Panthalis oerstedi Kinberg 1856

Panthalis oerstedi Kinberg, 1856

Panthalis oerstedi Kinberg, 1855 [1856]:387; 1858:25, pl. 7: fig. 34A–H, pl. 10: fig. 60.—Malmgren, 1865:85.—Marenzeller, 1893:28, pl. 1: fig. 2A–C; 1904:299.—Watson, 1895:169, pls. 9, 10 [tube-building].—McIntosh, 1900:400, pl. 25A: fig. 20, pl. 27: fig. 16, pl. 30: fig. 8, pl. 34: figs. 3–5, pl. 41: figs. 15–18.—Fauvel, 1914b:78; 1923:98, fig. 38a–h.—Åkesson, 1963:128, figs. 1–4 [brain, cerebral region].

Panthalis marenzlleri Pruvot and Racovitza, 1895:442, pl. 19: fig. 105, pl. 20: figs. 106–110 [fide Marenzeller, 1904:299].

Panthalis oerstedii.—Ditlevsen, 1917:52.

Not Polyodontes oerstedi sensu Strelzov, 1972:297 [= Acoetes sp.].

MATERIAL EXAMINED.—WESTERN SWEDEN: Bohuslän, 1839, S. Loven, collector, holotype of Panthalis oerstedi (NRS 5795). Northern Bohuslän, Iddefjorden, 11 m, 1863, Hj. Widegren, collector, 1 specimen (NRS 5792). Bohuslän, Kosterfjorden, 1865, A. Ljungman, collector, 1 specimen (NRS 5793, identified by Malmgren).

SHETLAND. 36 miles (58 km) off the Skerries, 137 m, 1867, J. Gwyn Jeffreys, collector, 2 specimens (BMNH 1921.5.1.568, identified by McIntosh).

TYPE MATERIAL.—Holotype of Panthalis oerstedi, now in three pieces, with pharynx extended (jaws had been cut out and present in vial), with 84 segments, 98 mm long, 15 mm wide with setae. Type of Panthalis marenzelleri not available (referred to Panthalis oerstedi by Marenzeller, 1904). The description was based on an anterior fragment of a mature female of 25 segments, 16 mm long, 2 mm wide, including setae. It was collected in the Mediterranean in the region of Lacase-Duthiers in 560 meters.

DESCRIPTION.—Body elongate, vermiform, flattened dorsoventrally, tapered slightly anteriorly and moreso posteriorly, with numerous pairs of elytra leaving middorsum uncovered (Kinberg, 1858, pl. 7: fig. 34A; McIntosh, 1900, pl. 26A: fig. 20). Elytra rounded to oval, delicate, pearly white, semitransparent, attached eccentrically near lateral sides to elytrophores; anterior 3 pairs flat, covering dorsum; elytra from segment 9 campanulate with lateral pockets (Figure 33C–E).

Bilobed prostomium with wide, cylindrical, colorless ommatophores on anterior half of prostomium, with transparent lenses; median antenna with short ceratophore near anterior notch, with style extending beyond ommatophores; lateral antennae arising ventrally close together below ommatophores, with styles similar to median antenna, their tips visible well beyond ommatophores; palps stout, long, tapered, smooth (Figures 32A, 33A,B). Tentacular segment distinct dorsally; tentaculophores lateral to and fused basally to prostomium, each with single aciculum, few capillary setae, few papillae on inner side, and dorsal and ventral tentacular cirri similar to but longer than antennae (Figures 32A,C, 33A,B; Kinberg, 1858, pl. 7: fig. 34B; Watson, 1895, pl. 9: fig 3; McIntosh, 1900, pl. 27: fig. 16; pl. 10: fig. 2; Pruvot and Racovitza, 1895, pl. 19: fig. 105).

Second segment with first pair of elytrophores, long ventral buccal cirri, and biramous parapodia; notopodium short, digitform, with bundle of long capillary finely spinous neurosetae; neuropodium larger, rounded, with anteroventral bract; neurosetae lanceloate (Figures 32D, 33A,F–I; Watson, 1895, pl. 9: fig. 3, pl. 10: fig. 2; Pruvot and Racovitza, 1895, pl. 20: fig. 107). Distal border of extended pharynx with 13 or 15 pairs of border papillae, middorsal and midventral ones on wide lobulated bases, middorsal one extra long and tapered (sometimes protruding from closed mouth), midventral one somewhat shorter than middorsal one; 2 pairs of strong hooked jaws, each with 6–8 lateral teeth (Figure 32B; Kinberg, 1858, pl. 7: fig. 34A,E, pl. 10: fig. 60; Watson, 1895, pl. 10: fig. 6; Pruvot and Racovitza, 1895, pl. 19: fig. 105; McIntosh, 1900, pl. 34: figs. 3, 4).

Third segment with first pair of dorsal cirri, with short cirrophores and styles extending about to tips of neurosetae; notopodia with fewer notosetae than on 2nd segment; upper and lower neurosetae similar, spinous, lanceolate; middle neurosetae stout, acicular with tips hairy, aristate (Figure 32E–H). Following parapodia similar through segment 8, with notosetae lacking (Figures 32I, 34A).

Beginning with segment 9, notopodium wide, rounded, flattened, anterodorsal to upper half of neuropodium, with notoaciculum and spinning glands; neuropodium with slightly bilobed presetal acicular lobe, truncate postsetal lobe and lower anteroventral bract; three groups of neurosetae: lower group numerous, within ventral bract, curved, with large spines basally, finely spinous distally, tapering to capillary tips; middle row (4–6 in number) stout, acicular, amber-colored, frayed distally along one side with aristate tips; upper group, emerging from low dorsoanterior bract, of 2 types: (a) longer, fewer, slender, with brush-like tips; (b) shorter (hidden by notopodium), more numerous, bipinnate (Figures 32J, 34B–H; Kinberg, 1858, pl. 7: fig. 34F,G; Watson, 1895, pl. 10: figs. 1, 3–5; Pruvot and Racovitza, 1895, pl. 20: figs. 108, 110; McIntosh, 1900, pl. 41: figs. 15–18). Dorsal cirri short, subulate, ventral cirri short, tapered (Figure 34G). Without parapodial branchiae. Pygidium with pair of long anal cirri (McIntosh, 1900, pl. 26A: fig. 20).

TUBES.—The tubes and their formation were well described by Watson (1895:169–188, pls. 9, 10). Panthalis oerstedi, collected off the Isle of Man in 110 meters, formed long, very soft muddy tubes, easily torn apart, composed of many thin parallel layers in which mud was loosely entangled, resembling “mud sausages.” One of the tubes had a length of about 90 mm, 32–39 mm in external diameter, 9 mm in internal diameter, with the wall in the middle of the tube about 6 mm thick. The tubes were open at both ends with loose mucus-like extensions concealing the entrances. Watson had the opportunity to observe the worms alive in an aquarium where a layer of mud was placed and to watch the formation of the tubes. The parapodia of the second or buccal segment, called the weaving feet, were used in manipulating the spinning fibers and forming cobwebs; fine mud was swept into the tube when the weaving feet moved backward. At intervals, the tube was enlarged by greatly expanding the anterior region of the body, thereby enlarging the diameter of the tube and pulling in additional mud through the collapsed opening. Layers were added internally from cobwebs of the spinning fibers and mud. Watson demonstrated how the tips of the brush-like neurosetae, composed of a central shaft and flexible distal bristles forming a minute brush, helped in separating the spinning fibers, formed from the long bronze rope-like coils found in all parapodia except for the anterior eight pairs. The fibers emerged from a cleft on the underside of the notopodia, just opposite to the upper group of brush-like neurosetae.

Lindroth (1941:498) observed that on freshly dredged material the tubes of Panthalis oerstedi had only a single functional opening that was elevated on a small crater on the muddy surface; the other end was black and reduced.

BIOLOGY.—Watson (1895) observed that P. oerstedi, at rest, lies on its back with its head end and two long palps protruding from the tube, ready to seize passing prey. In addition, the long middorsal tentacular papilla of the proboscis was sometimes protruding from the mouth. Watson observed a constant rising and falling of the campanulate elytra, which facilitates the passage of water for the purpose of respiration.

ASSOCIATIONS.—Tubes containing specimens of Panthalis oerstedi, collected by Franzén (1962:311–317, figs. 1A–C, 2A–C, pl. 1: figs. 1–5, pl. 2: fig. 1) in the Gullmar Fjord, Sweden in depths of 50–70 meters, and by Nielsen (1964:45, fig. 32A–D), in Kristineberg, Sweden, and the Kattegat, were found to contain colonies of epizoic entoprocts, Loxosomella glandulifera Franzén. The loxosomatids were anchored by their long peduncles in deep pockets on the inner layers of the soft mud tube. Each tube generally contained large numbers of individuals, up to 150, according to Nielsen (1964:45). Presumably, they were making use of the food-bearing current in the respiratory chamber of the host.

DISTRIBUTION.—Sweden, Norway, North Atlantic to Mediterranean, Northwest Africa. In 11 to 760 meters.

Known from seamounts and knolls