Nothria orensanzi, Paxton & Budaeva & Gunton, 2023

Paxton, Hannelore, Budaeva, Nataliya & Gunton, Laetitia M., 2023, Amazing Diversity of Nothria (Annelida, Onuphidae) in the Australian Deep Sea, Records of the Australian Museum (Rec. Aust. Mus.) 75 (3), pp. 215-247 : 237-240

Nothria orensanzi sp. nov.

urn:lsid:zoobank.org:act:A8958CCC-64F4-421F-903E-E229D5E62B23

Figs 1 , 21–23 , Tables 2 , S 1

Nothria sp. nov. 1.— Gunton et al., 2021:75, fig. 16C,D.? Nothria sp. , near solenotecton Chamberlin, 1919 .—

Orensanz 1990: 130, pl. 42, figs g–i.

Holotype. Australian Museum ( AM) W.49031, IN2015 _ E02_22; 11 Apr 2015; Australia, Tasmania, Huon Marine Park ; 44.33°S 147.36°E; 2010 m depth . Paratypes (7): AM W.49028, IN2015 _E02_21 (1). AM W.49033, IN2015 _ E02_21 (1). AM W.51447, IN2015 _E02_22 (1 SEM on pin). AM W.51444, IN2015 _ E02_22 (1 SEM on pin). AM W.53851, IN2015 _E02_22 (3).

Other material examined (91). AM W.47917, IN 2015_E02_021 (19). AM W.47920, IN 2015_E02_21 (3). AM W.47918, IN 2015_ E02_22 (17). AM W.49030, IN 2015_E02_22 (1). AM W.47919, IN 2015_E02_022 (48). AM W.53852, IN 2017_ V 03_004 (1). AM W.49940, IN 2017_ V 03_056 (2).

Diagnosis. Eyes absent; antennae extending to chaetiger 8–15; branchiae absent; first 3 chaetigers with anterior hooks; dorsal cirri absent from about chaetiger 30; slender bidentate simple and pseudocompound hooks on chaetiger 1, slender bidentate pseudocompound hooks on chaetiger 2; very slender bidentate pseudocompound to compound hooks on chaetiger 3; pectinate and limbate chaetae from chaetiger 2; subacicular hooks from chaetiger 11–13.

Description. All examined specimens lacking posterior ends. Length of holotype 10 mm for 21 chaetigers, width 2.5 mm; paratypes 13–18 mm (26–29 chaetigers) long, 2.3–2.6 mm wide. Non-type material ranging from 1.7–2.6 in width.

Preserved specimens overall whitish to cream coloured. Holotype and some paratypes with weak brown pigment splotches/spots laterally on prostomium, peristomium and first few segments. Prostomium anteriorly rounded to subtriangular, wider than long, with 2 ovoid frontal lips ( Fig. 21A,B ). Palpo- and antennophores with 1–2 proximal rings and longer distal ring. Palpostyles tapering, extending to chaetiger 1, antennostyles tapering gradually, lateral antennostyles extending to chaetiger 7 (6–11), median antennostyle to chaetiger 9 (8–15). Nuchal grooves straight, with small middorsal separation. Eyes absent. Ventral upper lip rounded to squared, lower lip subtriangular, neither with median section ( Fig. 21B ). Peristomium relatively long, peristomial cirri inserted subdistally on peristomium, about as long as peristomium ( Fig. 21A ).

First chaetiger greatly enlarged, about twice as long as peristomium, chaetiger 2 about as long as peristomium, chaetiger 3 and subsequent ones slightly shorter than peristomium. First 3 pairs of parapodia enlarged and modified; first pair greatly so, directed forward, extending slightly beyond anterior margin of prostomium, with large auricular prechaetal lobes and subulate postchaetal lobes ( Fig. 21A,B ). Second pair of parapodia similar but smaller, with smaller prechaetal but larger subulate postchaetal lobes. Third pair of parapodia only slightly larger than subsequent ones, with further reduced prechaetal lobes; prechaetal lobes present as little knobs to posterior part of body, last postchaetal lobes on chaetiger 13 (11–13). Ventral cirri of the first two chaetigers subulate, becoming rounded on chaetiger 3 as transitioning, glandular pads from chaetiger 4 ( Fig. 21B ). Dorsal cirri weakly subulate to cirriform from chaetiger 1 ( Fig. 21A ), becoming gradually thinner and shorter, very short by chaetiger 15, absent from chaetiger 20–30. Branchiae absent.

First pair of parapodia with 3–4 slender bidentate simple ( Fig. 22A ), almost simple ( Fig. 22B ) and pseudocompound hooks ( Fig. 22C ). Second pair with 2–3 similar sized bidentate pseudocompound hooks ( Fig. 22D ), 2–4 limbate and up to 10 scoop-shaped pectinate chaetae with 20–25 teeth ( Fig. 21C ). Third pair of parapodia with 3–4 very slender bidentate pseudocompound to compound hooks with serrated upper shafts and appendages ( Figs 21D , 22E ), 3–4 limbate chaetae and up to 20 pectinate chaetae. From chaetiger 4 anterior hooks absent, limbate and reduced number of pectinate chaetae present to end of fragments, presumably end of body, although number of pectinate chaetae greatly reduced. Subacicular hooks present singly from chaetigers 12 (11–13), as pairs from chaetiger 13 (12–14). Pygidium unknown.

Mandibles ( Fig. 22F ) highly calcified, almost white, except for darkly sclerotized protomandibles. High cutting plates with 2 median teeth and large distal tooth. Maxillae ( Fig. 22G ) also highly calcified with little sclerotization; left MII with distinct distal fang; maxillary formula: MI = 1+1; MII = 6+10; MIII = 9+0; MIV = 9+9; MV = M1+1. Ratio of mandibles/maxillae = 1.3. Flattened tube ( Fig. 23A ), made up of clear but strong inner secreted layer, covered with pieces of shells and pebbles dorsally and ventrally, with elongate fragments usually placed transversely, laterally filled in with foraminiferans and other small fragments; tubes very sturdy due to strong cementing substance.

Remarks. Prior to the present study only four abranchiate species of Nothria were known: Nothria abyssia Kucheruk, 1978 , N. paxtonae Imajima, 1999 , N. solenotecton ( Chamberlin, 1919) and N. textor Hartman & Fauchald, 1971 . Nothria abyssia and N. paxtonae are species with anterior hooks limited to the first two chaetigers. Both occur in Australian waters; they are treated below and are distinguished further from N. minima sp. nov. and N. orensanzi sp. nov. (both with anterior hooks on the first three chaetigers) in Table 2 . Nothria textor is a very small species (width 0.84 mm) from the North Atlantic. It differs from the two new species in having pectinate chaetae only on chaetigers 2 and 3 and subacicular hooks from chaetiger 7. The two new species resemble most closely N. solenotecton , a deep-sea species from off Panama. This goes particularly for N. orensanzi sp. nov.; however, the latter differs from the former in having longer antennae with well defined, rather than obscurely ringed or smooth ceratophores and simple and pseudocompound hooks rather than only pseudocompound hooks on chaetiger 1. Orensanz (1990) discussed N. solenotecton when reporting three specimens of a closely related species from South of Tasmania (2800–3000 m) and around New Zealand (“lower bathyal”) that he listed as Nothria sp. , near solenotecton Chamberlin, 1919 , but did not formally describe. We have examined a large number of specimens of N. orensanzi sp. nov. from off eastern Australia ranging from southern Tasmania to Jervis Bay Marine Park, concluding that our new species is most probably identical with his material and describe the new species in his honour.

Nothria orensanzi sp. nov., N. minima sp. nov. and N. solenotecton are all abranchiate, anoculate, have ceratophores with few rings, bidentate hooks on the first three chaetigers and pectinate chaetae from chaetiger 2. Despite these similarities, N. minima sp. nov. differs from N. orensanzi sp. nov. in its second pair of parapodia being hardly prolonged, having no simple hooks on chaetiger 1 and having pectinate chaetae with 16–20 rather than 20–25 teeth. Nothria minima sp. nov. is a smaller, more delicate species than N. orensanzi sp. nov. as is evident by having a maximum width of 1.6 mm rather than 2.6 mm. This does not mean that the former is a juvenile of the latter since members of both species contained mature gametes. Furthermore, the tubes of N. minima sp. nov. consist of similarly sized shells ( Fig. 20A ) while those of N. orensanzi sp. nov. are constructed from mixed shells with elongated pieces placed transversely ( Fig. 23A ).

Etymology. We dedicate this species to the late José M. Orensanz in recognition of his valuable contributions to the study of eunicemorph polychaetes.

Distribution. Nothria orensanzi sp. nov. appears to be widely distributed. It was collected off southern Tasmania, Freycinet and Huon Marine Parks, and New South Wales, Jervis Marine Park, at 2010–2820 m depth ( Fig. 23B ).

Figures

Figure 1. Consensus tree from the Bayesian analysis of the combined COI, 16S and 28S dataset; numbers on nodes indicate Bayesian posterior probabilities; capital letters correspond with the clades discussed in the text.Species delimitation results inferred by morphology and DNA-based methods (COI, 16S, and 28S) are indicated right to the consensus tree followed by the final hypothesis based on all evidence combined. White bars indicate missing data.

Figure 20. Nothria minima sp. nov. (A) photograph of tube AM W.51567; (B) map of distribution; red dot represents type locality.

Figure 21. Nothria orensanzi sp. nov.SEM micrographs of paratypeAM W.51444. (A) anterior part, dorsal view; (B) same, ventral view; (C) pectinate chaetae from chaetiger 2; (D) bidentate serrated compound hooks from chaetiger 3.

Figure 22. Nothria orensanzi sp. nov. Line drawings of paratype AM W.53851. (A) slender bidentate simple hook from chaetiger 1; (B) slender bidentate weakly pseudocompound hook from chaetiger 1; (C) slender bidentate pseudocompound hook from chaetiger 1; (D) slender bidentate pseudocompound hook from chaetiger 2; (E) very slender bidentate serrated compound hook from chaetiger 3; (F) mandibles; (G) maxillae.

Figure 23. Nothria orensanzi sp. nov. Photograph of tube AM W.51564; (B) map of distribution; red dot represents type locality, green dots other sites of collection.