Leodamas australiensis ( Hartmann-Schröder, 1979 ) Zhadan, 2020

Zhadan, Anna, 2020, Review of Orbiniidae (Annelida, Sedentaria) from Australia, Zootaxa 4860 (4), pp. 451-502 : 471-472

Leodamas australiensis ( Hartmann-Schröder, 1979) comb. nov.

Figure 11

Not Scoloplos dubia: Tebble, 1955: 123–124 , fig. 26a–c.

Scoloplos (Leodamas) ? dubia: Gallardo, 1968: 93–94 , Pl. XXXIX, figs. 4–5, Pl. XL, figs. 1–3.

Scoloplos (Leodamas) rubra australiensis Hartmann-Schröder, 1979: 131–132 , figs 276–282.

Scoloplos (Leodamas) dubia: Eibye-Jacobsen, 2002: 89–91 , fig. 8A–D.

Leodamas dubia: Zhadan et al. 2015: 789-792 , figs 7A–K, 8A–K.

Leodamas dubius: Blake, 2017: 50 , 53, 56.

Material examined. Queensland: Weipa, South Channel , 12°40’S, 141°57’E, AM W.30590, 01.10.1999, coll. CRC Reef Research Centre Ltd , benthic grab, 1 specimen ; Lizard Island, August 2013: off Casuarina Beach , 14°40’46”S, 145°26’49”E, snorkeling, depth 0.5 m, sand, seagrass, coll. K. Meissner, N. Budaeva, A. Murray, AM W.45480, 1 specimen ; off Casuarina Beach, in front of Lizard Island Research Station , 14°40’46”S, 145°26’49”E, intertidal, sand, coll. J. Parapar, Q. Parapar, P.A. Hutchings, P. Rodgers, AM W.44579, 3 specimens ; Casuarina Beach , 14°40’46”S, 145°26’49”E, intertidal, sand, coll. P.A. Hutchings, P. Rodgers, J. Zanol Silva, N. Budaeva, AM W.46094, 10 specimens ; AM W.44762, 5 specimens ; AM W.44765, 1 specimen ; Mangrove Beach , close to mangroves, 14°40’48”S, 145°27’46”E, intertidal, muddy sand, coll. N. Budaeva, T. Alvestad, AM W.45479, 1 specimen , AM W.44941, posterior fragments; Mangrove Beach , 14°40’47”S, 145°27’44”E, intertidal, sand, coll. N. Budaeva, T. Alvestad, AM W.46098, 7 specimens ; AM W.45478, 1 specimen ; Halifax Bay , 19°10’S, 146°38’E, Jan 1977, depth 5 m, coll . Queensland Nickel Pty Ltd, van Veen grab, AM W.43434, 4 specimens ; Halifax Bay , 19°10’S, 146°38’E, Jan 1977, depth 5 m, coll . Queensland Nickel Pty Ltd, van Veen grab, AM W.43437,1 specimen; Halifax Bay , 19°07’S, 146°33’E, Jan 1977, depth 2 m, coll . Queensland Nickel Pty Ltd, van Veen grab, AM W.43438, 1 specimen .

Additional material examined: Scoloplos dubia Tebble, 1955 , Holotype ( NHM 1953.3.1.1230) and four paratypes ( NHM 1953.3.1.1231-1234), off Accra , Ghana, West Africa, depth 3.6– 11 m.

Type locality. Port Hedland , Western Australia .

Description. Small worms, thoracic width 0.6–0.9 mm. Body long and slender, thorax flattened, abdomen cylindrical ( Fig. 11 A–C). Prostomium sharply conical ( Fig. 11B ). Thoracic chaetigers numbering 15–18 ( Fig. 11A ). Branchia from chaetiger 6, triangular with broad base and tapering tips; in abdomen becoming longer, same length or slightly shorter than notopodia ( Fig. 11A, C, E, H, J ). Thoracic postchaetal notopodial lobes developed from chaetiger 2, digitate; in abdomen becoming long, narrow foliaceous ( Fig. 11A, C, E, H, J ). Thoracic postchaetal neuropodial lobes as low ridges, in one specimen (AM W.30590) with single papilla in last thoracic chaetiger ( Fig. 11A, C, D ). No subpodal papillae. Abdominal neuropodia with outer lobe cirriform, inner lobe reduced; no subpodal notch and flange ( Fig. 11E, H ). Thoracic neurochaetae represented by almost straight uncini with pointed tips arranged in 3–5 rows and few capillaries in posterior row; anterior and superior uncini thicker than posterior and inferior; anterior row present only in dorsal part, and posterior only in ventral part of neuropodia ( Fig. 11C, D, F, G ). In abdomen both rami supported by thick aciculae; usually 2–3, thinner, straight and not projected in notopodia; thick, strongly projecting and hooked in neuropodia; degree of curvature of neuropodial aciculae differs between segments and even in two sides of one segment; it varies from almost straight to 180° ( Fig. 11 H–J). Abdominal chaetae crenlated capillaries in both rami, abdominal notopodia also bearing forked chaetae ( Fig. 11I ). Pygidium with four short cirri.

Distribution. (based on literature) Andaman Sea, South China Sea. Australia, Western Australia, Queensland.

Habitat. Intertidal and upper subtidal, sand, muddy sand, seagrass.

Remarks: Leodamas australiensis was described from Port Hedland (Western Australia) as L. rubra australiensis Hartmann-Schröder, 1979 . The main differences between the stem species L. rubra Webster, 1879 , described from Virginia (West Atlantic), are the smaller number of thoracic chaetigers (23 vs 24–25) and strongly curved abdominal neuropodial aciculae. Later, L. rubra australiensis was synonymised with Leodamas dubius ( Tebble, 1955) described from Ghana, West Africa ( Eibye-Jacobsen 2002). Earlier, Gallardo (1968), with some doubt, referred the posterior ends of Leodamas specimens from Vietnam to L. dubius , because of the characteristic strongly curved abdominal aciculae. These projecting neuroaciculae were regarded as a diagnostic character distinguishing L. dubius and L. rubra australiensis from other Leodamas species. The important difference between these species is the starting-point of the branchiae segment: from 6 th chaetiger in L. rubra australiensis and from 7 th chaetiger in L. dubius . Zhadan et al. (2015) redescribed L. dubius based on material from Lizard Island, Queensland; they also followed the synonymy with L. rubra australiensis , although they noticed that specimens from the West African and Indo-Pacific regions likely represent different species. This position was supported by Blake (2017). Even within one specimen, the shape of the abdominal neuropodial aciculae varies greatly, as noted by Eibye-Jacobsen (2002), Zhadan et al. (2015), and Blake (2017); it can be less curved and does not always have the characteristic appearance. We investigated type and non-type specimens of L. dubius from West Africa which aligned with Tebble’s description. All specimens have branchiae starting from the 7 th chaetiger. The shape and distribution of the thoracic neuropodial uncini are similar in both species, the type specimens of L. dubius have fewer rows of uncini. Forked chaetae were not found in the abdominal notopodia in L. dubius , as indicated in the original description. Similarly, forked chaetae were not found in specimens from Thailand ( Eibye-Jacobsen 2002), whereas they were present in specimens from Vietnam ( Gallardo, 1968) and Australia ( Hartmann-Schröder 1979; Zhadan et al. 2015; present study). Blake (2017) indicated the absence of abdominal notoacicula in L. dubius , despite its inclusion in the original species description. In the specimens from West Africa, very thin notoacicula could be seen when parapodia are examined in detail. The presence of 2–3 notoaciculae has been reported in Hartmann-Schröder (1979) and in the present study; they were not mentioned in Gallardo (1967) or Zhadan et al. (2015). From the above information, it can be concluded that L. australiensis should be raised to a full species. The main difference between L. australiensis and L. dubius is the starting-point of the branchiae at 6 th chaetiger in L. australiensis instead of 7 th in L. dubius . The characteristics of both species are given in Table 1 . The specimens studied in the present work differ from the descriptions by Hartmann-Schröder (1979) and Eibye-Jacobsen (2002) owing to the fewer number of thoracic chaetigers (max 18 instead of 21–23) and absence of podal papillae in most specimens. These differences could probably be attributed to the smaller size of the specimens studied here.

Figures

FIGURE 11. Leodamas australiensis, A–E: stereomicroscope, F–J: compound microscope.A–E, I–J: AM W.30590, F–H: AM W.43434. A. General view; B. Anterior end, dorsal view; C. Anterior end, lateral view; D. Thorax-abdomen transition, lateral view; E. Abdomen, dorsal view; F. Parapodium of chaetiger 10; G. Parapodium of chaetiger 16; H–J. Abdominal parapodia. a, acicula; br, branchia; cc, crenulated capillaries; fc, forked chaeta; ne, neuropodium; no, notopodium; u, uncini.