Megalomma carunculata Tovar-Hernández and Salazar-Vallejo, 2008

Tovar-Hernández, María Ana & Carrera-Parra, Luis F., 2011, Megalomma Johansson, 1925 (Polychaeta: Sabellidae) from America and other world-wide localities, and phylogenetic relationships within the genus 2861, Zootaxa 2861 (1), pp. 1-71 : 18-19

Megalomma carunculata Tovar-Hernández and Salazar-Vallejo, 2008

Megalomma carunculata Tovar-Hernández and Salazar-Vallejo, 2008: 1957–1961 , Figs 1–2 .

Type material examined. Holotype [ LACM – AHF] POLY 2169 , Mexican Pacific, Guerrero, Acapulco, Punta Manzanillo, Coll. S. I. Salazar, August 4, 1988, 1 m.

Additional material examined. [ ECOSUR] OH-P281 , Mexican Pacific, Guerrero, Acapulco, Hornos beach, 16° 51’ 6.4’’ N, 99° 54’ 1’’ W, Colls. S. I, Salazar & L. F. Carrera, in sponge .

Diagnosis. Eyes in most radioles (spherical and oval); dorsal margins of collar fused to faecal groove; caruncle present; thoracic and abdominal segments with interramal eyespots; thoracic chaetae Type B; abdominal chaetae narrowly hooded.

Additions to description. Branchial crown as long as thorax. Subdistal compound eyes spherical in most radioles, oval in the ventralmost radioles. Dorsalmost radioles with short tips increasing gradually towards ventral radioles. Dorsal pinnular appendages present. Dorsal collar margins rounded posteriorly, fused to faecal groove. Dorsal pockets present. Anterior peristomial ring exposed dorsally between dorsal pockets. Lateral collar margins covering the basal union of radioles. Ventral lappets rounded, overlapping or not overlapping. Ventral sacs absent. Caruncle long, erect, triangular. Thoracic and abdominal segments with interramal purple eyespots: large in thorax then decreasing towards posterior abdomen. Thoracic tori longest in chaetigers 2–3. Tori in chaetiger 2–3 occupying the entire distance between notopodia and ventral shields margins. All ventral shields in contacting with torus. Inferior thoracic chaetae Type B. Handle of thoracic uncini 2x length of main fang. Companion chaetae with teardrop-shaped membranes. Abdominal chaetae narrowly hooded. Pygidium broadly rounded, without eyespots.

BARCODE: A nucleotide sequence of 640 bp of the section of COI gene used for barcoding was obtained from one specimen collected from Acapulco, Guerrero, Mexican Pacific ( ECOSUR OH-P281 ) .

Remarks. The original description provided by Tovar-Hernández and Salazar-Vallejo (2008) contains two mistakes. Firstly, eyes from dorsalmost radioles are spherical (not spiraled as in original description); secondly, middorsal collar margins are fused to faecal groove as grouped by Tovar-Hernández and Salazar-Vallejo (2008: 1962, Table 1) but not “not-fused” as originally described.

Within Megalomma , M. acrophthalmos , M. carunculata , M. lobiferum , M. pigmentum , M. sp., and M. quadrioculatum are easy distinguishable from all others by having a caruncle. Megalomma pigmentum has eyes only in the dorsalmost radiolar pair and the dorsal collar margins are not fused to faecal groove (fused in the other five species). Megalomma lobiferum has eyes in all radioles; M. quadrioculatum has eyes only in 1–5 pairs of dorsal radioles and M. acrophthalmos , M. carunculata and M. sp., have eyes in most radioles. Megalomma carunculata and M. sp., have interramal eyespots (absent in M. acrophthalmos ) but M. carunculata lack of dorsal lappets (present in M. acrophthalmos and M. sp.).

Figures

FIGURE 1. Variations on dorsal margins of collar and inferior thoracic chaetae in Megalomma. A–C) Margins fused to faecal groove; D) margins not fused to faecal groove; E) chaeta type A; F) chaeta type B; G) chaeta type C. A–D) Schematized; E–G) modified from Fitzhugh (1989). Abbreviations: dlc dorsal lappets; fg faecal groove. The partial exposition of the anterior peristomial ring is marked in gray.

FIGURE 2. Megalomma acrophthalmos (Grube, 1878). A) Thorax, dorsal view; B) thorax, ventral view; C) collar and anterior segments, ventral view; D) peristomium, frontal view; E) thoracic chaetigers; F) dorsal and ventral lips; G) collar and anterior segments, dorsal view; H–I) inferior thoracic chaetae type B; J) dorsalmost radiolar eye; K) eye from a lateral radiole; L) eye from a ventral radiole. A–L) Specimens from Philippines, USNM, 38683. Abbreviations: apr anterior peristomial ring; ca caruncle; d dorsum; dl dorsal lip; dlc dorsal lappets of collar; nl notopodial lobe; v ventrum; vl ventral lobe; vs ventral sacs; vsc ventral shield of collar. Scale bars: A–D, G) 1 mm; E) 0.5 mm; F) 1 mm; H–I) 50 µm; J–L) 0.3 mm.