Branchiomma bairdi ( McIntosh, 1885 )

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 : 13-17

Branchiomma bairdi ( McIntosh, 1885)

Figures 3A–D, H–K , 9C–D , 10C , 11B , with figures 3E–G representing Branchiomma sp.

A.

Dasychone bairdi McIntosh, 1885: 495–497 , pl. 30A, figs 13–15; pl. 39A, figs 2, 9, Bermuda (only two syntypes present, one is Branchiomma sp. A , and the other is here designated lectotype.— Monro 1933a: 267, Dry Tortugas, Florida.

Material examined

Type material: Dasychone bairdi McIntosh, 1885 , lectotype [ NHML 1885.12.1.391] Bermuda shore, June 1873, “Challenger” ( MAT­H & PK­J) .

Non­type material: Florida ( Monro 1933a) [ NHML 1932.12.22.91–102, PK­J] Dry Tortugas, stns 328 & 347). New material ( MAT­H): Mexican Caribbean [ ECOSUR] Rio Huach , 18° 25’ 22” N, 87° 46’ 13” W, SAT6­0398, Coll. J. Schmitter (1). Isla Contoy, Camping, 21° 30’ 8.4’’ N, 86° 47’ 45.3’’ W, Coll. M. A. Tovar, March 01, 2001, 1 m (1) ; Coll. V. Delgado , March 01, 2001, 1 m (3) ; Coll. J. R. Bastida , Feb. 21, 1999, 1 m (1) ; Feb. 22, 1999, 1 m (1) . Hualalpich, Bahía Ascención , 19° 59’ 37.9’’ N, 87° 27’ 52’’ W, Coll. M. A. Tovar, June 19, 1986, 1 m (1) . Holbox , 21° 31’ 24’’ N, 87° 22’ 42’’ W, Coll. S. I. Salazar, May 04, 2000, 1 m (12) . San Felipe , 21° 27’ N, 88° 06’’ W, Coll. J. R. Bastida & S. I. Salazar, Feb. 19, 1999, 1 m (6) . Celestún , 20° 53’ N, 90° 21’ W, Coll. J. R. Bastida & S. I. Salazar, Feb. 17, 1999, 1 m (1) . Isla Mujeres, Bajo Pepito , 21° 13’ 39.7’’ N, 86° 43’ 53.5’’ W, Coll. M. Díaz, July 1997, 1 m (42) ; Feb. 5, 1997, 1 m (1) . Cancún, Laguna Nichupté , 21° 06’ 11.6’’ N, 86° 47’ 21.1’’ W, E2M1+1, July 05, 1 m (2) . Panama [ ECOSUR] Fuerte Sherman, Colon, Tercer Arroyo , 09° 33.2’ N, 79° 39.6’ W, Coll. S. I. Salazar, June 2, 2002, 1 m (32) ; LH02­756E, Coll. L. Harris, June 2, 2002 (1); Club Nautico, Colon, 09° 21.8’ N, 79° 53.7’ W, Coll. S. I. Salazar, June 3, 2002, 1 m (13) . Lesser Antilles [ ZMA] V. Pol. 181, Curaçao, Yacht Chazalie Marguerita, C. J. van der Horst, Jan. 24, 1896, in lagoon (4). V. Pol. 0068.01, Curaçao , Spaansche Water , Coll. C. J. van der Horst, Apr. 8, 1920, in mangrove roots (1); Apr. 19, 1920 (3); Apr. 25, 1920 (50). V. Pol. 1677, Jamaica, Kingston Harbour , Fort rocky lagoon, W of airport , Coll. P. Wagenaar Hummelinck, May 7, 1973, Rhizophora timber, muddy sand and coral debris, decaying wood, 0–1 m (55). V. Pol. 1008, Aruba , Spaans Lagoen, NW side , Coll. P. Wagenaar Hummelinck, Jan. 1, 1949, limestone shore of muddy lagoon with many algae near Rhizophora (23). V. Pol. 1674, Saint­Thomas, Benner Bay Lagoon, 0–1 m , Coll. P. Wagenaar Hummelinck, Apr. 30, 1973, Rhizophora in sandy mud (27).

Description

Dasychone bairdi as originally described by McIntosh was based on specimens of two species. The following redescription is based on the lectotype designated here (see remarks for comments on selection).

Small thin worm with body (excluding crown) 15 mm long, 1.7 mm wide; crown 10 mm long ( Fig. 3B ). Radiolar crown united at base by short web, bearing 20 radioles with apinnulate tips and stylodes. Basal stylode small, unpaired and digitiform. Stylodes: 26 pairs [s, s, s, s, s, s, s, s, m, m, m, m, m, L, m, m, XL, m, m, m, m, L, s, s, s, s]. Macrostylodes strap­like ( Fig. 9D ) up to four times as long as neighbouring pairs, mostly in distal half of radiole ( Fig. 3A ), with remaining stylodes digitiform ( Fig. 9C ); all stylodes about one third width of rachis ( Fig. 9C–D ). Eyes small and compound (with sub­conical lenses), not present between last four pairs of stylodes. Dorsal lips long and tapered, supported by longitudinal ridge (mid­rib) about one half length of radioles. Dorsal collar with free well separated margins each side of midline faecal groove ( Fig. 3C ), lateral margins above junction with crown and thorax ( Fig. 3D ), ventral lappets triangular and well spaced at the midline ( Figs 3B ). Thorax with nine segments with interramal dark spots. Ventral shields subquadrangular, anterior margin of first shield fairly straight ( Fig. 3G ). Collar chaetae slender, weakly geniculate, arranged in compact fascicles. Thoracic notochaetae arranged within each fascicle in irregular oblique rows of superior and inferior chaetae ( Fig. 10C ); each superior chaeta slender, weakly geniculate, knee region slightly wider than shaft; inferior chaetae with knee up to twice as wide as shaft ( Fig. 3K ). Thoracic tori abutting ventral shields; avicular uncini with the crest surmounted by two rows of teeth (side view), occupying about one third of crest ( Fig. 3H ), with three distinct teeth in anterior row and a few very small teeth above ( Fig. 11B ). Abdomen with about 70 segments, tori smaller than most in thorax. Fascicles of abdominal chaetae forming compact tufts, with outer geniculate chaetae arranged in C­shaped arcs around clusters of more slender capillary chaetae; number of chaetae per fascicle decreases gradually towards posterior. Abdominal uncini similar to those in thorax ( Fig. 3J ). Faecal groove passes around right side of body from the last thoracic segment to second segment of ventral abdomen ( Fig. 3D ) and on to bilobed pygidium.

In Mexican material body dark olive­green with small brown spots over the whole body. Interramal dark spots present, larger on first thoracic segments and progressively smaller toward the posterior region. Crown with olive­green bands around the radioles, each band occupying space of three pinnules, crown base bearing longitudinal bands of diffuse brown spots in line with each radiole axil. Midline ridge of dorsal lips orange and an orange spot between each pair of eyes.

Remarks

Two original syntypes of Branchiomma bairdi (McIntosh NHML 1885.12.1.391) with a label “Redet. by Prof J. H. Day as identical with D. nigromaculata Baird 1865 ” were examined. Both specimens have radioles with strap­like macrostylodes, that agree with McIntosh’s original radiole illustration ( Fig. 2 , pl. 39A), which are much longer than those of B. nigromaculatum (see above). The smaller more slender syntype is here designated as lectotype [ NHML 1885.12.1.391], because of McIntosh’s comments: “The long radioles are more flexible than usual so that they form a lax brush anteriorly.” and later “The flexibility of the radioles is apparently due to the diminution or alteration of the barred cartilaginous axis.” The crown of the designated lectotype is certainly unusual in that the radioles have a springy quality, differing from those of the other syntype. The lectotype also differs in having a fairly long narrow thorax, with length of the ventral shields no more than half the breadth (c.f. Figs 3B &G ).

The paralectotype, now labelled Branchiomma sp. A [ NHML 1885.12.1.391], is incomplete, the abdomen having been removed behind the 6 th abdominal segment ( Fig. 3G ). It differs from the lectotype in having a thorax with size and proportion similar to that of Branchiomma nigromaculatum (c.f. Fig. 1G and Fig. 3G ). It would have been this specimen that influenced, Day (1955) to wrongly suggest synonomy with B. nigromaculatum ( Baird, 1865) , but B. nigromaculatum differs from Branchiomma sp. A , in having narrower thoracic shields, compared with body width, fleshy ventral collar lappets touching at the midline and much shorter macrostylodes. McIntosh’s histology, gut content observations and figures must have come from Branchiomma sp. A . because of the evidence of sectioning, but the rest of his text description could apply to either species. McIntosh noted the average measurements of B. bairdi indicating that he originally had examined more specimens than two.

Monro (1933b) mentioned that his material differed from McIntosh’s description only in that they tend to be smaller and Monro’s collections (e. g. from stations 328 & 347, NHML 1932 12. 22, 91–102) agree well with the lectotype. He regarded McIntosh’s illustration of a single pair of more­distal stylodes (each wider with an embayed distal margin ( Fig. 9 , pl. 39A), as erroneous. Such stylodes were not seen in Monro’s abundant material ( PK­J), but similar macrostylodes occur in B. conspersum (see below). McIntosh (1885, at the start of his description of B. bairdi ) lists figures 5 and 6 from plate 38A as referring to B. bairdi , but the legend for those figures uses the name Dasychone occidentalis . There is no such species, either in the genus Branchiomma or described in his monograph.

Augener (1918) at first wrongly recorded B. bairdi (as Dasychone ) from the Ivory Coast. He described and figured (Fig. 230, pl. 7) a pair of broad stylodes each with an undulating distal border, similar to some of those found in B. conspersum ( Fig. 4H, J ). After looking at West Indian material Augener (1922b) realised that his 1918 West African material was different and he then called it Dasychone pseudoviolacea . It is in fact very different, because the dorsal collar margins are fused to the sides of the faecal groove ( ZMUH V 1788, PK­J) as in Group A. His 1922 records of Dasychone bairdi from Tortugas, Saint­Thomas, Jamaica, Haiti, Mexico, and Veracruz may well be correctly identified, but the material has not been examined by us.

Johansson (1927) was the first to give the new combination of Branchiomma bairdi . Rioja (1951) recorded B. bairdi from Isla Sacrificios (Veracruz, Mexico). His specimens (5–20 mm length, 1–2.5 mm width) were similar in size to the Bermudan lectotype. Day (1955) wrongly synonymised B. bairdi with B. nigromaculatum . Hartman (1951: 115) recorded B. bairdi from the Gulf of Mexico, but later (1959: 537), probably following Day (1955), listed the species as a possible synonym of B. nigromaculatum . Jones (1962) also wrongly synomyised B. bairdi (and B. conspersum ), with B. nigromaculatum . The most distinctive character separating Branchiomma bairdi from B. nigromaculatum and other species studied here are the slender springy radioles bearing long strap­like macrostylodes on the distal half of the radiole. These are up to four (or more) times the length of the smallest stylode. They may vary in size amongst themselves, but they are always much longer than other stylodes on the radiole, including their immediate neighbours. Other differences from B. nigromaculatum , apart from size, are that the ventral collar lappets are less fleshy and more pointed and the uncini bear two rows of crest teeth.

Distribution The present studies show that this species is widely distributed in tropical North

American waters from Bermuda in the north, Florida, Lesser Antilles, Veracruz in the Gulf of Mexico, Mexican Caribbean and Pacific Panama in the south.

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 3. Branchiomma bairdi lectotype (A–D, H–K) and Branchiomma species A. (E–G): A) radiole; B) whole worm in ventral view; C) anterior in dorsal view; D) anterior in lateral view; E–F) second radiole on left; G) anterior in ventral view; H) thoracic uncinus; J) abdominal uncinus; K) inferior thoracic chaeta. Scale bars: A 2 mm, B–D, G 3 mm, E–F 2.5 mm, H–J 30 m, K 95 m.

FIGURE 4. Branchiomma conspersum lectotype (posterior missing and tear on left side): A–C) dorsal, ventral, and lateral views respectively of thorax and adjacent areas; D) lateral anterior, showing crown length; E) inferior thoracic chaeta; F) superior thoracic chaeta; G) thoracic uncinus; H, J) radioles. Scale bars: A–B 2.2 mm, C 1.5 mm, D 2 mm, E–F 255 m, G 20 m, H 5.5 mm, J 2.25 mm.

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.