Branchiomma curtum ( Ehlers, 1901a )

Tovar-Hernández, María Ana & Knight-Jones, Phyllis, 2006, Species of Branchiomma (Polychaeta: Sabellidae) from the Caribbean Sea and Pacific coast of Panama, Zootaxa 1189 (1), pp. 1-37 : 20-24

Branchiomma curtum ( Ehlers, 1901a)

Figures 5A–G , 8D–E , 9H–J , 10F , 11E

Dasychone curta Ehlers, 1901a: 216–218 , pl. 25, figs 10–13, Masatierra, Juan Fernandez Is. — Ehlers, 1901b: 268 Masatierra, Juan Fernandez Is. — Ehlers, 1907: 28, New Zealand.

Dasychone cingulata (Grube) var. curta Ehlers. — Augener, 1922a: 211, Masatierra, Juan Fernandez Is. — Benham, 1927: 137–139, pl. 4, figs 124–125, Spirits Bay, and Otago Harbour, New Zealand.

Material examined

Type material: Dasychone curta Ehlers, 1901a , 5 syntypes [ ZMHUB 376 ] Masatierra , Juan Fernandez Is, Chile .

Non­type material: Chile, Masatierra, Juan Fernandez Is [ ZMUH V.9249; NMG Poly.1522, 1532; NRS UP 2286, PK­J]. New Zealand, Spirits Bay, Sta. 134, 32.18 m [ NHML 1928.2.29.100, Benham, 1927 as Dasychone cingulata var. curta , PK­J], Quarantine Is., Otago Harbour, littoral [ OMD A99.192, Benham, 1927, as D. curta ] and PK­J collection: littoral and shallow sublittoral, Aquarium Point, Portobello, Otago peninsula; Akaroa, Banks Peninsula and Point Kean, Kaikoura. Cape Verde Islands, Saint­Vincent [ Sabellidae, Crossland collection, BMNH 1924.6.13.165 (37), PK­J]. New material [ MAT­H]: Mexican Caribbean [ ECOSUR] Isla Mujeres, Bajo Pepito, 21° 13’ 39.7’’ N, 86° 43’ 53.5’’ W, Coll. M. Díaz, Feb. 5, 1997, 1 m (100), in Stypopodium zonata (41), in Halimeda incrasata (32), in Udotea flabellum (5), in Lobophora variegata (166); March 1997 (29), in Udotea (23); Apr. 1997 (95); May 1997, in Sargassum vulgaris (1); June 1997 (41); July 1997 (140); Oct. 1997 (239). Akumal, Coll. S. I. Salazar, Feb. 26, 1986, 1 m (18); Contoy, Punta Sur, 21° 27’ 33’’ N, 86° 46’ 06’’ W, Coll. M. A. Tovar, March 2, 2001, 1 m (11); Camping, 21° 30’ 8.4’’ N, 86° 47’ 45.3’’ W, J. R. Bastida & S. I. Salazar, Feb. 22, 1999, 1 m (1); dock, Coll. J. R. Bastida & S. I. Salazar, Feb. 21, 1999, 1 m (1); Cozumel, Playa Azul, 20° 32’ 07’’ N, 86° 56’ 10’’ W, Coll. M. A. Tovar, March 25, 2000, 4 m (2); Holbox, 21° 31’ 24’’ N, 87° 22’ 42’’ W, Coll. J. R. Bastida, May 4, 2000, 1 m (11); Hualalpich, Bahía Ascención, 19° 59’ 37.9’’ N, 87° 27’ 52’’ W, Coll. E. Donath, Feb. 27, 1986 (1), Coll. S. I. Salazar, June 19, 1986, 1 m (1); Xoquem, Coll. E. Donath, Feb. 27, 1986 (1). [ LACM­AHF] Isla Contoy, Punta Sur, 21° 27’ 33’’ N, 86° 46’ 06’’ W, Coll. L. Harris, March 2, 2001, coralline turf. Isla Contoy, Punta Sur, 21° 27’ 33’’ N, 86° 46’ 06’’ W, LH01­676 (2), Coll. L. Harris, March 2, 2001, coralline turf, mostly Amphiroa, Gelidium. Isla Contoy, Punta Sur, 21° 27’ 33’’ N, 86° 46’ 06’’ W, LH01­612 (1), Coll. L. Harris, March 1, 2001, rock and sand under rock. Isla Contoy, Punta Sur, 21° 27’ 33’’ N, 86° 46’ 06’’ W, LH01­664 (1), Coll. L. Harris, March 2, 2001, green felt (not codium) on coral rubble, rock, 0.3 m. LH01­557, Isla Contoy, Pelicanos, 21° 30’ 34’’ N, 86° 47’ 47’’ W, Coll. L. Harris, March 1, 2001, Ulva , Caulerpa, Dictyota on holdfasts of Caulerpa ; bottom of corals, rubble and rock, 0.9–1.8 m (11). LH01­590, Isla Contoy, Pelicanos, 21° 30’ 34’’ N, 86° 47’ 47’’ W, Coll. L. Harris, March 1, 2001 (23). LH01­687, Isla Contoy, Punta Sur, 21° 27’ 33’’ N, 86° 46’ 06’’ W, Coll. L. Harris, March 2, 2001, in Halimeda (6). Majahual, 18° 40’ 9.6’’ N, 87° 43’ 01.4’’ W, LH01­501 (1), Coll. L. Harris, Feb. 25, 2001, coral rubble.

Description

The following description includes dimension data of one specimen from Mexican Caribbean with the range of data given in parenthesis.

Body small, 8 mm long (3.12–12.5), with thorax 2.25 mm long (1.5–3.12) and 1.87 mm wide (1.37–2.75). Body green, without spots except for interramal dark eyespots; eyespots largest on first thoracic segments and smaller in posterior region ( Fig. 5A ). Radiolar crown long (half of body length) ( Figs 8D–E ), 4 mm length (3–9.25), united at base by short web or membrane (0.5 mm), interradiolar spots dark brown. Radioles, 9 pairs (7–9), with diffuse longitudinal bands of dark brown spots below the axils of radiole pairs. Radioles with apinnulate tips, as long as equivalent space of eight pinnules. Basal stylode unpaired, small, digitiform; stylode width one quarter of the rachis width. Stylodes: 4 pairs [s, s, s, s], all digitiform ( Figs 8D–E , 9H–J ). Eyes small with lenses coneshaped; eyes not present between last two pairs of stylodes. Dorsal lips olive green, short, one­quarter length of radioles, triangular with a distinct longitudinal ridge (mid­rib). Midline faecal groove deep on first segment forming mounds each side; collar well separated dorsally ( Fig. 8E ), lateral collar margins transverse to body axis covering junction between crown and body ( Fig. 5A ); ventral lappets short, rounded, slightly overlapping ( Figs 5A , 8D ). Thorax with five segments (4–6). Thoracic tori extending to sides of ventral shields ( Fig. 8D ). Collar chaetae slender, weakly geniculate, arranged in compact fascicles with 6–8 chaetae. Thoracic notochaetae arranged within each fascicle in irregular, oblique rows of superior and inferior chaetae ( Fig. 10F ); each superior chaeta slender, weakly geniculate, knee region slightly wider than shaft ( Fig. 5D–E ); inferior chaetae with knee up to twice as wide as shaft ( Fig. 5F ). Avicular uncini with the crest surmounted by three rows of teeth (side view), occupying ½ of the crest, with 3 or 4 teeth in anteriormost and following row and 2 to 3 vestigial teeth beyond that ( Fig. 11E ); short manubrium ( Fig. 5B ). Abdomen with 15 segments (14–36). Tori smaller than those in thorax (less than one half). Most fascicles of abdominal chaetae forming compact tufts, with outer chaetae geniculate, and arranged in a thick C­shaped arc around a cluster of capillary chaetae ( Fig. 5G ); number of chaetae per fascicle decreases gradually towards posterior. Abdominal uncini with short straight manubrium ( Fig. 5C ). Posterior end with a terminal depression along 13–15 segments. Faecal groove passes around right side of body from the last thoracic segment to second segment of ventral abdomen and on to bilobed pygidium.

Remarks

The specimens from Isla Mujeres ( Mexico) were collected among various algae ( Halimeda incrassata , Lobophora variegata , Stypopodium zonata and Udotea sp. ) from February to October 1997. In one sample, specimens of B. bairdi , B. nigromaculatum and B. curtum are all present, but each species shows a distinctive colour pattern: B. bairdi has a dark brown body (without pigment blotches) and dark brown crown; B. nigromaculatum has purple body blotches, a purple crown base and alternating purple bands around the radioles, and big interramal spots; whilst B. curtum has a green body without spots (except for interramal eyespots), a green crown base, and radioles with green bands.

The SEMs of two thoracic uncini from Mexican material ( Fig. 11E ) have been compared with similar SEMs of Branchiomma curtum from Juan Fernandez Island, Chile, New Zealand and the Cape Verde Is and found to be remarkably similar. The number of teeth are often specific in Branchiomma species that do not have numerous crest teeth on their uncini, but one uncinus differs from the normal complement with only three teeth on the anterior row ( Fig. 11E left hand uncinus). Otherwise the arrangement of thoracic uncinal crest teeth and the general morphology is the same as specimens from other locations. It was noticed that Branchiomma curtum from the Mexican Caribbean was found in gregarious clumps [ MAT­H], which is typical of a scissiparous species. Tubes from such clumps at Akaroa, New Zealand contained many developing scissiparous offspring posterior to the parents. The posteriormost parts of the abdomen separate into a few multi­segment fragments, and anteriorly each fascicle is gradually replaced by chaetae of thoracic type. Such regeneration is usually imperfect, producing individuals with fewer thoracic segments than the usual eight. If the posterior parts of the Mexican tubes had been examined, it is likely that budding and regenerating fragments (of abdominal origin) could have been found. There has been no suggestion of scissiparity in the other species described here.

Scissiparity in Branchiomma curtum has been previously noted by Ehlers (1907, as Dasychone curta ), Augener (1922a, 1926) and Benham (1927), both as Dasychone cingulata var curta . Scissiparity also occurs in species of other genera, e.g., Sabella discifera Grube, 1874 ( Knight­Jones & Bowden, 1984 as Sabella variabilis ), Pseudobranchiomma punctata ( Treadwell, 1906) , P. minima Nogueira & Knight­Jones (2002) , P. perkinsi and P. tarantoensis ( Knight­Jones & Giangrande, 2003) .

Distribution Chile, New Zealand, Cape Verde Islands and Mexican Caribbean.

Figures

FIGURE 5. Branchiomma curtum Mexican material: A) body in lateral view; B) thoracic uncinus; C) abdominal uncinus; D) superior collar chaeta; E) superior thoracic chaetae; F) inferior thoracic chaeta; G) superior abdominal chaeta. Scale bars: A 1 mm, B–C 10 m, D–G 0.04 mm.

FIGURE 8. Anterior thorax in Branchiomma coheni, B. iliffei, and B. curtum. A) B. coheni sp. nov. anterior thorax and lower crown in ventral view; B) B. iliffei sp. nov. collar in dorsal view; C) B. iliffei anterior thorax and lower crown in ventral view; D) B. curtum whole body in ventral view; E) B. curtum thorax and crown in dorsal view. Scale bars: A 285 m, B 200 m, C 1 mm, D–E 250 m.

FIGURE 9. Stylodes of Branchiomma nigromaculatum, B. bairdi, B. coheni, B. curtum, and B. iliffei ECOSUR specimens, mounted in gold for SEM. A–B) B. nigromaculatum stylodes from basal region and medial region; C–D) B. bairdi stylodes from basal region and medial region; E–G) B. coheni sp. nov. unpaired stylodes from base of radiole, paired stylodes from medial region, and from medial to distal region; H, J) B. curtum stylodes from basal region and, medial region; K–M) B. iliffei sp. nov. stylodes from basal region, medial region, and distal region. Scale bars: A, K 50

FIGURE 10. Parapodia of Branchiomma nigromaculatum, B. bairdi, B. coheni, B. conspersum, B. curtum, and B. iliffei ECOSUR specimens, mounted in gold for SEM. A–B) B. nigromaculatum thoracic and abdominal parapodia; C) B. bairdi thoracic parapodium; D) B. coheni sp. nov. thoracic parapodium; E) B. conspersum thoracic parapodium; F) B. curtum thoracic parapodia; G) B. iliffei sp. nov. abdominal parapodium. Scale bars: A 125 m, B 67 m, C, E 83 m, D 50 m, F 33 m, G 40 m.

FIGURE 11. Thoracic uncini of Branchiomma nigromaculatum, B. bairdi, B. coheni, B. conspersum, B. curtum, and B. iliffei ECOSUR specimens, mounted in gold for SEM. A) B. nigromaculatum; B) B. bairdi; C) B. coheni sp. nov; D) B. conspersum; E) B. curtum; F) B. iliffei sp. nov. Scale bars: A 6 m, B–C 10 m, D 5 m, E 5 m, F 4 m.