Megalomma lanigera ( Grube, 1846 )

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 : 37-39

Megalomma lanigera ( Grube, 1846)

Figures 13O–R , 15A–J

Sabella lanigera Grube, 1846: 51 .

Branchiomma vesiculosum neapolitana Claparède, 1868: 164–166 , Pl. 22, Fig. 5 fide Giangrande and Licciano, 2008: 209. Branchiomma köllikeri Claparède, 1869: 163–164 , Pl. 22, Fig. 4 fide Giangrande and Licciano, 2008: 209.

Megalomma neapolitana .— Knight-Jones, 1997: 314.

Megalomma lanigera .— Giangrande and Licciano, 2008: 209–213, Figs 2–4 , 5C–D .

Material examined. [ MCZ] 1517, topotypes, Gulf of Naples, Coll. Naples Zoological Station, label note R. V Chamberlin “Catalogue of worms” List # 1517 as Branchiomma köllikeri Claparède (3 specs). [ USNM] 97444, Aegean Sea, Gulf of Kassandra, Greece, Kassandra Peninsula, near the village of Kalithea, Coll. Lessios H, August 6, 1971, 4–5 m, as M. vesiculosum (2 specs).

Diagnosis. Eyes in most radioles (spherical, spiraled and oval); dorsal margins of collar fused to faecal groove; dorsal lappets and dorsal pockets present; thoracic chaetae Type B; abdominal chaetae narrowly hooded.

Description. Branchial crown longer than thorax with 23, 23, 17 pairs of radioles with brown bands. Outer surfaces of radioles quadrangular basally, rounded distally. Subdistal compound eyes present in most radioles. Dorsalmost pair of radioles with eyes distinctly larger, spherical, radiolar tips short ( Fig. 15G ). Other dorsal eyes spiraled, decreasing towards lateral radioles and radiolar tips longer gradually towards lateral radioles ( Fig. 15 ). Lateral radiolar eyes oval, smaller than dorsal radioles with radiolar tips longer than lateral radioles ( Fig. 15I ). Ventral radioles with small spherical eyes and very long radiolar tips relative to eyes size ( Fig. 15J ). Dorsal collar margins fused to faecal groove, forming a broad gap ( Figs 15A–B, D ). Dorsal lappets highly developed, rounded, covering junction of crown ( Fig. 13O , 15D ). Dorsal pockets well developed, folded and deep ( Figs 13O–P , 15A–B, D ). Dorsal margins of collar higher than lateral margins ( Figs 13O, R , 15D ). Epithelium of dorsal pockets translucent and narrow, as a membrane, it is easily broken longitudinally ( Fig. 15A ). Anterior peristomial ring exposed dorsally between dorsal pockets. Ventral lappets triangular, overlapFigs 13Q, 15C, E). Lateral collar margins not covering basal union of radioles ( Fig. 13R , 15E ). Caruncle absent. Keel absent. Dorsal lips erect, triangular about one-quarter length of branchial crown, with mid-rib and dorsal pinnular appendages ( Fig. 15F ). Ventral lips, about one quarter length of dorsal lips, broadly rounded ( Fig. 15F ). Ventral sacs present. Body long, depressed dorso-ventrally. Total thorax-abdomen length 63, 57, 48 mm, maximum width 5, 3.5, 3 mm throughout most of thorax. Six to eight thoracic chaetigers. Thoracic tori same length throughout. Tori in chaetigers 2–3 short, occupying a half of the distance between notopodia and ventral shield margins, not contacting shields ( Fig. 15E ). Inferior thoracic chaetae Type B. Thoracic uncini with crest surmounted by 11 rows of numerous minute teeth, handles 2x length of main fang. Companion chaetae with teardrop-shaped membranes. Abdomen with 98, 84, 62 chaetigers. Abdominal chaetae narrowly hooded; chaetae in posterior row longer than those in anterior row. Abdominal uncini with main fang surmounted by nine rows of numerous minute teeth. Pygidium rounded. Tubes composed of sand grains.

Remarks. Sabella lanigera Grube, 1846 , and Branchiomma köllikeri Claparède, 1869 , were previously considered by Hartman (1959) as junior synonyms of Megalomma vesiculosum (Montagu, 1815) . Knight-Jones (1997) considered both specimens as the same species, but different from M. vesiculosum in having collar margins, especially those of the dorsal lappets, well above the junction between crown and thorax, and as a consequence she suggested that M. lanigera should be considered a subspecies of M. vesiculosum , and M. köllikeri a junior synonym of lanigera . Giangrande and Licciano (2008) based on examination of type material, confirmed the synonymy of S. lanigera , B. köllikeri and B. vesiculosum neapolitana but recognized the validity of M. vesiculosum as an independent taxon. Megalomma lanigera is a Mediterranean species; M. vesiculosum is distributed in north Atlantic waters.

In the genus Megalomma , ten species share the presence of dorsal lappets (see remarks on M. acrophthalmos ). Among these, M. lanigera , M. acrophthalmos , M. phyllisae and M. vesiculosum have the anterior peristomial ring exposed dorsally between dorsal pockets. Megalomma lanigera and M. vesiculosum the lateral collar margins not covering the basal union of radioles (these cover the basal union of radioles in M. acrophthalmos and M. phyllisae ). Megalomma lanigera differs from M. vesiculosum in having the ventral lappets triangular, overlapping (rounded, not overlapping in M. vesiculosum ) and the handle of thoracic uncini 2x the length of main fang (1.5x in M. vesiculosum ).

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 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 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.