Nothria deltasigma, 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 : 225-227

publication ID	https://doi.org/ 10.3853/j.2201-4349.75.2023.1802
DOI	https://doi.org/10.5281/zenodo.10988791
persistent identifier	https://treatment.plazi.org/id/03C99027-FF86-A614-E80F-FD73FA91FB8F
treatment provided by	Felipe
scientific name	Nothria deltasigma
status	sp. nov.

Treatment

Nothria deltasigma View in CoL sp. nov.

urn:lsid:zoobank.org:act:700F6979-DC3B-481B-A897-62E9E97937DB

Figs 1 View Figure 1 , 6–8 View Figure 6 View Figure 7 View Figure 8 , Tables 1 View Table 1 , 2 View Table 2 , S 1 View Table 1

Holotype. Australian Museum ( AM) W.51639, IN2018 _ V06 _169; 14 Dec 2015; Australia, Tasmania, flat area south of Brians , 44.24– 44.23°S 147.29– 147.30°E; 1422–1443 m depth GoogleMaps . Paratypes (2): AM W.51640, IN2018 _ V06 _169 (1). AM W. 53497, mounted for SEM, IN2018 _ V06 _169 (1).

Other material examined (7). AM W.53846, IN 2018_ V 06_169 (7).

Diagnosis. Eyes absent; antennae extending to chaetiger 11–13; short branchiae from chaetiger 10–12; first 3 chaetigers with anterior hooks: robust uni- to weakly tridentate and slender bidentate simple hooks on chaetiger 1; robust uni- to bidentate simple hooks and slender bidentate weakly pseudocompound hooks on chaetiger 2 and very slender bidentate pseudocompound to compound hooks on chaetiger 3; pectinate and limbate chaetae from chaetiger 2; subacicular hooks from chaetiger 11–14.

Description. All examined specimens lacking posterior ends. Length of holotype 11 mm for 23 chaetigers, width 2.4 mm; paratypes 10 and 16 mm (15 and 32 chaetigers) long, 1.8 and 2.2 mm wide respectively. Non-type material ranging from 1.7–2.3 mm in width. Alcohol-stored specimens overall cream-coloured. Holotype lacking any pigmentation but some specimens with brown spot dorsally on anterior part of prostomium. Prostomium anteriorly rounded to subtriangular, wider than long, with 2 ovoid frontal lips, separated from each other by small space ( Fig. 6A,B View Figure 6 ). Palpo- and antennophores with 2–3 proximal rings and a longer distal ring. Palpostyles tapering, extending to chaetiger 1, lateral antennostyles extending to chaetiger 11, median antennostyle to chaetiger 13 (in holotype); antennostyles tapering gradually, becoming very thin towards distal end ( Fig. 6A View Figure 6 ). Nuchal grooves straight, with small middorsal separation. Eyes absent. Ventral upper lips rounded, lower lips subtriangular, neither with median section ( Fig. 6B View Figure 6 ). Peristomium short, peristomial cirri inserted subdistally on peristomium, slightly longer than peristomium.

First chaetiger greatly enlarged, about three times as long as peristomium, chaetiger 2 about twice length of peristomium, subsequent chaetigers about 1.5 times as long as peristomium ( Fig. 6A,B View Figure 6 ). Anterior 3 pairs of parapodia modified; first pair greatly enlarged, directed forward, extending slightly beyond anterior margin of prostomium ( Fig. 6A,B View Figure 6 ), with large auricular prechaetal lobes, subulate postchaetal lobes, dorsal and ventral cirri. Second pair of parapodia similar but smaller, with smaller prechaetal lobes ( Fig. 6C View Figure 6 ). Third pair only slightly larger than subsequent parapodia, directed laterally, with further reduced, tongue-like prechaetal lobes; ventral cirri transitioning to glandular pads ( Fig. 6B View Figure 6 ). From chaetiger 4 onwards parapodial structure becoming more uniform; dorsal cirri gradually becoming thinner and shorter, prechaetal lobes becoming short and rounded, postchaetal lobes gradually decreasing, last on chaetigers 16 (13–16), ventral cirri replaced by round glandular pads from chaetiger 4. Simple branchiae present as short filament from chaetiger 11 (10–12), increasing only slightly in length ( Figs 6D View Figure 6 , 7G View Figure 7 ) remaining as relatively short structure until end of incomplete worms; total extent unknown.

First pair of parapodia with 2–3 robust uni- to weakly bi- ( Fig. 7A View Figure 7 ) to tridentate ( Fig. 7B View Figure 7 ) simple hooded hooks and a lower slender bidentate simple hook ( Fig. 7C View Figure 7 ). Second pair of parapodia with 2–3 robust bidentate simple hooks ( Fig. 7D View Figure 7 ), a slender bidentate weakly pseudocompound hook ( Fig. 7E View Figure 7 ), as well as 2 limbate and numerous pectinate chaetae with 18–20 teeth. Third pair with 3–5 slender, bidentate pseudocompound to compound hooks with serrated upper shaft and appendage ( Fig. 7F View Figure 7 ), limbate chaetae and numerous scoop-shaped pectinate chaetae ( Fig. 6E View Figure 6 ). Hooks absent from chaetiger 4, limbate and pectinate chaetae present in reduced numbers presumably up to end of body. Subacicular hooks present singly from chaetiger 12 (11–14), as pairs from 14 (12–16). Pygidium unknown.

Mandibles ( Fig. 7H View Figure 7 ) highly calcified, almost white, except for darkly sclerotized, unusually long protomandibles. High cutting plates with weakly defined median and large distal tooth. Maxillae ( Fig. 7I View Figure 7 ) lightly sclerotized except for teeth and attachment lamellae; carriers with unusually dark outer edges and curved basal extensions, perhaps indicating imminent moult of jaws. Maxillary formula: MI = 1+1; MII = 8+8; MIII = 9+0; MIV = 8+11; MV = 1+1. Ratio of mandibles/maxillae = 1.3. Flattened tube ( Fig. 8A View Figure 8 ), covered mainly with larger pieces of shells dorsally and ventrally, sides filled in with foraminiferans; lining transparent.

Remarks. Orensanz (1974) described the subspecies N. conchylega anoculata lacking the eyes that are present in the stem species from off Buenos Aires, Argentina from a depth of 700–900 m; Fauchald (1982) subsequently raised the subspecies to full specific level. Nothria delta sp. nov. and N. deltasigma sp. nov. are morphologically similar to each other and to N. anoculata . Some of the noticeable differences are in the presence of simple vs. pseudocompound anterior hooks on chaetiger 1 and 2 ( Table 1 View Table 1 ). This could be interpreted as a function of size and thus a pseudocompound hook could be a juvenile characteristic as discussed by Orensanz (1990) and Budaeva & Paxton (2013). However, extrapolating from his drawings, the original Argentinian specimens consisted of a width of 1.2 mm ( Orensanz, 1974: pl 7, fig 1) while our material measured 1.7–2.7 mm in width, having three chaetigers with anterior hooks, and thus representing the adult stage.

The differences between the three species are detailed in Table 1 View Table 1 and to the remaining species in Table 2 View Table 2 . They can be summarized as follows: hooks of chaetiger 1 are only simple in N. anoculata and N. deltasigma sp. nov, simple and pseudocompound in N. delta sp. nov.; hooks of chaetiger 2 are only pseudocompound in N. anoculata and N. delta sp. nov, and simple and pseudocompound in N. deltasigma sp. nov.; hooks of chaetiger 3 are pseudocompound to compound in all three species. The antennae are shorter in N. anoculata (median to chaetiger 10) and longer (median to chaetiger 13–14) in N. delta sp. nov. and N. deltasigma sp. nov. Branchiae are about twice as long in N. anoculata as in the other two species.

In Table 1 View Table 1 we have listed the values stated in the original description of N. anoculata from Argentina separately from those given later for the subantarctic records by Orensanz (1990) as they do not always agree and seem to represent an expansion of the original N. anoculata definition to fit the wider distribution. Thus, it supports our suspicion that rather than a widely distributed species in the southern seas, N. anoculata as characterized by Orensanz (1990) represents a species complex.

Etymology. The specific epithet refers to the manuscript name “Ds” of the new species, referring to its great similarity and thus second version of “D” in the Greek language.

Distribution. The new species was only collected on the flat area south of Brians, south of Tasmania in 1422–1443 m depth ( Fig. 9B View Figure 9 ).

Diagnosis. Eyes present, ventral upper lip with median section; antennae extending to chaetiger 7–9; branchiae long, digitate, from chaetiger 9–10; 3 first chaetigers with anterior hooks: robust bidentate simple and very slender bidentate pseudocompound hooks on chaetiger 1; slender and very slender bidentate pseudocompound hooks on chaetiger 2 and very slender bidentate pseudocompound to compound hooks on chaetiger 3; pectinate and limbate chaetae from chaetiger 3; subacicular hooks from chaetiger 10–11.