Nothria delta, 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 : 221-225

Nothria delta sp. nov.

urn:lsid:zoobank.org:act:6A42BD06-7979-44A8-90EC-D0806F0632AF

Figs 1 , 2–5 , Tables 1 , 2 , S 1

Nothria sp. nov. 2.— Gunton et al., 2021:75, fig. 16E.

Holotype. Australian Museum ( AM) W.51342, IN2015 _ E02_22; 11 Apr 2015; Australia, Tasmania, Huon Marine Park ; 44.3°S 147.36°E; 2010 m depth . Paratypes (3): AM W.49029, IN2015 _E02_21 (1); AM W.51341, IN2015 _ E02_21 (1); AM W.51448.001, mounted for SEM, AM W.51448 worm tube, IN2017 _C01_207 (1).

Other material examined (13). AM W.53845, IN 2017_ C01_207 (9); SAMA E8968, IN 2017_C01_207 (3); AM W.49933, IN 2017_ V 03_56 (1).

Comparative material. AM W.198975. Nothria conchylega . Norway, Ramfjord near Tromsø, 63.55°N 19.08°E, in mud and sand, 50 m depth, coll. Eivind Oug, 23 Jan 1978 (5).

Diagnosis. Eyes absent; antennae extending to chaetiger 10–14; short branchiae from chaetiger 10–12; first 3 chaetigers with anterior hooks: robust uni- to weakly bidentate simple and slender bidentate pseudocompound hooks on chaetiger 1; slender bi- to weakly tridentate 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 10–14.

Description. All examined specimens lacking posterior ends. Length of holotype 18 mm for 29 chaetigers, width 2.7 mm; paratypes 7.5–18 mm (15–32 chaetigers) long, 2.5 mm wide. Non-type material ranging from 1.2–2.2 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. 2A–D ). Palpo- and antennophores with 2–3 proximal rings and longer distal ring. Palpostyles tapering, extending to chaetiger 1, lateral antennostyles to chaetiger 10 (4–10), median antennostyle extending to chaetiger 14 (9–14); antennostyles tapering gradually, becoming very thin towards distal end ( Fig. 2A–B ). Nuchal grooves straight, with small middorsal separation. Eyes absent. Ventral upper lip rounded, lower lip subtriangular, neither with median section ( Fig. 2D ). Peristomium short, peristomial cirri inserted subdistally on peristomium, about as long as peristomium.

First chaetiger greatly enlarged, about three times as long as peristomium, chaetiger 2 about twice length of peristomium, chaetigers 3–6 about as long as peristomium, subsequent ones slightly longer ( Fig. 2A,B ). Anterior 3 pairs of parapodia modified; first pair greatly enlarged, directed forward, extending slightly beyond anterior margin of prostomium, with large auricular prechaetal lobes, subulate postchaetal lobes, dorsal and ventral cirri ( Fig. 3A ). Second pair of parapodia similar but smaller, with smaller prechaetal lobes ( Fig. 3B ). Third pair ( Fig. 3C ) only slightly larger than subsequent parapodia, directed laterally, with further reduced prechaetal lobes; ventral cirri transitioning to glandular pads. From chaetiger 4 onwards parapodial structures becoming more uniform; dorsal cirri gradually becoming thinner and shorter, prechaetal lobes becoming short and rounded, postchaetal lobes gradually decreasing, last on chaetigers 15 (13–15), ventral cirri replaced by round glandular pads from chaetiger 4 ( Fig. 2B ). Simple branchiae present as very short oval filament from chaetiger 12 (10–12) ( Fig. 3D ), increasing only slightly in length ( Fig. 4A ) to remain as relatively short structure to end of incomplete worms; total extent unknown.

First pair of parapodia with 2 robust uni- ( Fig. 4B ) to weakly bidentate simple ( Fig. 4C ) and 1–2 slender bidentate pseudocompound ( Fig. 4D ) hooded hooks. Second pair of parapodia with slender bi- ( Fig. 4E ) to occasionally tridentate ( Fig. 4F ) pseudocompound hooks, as well as 2 limbate and many pectinate chaetae with 18–20 teeth. Third pair of parapodia with 2–4 slender, bidentate pseudocompound to compound hooks with serrated upper shaft and appendage ( Fig. 4G ), 3–4 limbate chaetae and numerous (up to 30) scoop-shaped pectinate chaetae with 18–20 teeth ( Fig. 3C ). Hooks absent from chaetiger 4, limbate and pectinate chaetae present in reduced numbers presumably to end of body. Subacicular hooks present singly from chaetigers 14 (10–14), as pairs from chaetiger 16 (12–16). Pygidium unknown.

Mandibles ( Fig. 4H ) highly calcified, almost white, except for darkly sclerotized, unusually long protomandibles. High cutting plates with weakly defined median and large distal tooth. Maxillae ( Fig. 4I ) with little sclerotization except for teeth and attachment lamellae. Maxillary formula: MI = 1+1; MII = 9+10; MIII = 9+0; MIV = 10+10; MV = 1+1. Ratio of mandibles/maxillae = 1.2. Flattened tube ( Fig. 5A ), covered with small pieces of shells and foraminiferans, lining transparent.

Remarks. The new species shares the possession of unidentate or falcate simple anterior hooks with five Nothria species: N. conchylega , N. edwardsi , N. occidentalis Fauchald, 1968 , N. anoculata Orensanz, 1974 and N. grossa Imajima, 1989 . Nothria edwardsi can be most easily distinguished from the group by having only two pairs of anterior parapodia bearing hooks ( Arias & Paxton, 2016) while the others have three. Although the morphometric and meristic characteristics of the remaining species are exceedingly similar, all but N. anoculata possess two large posterior eyes, leaving N. anoculata as the morphologically most similar species to N. delta sp. nov.

Directly below, we are describing another anoculate species with unidentate simple anterior hooks that also closely resembles N. anoculata . The relationship between the three species will be detailed in Table 1 and discussed in the Remarks section of the next new species.

Etymology. The specific epithet refers to the manuscript name “D” of the new species in the Greek language.

Distribution. The holotype and paratypes (AM W.49029 and AM W.51341) were collected from off southern Tasmania in 2010–2028 m depth. Paratype AM W.51448 and 11 specimens were collected from the GAB, 1772–1808 m, while W.49933 was collected at Jervis Bay Marine Park in 2636–2650 m depth ( Fig. 5B ).

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 2. Nothria delta sp. nov. SEM micrographs of paratype AM W.51448. (A) anterior part, dorsal view; (B) same, ventral view; (C) enlargement of prostomium and associated structures, dorsal view; (D) same, ventral view. ap, antennophore; as, antennostyle; fl, frontal lip; gp, glandular pad; la, lateral antenna; llp, lower lip; ma, median antenna; man, mandible; pa, palp; pc, peristomial cirrus; pe, peristomium; pp, palpophore; ps, palpostyle; pr, prostomium; ul, upper lip; vc, ventral cirrus; I–III, chaetigers 1–3.

Figure3. Nothria delta sp. nov.SEM micrographs of paratypeAM W.51448.(A) parapodium of chaetiger 1, posterior view;(B) parapodium of chaetiger 2, same view; (C) parapodium of chaetiger 3, anterior view; (D) parapodia 9–12 to show appearance of branchiae, dorsal view. br, branchia; dc, dorsal cirrus; pcl, postchaetal lobe; precl, prechaetal lobe; vc, ventral cirrus; IX–XII, chaetigers 9–12.

Figure 4. Nothriadelta sp.nov.Line drawings of paratypeAM W.51341.(A) parapodium of chaetiger 17 to show small branchia; (B) robust unidentate simple hook from chaetiger 1; (C) robust weakly bidentate simple hook from chaetiger 1; (D) slender bidentate pseudocompound hook from chaetiger 1; (E) slender bidentate pseudocompound hook from chaetiger 2; (F) slender tridentate pseudocompound hook from chaetiger 2; (G) slender bidentate compound hook from chaetiger 3; (H) mandibles, ventral view; (I) maxillae, dorsal view. br, branchia; ca, carrier; ccp, calcareus cutting plate; dc, dorsal cirrus; gp, glandular pad; llc, lower limbate chaetae; loman, length of mandible; lomax, length of maxillae; pc, pectinate chaetae; pco, pulp cavity opening; pm, protomandible; precl, prechaetal lobe; sah, subacicular hooks; sh, shaft; ulc, upper limbate chaetae.

Figure 5. Nothria delta sp.nov.(A) photograph of tube of paratype AM W.51448. (B) map of distribution; red dot represents type locality, green dots other sites of collection.

Tables

Table 2. Distinguishing features of Australian deep-water Nothria species collected during present study. n/a, not applicable; PC, pseudocompound; C, compound.

character	delta	deltasigma	digitata	josae	lizae	minima	orensanzi	otsuchiensis complex	cf paxtonae Imajima, 1999	simplex
maximum width (mm)	2.7	2.4	2.3	2.0	4.0	1.6	2.6	3.0	1.3	2.8
shape of anterior prostomium	rounded to subtriangular	rounded to subtriangular	rounded	subtriangular	rounded	rounded to subtriangular	rounded to subtriangular	rounded to subtriangular	rounded	rounded
antennae, to chaetiger	median 9–14; lateral 4–10	median 13; lateral 11	median 7–9; lateral 7–8	median 9–11; lateral 7–9	median 11–18; lateral 9–14	median 6–9; lateral 4–7	median 8–15; lateral 6–11	median 4–5; lateral 3–4	median 6; lateral 5	median 5; lateral 4
rings of palps and antennae	3–4	3–4	4–5	3–4	3–4	2–3	2–3	2–3	2–3	3–4
eyes	absent	absent	small anterior; large posterior	large posterior	absent	absent	absent	sm.ant.pres/abs la.post.pres/abs	none visible	absent
branchiae from chaetiger	10–12	10–12	9–10	11–13	12–14	absent	absent	8–9	absent	10
branchiae, length	short	short	long	short	short	n/a	n/a	short to long	n/a	long
last postchaetal lobe on chaetiger	13–15	13–16	11–12	13–16	13–15	8–12	11–13	15	19	11–13
anterior chaetigers with hooks	3	3	3	3	3	3	3	3	2	2
hooks of chaetiger 1	simple & PC	simple	simple & PC	simple & PC	simple & PC	PC to C	simple & PC	simple & PC	PC	simple
tips of hooks chaetiger 1	uni- bidentate	uni- tridentate	bidentate	bidentate	bidentate	bidentate	bidentate	bidentate	bidentate	bidentate
hooks of chaetiger 2	PC only	simple & PC	PC	simple & PC	simple & PC	PC to C	PC	simple & PC	PC	simple & PC
tips of hooks chaetiger 2	bi- to tridentate	bidentate	bidentate	bidentate	bidentate	bidentate	bidentate	bidentate	bidentate	bidentate
hooks of chaetiger 3	PC to C	PC to C	PC to C	PC to C	PC to C	PC to C	PC to C	PC to C	absent	absent
tips of hooks chaetiger 3	bidentate	bidentate	bidentate	bidentate	bidentate	bidentate	bidentate	bidentate	n/a	n/a
pectinates from chaetiger	2	2	3	3	3	2	2	3	8	3
number of teeth on pectinates	18–20	18–20	14–16	18–20	20–22	16–20	20–25	20	12	20–25
subacicular hooks from chaetiger	10–14	11–14	10–11	9–12	10–13	9–10	11–13	10–15	8–9	13–14
left maxilla II	no distal fang	no distal fang	no distal fang	distal fang	distal fang	distal fang	distal fang	distal fang	?	distal fang
ratio mandibles/maxillae	1.2	1.3	1.2	1.2	1.2	1.2	1.3	1.3	?	1.2
tube	forams and small shells	large shell fragments	large shells	mixed sized shells	large shell fragments, pavement-like	similarly sized shells	mixed shells, elongate pieces placed transversely	small shell fragments and forams	forams	forams & shells
depth (m)	1772–2650	1422–1443	400	1013–1093	1422–2028	1202–1221	2010–2850	400–1761	1772–2650	2342–2518