Myrianida pachycera ( Augener, 1913 )

Nygren, Arne, 2004, Revision of Autolytinae (Syllidae: Polychaeta)., Zootaxa 680, pp. 1-314 : 143-148

Myrianida pachycera ( Augener, 1913) (Fig. 71A–E)

Autolytus pachycerus Augener, 1913: 257 –260, pl. 2, fig. 11, 12, textfig. 40A–C; 1927: 157–158; Nygren & Sundberg 2003: GenBank sequences, 16S rDNA partial sequence AF474258 , and 18S rDNA partial sequence AF474304 .

Myrianida pachycera Imajima 1966: 79 –82, fig. 26A–L; Imajima 1967: 417.

Myrianida pachycerus Hartman 1966a: 362 –363, fig. 1A–B.

Autolytus purpureimaculata Okada 1933b: 332 –338, figs 6–11; 1937; Imajima & Hartman 1964: 100.

Myrianida crassicirrata Hartmann­Schröder, 1965a: 119 –121, figs 47–49; Hartman 1966b: 194 – 195.

Material examined. Australia: holotype ZMB 5336, Southwest Australia, Shark Bay, 3 m. USA: holotype of Myrianida crassicirrata ZMH P­ 14764, Hawaii, Kaneohe Bay, inside sponge ( Damiriana sp.), 15 Apr 1959; 4 spms (1 spm in formalin, 1 spm on slide, 2 spms in author's collection for DNA analyses), California , Los Angeles harbor, 33°45'N, 118°16'W, epifauna on ship, 1 m, 4 Jan 2001; 4 spms (1 mounted for SEM), Florida, Indian River, Fort Pierce inlet, south east part of Jim Island, 27°28.4'N, 80°18.4'W, intertidal oyster­banks, 18 Apr 1997.

Diagnosis. Myrianida with spectacular coloration, yellowish to orange with blue spots, and blue appendages; trepan with c. 11 large teeth and 26–28 smaller, 1 large alternating with 1–5 smaller, thin basal ring.

Description. Length of stock 4.2–8.5 mm for 30–33 stock chaetigers, width 0.4–0.7 mm. Stolon chain, with up to 10 stolons, often exceeds length of stock. Live specimens yellowish to orange (sometimes with stronger orange bands at irregular intervals in stock) with distinct blue spots on every segment except for tentacular segment and sometimes a few anterior chaetigers (Fig. 71A, B); in posterior part of stock sometimes one blue spot per two segments; median antenna, first dorsal cirri, all long cirri in stock, and anal cirri blue; prostomium sometimes blue; eyes red. Colour pattern fades in preserved specimens. Ciliation as 2 trochs per segment.

Eyes separated; eye spots present. Palps in dorsal view projecting 1/5 of prostomial length (Fig. 71B), fused. Nuchal epaulettes as grooves (Fig. 71B), extending to between beginning of chaetiger 4 and half of chaetiger 7 (Fig. 71B).

Median antenna reaching chaetiger 7–10 (n=2). Lateral antennae and dorsal tentacular cirri, length 1/2 of median antenna. Ventral tentacular cirri 1/2 as long as dorsal pair. First dorsal cirri as long as median antenna, second dorsal cirri as long as 1.5 times the ventral tentacular cirri. From chaetiger 1–27 with usual alternation in direction, followed by 1 or 2 DDU­groups (n=3). Dorsal cirri from chaetiger 3, alternate in length (Fig. 71B); short cirri equals 1/2–2/3 of body width, long cirri equals body width. Cirrophores present on tentacular cirri, and all dorsal cirri. Cirrophores equal, cirrostyles unequal (Fig. 71B); short cirrostyles 2/ 3 in length of long cirrostyles; cirrophores equal in length to parapodial lobes; cirrophores shorter than cirrostyles. Lateral antennae, tentacular cirri, and second dorsal cirri cylindrical; median antenna and first dorsal cirri cylindrical to thick, cirri in stock slightly flattened, long cirri generally more flattened than short cirri (Fig. 71B). Cirri in stolons similar in shape to short cirri in stock.

Parapodial lobes rounded, of medium–large size. Anterior chaetigers with 3 aciculae, 2 in posterior part of stock. Chaetal fascicle with 20–25 compounds in anterior chaetigers, 10–15 in posterior part of stock. Compound chaetae with small distal tooth; serration present (Fig. 71D). Single thin bayonet chaetae (Fig. 71E), beginning at chaetiger 25.

Pharynx with 1 sinuation anterior to proventricle. Trepan in chaetiger 2–4, with 37–39 unequal teeth (n=1), 11 large and 26–28 smaller; 1 large alternating with 1–5 smaller (Fig. 71C), arranged in 1 ring. Thin basal ring present; infradental spines present (Fig. 71C). Proventricle equal in length to 3–4 segments in chaetiger 7–14 with 26–29 rows of muscle cells (n=3). Anal cirri equal in length to body width.

Morphology of epitokous stages.

Male. Length in preserved specimens 2.4 mm for 3+19+0 chaetigers (n=3), width in region a 0.2 mm, width in region b 0.6 mm. Live specimens with same colour markings as in stock. Ciliation as in stock.

Prostomium with straight anterior margin. Nuchal epaulettes rounded, extending to beginning of chaetiger 1.

Median antenna reaching middle of region b, c. chaetiger 11–12. Lateral bifid antennae, 1.5 times as long as prostomial width. Basal part 1/3 of total length, outer ventral rami 2 times longer than inner dorsal rami. Frontal processes, equal to 1/8 of prostomial width. Tentacular cirri 1 pair, as long as prostomial width. First dorsal cirri, equal in length to median antenna. Achaetous knobs absent. Dorsal cirri on chaetiger 1 equal to 1.5 times body width, dorsal cirri on chaetiger 2–3 shorter, about equal to body width; cirri in region b about as long as cirri on chaetiger 2–3, reciprocally equal, measuring 1/3 of body width. Median ceratophore, cirrophores on tentacular cirri, and cirrophores on all dorsal cirri, present. Tentacular cirri, dorsal cirri on chaetiger 1–3, and anal cirri, slightly flattened, otherwise appendages cylindrical.

Single neuropodial acicula in all chaetigers; 2 anterodorsal, and 2 thick and 2 thin posteroventral notopodial aciculae in region b. Neuropodial chaetal fascicle with 6–10 compounds in all chaetigers; single bayonet chaetae beginning at chaetiger 1. Notopodial chaetal fascicle with 15–20 swimming chaetae. Anal cirri equal in length to cirri in region a.

Female. Length in preserved specimens 5.4–5.5 mm for (5–6)+(18–21)+8 chaetigers (n=4), width in region a 0.4 mm, width in region b 0.8 mm. Live specimens with same colour pattern as in stock.

Prostomium without anterior incision. Nuchal epaulettes rounded–triangular, extending to half of chaetiger 1.

Median antenna reaching chaetiger 4–6. Lateral antennae, 1/2–2/ 3 in length of median antenna. Tentacular cirri 2 pairs, dorsal pair as long as lateral antennae, ventral pair 1/ 2 in length of dorsal. First dorsal cirri, 3/4–4/ 5 in length of median antenna, situated above first chaetigerous lobe. Achaetous knobs absent. Cirri equal, or almost so, along whole specimen, equal to body width in region a. Tentacular cirrophores, and cirrophores on all dorsal cirri, present. Antennae, tentacular cirri, and first dorsal cirri, flattened, thick; antennae somewhat club shaped; dorsal cirri and anal cirri, slightly flattened.

Single neuropodial acicula in all chaetigers; 2 anterodorsal, and 2 thick and 2 thin posteroventral notopodial aciculae in region b. Neuropodial chaetal fascicle with 5–10 compounds in all chaetigers; single bayonet chaetae beginning at chaetiger 1. Notopodial chaetal fascicle with c. 15 swimming chaetae. Anal cirri equal in length to 2 times body width.

Reproduction. Schizogamous reproduction by gemmiparity, behind either chaetiger 31 or 34.

Habitat. Intertidal, shallow depths, together with rich epifauna.

Distribution. East Indian Ocean, Pacific, West Atlantic. Australia, Japan, Hawaii, California , Florida.

Remarks. Myrianida pachycera is a wide­spread taxon, and molecular data (unpublished) suggests that this might be a species that is spread by human activity. It is a highly decorative species, easily identified when alive. Preserved specimens may be confused with M. pulchella Day, 1953 , but the trepans differ (compare Fig. 71C and Fig. 76E), as well as the length of the cirrophores. In M. pulchella cirrophores alternate in length, in M. pachycera cirrophores are equal. Myrianida crassicirrata is considered a junior synonym after examination of type material, and the original description of Autolytus purpureimaculata is sufficient for synonymization.

Myrianida pentadentata ( Imajima, 1966) comb. n. (Fig. 72A–G)

Autolytus (Autolytus) pentadentatus Imajima, 1966: 32 , fig. 6A–H.

Autolytus pentadentatus Nygren & Sundberg 2003 : GenBank sequences, 16S rDNA partial sequence AF474253 , and 18S rDNA partial sequence AF474299 .

Material examined. Japan: 2 paratypes NSMT­Pol P­ 9, Seto, intertidal, seaweed, 5 Jan 1964. USA: 5 spms (3 spms in formalin, 2 spms on slides (rear ends in author's collection for DNA analyses)), California , Los Angeles harbor, 33°45'N, 118°16'W, 1 m, epifauna on ship, 4 Jan 2001; 7 spms (5 spms in formalin (1 rear end in author's collection for DNA analyses), 2 spms on slides (1 rear end in author's collection for DNA analyses)), California , San Diego, 32°43.48'N 117°13.38'W, 1 m, floating dock with tunicates, sponges, bryozoans, 8 Jan 2001.

Diagnosis. Myrianida with five teeth in trepan, long sinuation past small proventricle, with 7–8 rows of muscle cells; cirrophores on long cirri longer than cirrostyles.

Description. Length 2.3–6.2 mm for 26–53 chaetigers, width 0.2–0.35 mm. Colour in live specimens yellowish in anterior region, intestinal region brownish red, without colour markings (Fig. 72A); eyes red. Ciliation as 1 troch per segment.

Eyes separated (Fig. 72A); eye spots present. Palps in dorsal view projecting 1/3–1/2 of prostomial length (Fig. 72A), fused. Extension of nuchal epaulettes from end of chaetiger 1 to half of chaetiger 2 (Fig. 72A).

Median antenna reaching chaetiger 12–13 (n=3) in live specimens. 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 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 2 DUU­groups, and 1–3 DDUU­groups (n=3). Dorsal cirri from chaetiger 3, alternate in length (Fig. 72A, B); short cirri equals 1/2 of body width, long cirri equals 3/4 of body width. Cirrophores present on tentacular cirri, and all dorsal cirri. Cirrophores unequal, cirrostyles equal (Fig. 72B); short cirrophores 1/ 2 in length of long cirrophores; short cirrophores shorter or equal to parapodial lobes, long cirrophores longer than parapodial lobes; short cirrophores equal in size to cirrostyles, long cirrophores longer than cirrostyles. All appendages cylindrical (Fig. 72A, B).

Parapodial lobes rounded, of medium–large size (Fig. 72B). Anterior chaetigers with 2 aciculae, 1 in median and posterior. Chaetal fascicle with 7–10 compounds in anterior chaetigers, 5–7 in median and posterior. Compound chaetae with small distal tooth; serration present (Fig. 72E). Single thin bayonet chaetae (Fig. 72F), beginning between chaetiger 1– 19.

Pharynx with 1 long sinuation extending beyond proventricle (Fig. 72D). Trepan in tentacular segment or chaetiger 1–2, with 5 equal teeth (Fig. 72C). Basal ring absent or poorly developed; infradental spines absent (Fig. 72C). Proventricle equal in length to 1.5 segments in chaetiger 11–15 with 7–8 rows of muscle cells (Fig. 72D). Anal cirri equal in length to 1/3–2/3 of body width.

Reproduction. Posterior scissiparity behind chaetiger 26, 36, and 51 (Fig. 72A) (n=3).

Morphology of epitokous stages.

Male. Unknown.

Female. Length of one newly released specimen (most likely not fully developed) 2.6 mm for 3+16+2 chaetigers, width 0.4 mm, fairly equal in width along whole body. Live specimens brownish, without colour markings, eggs green (Fig. 72G).

Prostomium with concave anterior margin. Nuchal epaulettes rounded, extending to beginning of chaetiger 1.

Median antenna reaching chaetiger 1–2. Lateral antennae, 2/ 3 in length of median antenna. Tentacular cirri 2 pairs, dorsal pair as long as 1/3 prostomial width, ventral pair 1/ 3 as long as dorsal pair. First dorsal cirri, equal in length to following dorsal cirri, situated above first chaetigerous lobe. Achaetous knob absent. Cirri equal along whole specimen (Fig. 72G), measuring 1/2–3/4 of body width in region a. Cirrophores not detected on tentacular cirri, short equal cirrophores present on all dorsal cirri (Fig. 72G). All appendages cylindrical (Fig. 72G).

Single neuropodial acicula in all chaetigers; 2 anterodorsal, and 2 thick and 3 thin posteroventral, notopodial aciculae in region b. Neuropodial chaetal fascicle with c. 10 compounds in all chaetigers; single bayonet chaetae beginning at chaetiger 1. Notopodial chaetal fascicle with 5–10 poorly developed swimming chaetae. Anal cirri equal in length to 1–1.5 times body width.

Habitat. Intertidal, amongst seaweed and beneath encrusting bryozans.

Distribution. North Pacific. Japan, California .

Remarks. The annulus on long cirri, suggested by Imajima in the original description, could not be confirmed, neither in the newly collected material nor the type material; this is thus considered as a misinterpretation. Myrianida pentadentata is the only Myrianida with five teeth in its trepan.