Megalomma heterops Perkins, 1984

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 : 35-37

Megalomma heterops Perkins, 1984

Figures 13F–N , 14A–L , 28C , 29C

Megalomma heterops Perkins, 1984: 359–363 , Figs 42–43.— Tovar-Hernández and Salazar-Vallejo, 1996: 40–42, Fig. 9 .

Type material examined. [ USNM] 54721, Acc. No. 324461, holotype, St. Lucie County, Hutchinson Island , E of FP and L Electric generation plant, 27° 20’ 24’’ N, 80° 13’ 04’’ W, Colls Gallagher, Hollinger & Cobb, September 15, 1971 , Sta. 4, 12.1 m. [ USNM] 50480, Acc. No. 255041, one paratype, Florida, Whistle buoy, near alligator harbor, on sponge, Coll. Forbes M, July 02, 1958 . [ USNM] 54722, one paratype. [ USNM] 67953, Acc. 324461, five paratypes, 32.18 km W of Sanibel Island, 26° 24’ N, 82° 28’ W, Coll. Presley B., May 11, 1966 , Sta. J. Hernan Cortez R / V, Project Hourglass, 18 m, on Solenastrea coral. [ FSBC] I 27696, one paratype, St. Lucie Co., Hutchinson Island , 27° 20’ 24’’ N, 83° 13’ 04’’ W, Sta. 4, 12.1 m, Colls R. Gallagher & M. Hollinger, September 15, 1971 . [ FSBC] I 27698, one paratype, St. Lucie Co., Hutchinson Island , 27° 23’’ N, 80° 13’ 24’’ W, 11.2 m, Colls R. Gallagher & M. Hollinger, September 15, 1971 .

Additional material examined. [ ECOSUR] Mexican Caribbean , HOL–10, Holbox island, private pier, June 03, 2005, Colls. BYR & AR (1 spec.) . Xahuayxol , Colls SISV & LFCP, October 13, 1998 (1 spec.) . El Hueso, Campeche , Colls SISV & LFCP, May 25, 2005, 2 m (2 specs). [ OSCAR DIAZ, personal collection] Venezuela, Laguna Charupata, Coll. Liñero, April, 29, 1995 (1 spec.) . [ USNM] Florida , 090414, 29° 54’ 59’’N, 86° 04’ 59’’ W, November 1977, Sta. V –2528, MAFLA, 37 m, Acc. No. 332151 (1 spec.) . 185970 Everglades National Parks , Shark river delta, March 25, 1965 (1 spec.) . Georgia , 186511, Sapelo Island , 4.5 mi and 160 degrees from Sapelo Whistle , Sta. 157, Coll. Gray M, November 15, 1961, 16.7 m, in bryozoans tubes (8 specs). Louisiana , 06785, South Tombalier lease area, 28° 34’ 09’’ N, 90° 24’ 32’’ W, Coll. SWR1 for MML Biofouling study, June 14, 1978, Sta. 04P, 45 m, Acc. 333929 (1 spec.) . Panama, 182834, Margarita Island , 09° 23’ 02’’ N, 79° 53’ 54’’ W, STRI for MMS, September 4, 1986, oil spill project (2 specs). 073664, Galeta reef flat, Coll. Brattstrom, HO, 1973, Sta. 515–6, as M. vesiculosum (1 spec.) .

Diagnosis. Eyes in most radioles (spherical); dorsal margins of collar fused to faecal groove; thoracic chaetae Type C; companion chaetae with tear-drop and sickle-shaped membranes; abdominal chaetae broadly hooded.

Description. Branchial crown longer than thorax with 13–16 pairs of radioles. Branchial crown with row of elongate pigment spots on fused portion below beginning of radioles ( Fig. 14B ); 4–5 narrow, transverse, purple bands on radioles; bands formed of short pigmented areas on outer and lateral surfaces of radioles ( Fig. 14C–E ), pigment not extending onto pinnules. Outer surfaces of radioles rounded. Subdistal compound eyes present in most radioles. Dorsalmost radioles with eyes greatly enlarged, spherical and short radiolar tips ( Fig. 14H ). Others radioles with eyes much smaller, spherical, gradually decreasing ventrally. Radiolar tips increasing gradually towards ventral radioles ( Figs 13I–K , 14I–L ). Dorsal collar margins square, fused to faecal groove ( Figs 13F , 14B, E–F ). Dorsal lappets absent. Dorsal pockets well developed, U-shaped ( Figs 13F , 14B, E–F ). Ventral lappets triangular, overlapped slightly, as long as the ventral shield of collar ( Figs 13H , 14C ). Anterior peristomial ring exposed dorsally between dorsal pockets. Lateral collar margins covering the basal union of radioles ( Fig. 13G ). Dorsal lips pigmented on upper surface, erect, triangular, with mid rib. Dorsal pinnular appendages present ( Fig. 14G ). Ventral lips broadly rounded. Ventral sacs absent. Caruncle and keel absent. Body depressed with paired purple spots dorsally on anterior margin of collar segment below collar, paired spots on chaetigers 1–3 medial to notopodia ( Fig. 14E–F ); some specimens with similar paired spots ventrally on anterior segments and small pigment spots below thoracic and above abdominal tori on posterior thoracic and abdominal segments. Total thorax-abdomen length 23 mm, 1.8 mm wide. Seven thoracic chaetigers. Thoracic tori of equal length in all segments. Tori in chaetigers 2–3 occupying three quarters of the distance between notopodia and ventral shield margins, not contacting shields ( Fig. 14C–D ). Inferior thoracic chaetae Type C ( Fig. 28C ). Thoracic uncini with crest surmounted by 9–10 rows of numerous minute teeth, handles 2x length of main fang ( Fig. 13L ). Companion chaetae with tear-drop and sickleshaped membranes ( Figs 13N , 29C ). Abdominal chaetae broadly hooded. Abdominal uncini with main fang surmounted by nine rows of numerous minute teeth ( Figs 13M , 29C ). Pygidium broadly rounded with two groups of eyespots. Tube formed of small silicate sand grains in a rigid translucid matrix, with large shell fragments ( Fig. 14A ).

Remarks. Megalomma heterops is unique among the species in the genus in having paired purple spots dorsally on anterior margin of collar segment below collar and paired spots on chaetigers 1–3 medial to notopodia. As above mentioned, 14 species of Megalomma have radiolar eyes in most radioles (Appendix 1, Character 3, State 2). Among these species, M. claparedei , M. heterops , M. lanigera , M. pacifici , M. sp., M. georgiense n. sp., M. nechamae , M. mushaense and M. vesiculosum the eyes of the dorsalmost radioles are spherical. Megalomma lanigera , M. sp., M. nechamae , M. mushaense and M. vesiculosum have dorsal lappets while these structures are lacking in M. heterops , M. claparedei , M. pacifici and M. georgiense n. sp. In M. georgiense n. sp., the dorsal collar margins of collar are not fused to faecal groove (fused in M. heterops , M. claparedei , M. pacifici ). Megalomma heterops and M. pacifici have anterior peristomial ring exposed dorsally between dorsal pockets (not exposed in M. claparedei ). Tori in chaetigers 2–3 in M. heterops occupies three quarters of the distance between notopodia and ventral shields, and shields are separated from tori (tori in chaetigers 2–3 occupy the entire distance between notopodia and ventral shield margins and all shields are in contact with tori in M. pacifici ).

Figures

FIGURE 9. Megalomma coloratum (Chamberlin, 1919). A) Body, lateral view; B) branchial crown, dorsal view; C) thorax, dorsal view; D) dorsal and ventral lips; E) peristomium, frontal view; F) oocytes; G) abdominal uncinus; H–I) thorax, ventral views; J) superior thoracic narrowly hooded chaeta; K) inferior thoracic chaeta type C; L–M) abdominal broadly hooded chaetae; N) dorsalmost radiolar eyes; O–P) eyes from from 5th dorsal radiole in adult and juvenile stages, respectively; Q) ventral radiole; R–S) thoracic uncini and companion chaetae. A–S) Specimens from Mazatlán, México, ECOSUR. Abbreviations: bls basal lateral skeleton; d dorsum; dl dorsal lip; ep epithelium; no nuchal organ; rs radiolar skeleton; v ventrum; vl ventral lip. Scale bars: A–E, H–I) 1 mm; F) 15 µm; G, J–M, R–S) 20 µm; N) 125 µm.

FIGURE 13. Selected structures of Megalomma species. A, D, G, R) Thorax, lateral views; B, F, O–P) thorax, dorsal views; C, H, Q) thorax, ventral views; E) dorsalmost radiolar eye; I, K) eyes from ventral radioles; J) eye from lateral radiole; L) thoracic uncinus; M) abdominal uncinus; N) companion chaetae. A–E) Megalomma gesae Knight-Jones, 1997; F–N) Megalomma heterops Perkins, 1984; O–R) Megalomma lanigera (Grube, 1846). A–E) Paratype from El Salvador, ZMH, 15245; F–N) modified from Perkins, 1984; O–R) specimens from Naples, MCZ, 1517. Abbreviations: apr anterior peristomial ring; vs ventral sacs; vbf ventral basal flange. Scale bars: A–D) 0.5 mm; E) 0.25 mm; F–N) not scaled; O–P) 2 mm.

FIGURE 14. Megalomma heterops Perkins, 1984. A) Tube from posterior abdomen; B, E–F) thorax, dorsal view; C) same, ventral view; D) same, lateral view; G) dorsal lip; H) dorsalmost radiolar eye; I) eye from a dorsal radiole; J–K) eyes from lateral radioles; K) eye from a ventral radiole. A, D) holotype from Florida, USNM, 54721; B–C, E–H) paratype from Florida, USNM, 67953; I–L) specimen from Cozumel, México, ECOSUR. Abbreviations: dl dorsal lip; vsc ventral shield of collar. Scale bars: A) 1 mm; B–G) 0.5 mm; H) 0.2 mm; I–L) 0.3 mm.

FIGURE 28. Scanning electronic micrographs of thoracic and abdominal chaetae. A–F) Thoracic chaetae; G–H) abdominal chaetae. A–C, E) Type C (paleate); D) type B; G) broadly hooded; H) narrowly hooded. A, G) Megalomma circumspectum from La Paz, México, ECOSUR, B) Megalomma coloratum from Mazatlán, México, ECOSUR; C) Megalomma heterops from Campeche, Mexico, ECOSUR; D) Megalomma lobiferum from Colón, Panama, ECOSUR; E) Megalomma pigmentum from Bahía San Quintín, México, ECOSUR; F, H) Megalomma splendidum from Pt. Vicente Light, California, LACM, 2357–53. Scale bars: A–F) 100 µm; G–H) 50 µm.

FIGURE 29. Scanning electronic micrographs of uncini and companion chaetae. A–G) Thoracic uncini and companion chaetae. A) Megalomma circumspectum from La Paz, México, ECOSUR, B) Megalomma coloratum from Mazatlán, México, ECO- SUR; C) Megalomma heterops from Campeche, Mexico, ECOSUR; D) Megalomma lobiferum from Colón, Panama, ECOSUR; E) Megalomma pigmentum from Bahía San Quintín, México, ECOSUR; F) Megalomma splendidum from Pt. Vicente Light, California, LACM, 2357–53. G) Parasabella pallida from Mazatlán, EMU. Scale bars: A–D) 100 µm; E–G) 20 µm.