. acrophthalmos ( Grube, 1878 )

Capa, María & Murray, Anna 2015

Megalomma acrophthalmos

Tovar-Hernandez 2011: 15
Capa 2009: 208
Knight-Jones 1997: 316

Sabella acrophthalmos

Grube 1878: 258