Euthalenessa oculata (Peters)

Pettibone, M. H., 1970, Revision of the genus Euthalenessa Darboux (Polychaeta: Sigalionidae), Smithsonian Contribution to Zoology 52 : 6-12

Euthalenessa oculata (Peters)

Figures 1-5

Sigalion oculatum Peters , 1854, p. 610.

Sthenelais dendrolepis Claparede , 1868, p. 409, pi. 4: fig. 4, pi. 5: fig. 1.-Marenzeller, 1904, p. 301.-Fauvel, 1913, p. 30; 1914, p. 84, pi. 4: fig. 20; 1916, p. 44. [Not Mcintosh, 1869, p. 409; 1924, p. 13; 1925, p. 36.]

Leanira giardi Darboux , 1900, p. 123, figs. 24-28.

Euthalenessa insigni * Ehlers, 1908, p. 52, pi. 1: figs. 10, 11, pi. 2: figs. 1-9.-Augener, 1918, p. 108, pi. 3: fig. 53.

Euthalenessa dendrolepis .-Fauvel, 1923, p. 114, fig. 42, h-o.-Rioja, 1935, p. 18, figs. 27-36.-Bellan, 1961, p. 90; 1964, p. 36.-Rullier, 1965, p. 19.

Euthalanessa [sic] dendrolepis .-Monro, 1930, p. 70.

Euthalenessa oculata .-Day, 1953, p. 407 (part).

Thalenessa oculata .-Hartman, 1959, pp. 115, 119, 122.- Day, 1960, p. 294; 1967, p. 107, fig. 1.19, m-q.

Thalenessa dendrolepis .-Hartman, 1959, pp. 120, 122.- Laubier and Paris, 1962, p. 13.

Material examined.-South-East Africa: Inhambane, southeast Mozambique, 24° S, W. C. H. Peters, collector - holotype of Sigalion oculatum Peters ( ZMB 23 ) .

South Africa: Cape Agulhas , 35° 02' S, 19° 58' E. 80 meters, Valdivia Expedition, Station 96-4 syntypes of Euthalenessa insignis Ehlers ( ZMB 6724 ). False Bay , 34° 12.5' S, 18° 37' E, 48 meters, sand and shell, FAL Station 419L , 15 May 1961, J. H. Day, collector - 1 specimen ( BMNH 1961: 9: 839 ) .

West Africa: Cape Palmar , Liberia, 12.8 meters ; Munford , Gold Coast , 9 meters, A. Hupfer, collector - 7 specimens ( ZMH 601, 627-630 ). Off Annobon, Gulf of Guinea, 18-30 meters, Discovery Station 283-2 specimens ( BMNH 1930: 10: 8: 1412-1413 ) .

Mediterranean : Zoological Station , Bay of Naples - 2 specimens ( USNM 5129 ) . Mar echiaro, Bay of Naples, Posidonia bed, 26 August 1964, R. Barnes, collector - 1 specimen ( USNM 40574) . Collection of M. le Baron de Saint-Joseph, No. 20, 1911 (as Leanira giardi Darboux )-1 specimen (MNHNP) . Dredged near Marseille, France, by J. Picard (1960-1963), from H. Zibrowius - 15 specimens ( USNM 40573) .

Type-material.-The holotype of Sigalion oculatum from Mozambique ( ZMB 23) consists of anterior and middle fragments, totaling 42 mm in length, 4 mm in width, including setae, and 97 segments. The integument is transparent, poorly preserved, and shows no pigmentation.

The type-material of Euthalenessa insignis from South Africa ( ZMB 6724) consists of 2 large syntypes with a width of 9 mm, including setae; one is complete(in two pieces) with a total length of 170 mm for about 190 segments; the other is an anterior fragment of 35 mm for 39 segments; both specimens have the pharynx completely extended (Figures 1, 2; in Ehlers, 1908, pi. 1: figs. 10a, 11 and pi. 2: figs. 3-6, 8, 9). A 3rd syntype is more slender, having a length of 90 mm, a width of 6 mm, and 112 segments, being incomplete posteriorly; the pharynx is partially extended; the prostomial antennae and right anterior segments had been cut off (figured by Ehlers, pi. 1: fig. lOfc, pi. 2: figs. 1, 2, 7). The 4th syntype is the smallest, with a length of 30 mm, width of 4 mm, and 65 segments, with the posterior end missing (Figure 3). The latter syntype corresponds in size and some other features with the holotype of Sigalion oculatum .

Specimens from the Bay of Naples in the Méditerranean, the type-localities of Sthenelais dendrolepis Claparede and Leanira giardi Darboux , deposited in the Smidisonian Institution ( USNM 5129-2 large specimens and USNM 40574-small specimen) and the Paris Museum ( MNHNP— 1 large specimen) were examined. The 3 large specimens measure 145 to 170 mm in lengdi, 7 mm in widdr, including setae, and have numerous segments (about 200; Figures 4b-j; 5). The smaller specimen (a female with large yolky eggs) has a length of more than 70 mm (incomplete posteriorly) and width of 3 mm, including setae (Figure 4a).

Description.-The body has a length up to 200 mm, width, including setae, 3 to 9 mm, with numerous segments - up to 200 or more. The body may be variously pigmented with reddish brown coloration, usually widi conspicuous darker bands on segments 14- 16, followed by lighter pigmentation, which may be more or less banded. The anterior elytra have the pigmentation confined to crescent-shaped bands. On more posterior elytra, the pigmentation becomes more diffused, with darker spots anteromedially.

The elytra change in size and shape along die body. At first they are small and oval, then larger, subtriangular, subreniform to subcordiform (Figures lf-h; Ae-j). The 1st pair of elytra lack papillae. The anterior elytra have fringes of papillae extending along most of their lateral borders, with 7 to 19 papillae; more posteriorly, die papillae are confined to the anterior halves of the lateral elytral borders, with 14 to 9 papillae. Most of the papillae are irregularly palmately or dichotomously branched, with 2 to 7 filaments per papilla. The small syntype of E. insignis has elytral papillae with up to 14 filaments per papilla, perhaps due to a fusion of some of die papillae (Figure 3g,h).

When fully extended, the pharynx has a lengdi about equal to the anterior 20 segments of the body (Figure 1*),

The fused prostomium and tentacular segment are withdrawn within die anterior few setigers (Figures la; 4a, b). The 2 pairs of eyes are moderately large, located on the anterior slightly raised oval area of the prostomium, die anterior pair being slightly larger than die posterior pair; die posterior two-diirds of the prostomium is covered dorsally by setigers 2-4. The ceratophore of die median antenna extends from a wider median area between die anterior pair of eyes, narrowing more distally where it is fused to the dorsal sides of the fused tentacular parapodia.The ceratophores of die lateral antennae, which are also fused to die dorsal sides of die tentacular parapodia, extend beyond die median ceratophore; die 3 free antennal styles are subequal in size, short, and subulate. The long palps extend posteriorly to setigers 10 to 20. The dorsal tentacular cirri are short and tapered; die ventral tentacular cirri are about twice as long as die dorsal. The inner dorsal tentacular ridges are located on die distal halves of die tentacular lobes, widi 2 groups of capillary setae emerging laterally from near bodi ends of die ridges; die setae are few in number or may be absent. The bulbous facial tubercle is visible anterior to die medial fused parts of the tentacular parapodia, when die pharynx is extended, or medial to the inner palpal sheatíis, when die pharynx is wididrawn; a pair of small labial ctenidia are found on die lateral lips.

The parapodia of setigers 2-5 are greatly modified, widi well-developed notopodial and neuropodial bracts (Figures \c-e\ Aa, c, d). The notopodial bracts, encircling die compact bundles of notosetae, are variously slashed, widi 1-6 anterior and 2-6 posterior stylodes. The neuropodial bracts consist of die following: (/) lower-anterior-ventral bracts, greatiy enlarged and flaring; they are longest on setigers 2 and 3, becoming shorter on setigers 4 and 5; (2) upper-anterior bracts, shorter and wider; die lower distal parts gradually form distinct rounded lobes or ligules, directed inward; (3) lower-posterior bracts, retort-shaped, bulbous basally, narrowing distally and directed upward; (4) upper-posterior bracts, formed of digitiform stylodes in number of 4 to 10. In die following transitional setigers, the lower-anterior and upper-anterior bracts become shorter and truncate, widi a notch between; die lower-posterior bracts become shorter and subcorneal to oval; die upper-posterior stylodes are fewer in number, die lower one becoming gready enlarged and surpassing in size die lower-posterior bract. By setigers 8-10, die stylodes have disappeared and the posterior bract is continuous, aldiough it may be notched distally. The long slender compound neurosetae of die anterior setigers have multiarticulate blades widi 3-9 articles; some of die neurosetae are stouter, tiieir blades shorter, witii 1-2 articles; tiie stems are smooth or have few spinous rows (Figures id; Ad). The dorsal cirri on setiger 3 are short, subulate, borne on short cirrophores; small ctenidia encircle die elytriphores of setiger 2 and die dorsal cirri of setiger 3 (Figures lc; Aa-c).

The branchiae begin on setigers 4-6. The parapodial ctenidia are large, cup-shaped, 3 per parapodium. The parapodia of die anterior segments have small clubshaped notopodia and larger neuropodia (Figures 2a-d; 5a-c). The notopodial bracts have a single posterior stylode and 2-5 anterior stylodes. The notosetae form rather small bundles; they are slender, spinous, and taper to capillary tips. The neuropodial acicular lobes are enclosed in anterior and posterior bracts. The C-shaped posterior bracts are truncate or slightly undulate and enclose die C-shaped row of neurosetae. The smaller lower-anterior bracts are truncate and enclose the lower diagonal row of neurosetae. The larger upper-anterior bracts are rounded, widi more or less distinct rounded lobes or ligules on tiieir lower borders; die ligules are directed inward below die tips of the acicular lobes; die upper borders of die bracts curve around die upper diagonal row of neurosetae. The compound neurosetae are stout; die distal tips of die enlarged stems have few faint spinous rows; die blades are all radier short, widi bifid hooked tips; the neurosetae of the upper and lower diagonal rows are more slender, with somewhat longer blades (Figures 2d; 5c). The anterior parapodia of the smaller specimens differ somewhat in appearance (Figure 3a-c). The posterior bracts have a shallow notch; the lower rounded lobes or ligules of the upper-anterior bracts are more prominent; die neurosetae are more slender. The ventral cirri are slender, tapering, extending to the distal tips of the neuropodia.

The parapodia of the middle and posterior regions of the body differ in some respects (Figures 2e-j; 3d-f; 5rf-/). The notopodia are similar, having a single posterior and 2-5 anterior stylodes. The neuropodia show marked changes, however. The posterior bracts are more elongate and subcorneal. The upper-anterior bracts are smaller and more or less fused with the acicular lobes in die areas where the neurosetae are lacking; this includes dieir lower ligules. The neurosetae are longer; tíieir stems may have more numerous distinct spinous rows and the blades are somewhat longer. The ventral cirri are longer and extend beyond die distal tips of the neuropodia.

Biology.-The species is very common and abundant in die Mediterranean, where it is localized in biotopes of coarse substrate - fine gravel, coarse sand, widi bryozoans, coralline algae, shells, detritus, and where diere are strong currents on the bottom (Bellan, 1961, 1964, as Euthalenessa dendrolepis ). The species has been reported from numerous stations in South Africa on bottoms of sand, mud, rock, gravel, rock, with broken shells, Uthothamnion, in 13 to 82 meters by Day (1960, as Thalenessa oculata ). The females form large yolky eggs. Fauvel (1914, as Sthenelais dendrolepis ) reported that quite large specimens were found swimming at the surface in the Gulf of Gascony.

Distribution.-Gulf of Gascony, Mediterranean, West, South and East Africa. In 12 to 1250 meters.

Remarks. -- Leanira giardi was referred to Sthenelais dendrolepis by Marenzeller (1904). Euthalenessa insignis was referred to E. dendrolepis by Monro (1930). The holotype of Sigalion oculatum Peters , deposited in the Berlin Museum, was examined by Day (1953: 407) when he referred the species to Euthalenessa and included in its synonymy Sthenelais dendrolepis Claparede and E. insignis Ehlers . One of the specimens from Day's collection from Table Bay, South Africa, deposited in the British Museum ( BMNH 1952: 1: 12: 2) proved to be a species of Thalenessa ; the observation by Day (1953: 407) regarding the type of burrowing apparently applies to the latter species, rather than to E. oculata .