Scoloplos dayi Hartmann-Schröder, 1980

Zhadan, Anna, Stupnikova, Alexandra & Neretina, Tatiana, 2015, Orbiniidae (Annelida: Errantia) from Lizard Island, Great Barrier Reef, Australia with notes on orbiniid phylogeny, Zootaxa 4019 (1), pp. 773-801 : 781-785

Scoloplos dayi Hartmann-Schröder, 1980

( Figs 2 , 3 , 12 B)

Scoloplos dayi Hartmann-Schröder, 1980: 67 –68, figs 74–68.

Type material. Holotype: HZM P–16373 (photographed). Paratype: HZM P–16374 (photographed).

Other material examined. AM W.44249, MI QLD 2376 (2); AM W.45476, MI QLD 2440; AM W.45476.001, tissue for molecular studies; AM W.46093, MI QLD 2422 (3, 1 photographed on SEM); AM W.46095, MI QLD 2429 (9); AM W.44764, MI QLD 2429 (photographed); AM W.44764.001, tissue for molecular studies; AM W.45477, MI QLD 2376 (photographed); AM W.45477.001, tissue for molecular studies.

Examination of type material. Holotype: complete specimen, with cylindrical body, 20 thoracic chaetigers. Branchiae from chaetiger 8, as minute papillae. Flange papillae present in all abdominal segments. Prostomium conical, acute. Bilobed neuropodia from chaetiger 14–16. Hooks very short and inconspicuous, only detectable after examination under compound microscope. Pygidium with 2 short cirri, attached ventrally. Paratype: anterior fragment with 25 thoracic chaetigers. Branchiae from chaetiger 8, well developed from first pair. Bilobed neuropodia from chaetiger 11. Hooks easily observed. Flange papillae present in all abdominal segments.

H. Forked chaetae from abdominal neuropodia.

anal cirri are broken.

Description. Body cylindrical; anterior thorax often swollen, posterior thorax slightly wider than abdomen ( Figs 3 A, 4A). Colour in life orange-brown with red blood vessels, ventral part of abdomen grey ( Fig. 12 B). Thoracic width up to 2.2 mm. Prostomium sharply conical. Peristomium with a pair of dorso-lateral nuchal organs. Thoracic chaetigers numbering 21–26 (usually 24–25). Branchiae starting from chaetiger 8 (rarely 9–11) as minute papillae, gradually increasing in size; in chaetiger 17–20 becoming large, triangular with tapered tips ( Fig. 3 B, D); in abdomen long narrow triangular, as long as notopodia or slightly longer ( Fig. 3 D, G). Thoracic post-chaetal lobes present from chaetiger 1, first neuropodial lobe very small; both notopodial and neuropodial lobes gradually increasing in size, becoming digitiform; in anterior thorax similar in size, in posterior thorax notopodial lobes longer ( Figs 3 A, B, 4B). Lateral organs developed at base of notopodia ( Fig. 4 B). Neuropodial lobes becoming bilobed from chaetiger 10–12, in some specimens 13–14 ( Figs 3 A, B, F, 4D). No subpodal or stomach papillae. Abdominal notopodial lobes narrowly foliaceous, with slightly swollen basal part ( Fig. 3 D, G). Abdominal neuropodial lobes supported by two thin aciculae and bilobed; with elongate triangular lobes, inner lobe 2–3 times longer than outer ( Figs 3 D, G, 4F). Subpodal flange well developed, upper edge forming flange papilla (ventral cirrus) in all abdominal segments ( Figs 3 D, G, 4F). Low interramal papilla present between rami in some specimens ( Fig. 3 G). Ciliated dorsal organs with two curved ciliated strips present mid-dorsally in each segment. Thoracic notopodia bearing only crenulated capillary chaetae; all thoracic neuropodia with an anterior J-shaped row of slightly curved hooded hooks and 3–4 rows of crenulated capillary chaetae ( Figs 3 C, E, F, 4B–E); hooks smooth or slightly serrated ( Fig. 4 C, E). Crenulated capillary chaetae accompanied by forked chaetae in abdominal notopodia ( Figs 3 H, 4G) and flail chaetae in abdominal neuropodia. Pygidium with two anal cirri ( Fig. 4 H).

Remarks. Scoloplos dayi was described in 1980 from Northwest coast of Australia (Exmouth: Town Beach) and this represents the first record since then. Specimens from Lizard Island agree with the original description and type material examined, although some variability occurred in the number of thoracic chaetigers (21–26 instead of 20–24 in original description), chaetiger where branchiae begin (8–11 vs 8–9), and chaetiger where bilobed neuropodia start (10–14 vs 14–15). Scoloplos dayi is very similar to Leitoscoloplos bifurcatus ( Hartman, 1957) , which co-occurs with this species in our samples from Lizard Island. The only differences between two species are the presence of thoracic hooks (sometimes very short and inconspicuous) and flange papillae in S. dayi . This species also has more thoracic chaetigers in general, but this character overlaps with L. bifurcatus .

Type locality. Northwest coast of Australia (Exmouth: Town Beach, Western Australia).

Distribution. Northwest coast of Australia, Lizard Island, Queensland.

Molecular analyses. According to data obtained for three specimens ( Figs 13–15 ), S. dayi does not belong to the Scoloplos armiger - S. acmeceps - Leitoscoloplos pugettensis clade. The analysis showed that one of the three studied specimens genetically differed from the other two. The genetic distance between these specimens was 1.7% for 18S sequence fragments and 6.2% for both 16S and CO1 fragments. Two other specimens did not differ genetically and had no substitutions in any of the studied sequences. These results may be indicative of an unrecognized complex of cryptic sympatric species.

Figures

FIGURE 2. Scoloplos acutissimus, AM W. 46096, SEM images. A. Anterior end, left lateral view; B. Same, close-up, arrows indicate lateral organs; C. Thorax-abdomen transition; D. Parapodia of chaetiger 1; E. Neuropodia hooks of chaetiger 1; F. Parapodia of chaetiger 11; G. Neuropodial hooks of chaetiger 11; H. Forked chaeta of abdominal segment; I. Middle part of abdomen, dorsal view; J. Dorsal organ; K. Posterior end of abdomen with pygidium.

FIGURE 3. Scoloplos dayi, A – D: methylene blue staining. A – C: AM W. 45477. A. Anterior end, left lateral view; B. Anterior end, dorsal view; C. Neuropodia of segments 3 and 4; D. AM W. 44764, thorax-abdomen transition, dorsal view; E – H: AM W. 45477, glycerol mounts of parapodia. E. Chaetiger 13; F. Close-up of neuropodia of chaetiger 13; G. Abdominal chaetiger;

FIGURE 4. Scoloplos dayi, AM W. 46093, SEM images. A. Anterior end, left lateral view; B. Parapodia of chaetigers 1 – 3, arrows indicate lateral organs; C. Neuropodia hooks of chaetiger 2; D. Neuropodia of chaetiger 12; E. Neuropodial hooks of chaetiger 18; F. Thorax-abdomen transition; G. Forked chaetae from abdominal neuropodia; H. Posterior end with pygidium,

FIGURE 12. Photographs of live specimens. A. Scoloplos acutissimus; B. Scoloplos dayi; C. Leodamas dubia; D. Naineris

FIGURE 13. Neighbor-Joining phylogenetic tree of 53 specimens based on 18 S gene sequences (Table 2). The tree is drawn to scale, with branch lengths in the same units as those of the evolutionary distances used to infer the phylogenetic tree. Statistical support for clades in the tree was assessed using the bootstrap analysis with 1,000 replicates.

FIGURE 14. Neighbor-Joining phylogenetic tree of 55 specimens based on 16 S gene sequences (Table 2). The tree is drawn to scale, with branch lengths in the same units as those of the evolutionary distances used to infer the phylogenetic tree. Statistical support for clades in the tree was assessed using the bootstrap analysis with 1,000 replicates.

FIGURE 15. Neighbor-Joining phylogenetic tree of 106 specimens based on CO 1 gene sequences (Table 2). The tree is drawn to scale, with branch lengths in the same units as those of the evolutionary distances used to infer the phylogenetic tree. Statistical support for clades in the tree was assessed using the bootstrap analysis with 1,000 replicates.