Megalomma splendidum ( Moore, 1905 )

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 : 52-56

Megalomma splendidum ( Moore, 1905)

Figures 24A–J , 25A–K , 28F, H , 29F

Pseudopotamilla splendida Moore, 1905: 564–566 , Pl. 37, Figs 23–27 .

Pseudopotamilla anoculata Moore, 1905: 566–569 fide Hartman, 1959: 556.

Branchiomma disparoculatum Treadwell, 1914: 223–224 , Pl. 12, Figs 44–46 fide Hartman, 1956: 298.

Branchiomma burrardum Berkeley, 1930: 7–8 , Fig. 1 fide Knight-Jones, 1997: 314.

Megalomma splendida .— Rioja, 1962: 212–213, Figs 143–144.

Type material examined. [ ANSP] I 2205, syntype, Pseudopotamilla splendida Moore, 1905 , right side of branchial crown removed, left side in regeneration, posterior abdomen lost, Kassan Bay, Prince of Wales Island, Alaska, Albatross Sta. 4245, 173– 179 m, in a bottom of dark green mud and sand mixed with shell and rock fragments, July 11, 1903. [ USNM] 5534, holotype, Pseudopotamilla anoculata Moore, 1905 , with histolysis, tube complete, dissected transversally along the entire length, Vicinity of Naha Bay, Behm Cannal, Sta. 4230, 197– 438 m, SE Alaska. [ LACM – AHF] n 4257, 003463, lectotype, Branchiomma disparoculatum Treadwell, 1914 , designated in this study from San Diego, California. [ USNM] 32828, Acc. No. 256920, holotype, Branchiomma burrardum Berkeley, 1930 , Burrard inlet, British Columbia, September 15, 1928, Colls E. & C. Berkeley. [ USNM] 32829, Acc. No. 256920, two paratypes (one entire, second broken into two pieces), Branchiomma burrardum Berkeley, 1930 , Burrard inlet, off five fingers, British Columbia, June 5, 1929, lime, Colls E. & C. Berkeley.

Additional material examined. [ LACM – AHF] California, USA, Velero III , 003438, Sta. 1417–41, 7.2 km NE of Sandy Point, Santa Rosa Island , 34º 04’ 30’’ N, 120º 13’ 14’’ W, September 16, 1941, 64 m, flat rocks (1 spec.). Velero III , 003440, Sta. 1151–40, SE end of Santa Catalina Island , 33º 15’ 55’’ N, 118º 13’ 50’’ W, July 5, 1940, 234 m (1 spec.). Velero III , 003441, Sta. 1123–40, off San Nicolas Island , California, 33º 16’ 10’’ N, 119º 24’ 30’’ W, April 10, 1940, 56.6 m, sponge, rock (1 spec.). Velero III , 003443, Sta. 1384–41, 0.8 km. NE of Long Point, Santa Catalina Island , 33º 00’ 10’’ N, 118º 21’ 40’’ W, August 10, 1941, 199.3 m, green, sandy mud (1 spec.). Velero III , 003444, Sta. 1435–41, 2.4 km. SW off Santa Cruz Island , 33º 56’ 00’’ N, 119º 50’ 55’’ W, November 8, 1941, 87.7 m, mud, sponge (3 specs). Velero III , 003466, 2249, False Navaos , Departure Bay, BC, July 18, 1940 (1 spec.). Velero III , 003467, n 4266 Monterrey Bay , California, Colls Chin Yip & Ricketts, June 25, 1932, 64–128 m, rocky bottom (4 specs). Velero III , Sta. 1010–39, F3352, off San Benito Islands , August 20, 1939, 28º 12’ 45’’ N, 115º 34’ 05’’ W, 173 m, fine green sand (4 specs) as E. tenella . Velero III , Sta. 1252–41, T3280 , 13.6 km. S of San Benito Islands , México, 28º 10’ 00’’ N, 115º 34’ 20’’ W, February 26, 1941, 131 m, coral sand, fine pebbles (2 specs) as E. tenella . Velero III , Sta. 1304–41, 4.8 km. N of Arch Rock, Santa Cruz Island , California, 34º 06’ 20’’ N, 119º 48’ 25’’ W, April 1941, 100 m, mud, broken shell (1 spec.). Velero IV, 003437, Cruise 324, Sta. 5502–57, 3.2 km, 246.5º, T . from Pt. Fermin Light, 33º 41’ 30’’ N, 118º 19’ 50’’, December 16, 1957, fine gray and silty sand (6 specs). Velero IV, 003445, Cruise 89, Sta. 2126–52, 14.8 km. 156.5º from Los Angeles lighthouse, 33º 34.5’ N, 118º 10’ 41’’ W, June 25, 1952, coralline clumps (1 spec.). Velero IV, 003446, Cruise 89, Sta. 2127- 52, 18 km 152º T . from Los Angeles Lighthouse , 33º 32’ 38’’ N, 118º 8’ 39’’ W, June 25, 1952, mud and sand (1 spec.). Velero IV, 003447, Cruise 132, Sta. 2436–53, 8.7 km 143º T . from Long Pt. Light, Santa Catalina Island, November 10, 1953 (1 spec.). Velero IV, 003448, Cruise 222, Sta. 3539–55 Santa Monica Bay , California, 33º 54’ 18’’ N, 118º 33’ 18’’ W, 67.6 m, December 10, 1955, hung up on bottom, rocky bottom (1 spec.). Velero IV, 003491, Cruise 131, Sta. 2417–53, 3.4 km 261º T . from Pt. Fermin Light, California, 33º 41’ 57’’ N, 118º 20’ 8’’, September 29, 1953 (2 specs). Velero IV, Cruise 121, Sta. 2357–53, February 07, 1953, 1.7 km 252º T . from Pt. Vicente Light, CA , 33º 44’ 8’’ N, 118º 25’ 48’’ W (1 spec.). [ LACSD – MBL] California, USA, 0101–1B (1 spec.), 0704–10B (1 spec.), 0705– 10B (1 spec.), 0796–2B (1 spec.). [ CSD – MBL] California, USA, PLOO , P–207, Sta. A4– 3, 79 m, April 07, 1988 (2 specs), PSDBE , P–207 Dup , Sta. PSDBE 8230, 112 m, August 16, 1994 (1 spec.), Bight 98, 981077, Sta. 2411, 89 m, August 06, 1998 (1 spec.), Bight 03, 3972, Sta. 4561, 119 m, August 19, 2003 (1 spec.), PLOO , Sta. B10– 1, 120 m, July 23, 2007 (1 spec.), Sta. A4, 4, October 23, 1990, 80 m, DN (1 spec.), A4, 4, October 7, 1991, 79.5 m (1 spec.). [ CMN] Canada , British Columbia, Straits of Georgia , 49º 23’ N, 123º 44.2’’ W, Coll. R . M. O’Clair, 1976– 6, Sta. 74–21, Cat. 5542 (1 spec.). Swanson Bay , 53º 0’ 50’’ N, 128º 30’ 30’’ W, Coll. C. D. Levings, November 18, 1975, Sta. 51B, 005, Acc. 1979–191 (1 spec.). [ USNM] Canada, 5739, Gulf of Georgia , Halibut Bank , British Columbia, Sta. 4197, Coll. Str. Albatross, 1903, 164–85.9–56.6 m (1 spec.). 41506, Departure Bay , British Columbia, April 16, 1937, as M. burrardum (1 spec.). 41511, off Shake Island , British Columbia, 109 m, July 7, 1926 (2 specs). 41510, Pendrell harbor, Vancouver Island, June 6, 1960, Coll. Quayle (2 specs). 41509 Head of Princess Louise inlet , British Columbia, 36.5 m, August 15, 1934 (2 specs). Washington, 38237, Puget Sound Washington, Sta. 4, 47° 44’ 31’’ N, 122° 32’41’’ W, Haul 6, 12 m, January 9, 1963, Coll. K. Banse (2 specs). California , 123272, 41° 30’ 51’’ N, 124° 21’ 38’’ W, Coll. Saic & Mec for MMS , November 22, 1987, Sta. SB 05, 95 m (1 spec.). 41508, Monterey Bay, 91–109 m, August 15, 1932, Coll. McGinites (1 spec.). 41507, Pacific Grove, California , November 25, 1960, Coll. McLean (2 specs) .

Diagnosis. Eyes in dorsalmost, second or third dorsal radioles (spiraled); dorsal margins of collar fused to faecal groove; thoracic chaetae Type B; companion chaetae with teardrop and sickle-shaped membranes; abdominal chaetae narrowly hooded.

Description. Branchial crown longer than thorax with 33–34 pairs of radioles (20 pairs in syntype). Radioles with 4–6 purple bands distributed over outer and lateral radiole margins and adjacent pinnules. Outer surfaces of radioles quadrangular basally, rounded distally. Sub-distal spiraled compound eyes, present in dorsalmost radiolar pair ( Figs 24G , 25F ), sometimes also in the second ( Figs 24H , 25G ) or third dorsalmost radiolar pairs ( Figs 24I , 25H ). All radioles with short tips. Dorsal collar margins rounded posteriorly, fused to faecal groove, forming narrow gap ( Fig. 24B ). Dorsal lappets absent. Dorsal pockets well developed, U-shaped ( Figs 24B , 25C ). Lateral collar margins not covering the bases of radioles ( Figs 24B–C , 25A–B ). Ventral rounded lappets, not overlapping ( Figs 24A, D , 25A ). Anterior peristomial ring exposed dorsally between dorsal pockets ( Fig. 24B ). Dorsal lips erect, triangular, long, with mid-rib and dorsal pinnular appendages ( Fig. 25E ). Ventral lips rounded with ventral parallel lamellae well developed, completely concealed by ventral collar margin ( Fig. 24D ). Ventral sacs present ( Fig. 24D ). Caruncle absent. Keel unknown. Total thorax-abdomen length 46–134 mm (57 mm in syntype), maximum width 2–6 mm throughout most of thorax (3.5 mm in syntype). Six-10 thoracic chaetigers (8 in syntype). Thoracic tori longest on chaetigers 2–3. Tori in chaetigers 2–3 occupy the entire distance between notopodia and ventral shield margins ( Fig. 24A, C, E ), contacting shields. Thoracic fascicles ( Fig. 24F ) with superior group of elongate, narrowly hooded chaetae; and inferior group of chaetae Type B ( Fig. 28F ). Thoracic uncini with crest surmounted by 9–10 rows of numerous minute teeth, handles 2x length of main fang and extending beyond the base of shaft of companion chaetae ( Fig. 24I ). Companion chaetae with teardrop and sickle-shaped membranes within the same torus ( Fig. 24I , 29F ). Abdomen with 80–144 chaetigers (59 in syntype but it is incomplete). Abdominal chaetae narrowly hooded ( Fig. 28H ). Chaetae from posterior abdomen twice longer than those in anterior abdomen. Abdominal uncini with main fang surmounted by 7–8 rows of numerous minute teeth ( Fig. 25K ). Pygidium rounded. Soft tubes with fine sand grains, some covered with sponges, small anemones and calcareous algae.

GAMETES: Sperm in posterior abdomen with a rounded nucleus, small acrosome, two rounded mitochondria and a long flagellum ( Fig. 25J ).

Remarks. In this study, the synonymies of M. splendidum with M. disparoculatum by Hartman (1956), and of M. splendidum with M. anoculata ( Moore, 1905) by Hartman (1959) were corroborated based on examination of type material. Based on comparison of figures of M. splendidum and M. burrardum ( Berkeley, 1930) , Knight-Jones (1997) suggested a new synonymy for these two species. In this study, examination of holotype and paratypes of M. burrardum confirms the synonymy suggested by Knight-Jones (1997).

Rioja (1947: 214–215) recorded M. mushaense Gravier from La Paz (Baja California Sur); later in 1962 he corrected this identification to M. splendidum and recorded some specimens from Macapule (Sinaloa) and Salina Cruz (Oaxaca). Re-examination of Rioja’s material was not possible since its collection is lost.

Megalomma splendidum and M. inflata have spiraled eyes in 1–3 dorsalmost radiolar pairs; but the ventral lappets are rounded and as long as the ventral shield of collar in M. splendidum (triangular, longer than the ventral shield of collar in M. inflata ); the length of thoracic torus in chaetigers 2–3 occupy the entire distance between notopodium and ventral shield margins (occupying ¾ in M. inflata ) and all ventral shields are in contact with tori (separated from tori in M. inflata ).

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 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 24. Megalomma splendidum (Moore, 1905). A) Body, anterior end, ventro-lateral view; B) anterior end, dorsal view; C) same, lateral view; D) collar, ventral view showing the parallel lamellae as indicated with arrows; E) thoracic torus and chaetigers; F) thoracic chaetigers; G–H) eyes from dorsalmost radioles; I) eye from 2nd dorsalmost radiole; J) abdominal chaetiger. A–J) Specimens from British Columbia, Canada, LACM, 003466. Abbreviation: apr anterior peristomial ring. Scale bars: A–B) 2 mm; C–F) 1 mm; G–J) 0.5 mm.

FIGURE 25. Megalomma splendidum (Moore, 1905). A–B) Thorax, lateral views; C) thorax, dorsal view; D) thorax, ventral view; E) dorsal and ventral lips; F–H) eyes from dorsal radioles; I) thoracic uncini and companion chaeta; J) spermatozoon; K) abdominal uncinus. A–K) Specimens from British Columbia, Canada, LACM, 003466. Abbreviations: dl dorsal lip; vl ventral lip. Scale bars: A–C) 2 mm; D–E) 1 mm; F–H) 0.5 mm; I, K) 40 µm; J) not scaled.

FIGURE 26. Megalomma georgiense n. sp. A) Thorax, dorsal view; B–C) same, ventral views; D) dorsalmost radiolar eye; F) eye and spot of a lateral radiole; G) eye and spot of a ventral radiole; H) thoracic paleate chaetae; I) thoracic narrowly hooded chaetae; J) abdominal parapodium; K) thoracic uncini; L) abdominal uncini. A–B, D–L) Holotype from Georgia, USNM, 061328; C) paratype, USNM, 061328. Scale bars: A–C) 1 mm; D–F) 0.3 mm; H–L) 0.02 mm.

FIGURE 27. Megalomma sp. A) Collar dorsal view; B) collar, ventral view; C) thoracic chaetigers; D) dorsalmost radiolar eye; E) eye from a lateral radiole; F) eye from a ventral radiole. A–F) Specimen from New Zealand, USNM, 300653. Scale bars: A–B) 1 mm; C) 0.5 mm; D–F) 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.