Megalomma

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: 132

publication ID

http://dx.doi.org/10.11646/zootaxa.4019.1.8

publication LSID

lsid:zoobank.org:pub:8C14F828-F8FB-4783-928B-399B33B4246D

DOI

http://doi.org/10.5281/zenodo.5064500

persistent identifier

http://treatment.plazi.org/id/039D9472-FFF9-2A16-DA94-0897D07DC92C

treatment provided by

Plazi

scientific name

Megalomma
status

 

Megalomma   sp.

( Fig. 13 View FIGURE 13. A – D E–I)

Material examined. AM W. 44466, MI QLD 2424.

Description of material examined. Specimen incomplete, over 20 mm long and 3 mm wide. Seven thoracic and numerous abdominal chaetigers. Live specimen with radiolar crown with several orange and white transverse bands of different widths, especially conspicuous in inner margin of radioles and in pinnules ( Fig. 13 View FIGURE 13. A – D E–F). Dorsalmost radiolar eyes orange, in some cases with a white reticule ( Fig. 13 View FIGURE 13. A – D F), other smaller eyes brown ( Fig. 13 View FIGURE 13. A – D F). Body is pale cream, with anterior end covered in white spots ( Fig. 13 View FIGURE 13. A – D E). Specimens lose pigmentation after fixation, only a few pigmented bands stay on radioles, and are white with dark brown radiolar eyes. Radiolar crown with semicircular lobes ( Fig. 13 View FIGURE 13. A – D E). Dorsal and ventral flanges absent. Basal membrane or radiolar flanges absent. About six vacuolated cells supporting radioles in cross section at the base. Dorsalmost pair of radioles longer than the rest, each with a large subdistal compound eye almost surrounding the whole radiole, all other radioles with smaller, spherical and similarly-sized subdistal eyes ( Fig. 13 View FIGURE 13. A – D E–F). Dorsal lips with medium radiolar appendages, dorsal pinnular appendages absent. Caruncle absent. Ventral lips and parallel lamellae present, ventral sacs inside radiolar lobes. Posterior peristomial ring with margins separated by a wide gap, not fused to faecal groove, not forming dorsal pockets ( Fig 13 View FIGURE 13. A – D E); triangular ventral lappets separated by a midventral incision ( Fig. 13 View FIGURE 13. A – D G). Glandular ridge absent on anterior chaetigers. Thoracic ventral shields separated from adjacent neuropodial tori by a gap ( Fig. 13 View FIGURE 13. A – D G). First ventral shield with M-shaped anterior margin ( Fig. 13 View FIGURE 13. A – D G). Interramal eyespots absent. Collar chaetae elongate narrowly-hooded in two oblique rows. Following thoracic chaetigers with conical notopodia; superior elongate narrowly-hooded and inferior broadly-hooded notochaetae (type B, Fig. 13 View FIGURE 13. A – D H). Thoracic neuropodial uncini avicular, with several rows of small teeth, all similar in size above main fang, well developed breast and medium-sized handle ( Fig. 13 View FIGURE 13. A – D I). 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 not observed.

Remarks. This specimen resembles M. interrupta   , described above, in that the dorsal collar margins are not fused to the faecal groove and ventral shields are separated by a gap from adjacent neuropodial tori. However, unlike M. interrupta   , it possesses distal eyes on all radioles, all spherical and similar in size, except for the dorsalmost pair, which are larger and surround the radiolar tip almost completely. According to artificial grouping of Megalomma   species, this species belongs to ′′Group 2 C′′ together with M. trioculatum Reish, 1968   , described from Marshall Islands and Megalomma   sp. 2 described from Victoria, Australia ( Knight-Jones 1997; Capa & Murray 2009). Megalomma trioculatum   is distinguished from the specimen described herein by the type of inferior thoracic chaetae, which have abruptly narrowing tips (type A), whereas in this specimen they are progressively tapering (type B) ( Capa & Murray 2009). Megalomma   sp. 2 also differs from this specimen as it only bears radiolar eyes on the two dorsalmost pairs of radioles instead of on all radioles ( Capa & Murray 2009).

Habitat. Coral rubble, between 5–12 m depth.

Type locality. Lizard Island.

Distribution. Australia (Queensland: Lizard Island).