Megalomma circumspectum ( Moore, 1923 )

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 : 19-24

Megalomma circumspectum ( Moore, 1923)

Figures 4A–J , 6A–V , 28A, G , 29A

Branchiomma circumspectum Moore, 1923: 239–241 , Pl. 18, Figs 41–42.

Megalomma circumspectum .— Hartman, 1959: 550.— Hartman, 1961: 43.— Hartman, 1969: 707, Figs 1–6 .— Rioja, 1962: 213–216, Figs 145–148.— Fauchald, 1972: 33.— Perkins, 1984: 363.— Knight-Jones, 1997: 314.— Hernández-Alcántara and Solís-Weiss, 1999: 29.

Type material examined. [ USNM] 17021, Acc. No. 60417, holotype, off Brockway Pt. Santa Rosa, California, Albatross , April 15, 1904, Sta. 4431, 74.98 m .

Additional material examined. [ CSD – MBL] California, USA, Sta. A4, 4, 32º 41’ 4’’ N, 117º 18’ 25” W, October 23, 1990, 80 m, Coll. DN (1 spec.). Sta. A4, 4, 32º 41’ 4’’ N, 117º 18’ 25” W, October 7, 1991, 80 m (1 spec.). [ ECOSUR] Baja California Norte , México, Ensenada, Punta Morro, Colls SISV, NEG & ASG , March 19, 2004, in mussels (4 specs). Playa las Rosas , July 30, 1987, Coll. SISV (4 specs) . Baja California, May , 07, 1981, Coll. SISV (4 specs) ; June 04, 1982, Coll. SISV (1 spec.) . Baja California Sur, México, Bahía la Paz , Presidente, Coll. SISV & JALG , August 23, 1987 (1 female); October 04, 1987 (5 specs); October 10, 1987 (3 specs); La Paz, Coll. AASD , March 02, 2004, 1 m (3 specs); Enfermería, Colls SISV & JALG , June 12, 1987 (1 spec.); June 15, 1987 (12 specs). Bahía de los Ángeles, Playa Municipal, Coll. SISV , November 11, 1985 (4 specs); Moradas, Coll. SISV , May 25, 1986 (1 spec.); March 17, 1985, Coll. Carmina (2 specs). Bahía Concepción , Tasajera, Coll. SISV , October 22, 1985 (8 specs). Nayarit, México, Aticana , Colls PSS & BYR , November 25, 2004 (4 specs, 1 female, 1 male). La Manzanilla, Colls PSS & BYR , November 29, 2004 (3 females). [ LACM – AHF] California, USA, Arroyo Hondo , St. 315ARRHON, SubID 4384, 34.47191º N, 120.14616º W, Coll. Marine Pollution Studies Lab / Moss Landing Marine Laboratories, Invasive Species Survey, October 08, 2007, subtidal rocky habitat, 7 m (1 spec.). Velero III , 003489, Sta. 1295–41, 1.8 km SE of Smugglers Cove, Santa Cruz Island , 34º 00’ 35’’ N, 119º 31’ 30’’ W, April 12, 1941, coralline, sand, pebbles, 38.2 m (1 spec.). Velero IV, Sta. 2315–53, Cruise 118, 4.18 km from Los Angeles Breakwater Lighthouse, 33º 40’ 4’’ N, 118º 16’ 2’’ W, May 19, 1953, sandy mud-shells fragments (1 spec.). Gulf of California, México, Velero III, F3279 , Sta. 1105–40, West coast, 7.4 km SE of Marcial Point, 25º 28’ 28’’ N, 110º 58’ 00’’ W, February 13, 1940, 205.66 m, green mud (4 specs). Velero IV, F3299, Sta. 1711– 49, 53 km 191º T from Abre Ojos Light , S of Punta Abre Ojos, 26º 15’ 56’’ N, 113º 40’ 30’’ W, March 03, 1949, 94.6 m, brachiopods and alcyonarians, coarse sand, broken shell and shale (3 specs). Velero IV, F3269, Sta. 1922–49, Cruise 35, 5.04 km 352º T from S Bluff, 28º 55’ 23’’ N, 118º 13’ 21’’ W, December 19, 1949, 72.8 m, sandy bottom (2 specs). Velero IV, Cruise 63, F3350, Sta. 2026–51, S. Bay, Isla Cedros , 28º 5’ 00’’ N, 115º 19’ 45’’ W, April 19, 1951, 34.5 m, mud sand and bottom (1 spec.). Velero IV, F3320, Sta. 1703–49, S Bay, Isla Cedros , 28º 4’ 25’’ N, 115º 17’ 58’’ W, Mach 05, 1949, 29.12 m, sand and mud (2 specs). N 15198 , Sta. 116, Gulf of California , Knudsen , July 1955 (1 spec.). F3341, Sta. 634.37, San Gabriel Bay, Espiritu Santo Island, March 06, 1937, shore (2 specs). F3376, Sta. 510–36, Cove S of Ballena Bay, Espiritu Santo Island, February 22, 1936, shore (2 specs). F3379 , N 15202 , n 1295, San Gabriel Bay , Espiritu Santo Island, Coll. E. F. Ricketts, April 12, 1940, in sand (16 specs). Velero III, F3370 , Sta. 1079–40, Point island, Angel de la Guardia Island , 29º 02’ 35’’ N, 113º 07’ 40’’ W, February 4, 1940, shore, rock (3 specs). Velero IV, F3301, Sta. 1919–49, Cruise 35, Melpomene Cove, Guadalupe Island , 28º 52’ 15’’ N, 118º 16’ 56’’, 66.52 m, December 19, 1949, sandy (1 spec.). F3362, N 15195 , n 10466, P 196–60, off coast Hermosillo , 28º 45.8’ N, 112º 04.0’ W, Coll. Parker, March 27, 1960, 23.4 m, shelly sand (1 spec.). Velero III , 003435, Sta. 1412–41, 1.5 mi S of Crook Point, San Miguel Island, 33º 59’ 00’’ N, 120º 22’ 18’’ W, September 16, 1941, 78.26 m, sand, shell (3 specs). Velero III, F3252 , Sta. 1045–40, S. Shore of Tiburon Island , 28º 45’ 35’’ N, 112º 17’ 45’’ W, January 25, 1940, shore (2 specs). Sta. 473, Punta Choya, Puerto Peñasco, Sonora, Coll. S.A. Glassell, May 09, 1941, intertidal (2 specs). F3383, N 15205 , n. 714, Punta Choya , Puerto Peñasco, Sonora, Coll. S.A. Glassell, May 14, 1941, sand and shell incrustated tubes at low tidal zone (2 specs). F3314, V – 1, 15172, Puerto Peñasco , Gallardo’s (1 spec.). Sta. 1292, Ca 3, Coronado Islands , Colls Steinbeck & Ricketts, March 27, 1940 (2 specs). [ LACSD – MBL] California, USA, Sta. 0191–2D , 33° 44’ 34’’ N, 118° 25’ 13’’ W, January 16, 1991, 31 m (1 spec.). Sta. 0196–1D, 33° 46’ 01’’ N, 118° 26’ 02’’ W, January 24, 1996, 31 m (1 spec.). Sta. 0700–1D, 33° 46’ 01’’ N, 118° 26’ 02’’ W, July 12, 2000, 31 m, 13.5°C, dark olive silty sand (1 spec.). [ USNM] California, USA, 41461, La Jolla , California, January 19, 1938 (1 spec.). Gulf of California, México, 41462, Isla Cerralvo , Gulf of California, October 16, 1956, Coll. Klawe (1 spec.) .

Diagnosis. Eyes in most radioles (spherical); ocular spots in ventralmost radioles; dorsal margins of collar fused to faecal groove; keel present; thoracic chaetae Type C; companion chaetae with teardrop and sickle-shaped membranes.

Description. Branchial crown longer than thorax with 13 pairs of radioles (13–29). Radioles with four purple bands distributed over outer and lateral radiole margins and adjacent pinnules, each band occupies a space of 3–4 pairs of pinnules. Outer surfaces of radioles quadrangular along the entire length. Sub-distal compound eyes present in most radioles ( Fig. 4F ). Dorsalmost pair of radioles longer than others, rigid, rachis notably thick in lateral view ( Fig. 6H ), eyes distinctly larger, spherical, radiolar tips very short ( Fig. 4G ) with a thick epithelium near the compound eye ( Fig. 6I ). Second to lateral and ventral pairs of radioles with spherical eyes distinctly smaller than dorsalmost ones ( Figs 4H–I , 6J–L ). Radiolar tips longer gradually towards ventral radioles ( Fig. 4H–J ) with narrow rachis in lateral view ( Fig. 6M ). Ventralmost radioles with ocular spots ( Fig. 4J ). Dorsal collar margins rounded posteriorly, fused to faecal groove ( Figs 4A, D , 6Q ). Dorsal lappets absent. Dorsal pockets present ( Figs 4A , 6C ). Epithelium of dorsal pockets translucent and narrow, as a membrane, it is easily broken longitudinally ( Fig. 6E ). Triangular ventral lappets, not overlapped, as long as ventral shield of collar ( Fig. 4B, D ) and vascularized by a dense net of blood vessels. Anterior peristomial ring not exposed beyond collar margins. Lateral collar margins covering basal union of radioles ( Figs 4C , 6A, D ). Dorsal lips purple, triangular, very long (about 1/2 of branchial crown length) with mid-rib. Dorsal pinnular appendages present. Ventral lips about one-quarter as long as dorsal lips, broadly rounded. Ventral sacs present ( Fig. 4D ), in some specimens sacs full of sand. Caruncle absent. Low smooth keel, projecting dorsally to the mouth. Body cream colored, depressed. Total thorax-abdomen length 27 mm (10–94), maximum width 2 mm throughout most of thorax (2–4). Seven thoracic chaetigers. Tori in chaetigers 2–3 short, occupying a half of the distance between notopodia and ventral shield margins, not contacting shields ( Figs 4B , 6B ). Notopodial fascicles with a superior group of elongate, narrowly hooded chaetae ( Fig. 6R–S ); inferior group of chaetae Type C ( Figs 6T–U , 28A ). Thoracic uncini with main fang surmounted by 7–9 rows of numerous minute teeth ( Fig. 6P ), handles 1.5x length of main fang; slightly longer than companion chaetal shaft ( Fig. 6V ). Companion chaetae teardrop ( Fig. 6V ) and sickle-shaped membranes within same torus ( Fig. 29A ). Abdomen with 58 chaetigers (32–108). Abdominal chaetae broadly hooded ( Fig. 28G ). Abdominal uncini with main fang surmounted by 8–10 rows of numerous minute teeth ( Fig. 6Q ). Pygidium broadly rounded ( Fig. 4E ) with two groups of purple eyespots. Tubes covered with sand grains, shell fragments, gravel, echinoderm spines and green algae.

GAMETES: Females from Nayarit ( México) with oocytes ( Fig. 6O ) distributed along entire abdomen, visible though epithelium among chaetiger and torus. Male with sperm in abdomen with rounded nucleus, small acrosome, two rounded mitochondria and a long flagellum ( Fig. 6N ).

SYMBIOSIS: Five large individuals (~ 8 cm length) from Punta Choya, Ángel de la Guardia Island, Coronados Island and Espíritu Santo Island in the Gulf of California, and Santa Cruz Island in California, USA, were found with several specimens of a cyclopoid copepod attached to the radioles, in the inner base of the branchial crown, dorsal lips and attached to the dorsal pockets of collar ( Fig. 6F–G ). These copepods were identified as gastrodelphyid Gastrodelphys dalesi Dudley, previously known from the crown of the sabellid polychaete Eudistylia polymorpha (Johnson) from Zuma Beach, California (Green) and from E. vancouveri (Kinberg) from Bodega Bay, California ( Gómez & Tovar-Hernández 2008).

Remarks. Megalomma circumspectum was described by Moore (1923) as Branchiomma from Santa Rosa

Island, California. It is distributed in Southern California, Western coast of Baja California Peninsula, Gulf of California and Nayarit, from intertidal waters to 80 m, in muddy or sandy muddy sediments. Megalomma circumspectum , M. coloratum , M. pigmentum and M. splendidum are common in California; among these M. coloratum is unique by having a glandular ridge on chaetiger 3; M. pigmentum has a caruncle; M. splendidum has spiraled eyes only in dorsal radioles and M. circumspectum is distinguished by having spherical eyes in most radioles.

Fourteen species of Megalomma have radiolar eyes in most radioles (Appendix 1, Character 3, State 2). Among these species, M. acrophthalmos , M. multioculatum and M. phyllisae have spiraled eyes in dorsalmost radioles; in M. perkinsi eyes in these radiolar pair are oval and in M. circumspectum , M. claparedei , M. heterops , M. lanigera , M. pacifici , M. sp., M. georgiense n. sp., M. nechamae , M. mushaense and M. vesiculosum these are spherical. Megalomma circumspectum , M. pacifici and M. georgiense n. sp., share the presence of ocular spots in ventral radioles. In M. circumspectum and M. pacifici the dorsal margins of collar are fused to the faecal groove (not fused in M. georgiense n. sp.). In M. circumspectum the thoracic ventral shields are separated from tori and the length of handle in thoracic uncini is 1.5 times the length of main fang (all ventral shields in contact with tori and handle is two times the length of main fang in M. pacifici ).

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.

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 6. Megalomma circumspectum (Moore, 1923). A, D, G) Thorax, lateral views; B) thorax, ventral view; C, E–F) thorax, dorsal views; H) base of the dorsalmost radiole, lateral view; I) dorsalmost radiolar eye; J–K) eyes from lateral radioles; L) eye from a ventral radiole; M) base of 2nd dorsal radiole, lateral view; N) spermatozoon; O) oocytes; P, V) thoracic uncini; Q) abdominal uncinus; R–S) superior thoracic narrowly hooded chaetae; T–U) inferior thoracic chaetae type C. A–E, H–V) specimens from Nayarit, México, ECOSUR; F–G) specimen from Santa Cruz, California, LACM, 003489. In F–G parasitic copepods are indicated with arrows. Scale bars: A–G) 1 mm; H–M) 125 µm; N) not scaled; O) 25 µm; P–V) 20 µm.

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.