Virchowia Langerhans, 1879
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|Virchowia Langerhans, 1879|
Virchowia Langerhans, 1879: 582 –583, fig. 31 A –F.
Autosyllis Imajima & Hartman, 1964: 103 –105, pl. 22, fig. D –H.
Linnean name definition. Type species Virchowia clavata Langerhans, 1879 by monotypy.
Apomorphies. Clade supported by 10 morphological apomorphies ( Fig. 4View FIGURE 4): 1) nuchal epaulettes on special outgrowths (character 7), other most parsimonious reconstructions (MPR) possible, character state change is a parallelism; 2) cirrostyles club shaped (character 15), character state change is a parallelism, V. spirifer is polymorphic; 3) cirrostyles alternate in length present (character 16), other MPRs possible, character state change is a parallelism; 4–5) cirrophores on short cirri, and cirrophores on long cirri shorter than parapodial lobes (characters 17–18), other MPRs possible, character state changes are reversals and parallelisms, unknown states in V. pectinans ( HartmannSchröder, 1983) ; 6) cirrophores alternate in length present (character 21), other MPRs possible, character state change is a parallelism, character state unknown in V. pectinans ; 7) insertion of cirri at distinctly separate levels (character 23), other MPRs possible; 8) blade length very short absent (character 33), character state change is a reversal; 9) number of different sizes in trepan equals 2 (character 41), other MPRs possible, character state change is a parallelism, later reversed within clade; 10) infradental spines present (character 46), character state change is a reversal, and a parallelism, unknown state in V. pectinans , V. longipharyngea ( HartmannSchröder, 1989) , and V. branchiata ( Averincev, 1972) .
Atokous form. Length 1.6–15 mm for 16–35 chaetigers; width, measured at level of proventricle and excluding parapodial lobes, 0.15–1.5 mm. Body shape, excluding parapodial lobes, cylindrical in transection, venter flattened; body width fairly constant with tapering end. Ciliation present on prostomium, nuchal epaulettes, and as a midventral longitudinal broad band (only known in V. clavata ). Prostomium rounded rectangular, wider than long. Four eyes, with lenses, in trapezoid arrangement, anterior pair larger. Eyes separated, eye spots absent or present. Palps fused at base (unknown in some taxa), in dorsal view not projecting in front of prostomium. Nuchal epaulettes on special outgrowths, originating from backside of prostomium, extending to between end of chaetiger 1 and end of chaetiger 3.
Prostomium with 3 antennae; median antenna inserted medially on prostomium, lateral antennae on anterior margin. Tentacular cirri 2 pairs. Cirri, cirrophores, and cirrostyles alternate in length, and shape (reported length compared to body width, excluding parapodial lobes). Appendages cylindrical or club shaped.
Parapodial lobes small to medium in size, rounded to rounded conical. Except for bayonet chaetae, chaetae mostly compounds, simple chaetae of "fused type " only present in V.
spirifer . Both compounds and simple chaetae with small distal tooth, sometimes minute; blade serration absent or present. Single thick bayonet chaetae, distally dilated with distal denticulation, present.
Pharynx with single to multiple sinuations anterior and lateral to proventricle. Trepan teeth arranged in single ring, with equal or unequal teeth. Basal ring present; infradental spines present (unknown in some taxa). Proventricle with varying number of rows of square shaped muscle cells. Pygidium with 2 cirri (reported length compared to body width, excluding parapodial lobes, at level of proventricle if not otherwise stated), median papilla absent.
Female. See description under V. c l a v a t a.
Virchowia branchiata ( Averincev, 1972) comb. n. (Fig. 31 A –G)
Phyllosyllis albida Ehlers 1913: 494 –495, pl. 33, fig. 7, 8; Augener 1918: 304 –305. NOT Phyllosyllis albida Ehlers, 1897: 61 –63, pl. 4, fig. 77–80 (= nomen dubium). Autolytus branchiatus Averincev, 1972: 167 –168, pl. 28, fig. 7–10.
Diagnosis. Virchowia with nuchal epaulettes as branching outgrowths.
Description. Length 8–15 mm for 47–70 chaetigers, width 1–1.5 mm. Preserved material yellowish, no colour markings. Ciliation not possible to assess.
Eyes almost confluent (Fig. 31 G); eye spots present. Palps small, not projecting in front of prostomium (Fig. 31 G), fusion not assessed. Nuchal epaulettes on outgrowths, originating from backside of prostomium, reaching end of chaetiger 2; nuchal epaulettes branching, treelike (Fig. 31 A).
Median antenna reaching chaetiger 5–6. Lateral antennae and dorsal tentacular cirri, length 1 / 2 – 2 / 3 of median antenna. Ventral tentacular cirri 1 / 2 as long as dorsal pair. First dorsal cirri c. 3 / 4 as long as median antenna, second dorsal cirri as long as ventral tentacular cirri. From chaetiger 1–27 cirri with usual alternation in direction, followed by 3 DDUUgroups and 1 DDUgroup (n= 1), more posterior difficult to assess. Dorsal cirri from chaetiger 3, alternate in length; short cirri equals 1 / 3 – 1 / 2 of body width, long cirri equals 1–1.5 times body width; cirri with distinct alternation in placement, long cirri inserted dorsal to short cirri (Fig. 31 C). Cirrophores present on tentacular cirri, and all dorsal cirri. Cirrophores and cirrostyles unequal; cirrophores and cirrostyles on short cirri c. 1 / 3 in length of its counterpart in long cirri (Fig. 31 C); cirrophores on short cirri with thin base, cirrophores on long cirri with broad base; cirrophores shorter than parapodial lobes; cirrophores shorter than cirrostyles. All appendages more or less clavate (Fig. 31 A, C, D), long cirri more distinctly so.
Parapodial lobes conical, small. Anterior chaetigers with 1–2 aciculae, 1 in median and posterior. Chaetal fascicle with c. 20 compounds in anterior chaetigers, 5–15 in median and posterior. Compound chaetae with small distal tooth; serration present (Fig. 31 E). Single thick bayonet chaetae, distally dilated (Fig. 31 F), present in posterior chaetigers.
Pharynx with single to multiple sinuations anterior and lateral to anterior half of proventricle. Trepan in chaetiger 2, not possible to evaluate detail structure. Proventricle equal in length to 2–3 segments in chaetiger 6–8 with c. 50 rows of muscle cells (n= 2). Anal cirri equal in length to short cirri.
Reproduction. Schizogamy by anterior scissiparity behind chaetiger 13. The holotype as well as one of the nontype specimens with developing heads, with 3 small antennae (Fig. 31 B), behind chaetiger 13.
Morphology of epitokous stages. Unknown.
Additional information. The trepan is described by Avernicev (1972); it has 20 unequal teeth, 1 large alternating with 1–3 smaller.
Habitat. Rocky bottom, 25– 40 m.
Distribution. Antarctic, Davis Sea.
Remarks. Virchowia branchiata is the only autolytine that has nuchal epaulettes as furcating outgrowths; it is thus very easily identified. There is no doubt that Ehlers' second description and Augener's redescription of Phyllosyllis albida are of V. branchiata . However, Ehlers' original description of P. albida is not the same as V. branchiata . See also remarks for P. albida nomen dubium.
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