Megalomma pigmentum Reish, 1963

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 : 48-52

Megalomma pigmentum Reish, 1963

Figures 22A–K , 23A–O , 28E , 29E

Megalomma pigmentum Reish, 1963: 430–433 , Figs 16A–I .— Knight-Jones, 1997: 314.

Megalomma monoculata Hartman-Schröder, 1965: 273–276 , Figs 276–278 fide Knight-Jones, 1997: 316.

Type material examined. [ USNM] 30451, holotype of Megalomma pigmentum Reish, 1963 , San Quintín Bay, Baja California, April 1960, Acc. No. 244910, Sta. 43, complete but crown separated from body. [ USNM] 30451, 8 paratypes of Megalomma pigmentum Reish, 1963 , San Quintín, Baja California, April 1960, Acc. No. 244910, Sta. 43. [ ZMH] P–5227 holotype of Megalomma monoculata Hartman-Schröder, 1965 , Topocalma, off south Chile, Exp. Mar Chile I, March 03, 1960, incomplete (lacking posterior abdomen). [ ECOSUR] topotypes, Baja California, México, San Quintín, Coll. L. E. Calderón, December 08, 1981 (16 specs).

Additional material examined. [ CSD – MBL] California, USA, B2, 4, January 1994, DN (1 spec.), A13, 4, 202, 1–28–86 (1 spec.), ITP , Sta. I33–1, January 9, 2008, 31 m (2 specs), Survey 5300, Sta. I27, 1, January 3, 2008, 30 m, KL (1 spec.), Survey SB00, Sta. I–16–I, January 14, 2008, 29 m, VRV (1 spec.), Sta. 2140, July 18, 2007, 39 m, RML (1 spec.), ITP, I 15–2 , January 14, 2008, 31 m, RML (1 spec.), Survey OLDOUT Sta. A8–2, July 11, 2007, 61 m, RML (1 spec.). [ CSD – MBL] California, USA, PLOO, Sta. A 13–1, 48.1 m, April 04, 1994 (1 spec.), Bight 98, 981077, Sta. 2230, 3.5 m, 08/5/1998 (1 spec.), Bight 03, 3971, Sta . 4036, 48 m, July 23, 2003 (1 spec.). [ EMU] Sinaloa, México, Topolobampo, EMU – 4383, Coll. LIB, October 21, 1996 (2 specs); EMU – 4400 (1 spec.). Bahía de Mazatlán , EMU – 4550, Coll. LIB, December 08, 1996 (4 specs). Estero Urias , EMU – 5073, Coll. LIB, February 26, 1997 (1 spec.); EMU –5016 (26 specs); EMU – 5078 (1 spec.); EMU –5052 (5 specs). [ LACM – AHF] California, USA, Velero IV, 003480, Cruise 97, Sta. 2152–52, 003480, 11.52 km 249º T . from Redondo Beach Pier , 33º48’ 6’’ N, 118º 30’ 39’’ W, September 26, 1952 (2 specs). Santa Catalina Island, Avalon Harbor, St. 406 AVAL02 , SubID 3417, 33.34424º N, 118. 3225º W, Coll. Marine Pollution Studies Lab/Moss Landing Marine Laboratories, Invasive Species Survey, October 10, 2006, 10.3 m, coarse and sandy with shells (5 specs). South California 003472, N 2677 (1 spec.). Costa Rica, Velero III , 003526, Sta. 477-35, Salinas Bay, 11º 03’ 20’’ N, 85º 43’ 30’’ W, 3.6 m, coarse sand, February 11, 1935, as M. roulei (1 spec.). Perú, Velero III , 003528, Sta. 834–38, Off Independencia Bay, 14º 16’ S, 76º 10’ W, 38.4 m, mud, February 10, 1938, as M. roulei (1 spec.). Velero III , 003527, Sta. 833–38, Off Independencia Bay, 14º 13’ S, 76º, 13’ W, 14.6 m, sand, shell, February 10, 1938, as M. roulei (1 spec.). [ LACSD – MBL] California, USA, D1D 3, 30 m , 33° 46.02’ N, 118° 26.03’ W, September 21, 1973 (1 spec.). J1D 1, 30 m, 33° 46.02’ N, 118° 26.03’ W, January 21, 1976 (1 spec.). P8D 1, 30 m, 33° 42.44’ N, 118° 19.63’ W, July 16, 1979 (1 spec.). Q6D 1, 30 m, 33° 43.03’ N, 118° 20.82’ W, January 07, 1980 (1 spec.). PSCBE 06210 LA/TP, 34° 13.20’ N, 119° 22.43’ W, August 16, 1994, 26 m (1 spec.). 0799–OC3, 33° 48.44’ N, 118° 25.90’ W, July 20, 1999, 60 m (1 spec.). 0791–1B, 33° 44.98’ N, 118° 26.62’ W, July 12, 1991, 150 m (1 spec.). 0700–2B, 33° 44.07’ N, 118° 25.48’ W, July 11, 2000, 150 m (1 spec.). 0701–1B, 33° 44.98’ N, 118° 26.62’ W, July 18, 2001, 150 m (1 spec.). 0701–7D, 33° 42.83’ N, 118° 20.55’ W, July 18, 2001, 30 m (1 spec.). 0703–7D, 33° 42.83’ N, 118° 20.55’ W, July 09, 2003, 30 m (1 spec.). 0703–OD, 33° 48.14’ N, 118° 25.38’ W, July 10, 2003, 30 m (1 spec.). 0704–OD, 30 m, 33° 48.14’ N, 118° 25.38’ W, July 15, 2004 (1 spec.). [ MCZ 61884] Costa Rica, Punta Morales, no more available data (1 spec.) .

Diagnosis. Eyes only in dorsalmost radioles (spherical); dorsal margins of collar not fused to faecal groove; anterior peristomial ring exposed dorsally and laterally; base of branchial crown with ventral flanges; caruncle present; ventral shield of collar divided transversally in two parts; thoracic chaetae Type C; companion chaetae with teardrop and sickle-shaped membranes; abdominal chaetae narrowly hooded.

Description. Branchial crown longer than thorax with 14–16 pairs of radioles. Basal union of the radioles brown colored ( Fig. 22C ). Radioles with four reddish-brown pigmented bands distributed over outer and lateral radiole margins and adjacent pinnules. Outer surfaces of radioles quadrangular basally, rounded distally. Base of the branchial crown with ventral translucent flanges ( Figs 22B–C, F , 23B–D ). Sub-distal compound eyes present only in the dorsalmost radiolar pair, spherical covering a short radiolar tip ( Figs 22H , 23F ). Other radioles with tips as long as equivalent space of eight pinnules ( Fig. 22I ). Dorsal collar margins diagonal, not fused to faecal groove ( Figs 22A, E , 23A, H ). Dorsal lappets absent. Dorsal pockets absent ( Fig. 23A ). Anterior peristomial ring exposed dorsally and laterally above collar ( Figs 22A, E, G , 23A–B ). Ventral lappets triangular, not overlapped ( Figs 22B, F , 23B–D, G ). Ventral shield of collar rectangular, divided transversally in two parts ( Figs 22B, F , 23D, G ). Lateral collar margins not covering bases of radioles ( Fig. 22C , 23B ). Dorsal lips purple dorsally, very long (about ¼ of branchial crown length), erect, with mid-rib forming two well developed lateral lamellae ( Fig. 22G , 23E, H ). Dorsal pinnular appendages present. Ventral lips small, rounded ( Fig. 23E ). Caruncle long, erect, triangular, placed above mouth, between dorsal lips ( Fig. 23H ). Ventral sacs prominent ( Fig. 23B–C, G ) full of sand in most specimens. Keel absent. Body slender, cylindrical in thorax, flattened in abdomen. Total thorax-abdomen length 23 (37– 38) mm, maximum width 1 mm (1.5–1.8) mm throughout most of thorax. Seven thoracic chaetigers. Dorsal thoracic segments brown laterally. Thoracic tori of same length along thorax. Tori in chaetigers 2–3 short, occupying a half of the distance between notopodia and ventral shield margins ( Figs 22C , 23B ), not contacting shields. Superior thoracic chaetae elongate, narrowly hooded chaetae ( Fig. 23M–N ); inferior thoracic chaetae Type C ( Figs 23L , 28E ). Eight thoracic uncini with crest surmounted by 6–8 rows of numerous minute teeth ( Fig. 29E ), handles extending beyond base of shaft of companion chaetae, 2x length of main fang ( Fig. 23I ). Companion chaetae with teardrop and sickle-shaped membranes within same torus ( Fig. 29F ). Abdominal segments 63–83. Abdominal chaetae elongate, narrowly hooded chaetae ( Fig. 23O ); chaetae in posterior row longer than those in anterior row. Abdominal uncini with main fang surmounted by 8–9 rows of numerous minute teeth ( Fig. 23K ). Posterior margin of pygidium triangular ( Fig. 22J–K ) without eyes. Tubes covered with sand grains ( Fig. 22D ).

GAMETES: Females with the abdomen full of oocytes. Posterior abdominal chaetigers with nephridia visible, full with sperm tissue ( Fig. 23O ). Sperm in posterior abdomen with a rounded nucleus, small acrosome, two rounded mitochondria and a long flagellum ( Fig. 23J ).

Remarks. The original description of M. pigmentum , did not include some details. The redescription provided here is to point out that in M. pigmentum : 1) ventral basal flanges are present in the base of the branchial crown; 2) a caruncle is present, located above mouth between dorsal lips; 3) the anterior peristomial ring is exposed dorsally and laterally above collar; 4) dorsal margins of collar are not fused to the faecal groove and 5) it lacks dorsal pockets. Megalomma pigmentum and M. gesae are unique in having ventral basal flanges, mid-dorsal collar margins not fused to the faecal groove and radiolar eyes only in dorsalmost pair. Megalomma pigmentum have caruncle and the ventral shield of collar is divided transversally in two parts (caruncle absent and ventral shield of collar entire in M. gesae ).

The first records of M. pigmentum outside its type locality were provided by Perkins (1984) from several localities of Florida and Venezuela. Tovar-Hernández and Salazar-Vallejo (1996) examined few specimens from Cumaná and Tampa recorded as M. pigmentum but they found some characteristics different from those of M. pigmentum . They recognized two undescribed morphs and called them as Megalomma sp. 1 (Cumana) and Megalomma sp. 2 (Tampa) . Other Caribbean records of M. pigmentum were not possible to review but a full revision of these materials is needed in order to confirm the amphi-american status of M. pigmentum .

Knight-Jones (1997) synonymized M. pigmentum and M. monoculata , a species described from off south Chile but no comments were provided. During this study the holotype of M. monoculata was re-examined. Both species have a caruncle, the peristomium is exposed dorsally and laterally above collar and eyes are only present in the dorsalmost radioles. New mounts of chaetae were not made since these were well illustrated in the original description. Megalomma pigmentum and M. monoculata are cryptic species, and no reproductive features have been studied in order to find any possible dissimilarity.

Figures

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 22. Megalomma pigmentum Reish, 1963. A) Anterior end, dorsal view; B) same, ventral view; C) same, lateral view; D) tube; E) collar, dorsal view; F) same, ventral view; G) same, lateral view; H) dorsalmost radiolar eye; I) lateral radiole; J–K) posterior abdomen. A–K) Specimens from Bahia San Quintín, México, ECOSUR. Ventral flanges in B–C, F as indicated with arrows. Scale bars: A–D) 1 mm, E–G, J–K) 0.5 mm, H–I) 0.2 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.

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.