Megalomma coloratum ( Chamberlin, 1919 )

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: 25-31

publication ID

http://doi.org/ 10.11646/zootaxa.2861.1.1

persistent identifier

http://treatment.plazi.org/id/03CF87C4-2966-127C-FF5C-5ED8FC7E4310

treatment provided by

Felipe

scientific name

Megalomma coloratum ( Chamberlin, 1919 )
status

 

Megalomma coloratum ( Chamberlin, 1919)  

Figures 7A–L View FIGURE 7 , 8A View FIGURE 8 , 9A–S View FIGURE 9 , 10A–B View FIGURE 10 , 28B View FIGURE 28 , 29B View FIGURE 29

Potamilla clara Chamberlin, 1919: 20   .

Potamilla colorata Chamberlin, 1919: 21   .

Megalomma coloratum   .— Knight-Jones, 1997: 318, Figs 2M–T View FIGURE 2 .— Tovar-Hernández et al. 2009: 326–327, Figs 2c, g View FIGURE 2 , 3e–f View FIGURE 3 , 4f– g View FIGURE 4 .

Type material examined. [ MCZ] 2173, holotype of Potamilla colorata Chamberlin, 1919   , California, Laguna Beach, low tide, Coll. W. A. Hilton, incomplete (last posterior abdominal segments are missing). [ MCZ] 2171   , holotype of Potamilla clara Chamberlin, 1919   ( Fig. 15C, E, I View FIGURE 15 ), California, Laguna Beach, low tide, Coll. W. A. Hilton, complete but broken in anterior abdomen   .

Additional material examined. [ ECOSUR] Baja California Norte, México, Ensenada, Playa las Rosas, July 30, 1987, Coll. SISV (11 specs, one female). Villa las Rosas, March 06, 2004 (2 specs). Bahía de Todos Santos, Coll. SISV (3 specs). Baja California Sur, México, La Paz, CICIMAR, March 01, 2004, Coll. PSS, 50 cm, on basaltic rock (3 specs). Sinaloa, México, Mazatlán, Playa Cerritos, Facultad de Ciencias del Mar, February 27, 2004, on rock oyster covered with red and green algae, 4 m, Coll. Esteban (7 specs, 1 juvenile, one female); February 22, 2004, 12 m (10 specs). Nayarit, México, Islas Marías, November 02, 1979, Coll. SISV (1 spec.). Nayarit, North of Bucerias, March 09, 2008, 20° 45’ 44.7’’ N 105° 21’ 28.6’’W, Coll PSS, in oyster, OH-P 0293 (1 spec). Nayarit, La Cruz de Huanacaxtle, Vallarta Garden, February 23, 2008, 20° 45’ 4.3’’ N, 105° 22’ 25.7’’ W, Coll PSS, in coralline rock, OH-P 0294 (1 spec). Nayarit, La Cruz de Huanacaxtle, Vallarta Garden, February 23, 2008, 20° 45’ 4.3’’ N, 105° 22’ 25.7’’ W, Coll PSS, in coralline rock, OH-P 0295 (1 spec). Nayarit, North of Bucerias, March 09, 2008, 20° 45’ 44.7’’ N, 105° 21’ 28.6’’ W, Coll PSS, in oyster, OH-P 0296 (1 spec). Nayarit, North of Bucerias, March 09, 2008, 20° 45’ 44.7’’ N, 105° 21’ 28.6’’ W, Coll PSS, in oyster, OH-P 0299 (1 spec). [ EMU] Baja California Sur, México, Playa el Tesoro, EMU –4464, Coll. LIB, July 17, 1996 (1 spec.). Sinaloa, México, Mazatlán port, EMU 8914–8953, 2009, on metallic buoys, 50 cm depth, Station 1: 23º 12’ 13’’ N, 106º 24’ 31.4’’ W, Sta. 1–I (1 spec.), Sta. 1– III (1 spec.), Sta. 1–IV (3 specs), Sta. 1– V (2 specs), Sta. 1– VI (5 specs), Sta. 1–VII (8 specs), Sta. 1–VIII (4 specs), Sta. 1–IX (1 spec.), Sta. 1–X (1 spec.). Station 2: 23º 12’ 13’’ N, 106º 24’ 30.1’’ W, Sta. 2–I (1 spec.), Sta. 2–II (2 specs), Sta. 2– III (8 specs), Sta. 2–IV (11 specs), Sta. 2– V (20 specs), Sta. 2–VII (2 specs). Sta. 3: 23º 11’ 48.7’’ N, 106º 24’ 31’’ W, Sta. 3–I (3 specs), Sta. 3–II (3 specs), Sta. 3–IV (7 specs), Sta. 3– V (9 specs), Sta. 3– VI (8 specs), Sta. 3–VII (14 specs), Sta. 3–VIII (3 specs), Sta. 3–IX (1 spec.), Sta. 3–X (2 spec.), Sta. 3–XII (1 spec.). Sta. 4: 23º 11’ 31.1’’ N, 106º 24’ 43.9’’ W, Sta. 4–I (1 spec.), Sta. 4–II (1 spec.), Sta. 4–IV (2 specs), Sta. 4– V (15 specs), Sta. 4– VI (1 spec.), Sta. 4–VII (4 specs). Sta. 5: 23º 11’ 8.9’’ N, 106º 24’ 55.8’’ W, Sta. 5–I (5 specs), Sta. 5–II (9 specs), Sta. 5– III (3 specs), Sta. 5–IV (1 spec.), Sta. 5– V (10 specs), Sta. 5– VI (5 spec.), Sta. 5–VII (12 specs), Sta. 5–VIII (7 specs), Sta. 5–XII (5 specs). Nayarit, México, Punta Raza, EMU –5113, Coll. LIB, April 11, 1996, coralline algae (1 spec.); EMU –5114 (1 spec.). [ LACM – AHF] California, USA, Point Dume, St. 404, POIDUM, SubID 4246, 34.00867º N, 118.79386º W, Coll. Marine Pollution Studies Lab/Moss Landing Marine Laboratories, Invasive Species Survey, July 16, 2007, low rocky intertidal, lots of Chondrachanthus, some Codium   , Ulva   , tunicates, anemones, small laminarians and coralline mats (8 specs). Point Dume, Sta. 404, MLML – 155, 1 DORG 471, 1 R –C–1, SB ¼, 0471, Coll. Marine Pollution Studies Lab/Moss Landing Marine Laboratories, Invasive Species Survey, January 22, 2005, low rocky intertidal (36 specs). Point Dume, Sta. 404, MLML –155, 1 DORG 249, SR–2, Coll. Marine Pollution Studies Lab/Moss Landing Marine Laboratories, Invasive Species Survey, April 05, 2005, 5.4 m (30 specs). Velero III, 003488, Sta. 1139–40, 33º 50’ 30’’ N, 118º 24’ 15’’ W, off Redondo Beach, 3 m, sand (1 spec.). Sinaloa, México, Mazatlán, F3363, N 15196 View Materials , n 10118, reef 3.2 km N of Mazatlán, Colls E. Yale & Dawson, June 7, 1952, among algal clumps (3 specs).

Diagnosis. Eyes in dorsalmost and fifth dorsal radioles (spherical); dorsal margin of collar fused to faecal groove; a glandular ring on segment 3; thoracic chaetae Type C; abdominal chaetae broadly hooded.

Description. Branchial crown length 2.94±0.77 mm (n = 100; 1.1– 5 mm), as long as thorax ( Figs 7A View FIGURE 7 , 8A View FIGURE 8 , 9A View FIGURE 9 ), with 15±2 pairs of radioles (n = 100; 8–21 pairs). Branchial lobes semi-circular ( Fig. 9E View FIGURE 9 ). Radiolar bases olive green. Radioles with several narrow red or purple bands distributed over outer and lateral radiole margins and adjacent pinnules, each band occupies a space of 4–6 pairs of pinnules. Outer surfaces of radioles quadrangular basally, rounded distally. Sub-distal compound eyes spherical, present in dorsalmost pair of radioles (23%, n= 100) or dorsalmost and fifth dorsal radioles (77%, n= 100) ( Figs 7G View FIGURE 7 , 9N View FIGURE 9 ). Eyes from fifth dorsalmost radiolar pair smaller than dorsalmost ones ( Figs 7H View FIGURE 7 , 9O–P View FIGURE 9 ). Dorsalmost pair of radioles rigid, erect and longer than other radioles ( Figs 7E View FIGURE 7 , 9B View FIGURE 9 ); ommatidia purple with minute small, white lens; and epithelium near to tip wider than posterior epithelium ( Fig. 9N View FIGURE 9 ). All radioles with short tips ( Fig. 7F View FIGURE 7 ). Dorsal collar margins square, fused to faecal groove, forming broad gap ( Figs 7C, E View FIGURE 7 , 9B–C View FIGURE 9 ). Dorsal lappets absent. Dorsal pockets present ( Figs 7B–C View FIGURE 7 , 9B–C View FIGURE 9 ). Epithelium of dorsal pockets translucent and very narrow, as a membrane ( Fig. 7E View FIGURE 7 ). Ventral lappets rounded, not overlapped, as long as ventral shield of collar ( Figs 7D View FIGURE 7 , 9H–I View FIGURE 9 ). Anterior peristomial ring not exposed. Lateral collar margins of collar covering base of radioles ( Figs 7B–C View FIGURE 7 , 9A View FIGURE 9 ). Mouth located in middle of anterior peristomial ring. Two small patches of nuchal organs presented near mouth and two horns of basal lateral skeleton ( Fig. 9E View FIGURE 9 ). Dorsal lips red colored, erect, triangular about 1/4 length of branchial crown, with mid-rib ( Fig. 9D View FIGURE 9 ). Dorsal pinnular appendages present. Ventral lips about one quarter the length of dorsal lips, broadly rounded ( Fig. 9D View FIGURE 9 ). Ventral sacs present. Caruncle and keel absent. Body plump, cylindrical, ( Figs 7A View FIGURE 7 , 8A View FIGURE 8 ) green olive or pale with ventral shields cream colored and white spots surrounding the lateral sides of the faecal groove and dispersing in all thoracic dorsal epithelium. A whitish glandular ring on segment 3 ( Fig. 7C View FIGURE 7 ). Total thorax-abdomen length 13.41±5.16 mm (n = 100; 4.1– 28 mm) (25 mm holotype), and maximum width 2.04±0.56 mm (n = 100; 0.8–3.8 mm) (2.2 mm holotype) throughout most of thorax. Thorax with 8±1 segments (n = 100; 4–8 segments). Thoracic tori longest on chaetigers 2–3. Tori in chaetigers 2–3 occupy the entire distance between notopodia and ventral shield margins ( Figs 7B View FIGURE 7 , 8A View FIGURE 8 ), contacting shields ( Figs 7D View FIGURE 7 , 8A View FIGURE 8 ). Notopodial fascicles with superior group of elongate, narrowly hooded chaetae ( Fig. 9J View FIGURE 9 ); an inferior group of chaetae Type C ( Figs 9K View FIGURE 9 , 28B View FIGURE 28 ). Thoracic uncini with main fang surmounted by 8–10 rows of numerous minute teeth ( Fig. 29B View FIGURE 29 ), handles 1.5x length of main fang; not extending beyond base of shaft of companion chaetae ( Fig. 9R–S View FIGURE 9 ). Companion chaetae with teardrop-shaped membranes ( Figs 9R–S View FIGURE 9 , 29B View FIGURE 29 ). Tori slightly shorter than those on chaetiger 7 ( Figs 7I View FIGURE 7 , 8A View FIGURE 8 ). Abdominal segments 42±7 (n = 100; 28–64 segments) (43 holotype). Abdominal chaetae broadly hooded ( Fig. 9L–M View FIGURE 9 ); chaetae in posterior row longer than those in anterior row. Abdominal uncini with main fang surmounted by 8–10 rows of numerous minute teeth ( Fig. 9G View FIGURE 9 ). Pygidium broadly rounded ( Figs 7J View FIGURE 7 , 8A View FIGURE 8 ), sometimes forming two or three lobes ( Fig. 7L View FIGURE 7 ). Three groups of 4–5 red pygidial eyespots, each unequalsized ( Fig. 7J–K View FIGURE 7 ). Tubes covered with fine sand grains, and brown algae incrustrating.

GAMETES: From 100 specimens selected from southern Gulf of California, 91% were sexually mature (32% males, 59% females) and 9% unripe. Gametes in mature females are distributed mostly from first abdominal chaetiger to the posterior abdomen, visible through the epithelium between notopodium and neuropodium. Ovogenesis is continuous throughout the entire year, except for November (no specimens were found) and asynchronous as indicated by change in shape (rounded to polygonal) ( Fig. 9F View FIGURE 9 ), the appearance of the cytoplasm and oocyte size: 103.8±45.27 µm (n = 72; 30–180 µm). In males, sperm is distributed from median to posterior abdomen. Sperm morphology was described in Tovar-Hernández et al. (2009). Based on branchial crown and body colour, M. coloratum   does not show sexual dimorphism.

SPECIMEN VARIATION: Among specimens from Southern Gulf of California, the number of radiolar eyes was found to vary. The most common condition is the presence of two pairs of eyes in dorsalmost and fifth dorsalmost radioles (77%, n = 100) while eyes only present in dorsalmost radioles is less common (23%, n = 100). In the phylogenetic analysis presented here, this character (character 3) was scored as state 5, i.e. eyes only in dorsalmost and fifth dorsal radioles, as this was the most common distribution.

GROWTH: The relationship between the body length (y) and the number of abdominal segments (x) is described by the power function y= 0.0086x 1.9528 (r= 0.786, p<0.001, n = 100) indicating a continuous growth in M. coloratum   ( Fig. 10A View FIGURE 10 ). Body length (x) was significantly correlated with the branchial crown length (y) and is described by the power function y= 0.6629x 0.5775 (r= 0.837, p<0.001, n = 100) ( Fig. 10B View FIGURE 10 ).

BARCODE: Nucleotide sequences between 433–616 bp of the section of COI gene used for barcoding were obtained from four specimens, two from La Cruz de Huanacaxtle, Nayarit, Mexican Pacific ( ECOSUR OH-P0294, ECOSUR OH-P0295) and two from North of Bucerias , Nayarit, Mexican Pacific ( ECOSUR OH-P0296, ECOSUR OH-P0299). The averange evolutionary divergence over the four sequence pairs was 0.9   %.

Remarks. Chamberlin in 1919 described Potamilla clara   and P. colorata   from low tide in Laguna Beach, California. Original descriptions of both species are brief, do not include diagnostic characters and lack illustrations. Hartman (1938) stated that the type of P. clara   is a Megalomma   and has affinities with M. roulei (Gravier)   . Later, in the catalogue of the polychaetes of the world, Hartman (1959) listed the type of Potamilla colorata   as Megalomma sp.   Hartman (1969) recorded M. roulei   from Corona del Mar, southern California, but her diagnosis is a translation of original description by Gravier (1908a), illustrations were redrawn from Gravier (1909) and her materials were not located at LACM in order to confirm identification. At the end of her diagnosis (pp. 710) Hartman stated that “The record from California may refer to Megalomma pigmentum   , if it is shown that the oculate radioles have short, instead of long free tips”. Later, in 1995, Knight-Jones labeled the type of P. colorata   as “this is not synonymous with M. roulei   but a good species of Megalomma   ”. Knight-Jones (1997) synonymized M. clara   with M. modestum ( de Quatrefages, 1866)   and provided a redescription for M. coloratum   . In this study, the synonymy between M. clara   with M. modestum   proposed by Knight-Jones is not supported since both species have distinguishable features (see remarks on M. modestum   ) and M. roulei   is declared as insertae sedis (see remarks on M. roulei   ). Based on examination of both types ( M. clara   and M. coloratum   ), these constitute the same species. Apparently, pigmentation was the only feature used by Chamberlin to describe the taxa as different species. Individuals of M. coloratum   from Mazatlán show some variation in body color: some bodies are olive green, others pale, and radioles have narrow red or purple bands distributed over outer and lateral radiole margins.

As stated above, original descriptions of M. clara   and M. coloratum   both are brief, do not include diagnostic characters and lack illustrations. Both species names were simultaneously published by Chamberlin (1919): M. clara   on page 20 and M. coloratum   on page 21. We follow the recommendations of article 23.9 (and subsequents) of the International Code of Zoological Nomenclature (1999) to consider M. clara   as a nomen oblitum and M. coloratum   as a nomen protectum since the last name has been widely used in the literature. Furthermore, the type material of M. coloratum   was characterized and illustrated by Knight-Jones (1997) and Tovar-Hernández et al. (2009) provided a complete description of the morphological features including some reproductive characters.

The most distinctive character separating M. coloratum   from other species from the tropical Eastern Pacific ( M. carunculata   , M. circumspectum   , M. gesae   , M. pacifici   and M. pigmentum   ) is the presence of a dorsal, broad whitish glandular ring on segment 3. On the other hand, M. cinctum   from Taiwan has two glandular rings on segments 2 and 3 respectively, but in M. cinctum   the branchial crown is shorter than the thorax (as long as thorax in M. coloratum   ) and the radiolar tips are short dorsally, increasing gradually towards ventral radioles (all short in M. coloratum   ).

The specimens reviewed here agree with the description provided by Knight-Jones (1997) for the type of M. coloratum   , described from Laguna Beach (California) except that the type has just one pair of subdistal eyes in the dorsalmost radioles. All adult specimens reviewed here, have eyes in dorsalmost and fifth dorsalmost radioles (77%, n = 100) while in juveniles, eyes are only present in dorsalmost radioles (23%, n = 100). This variation is not surprising since as Fitzhugh (2003) pointed out, there exists variation in the number of radiolar eyes in paratypes of M. cinctum   , although the most common condition is the presence of only one pair of eyes on the dorsalmost radioles. For M. interrupta, Capa and Murray (2009)   recorded the presence of eyes only in dorsalmost and lateral radioles, but the eyes in lateral radioles can be absent entirely from some specimens.

Information on the reproductive biology of species of Megalomma   is scarce, but in M. coloratum   and in M. vesiculosum   , M. bioculatum   and M. carunculata   gonochorism and gametes distributed in abdominal segments seems to be a pattern. Megalomma coloratum   is native in the Californian Province, known from Mazatlán and southern California ( USA) from intertidal and shallow waters (12 m). In the Mazatlán port ( México) it is a very common hull fouling species, found on floating docks, metal buoys, and also on rock oysters covered with red and green algae. On metal buoys it reaches densities about 4–80 ind/m 2.

MCZ

Museum of Comparative Zoology

ECOSUR

El Colegio de la Frontera Sur (Mexico)

CICIMAR

Centro Interdisciplinario de Ciencias Marinas

PSS

Paleontology and Stratigraphic Section of the Geological Institute of the Mongolian Academy of Sciences

EMU

Eastern Michigan University, T. L. Hankinson Vertebrate Museum

V

Royal British Columbia Museum - Herbarium

VI

Mykotektet, National Veterinary Institute

LACM

Natural History Museum of Los Angeles County

AHF

Allan Hancock Foundation, University of Southern California

R

Departamento de Geologia, Universidad de Chile

Kingdom

Animalia

Phylum

Arthropoda

Class

Insecta

Order

Coleoptera

Family

Carabidae

Genus

Megalomma

Loc

Megalomma coloratum ( Chamberlin, 1919 )

Tovar-Hernández, María Ana & Carrera-Parra, Luis F. 2011
2011
Loc

Megalomma coloratum

Tovar-Hernandez, M. A. & Mendez, N. & Villalobos-Guerrero, T. F. 2009: 326
2009
Loc

Potamilla clara

Chamberlin, R. V. 1919: 20
1919
Loc

Potamilla colorata

Chamberlin, R. V. 1919: 21
1919