Megalomma lobiferum ( Ehlers, 1887 )

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 : 39-40

Megalomma lobiferum ( Ehlers, 1887)

Figure 8B–C , 16A–H , 28D–E

Branchiomma lobiferum Ehlers, 1887: 254–259 , Pl. 53, Figs 10–15 .

Megalomma lobiferum .— Johansson, 1927: 132.— Hartman, 1951: 115.— Hartman, 1959: 550.— Perkins, 1984: 354–357, Figs 39–40.— Tovar-Hernández and Salazar-Vallejo, 2006: 42–43, Fig. 10 .— Tovar-Hernández and Salazar-Vallejo, 2008: 1961, 1963–1964, Figs 3–5 .

Type material examined. [ MCZ] 835, holotype, Florida, Key West , 1.82–3.6 m .

Additional material examined. [ ECOSUR] Mexican Caribbean , RIA 1 , May 30, 2005 (2 specs) Cayo Valencia, Quintana Roo, Coll. SISV, April 29, 1983 (1 spec.) . Xcacel, Quintana Roo. Coll. SISV, April 3 1992 (1 spec.) . [ ECOSUR] OH-P0283 , Quintana Roo, Isla Contoy, Northern point pier, 21° 31’ 43.8’’ N, 86° 48’ 10.1’’ W, Colls. SISV & LFCP, February 23, 2008 (1 spec) . [ ECOSUR] OH-P0286 , Quintana Roo, Isla Contoy, Ixlache reef, 21° 26’ 2.5’’ N, 86° 46’ 56.1’’ W, coralline rock, Colls. SISV & LFCP, February 25, 2008 (1 spec) . [ ECOSUR] OH- P497, Quintana Roo, Cabo Catoche, 1 km off Cabo Catoche , 21° 36’ 49.47’’ N, 87° 6’ 8.93’’ W, Colls. SISV & LFCP, June 10, 2009 (1 spec) . [ ECOSUR] OH-P476 , Yucatan, 1 km off Ria Lagarto beach, 21° 37’ 50’’ N, 88° 9’ 5’’ W, Colls. SISV & LFCP, June 14, 2009 (1 spec) . [ MCZ] Florida, 47064, 0.5 Km SE of entrance to Safe Harbor, stock island near Key West , 1.5 m, 24° 33.3’ N, 81° 43.8’ W, Coll. J. Thomas, July 29, 1977 (1 spec.) . [ USNM] North Carolina, 108231, 34 24’ 06’’ N, 76° 35’ 48’’ W, Coll. Duke University for MMS /BLM, October 22, 1981, Sta. 1505, on slow bay R / V, 18 m, Acc. 348038 (1 spec.) . Florida, 67959, St. Petersburg Beach , Coll. Salomon, C. H, January 29, 1966, Acc. No. 324461 (1 spec.) . Off Florida, 130081, 25° 17’ 48’’ N, 81° 39’ 48’’ W, Coll. MML for MMS, December 10, 1982, Sta. 52, SOFLA 14 m, Acc. 345592 (1 spec.) . 18596, Everglades National Park , Shark River Delta, Sta. SRD, Coll. Heald, E. J, March 25, 1965 (1 spec.) . Puerto Rico, 52061 Bahia de San Juan, Sta. 14, May 31, 1974 (1 spec.) . Antigua, 24484 Antigua, Falmouth Harbor , Coll. University of Iowa, Summer 1918, Barbados /Antigua Expedition (1 spec.) . Panama, 073019 Galeta Reef , Panama, Coll. A. A. Reimer, Acc. 318803 (4 specs) .

Diagnosis. Eyes in all radioles (spherical); dorsal collar margins fused to faecal groove; caruncle present; interramal eyespots present; thoracic chaetae Type B; companion chaetae with teardrop and sickle-shaped membranes; abdominal chaetae narrowly hooded.

Description. Branchial crown longer than thorax with 15–27 pairs of radioles. Radioles purple with crossbanded yellowish-orange pigment extending to pinnules. Outer surfaces of radioles rounded. Sub-distal compound eyes present in all radioles, spherical, moderately larger on dorsalmost pair, gradually decreasing in size laterally and ventrally ( Fig. 16E–G ). Radiolar tips longer gradually towards ventral radioles ( Fig. 16E–G ). Dorsal collar margins square, fused to faecal groove ( Fig. 16A ). Collar purple ventrally. Dorsal lappets absent. Dorsal pockets well developed ( Fig. 16A, D ). Ventral lappets rounded, not overlapped ( Fig. 16B ), as long as the ventral shield of collar. Anterior peristomial ring not exposed dorsally. Lateral collar margins covering base of radioles ( Fig. 16C ). Dorsal lips erect, triangular, very long, with mid-rib. Dorsal pinnular appendages present. Ventral lips about a half as long as dorsal lips, broadly rounded. Ventral sacs absent. Caruncle placed above mouth, between dorsal lips, erect, triangular with rough surface ( Fig. 8B–C ). Keel absent. Thorax purple dorsally, except for faecal groove. Total thorax-abdomen length 15–41 mm, maximum width 3–6 mm. Seven thoracic chaetigers. Interramal eyespots present. Thoracic tori longest on chaetigers 2–3. Tori in chaetigers 2–3 occupy the entire distance between notopodia and ventral shield margins ( Fig. 16B–C, H ), all tori contacting shields. Inferior thoracic chaetae Type B ( Fig. 28D ). Thoracic uncini with main fang surmounted by 10–13 rows of numerous minute teeth ( Fig. 28D ), handles 2x length of main fang. Companion chaetae with teardrop and sickle-shaped membranes ( Fig. 28D ). Abdomen with 78 chaetigers. Abdominal chaetae narrowly hooded. Abdominal uncini with main fang surmounted by 10–13 rows of numerous minute teeth. Pygidium broadly rounded with two groups of purple eyespots. Tube thick, rigid, covered with layer of mud with small pieces of sand and shell fragments.

BARCODE: Nucleotide sequences between 606–655 bp of the section of COI gene used for barcoding was obtained from three specimens, one from the Mexican Caribbean ( ECOSUR OH-P283 ), and two from the Gulf of Mexico ( ECOSUR OH-P476 , ECOSUR OH-P497 ). The average evolutionary divergence over the three sequence pairs was 0.7 %.

Remarks. Megalomma lobiferum ( Fig. 8B–C ), M. acrophthalmos ( Fig. 2D ), M. carunculata , M. pigmentum ( Fig. 23H ), M. sp., and M. quadrioculatum share the presence of a caruncle (for differences among these species see remarks on M. carunculata ). The caruncle of M. lobiferum was characterized by Tovar-Hernández and Salazar- Vallejo (2008) as a structure innervated directly form the cerebral ganglion, supported with hyaline cartilage constituted by a homogeneous eosiniphilic matrix and hyperthrophied lateral bands of cilia, although its function is still unknown.

Figures

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.

FIGURE 3. Megalomma bioculatum (Ehlers, 1887). A) Thorax, dorsal view; B) same, ventral view; C) dorsalmost radiolar eye. A–C) Specimen from Florida, MCZ, 47066. Abbreviation: apr anterior peristomial ring. Scale bars: A–B) 1 mm; C) 0.3 mm.

FIGURE 4. Megalomma circumspectum (Moore, 1923). A) Thorax, dorsal view; B) same, ventral view; C) same, lateral view; D) ventral sacs as indicated with arrows, branchial crown removed; E) posterior end; F) eyes from dorsal radioles; G) dorsalmost radiolar eye; H) eye from 2nd dorsal radiole; I) eye from a lateral radiole; J) ventralmost ocular spot. A–J) Specimens from La Paz, México, ECOSUR. Scale bars: A–C, E) 1 mm; D) 0.5 mm; F) 2 mm; G–J) 0.3 mm.

FIGURE 5. Megalomma bioculatum (Ehlers, 1887) and M. claparedei (Gravier, 1908). A, I) Thorax, dorsal views; B–C, H) thorax, ventral views; D, P) thoracic uncini; E–F, N) companion chaetae; G) inferior thoracic chaeta type B; J) dorsalmost radiolar eye; K) abdominal uncinus; L) superior thoracic narrowly hooded chaeta; M) abdominal broadly hooded chaeta; O) inferior thoracic chaeta type B. A–G) Megalomma bioculatum; H–P) Megalomma claparedei. A) Specimen from Florida, MCZ, 47066; B–G) modified from Perkins, 1984; H–I) syntype from Djibouti, MNHN 559; J–P) modified from Gravier, 1908. Abbreviations: apr anterior peristomial ring; dl dorsal lip; dp dorsal pockets; vsc ventral shield of collar. Scale bars: A) 1 mm; H–I) 0.5 mm; B–G, J–P) not scaled.

FIGURE 8. Scanning electronic micrographs of body and caruncle. A) Lateral view of Megalomma coloratum (Chamberlin, 1919) from Mazatlán, México, ECOSUR; B–C) lateral and dorsal views of caruncle of Megalomma lobiferum (Ehlers, 1887) from Ria Lagartos, México, ECOSUR. Scale bars: A) 1 mm, B–C) 0.2 mm.

FIGURE 10. Relationships between biometrical features in Megalomma coloratum (Chamberlin, 1919).

FIGURE 11. Megalomma fauchaldi Giangrande et al. 2007. A) Thorax, dorsal view; B) same, lateral view; C) same, ventral view; D) dorsalmost radiolar eye; E–G) eyes from lateral radioles. A–G) Specimen from Galeta Reef, Panama, USNM, 066403. Abbreviations: dlc dorsal lappets. Scale bars: A–C) 0.5 mm, D–G) 0.3 mm.

FIGURE 12. Megalomma gesae Knight-Jones, 1997. A) Collar and keel as indicated with arrow; B) thorax, dorsolateral view; C) ventral sacs as indicated with arrow; D) dorsalmost radiolar eye; E) posterior abdomen and pygidium. A–E) Specimen from Balboa, Panama, ECOSUR. Abbreviations: apr anterior peristomial ring. Scale bars: A–C, E) 1 mm; D) 0.3 mm.

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 15. Megalomma lanigera (Grube, 1846). A, D) Thorax, dorsal view; B) collar, dorsal view; C) collar, ventral view; E) thorax, ventral view; F) ventral and dorsal lip; G) dorsalmost radiolar eye, spherical; H) spiraled eye from a dorsal radiole; I) oval eye from a lateral radiole; J) spherical eye from a ventral radiole. A–C, G–J) Specimens from the Aegean Sea, USNM, 97444; D–F) specimen from Naples, MCZ, 1517. Abbreviations: dl dorsal lip; vl ventral lip. Scale bars: A–F) 2 mm; G–J) 0.25 mm.

FIGURE 16. Megalomma lobiferum (Ehlers, 1887). A) Thorax, dorsal view; B) same, ventral view; C) same, lateral view; D) collar, dorsal view; E) dorsalmost radiolar eye; F) eye from a lateral radiole; G) eye from a ventral radiole; H) thoracic noto- and neurochaetae. A–B) Specimen from Florida, USNM, 67959; C–H) specimen from Isla Contoy, México, ECOSUR. Scale bars: A–D) 1 mm; E–G) 0.3 mm; H) 0.5 mm.

FIGURE 23. Megalomma pigmentum Reish, 1963. A, H) Thorax, dorsal views; B) thorax, lateral view; C–D, G) thorax, ventral views; E) dorsal and ventral lips; F) dorsalmost radiolar eye; I) thoracic uncini and companion chaeta; J) spermatozoon; K) abdominal uncinus; L) inferior thoracic chaetae type C; M–N) superior narrowly hooded thoracic chaetae; O) last abdominal chaetiger, nephridia and sperm tissue in grey. A–O) Specimens from San Quintín, México. Abbreviations: apr anterior peristomial ring, ca caruncle, dl dorsal lip, fl flange, vl ventral lip, vs ventral sacs, vsc ventral shield of collar. Scale bars: A–D, G–H: 1 mm; E: 0.5 mm; F: 0.25 mm; I, K–O: 40 µm; J: not scaled.

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.