Enoplobranchus sanguineus ( Verrill, 1873 )

Londoño-Mesa, Mario H., 2009, Terebellidae (Polychaeta: Terebellida) from the Grand Caribbean region 2320, Zootaxa 2320 (1), pp. 1-93 : 16-18

Enoplobranchus sanguineus ( Verrill, 1873)

Figures 4 A-I

Chaetobranchus sanguineus, Verrill, 1873:616–617 .

Chaetobranchus (Enoplobranchus) sanguineus, Hessle, 1917:227 .

Enoplobranchus sanguineus, Verrill, 1879:10 ; 1881:pl.11, Figs 4 A-B.— Hartman, 1942:75–76. — Day, 1973:120.— Holthe, 1986b:166.

Type material: Syntypes YPM 181 (1 middle fragment) Long Island Sound, 1866; Coll. Class. A.E. Verrill; [= Enoplobranchus sanguineus (V.)] . YPM 890 (3 anterior ends and 21 middle fragments) Sarin Rock, West Haven , Connecticut, V.1872; Id. Coll. A.E. Verrill; [= Enoplobranchus sanguineus (V.)] . YPM 2723 (24 middle and posterior fragments) Stony Creek , Connecticut. Coll. A.E. Verrill (no more data) [= Enoplobranchus sanguineus (V.)] .

Additional material: YPM 36715–36716 (slide). Gulf of Mexico : USNM 75688 (1) Mississippi Sound , Alabama (30°02'18"N 87°52'12"W), 1.XI.1980; 21m. USNM 45679 (1) Tampa Bay, Florida, 1963 . ECOSUR TERE-27 CHA-14 (2) Champoton, 16.II.1999. TERE-27 XEN1 (2) Xen Point, Yucatan Peninsula , 24.V.2005; 1m.

Description: Best syntype (one anterior end YPM 890) incomplete, 20 segments, 20mm long and 5mm wide. Dorsal surface irregular, with transverse bands of granules or small tubercles ( Figs 4A,B ). Tentacular membrane long, with thick and undulating ridge and swollen dorsal base ( Fig. 4B ). Tentacles numerous forming mass, some of them thick and others thin, with swollen tips. Upper lip joined to tentacular membrane; lower lip tongue-shaped, narrow, swollen and projected ventrally, with longitudinal wrinkles ( Fig. 4C ). Six separated non-glandular, ventral shields from segment 2, reduced, in ventral groove formed by two lateral ridges of swollen and irregular glandular shields ( Fig. 4D ). Nephridial papillae on segments 4–9 anterior to each notopodium, rounded, with central pore ( Fig. 4E ). First 9 notopodia long, simple, conical with swollen base ( Figs 4F,G ); then, notopodia on segment 11 with bifid cirri, on segment 12 trifid, on segments 13–14 tetrafid, on segments 15–17 hexafid, and on segments 18–20 heptafid ( Fig. 4H ). Some cirri dichotomous, and some as simple filaments, all increasing in length toward posterior thorax, and emerging from common wide base. Notochaetae smooth basally, one or two emerging from tip of each cirri in midthoracic segments. Abdominal notopodia as ( Fig. 4I ) with simple cirrus, similar to those in anterior thoracic segments, but longer. Pygidium not seen.

Staining pattern: Lower lip stains deeply on oral surface; transverse thick bands on thoracic dorsum and ventral muscular ridges stain lightly; nephridial papillae and notopodial glandular tissue also stain deeply. The remaining structures do not stain significantly.

Variations: Two incomplete anterior ends, syntypes YPM 890, having both 11 thoracic segments, 6.9– 7mm long and 1.4mm wide. Non-type specimens from Mexican Caribbean also incomplete, having 14 and 16 thoracic segments, 5.5 and 13mm long and 1 and 2mm wide, respectively. They differ from syntypes by presenting bifid notopodia on segment 12, trifid on segment 13–14, and hexafid on segment 16. Other syntypes anteriorly incomplete (some only fragments from middle region), with notopodia strongly branched,

having up to 17 cirri. Only one long posterior fragment present (in YPM 890), with 128 segments, 52.5mm long and 1.2mm wide in its first segment and 0.5mm near pygidium. First segment with trifid notopodia, next two pairs of notopodia have bifid cirri; subsequent 30 odd segments with simple long cirrus projected backwards. Posterior abdomen without notopodia, with segments short, gradually decreasing in width and length until pygidium. Ventral groove from first segments, posteriorly continues towards near pygidium, formed by two thin muscular ridges. Pygidium small and smooth.

Discussion: Verrill (1973) first referred to notopodial branchial cirri, although he did not include comments about their respiratory function. Hartman (1942) also described these structures and mentioned their importance as an increase in number of cirri resulted in an increase in respiratory surface. Holthe (1986b) comments that dorsal branchiae on Terebellomorpha may have had a notopodial origin, as occurs in the Eunicemorpha. Nevertheless, in this genus, the notochaetae appear in the tip of each cirrus ( Fig. 4H ), which differs from the branchial achaetigerus cirri in eunicids. Thus, I consider that this structure could not have a respiratory function as it necessary for such a structure to have a ciliated surface and/or internal vessels for oxygen interchange. So, as the cirri lack these structures, they cannot be considered as branchiae.

The original description states that cirri start on segment 9 and are composed of one cirrus, then divided in two on segment 10, then divided in 3–4 cirri on segment 11, and then with numerous branched cirri. Since the syntypes examined have notopodia from segment 2, the segment on which the cirri starts dividing is the 11th instead of the 10th, as was mentioned in this redescription. Verrill also observed small chaetae on the posterior abdominal segments until the end of the abdomen. Nevertheless, the specimens observed here do not have chaetae after the abdominal cirri finish. Although the pygidium was described with crenulated margins, all incomplete syntype specimens have small pygidium, and it was not possible to determine whether it is smooth or crenulated.

Since the syntype described above has 7 notopodial cirri on its last segment (20), and this long posterior fragment has 3 notopodial cirri on the first segment and 2 on the next two, I consider that there is still a middle fragment missing between these two. Additional specimens deposited in USNM have more segments on thorax and abdomen; this shows that the number of notopodial cirri on posterior thoracic region decreases gradually toward abdomen, finishing as only one long cirrus on posterior 20 segments. The number of notopodia with single cirri in anterior thoracic region is 9–10, then, increasing gradually in number of cirri until segments 20–22, with the highest number of cirri (up to 17 in syntype YPM 181 , one specimen anteriorly incomplete). After this, the number of cirri decreases also gradually, until segment 30–32. Thereafter, single cirrus per notopodium along 30 segments. Posterior abdomen without notopodia. According to these observations, there is no clear separation between thorax and abdomen beyond the reduction in body thickness presented by some specimens in the last thoracic segments, which have few notopodial cirri (about segment 25–30) .

Type locality: Connecticut and Long Island Sound.

Distribution: US: Connecticut, Florida, Alabama. Mexico: Campeche. Intertidal to 6.5m deep. Day (1973) reports this species from Cape Hatteras to Beaufort, Northwestern Atlantic, on intertidal mudbanks and coral at 6.5m.

Figures

FIGURE 4. Enoplobranchus sanguineus (Syntype YPM 8909): A. Dorsal view. B. Anterior end in dorsal view. C. Anterior end in ventral view. D. Ventral view. E. Lateral view. F. Thoracic notopodia from segment 4. G. Notopodia from segment 5. H. Notopodia from mid-thoracic region. I. Abdominal notopodia. Scale bars: A,D,E: 5.5mm; B,C: 2.7mm; F: 0.4mm; G: 0.5mm; H: 0.5mm; I: 0.6mm.