Leitoscoloplos bifurcatus ( Hartman, 1957 )

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 : 786

Leitoscoloplos bifurcatus ( Hartman, 1957)

( Figs 5 , 6 )

Haploscoloplos bifurcatus Hartman, 1957: 277 –279

Leitoscoloplos bifurcatus .— Day 1977: 223 –224; Hutchings & Rainer 1979: 760 –761; Mackie 1987: 13 –14, fig. 14a–f.

Material examined. AM W.46089, MI QLD 2376 (photographed); AM W.44761, MI QLD 2429 (4, 1 photographed on SEM); AM W.44299, MI QLD 2378 (2); AM W.44938, MI QLD 2439 (photographed); AM W.44938.001, tissue for molecular studies.

Description. Body cylindrical, thorax slightly wider than abdomen ( Fig. 5 A). Thoracic width up to 2.5 mm. Prostomium sharply conical. Peristomium bearing pair of dorso-lateral nuchal organs ( Fig. 6 A). 19–21 thoracic chaetigers ( Fig. 5 A). Branchiae starting from chaetiger 8 as minute papillae, well developed from chaetiger 15–16; in abdomen triangular, narrow lanceolate in posterior part of abdomen; slightly shorter or equal to notopodial lobes ( Figs 5 A, D, G, H, 6F). Thoracic post-chaetal lobes developed from chaetiger 1, gradually increase in size, narrow triangular in shape; in anterior thorax equal size or neuropodia lobes longer, in posterior thorax notopodial lobes longer ( Figs 5 C–F, 6A, D, E). Lateral organs developed at base of notopodia ( Fig. 6 A, E, F). Neuropodial lobes becoming bilobed from chaetiger 10–12 ( Fig. 5 A). No subpodal or stomach papillae. Abdominal notopodial lobes narrow lanceolate; neuropodial lobes bilobed with inner lobe longer than outer, with two or three aciculae; in anterior abdomen lobes short, subequal, in posterior abdomen inner lobe very long, 2–3 times longer than outer ( Figs 5 G, H, 6E, F, G). Subpodal notch and flange present, in first abdominal chaetiger subpodal flange can form papilla (ventral cirrus) in some specimens, but in other segments its upper margin rounded; all other abdominal neuropodia without flange papillae ( Figs 5 B, D, G, H, 6E, F, G). Elongate ciliated dorsal organs present middorsally as two lateral curved ciliated strips ( Fig. 6 H) in all segments from posterior thorax. Chaetae crenulated capillaries in all parapodia ( Figs 5 C, E, F, 6B, C), forked chaetae in abdominal notopodia not found. Pygidium with two anal cirri ( Fig. 6 I).

Remarks. Leitoscoloplos bifurcatus has been described from South Australia and later reported also from Victoria, New South Wales, Queensland and Northern Territory ( Hutchings & Rainer 1979). Specimens described in present study agree well with previous descriptions. Leitoscoloplos bifurcatus is very similar to S. dayi in general appearance, shape of thoracic neuropodia, and the first segment with branchiae. Differences between these two species are listed above.

Molecular analyses. The 18S and 16S sequence analyses ( Figs 13 , 14 ) support the inclusion of Leitoscoloplos bifurcatus in the clade that contains representatives of the genus Leodamas : L. dubia , L. rubra and L. johnstonei . This result strongly incongruent with the morphology indicate possible paraphyly of Leitoscoloplos . The analysis of CO1 sequences ( Fig. 15 ) showed that Leitoscoloplos bifurcatus does not form a clade with Leodamas or with other Leitoscoloplos species. It is interesting that three clades including species assigned to Leitoscoloplos appeared to show agreement with three of the five morphological subgroups recognised by Mackie (1987). Leitoscoloplos pugettensis belongs to group 3 (species with more than 10 thoracic chaetigers, mammiform or mammiform/triangular thoracic neuropodial lobes, and strap-like branchiae; no interramal cirri or subpodal papillae); L. bifurcatus belongs to group 4 (species with more than 10 thoracic chaetigers, single triangular or triangular/bifurcate thoracic neuropodial lobes, and triangular branchiae; no interramal cirri or subpodal papillae), and L. robustus and L.fragilis to group 5 (species with more than 10 thoracic chaetigers, single triangular, triangular/bifurcate or mammiform/bifurcate thoracic neuropodial lobes, and triangular branchiae; interramal cirri and subpodal papillae present). Whether this would hold up with the inclusion of additional taxa is unknown.

Figures

FIGURE 5. Leitoscoloplos bifurcatus, A – D: AM W. 44938, methylene blue staining. A. Anterior end, left lateral view; B. Thorax-abdomen transition, left lateral view; C. Parapodia of chaetigers 2 and 3; D. Abdomen, lateral view. E – H: AM W. 46089, glycerol mounts of parapodia. E. Chaetiger 4; F. Chaetiger 13; G. Anterior abdominal chaetiger; H. Posterior

FIGURE 6. Leitoscoloplos bifurcatus, AM W. 44761, SEM images. A. Anterior end, left lateral view, arrows indicate lateral organs; B. Neuropodium of chaetiger 2; C. Neuropodium of chaetiger 12; D. Parapodia of chaetigers 11 – 14, arrows indicate lateral organs between rami; E. Thorax-abdomen transition, dorsal organs (do) are seen mid-dorsally, arrows indicate lateral organs; F. Abdominal segments, dorsal view, dorsal organs (do) are seen mid-dorsally, arrow indicates lateral organ; G.

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.