Branchiomma nigromaculatum ( Baird, 1865 )

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 : 7-13

Branchiomma nigromaculatum ( Baird, 1865)

Figures 1A–H, 2A–H, 9A–B, 10A–B, 11A

Sabella crispa Krøyer, 1856: 28 , Antilles.

Sabella nigro –maculata Baird, 1865: 159, pl. V, figs 5–6, Saint–Vincent. Reversal of priority of this name over Sabella crispa is discussed in remarks.

Dasychone nigromaculata .— McIntosh, 1885: 503–504, pl. 31A, figs 4–6; pl. 39A, fig. 6; pl. 53, fig. 5, Saint–Thomas.

Dasychone ponce Treadwell, 1901: 209 , figs 76–78, Playa de Ponce, Puerto Rico.

Branchiomma nigromaculatum .— San Martín et al. 1994: 555, Cuba.— Knight–Jones, 1994: 192 (list of valid species of Branchiomma and synonyms).

Material examined

Type material: Sabella lynceus Krøyer, 1856 , type [ ZMUC, PK­J]. Sabella nigro ­ maculata Baird, 1865, syntypes [ NHML 1839.12.27, 16–18]; lectotype [ NHML 1839.12.27, 16, PK­J, MAT­H] Nomen protectum, Saint­Vincent, West Indies, Rev. Coll. Landstone Guilding; paralectotype [1839.12.27.17]; third syntype [ NHML 1839.12.27.18] identified as Bispira melanostigma ( PK­J). Sabella crispa Krøyer, 1856 , syntypes [ ZMUC, PK­J]. Dasychone ponce Treadwell, 1901 , holotype [ USNM 16195, PK­J] Coll. 1898–99, Playa de Ponce, Puerto Rico. Dasychone corallifera Ehlers, 1913 , type [ ZMHUB 5921, PK­J].

Non­type material: Dasychone nigromaculata .— West Indies, Saint­Thomas, McIntosh [ NHML 1921.5. 14339]. Cape Verde Islands [ MNHNP, A311 and NHML, 1924.6.13.21–24 as Sabellidae , PK­J]. Cuba San Martín et al. 1994: 555 ( PK­J). New material ( MAT­H): Florida [ UMML] Sunshine Pl. Coral Gables, Apr. 12, 1959 (3). Gulf of Mexico [ ECOSUR] La Galleguilla, Veracruz, Coll. M. A. Tovar, May 12, 2001, 1.5 m (1). Mexican Caribbean [ ECOSUR] Isla Mujeres, Bajo Pepito, 21° 13’ 39.7’’ N, 86° 43’ 53.5’’ W, in Udotea flabellum, Coll. M. Díaz, Feb. 5, 1997, 1 m (13); in Stytopodium zonata (7); in Lobophora variegata (16); in Udotea sp. March 1997 (5); Apr. 1997 (14); in Halimeda incrassata , June 1997 (24); July 1997 (21); Oct. 1997 (38). Holbox, 21° 31’ 24’’ N, 87° 22’ 42’’ W, Coll. S. I. Salazar, May 4, 2000, 1 m (2). Isla Contoy, Camping, 21° 30’ 8.4’’ N, 86° 47’ 45.3’’ W, Coll. J. R. Bastida & S. I. Salazar, Feb. 22, 1999, 1 m (1). Panama [ ECOSUR] Club Nautico, Colon, 09° 21.8’ N, 79° 53.7’ W, Coll. S. I. Salazar, June 3, 2002, 1 m (6). Fuerte Sherman, Colon, 09° 33.2’ N, 79° 39.6’ W, Coll. S. I. Salazar, June 2, 2002, 1 m (6). British Virgin Islands [ LACM­AHF] Guana, Bigelow Beach, Coll. L. Harris, Nov. 7, 2000, 1 m (2); White Bay, Sta. 58, Vc 0554, Coll. K. Fitzhugh, Nov. 7, 2000 (2); Beef Island, Trellis Bay, Sta. 59, BVI­00, Coll. L. Harris, Nov. 7, 2000 (4); North Beach, Sta. 76Ba, Vc 1170, Coll. T. Zimmerman, J. Martin, T. Hendler & R. Wear, July 18, 2000 (1). Lesser Antilles [ UMML] R / V Pillsbury, Cruise 6907, Antigua, Sta. 967, 17° 16’ N, 62° 02’ W, July 20, 22 m. [ ZMA] V. Pol. 1540 B, Antigua, Dickinson Bay N, July 26, 1967, eroded Thalassia sp. flat, 1 m (1). V. Pol. 0068.01, Curaçao, Spaansche Water, Coll. Dr. C. J. van der Horst, Apr. 3, 1920 (1); Apr. 8, 1920, mangrove roots (1); Apr. 13, 1920 in Porites porites (1); Apr. 29, 1920 (3); May 25, 1920 (7); Spaansche Laven, Caracasbaai in Boca Labadero, Coll. C. J. van der Horst (1).

Description

The following redescription is based on new material with first data in parentheses referring to the lectotype, the second to the paralectotype.

Specimens fairly large and plump (Figs 1A–B), body without crown 34–43 mm (42, 35) long, thorax 6 mm long (5, 4.5), 7 mm wide (7, 7). Body pink with numerous and irregular dark spots on the dorsal and ventral surfaces (Figs 1A–B, G–H), larger in thorax, especially on dorsal surface. Interramal dark spots, larger on first thoracic segments and smaller in posterior region. Radiolar crown 16–18 mm (18, 16) long (half body length, Fig. 1B), united at the base by short web or membrane, 3.2 mm long ( Fig. 2B ). Radiolar base with longitudinal bands of diffuse purple spots, below web (Fig. 1G). Radioles, 46 pairs (44, 40), with stylodes and dark brown bands alternating with bands of white and orange; five or six ventralmost radioles on each side without stylodes, arising from inrolled parts of crown basis; rachis with segmented appearance (regular obtuse indentations, Fig. 2A ), and pigmented bands extending inwards towards pinnular tips, each band occupying space of 11 pinnules. Radioles with apinnulate tips, as long as equivalent space of six pinnules. Basal stylode unpaired, small, sub­digitiform, located between the bases of two adjacent radioles ( Fig. 2B ), width one quarter of the rachis width. Stylodes: 19 pairs [s, s, s, s, s, s, M, s, s, s, s, s, M, s, s, s, s, s, s]; macrostylode pairs only twice as long as their neighbouring pairs, flanking median area of radiole (Fig. 1E) and within white bands. Small stylodes sub­digitiform (Figs 1C–F, 9A), those from basal region of radiole one quarter of rachis width ( Fig. 2B ); macrostylodes from median region more flat and a half of rachis width ( Fig. 9B ). Eyes paired compound and small, one each side of rachis, lenses sub­conical, sloughed in lectotype; those of median and distal region surrounded by an accumulation of pigment cells ( Fig. 2A ). Eyes not present between last five pairs of stylodes. Dorsal lips long, one half length of radioles, triangular with distinct longitudinal ridge (mid­rib); transverse section of dorsal lips showing numerous supporting cells of radiolar appendage (mid­rib), flanked by lamellae with blood vessels, thick fibrous connective tissue, and without surrounding sheath ( Fig. 2C ). Midline faecal groove deep on first segment forming mounds each side, collar well separated dorsally (Fig. 1H), lateral collar margins transverse to body axis covering junction between crown and body (Fig. 1A). Ventral lappets (with purple spots) sub­triangular with round apices, nearly reaching the posterior margin of the first ventral shield, not overlapping medially when reflexed (Fig. 1G). Thorax with eight segments (7, 8). Thoracic tori extending to sides of brown trapezoidal ventral shields, latter three times wider than long (Fig. 1G). Collar chaetae slender, weakly geniculate arranged in compact fascicles. Thoracic notochaetae arranged within each fascicle in irregular oblique rows, two oblique groups of superior and inferior chaetae ( Fig. 10A ); each superior chaeta slender, weakly geniculate, knee region slightly wider than shaft ( Figs 2E–F ); inferior chaetae with knee up to twice as wide as shaft ( Figs 2G–H ). Avicular uncini with the crest surmounted by one row of teeth (side view) occupying one quarter of the crest length ( Fig. 2D ), with three or four teeth ( Fig. 11A ), with short, curved manubrium ( Fig. 2D ). Abdomen with 67–124 segments (84, 79). Tori smaller than those in thorax. Most fascicles of abdominal chaetae forming compact tufts ( Fig. 10B ), outer chaetae geniculate, arranged in thick C­shaped arc around a cluster of capillary chaetae (Fig. 1A); number of chaetae per fascicle decreases gradually towards posterior. Abdominal uncini with short straight manubrium. Faecal groove passes around right side of body from the last thoracic segment to second segment of ventral abdomen (Fig. 1G) and on to bilobed pygidium. Tubes made of dried mucus and fine sand.

Variation

San Martín et al. (1994) studied B. nigromaculatum from Cuba and found specimens with four thoracic segments. In this study, some specimens from Isla Mujeres and one from Cape Verde Islands have only five thoracic segments, probably a consequence of imperfect regeneration after damage rather than scissiparity as in B. curtum ( Ehlers, 1907, see below). Scissiparity has not been found in B. nigromaculatum or any other large sabellid species.

The presence of a smaller number of thoracic segments is, therefore, relatively unimportant, but the size and shape of stylodes, numbers of thoracic uncinal crest teeth (in side view), rows of such teeth as a proportion of the main fang and the shape of ventral collar lappets are stable and useful characters ( Table 1) in the diagnoses of Branchiomma species. The number of lenses per eye shows a tendency to diminish gradually from the median radiolar region both towards the base and towards the tip. Specimens can lose radiolar eyes and body spot patterns due to sloughing after imperfect fixation and preservation, but the random spot patterns retained on the bodies of the lectotype, paralectotype and those of B. crispum are typical of specimens examined from the Mexican Caribbean, Florida, Guana, and Panama ( MAT­H). Only B. nigromaculatum of the species included in this study has rachids with regular indentations, giving a segmented appearance ( Fig. 2A ), but internally the radioles are not segmented.

Remarks

Knight­Jones (1994: 192) noted that B. nigromaculatum Baird (1865) was conspecific with Sabella crispum ( Krøyer, 1856) . Although Sabella crispum has date priority over B. nigromaculatum , the name has not been used since its original description except by Hartman (1959: 559), who regarded it as indeterminable. Conversely the name nigromaculatum has been in frequent use since its inception and is the name used by most museum curators. Therefore, to conserve the name nigromaculatum the precedence of Sabella crispum is reversed and S. crispum becomes a nomen oblitum (Art. 23, Sect. 9, International Code of Zoological Nomenclature, 2000).

Baird’s (1865: 159) description for B. nigromaculatum is brief, but one whole specimen, now designated the lectotype, is well illustrated and has seven thoracic segments, whereas a second syntype, now a paralectotype, has nine thoracic segments, perhaps due to disproportionate regeneration after predation, but is otherwise the same as the lectotype. Baird’s detailed figure of a radiole in lateral view, however, is odd as the base of the radiole is at the top and the stylodes therefore point the wrong way. Baird also stated “… on the rachis there are at regular distances about twenty very short filaments set in pairs. Near the base of the filament spring a pair longer and broader, and near to the middle of its length another pair of the same kind”. It is likely that when Baird wrote that, he was looking at the upside­down figure of the radiole, which may have been drawn by someone else. A radiole from the lectotype is figured here (Fig. 1C) with inserts showing detail and position of the two pairs of macrostylodes relative to the whole radiole. To show the gradation of pinnule length, only four pinnules are fully figured. The eyes can be identified only as scars, due to some sloughing of the epithelium, therefore a compound eye is illustrated ( Fig. 2A ) from a recently­collected specimen of B. nigromaculatum . Also Baird’s type material ( NHML) includes a slide of chaetae labelled “schizosyntype Dasychone nigromaculata ” but as more than one uncinus has crest teeth in two distinct rows, this slide cannot have been taken from a specimen of B. nigromaculatum , which has only one row of teeth, appearing as a single tooth in side view ( Fig. 2D ).

FIGURE 1. Branchiomma nigromaculatum lectotype (A, G, H) and paralectotype (B–F): A–B) whole worm in lateral and ventral views respectively; C–F) third dorsal left radiole; G) thorax and anterior abdomen in ventral view; H) anterior thorax in dorsal view. Scale bars: A–B 6.5 mm, C 1 mm, D–F 0.5 mm, G–H 2 mm.

McIntosh (1885) recorded B. nigromaculatum from Saint­Thomas. His ventral figure of anterior body and crown is typical of Baird’s material, as is the side view of an uncinal crest showing one row of teeth. He figured in his pl. 39A, fig. 6 part of a radiole with a series of five evenly short stylodes, but not the part of the radiole where the few slightly larger pairs of macrostylodes were showing.

The holotype of Dasychone ponce Treadwell (1901) is conspecific with B. nigromaculatum ( Knight­Jones, 1994: 192) although it is not the specimen that Treadwell figured. Johansson (1927) tentatively, but wrongly synonymised Dasychone conspersa Ehlers (1887) and Sabella lynceus Krøyer (1856) with Branchiomma nigromaculatum . Branchiomma conspersum , however, is a good species (see below) and B. lynceus seems to be (more study needed) a junior synonym of Branchiomma bombyx ( Dalyell, 1853 as Amphitrite ). Branchiomma bombyx is distinct from B. nigromaculatum and other species described here in having the dorsal collar ‘margins’ fused to the sides of the midline faecal groove ( Knight­Jones, 1990, fig. 6.19 and Knight­Jones et al. 1991, fig. 6 A–D) as in Group A (see introduction). The location was merely West Indies. Branchiomma bombyx has not otherwise been recorded from the Caribbean region.

Day’s (1967) figure of B. nigromaculatum from South Africa, with very enlarged basal stylodes, is unlike those of B. nigromaculatum and according to material from Saint­ James, East coast of South Africa ( PK­J, pers. obs) it is likely to be B. coralliferum ( Ehlers, 1913) , a well figured species which Day (1955) wrongly synonymised with B. nigromaculatum .

Distribution

The present studies show that this species is widely distributed in the Caribbean Sea and thus the records from Curaçao of Augener (1927), Veracruz of Rioja (1958), Jamaica of Marsden (1960), Colombia of Dueñas (1981), Venezuela of Rodríguez (1979) and Rodríguez­Gómez (1988), Cuba of Ibarzábal, (1989, 1997) and Bahamas of Long & Zottoli (1997) could well be B. nigromaculatum . Material from the Cape Verde Islands [ NHML and MNHNP] agrees well with B. nigromaculatum . However, B. nigromaculatum probably does not occur in the cooler waters of South Africa, as Day’s (1967) figure of B. nigromaculatum is doubtless Branchiomma coralliferum Ehlers, 1913 . The Hawaiian record of B. nigromaculatum ( Bailey­Brock, 1987) seems to be B. japonicum ( McIntosh, 1885) , (more study needed, PK­J pers. obs).

Figures

FIGURE 2. Branchiomma nigromaculatum Panama material (A–C) and lectotype (D–H): A) dorsal right radiole in lateral view; B) base of the branchial crown; C) dorsal lip in transverse section (bv blood vessels, dl dorsal lip lamellae, c coelom, rs radiolar skeleton, ra radiolar appendage); D) thoracic uncinus; E–F) superior thoracic chaetae; G–H) inferior thoracic chaetae. Scale bars: A 0.3 mm, B 0.25 mm, C 0.12 mm, D 30 m, E–F 125 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.