Nothria, Malmgren, 1867

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 : 244-245

Key to Australian deep-water Nothria species collected by RV Investigator

1 Branchiae absent ........................................................................................................................ 2

—— Branchiae present ...................................................................................................................... 4

2 Anterior 2 pairs of parapodia with hooks ................................... N. cf. paxtonae Imajima, 1999

—— Anterior 3 pairs of parapodia with hooks .................................................................................. 3

3 Parapodia 1 and 2 prolonged; hooks of chaetiger 1 simple and pseudocompound; robust species (max. width 2.6 mm); tube with smallish fragments and rubble ( Fig. 23A ) .......................................... N. orensanzi sp. nov.

—— Parapodia 1 greatly prolonged, parapodia 2 hardly so; hooks of chaetiger 1 pseudocompound to compound; slender, delicate species (max. width 1.6 mm); tube covered with similarly sized shells ( Fig. 20A ) ............................................................................................ N. minima sp. nov.

4 Anterior 2 pairs of parapodia with hooks ...................................................... N. simplex sp. nov.

—— Anterior 3 pairs of parapodia with hooks .................................................................................. 5

5 Hooks of chaetiger 1 uni- to bi- or tridentate ............................................................................ 6

—— Hooks of chaetiger 1 clearly bidentate ...................................................................................... 7

6 Hooks of chaetiger 1 simple and pseudocompound; tube with foraminiferans and other small fragments ( Fig. 5A ) ......................................... N. delta sp. nov.

—— Hooks of chaetiger 1 simple only; tube with large shell fragments ( Fig. 8A ) ................................................................................................... N. deltasigma sp. nov.

7 Branchiae short, starting from chaetiger 11–14 ........................................................................ 8

—— Branchiae long, starting from chaetiger 8–10 ........................................................................... 9

8 Prostomium subtriangular; large posterior eyes present; tube with some very large shells ( Fig. 14A ) ............................................................. N. josae sp. nov.

—— Prostomium anteriorly rounded; eyes absent; tube with evenly sized shell fragments, resembling pavement ( Fig. 17A ) .................................... N. lizae sp. nov.

9 Branchiae from chaetiger 9–10; ventral upper lip with median section ( Fig. 9B ); postchaetal lobes on first 11–12 chaetigers ...................... N. digitata sp. nov.

—— Branchiae from chaetiger 8–9; ventral upper lip without median section; postchaetal lobes on first 14–17 chaetigers ..... N. otsuchiensis Imajima, 1986 complex Discussion

The type-species of Nothria , N. conchylega , was described from shallow waters in western Norway (M. Sars, 1835). The original description is very general, giving few characters presently known to be of taxonomic importance. Fauchald (1982) redescribed the species and designated a lectotype from Florø, Western Norway.

Species of Nothria are superficially very similar and their lack of clear diagnostic features has hampered and complicated the taxonomy of the genus (Pettibone, 1970; Fauchald, 1982; Kucheruk, 1985). Chaetae, which are usually such useful characters in specific polychaete classification, are too generalized in this genus to be of much help. The specialized hooks of the anterior three, or rarely two, pairs of modified parapodia are distally almost all bidentate and the state of their fracture, i.e. whether they are simple, pseudocompound or compound, can be dependent on their stage during ontogeny where the final or adult state is only reached at a certain size ( Orensanz, 1990; Budaeva & Paxton, 2013; Arias & Paxton, 2016). However, during the present study this problem did not arise since we encountered few juvenile specimens.

This is the first integrative study of the genus, sequencing the markers COI, 16S rDNA and 28S rDNA from 37 specimens and employing conventional and exploratory morphological characters as well as tube structure for identification. In search for the exploration of new diagnostic features we evaluated the widths of the anterior hooks, certain jaw features with respect to mandibles and maxillae, and the consistency and structure of the tubes which are constructed by their inhabitants. These characters have been incorporated into the taxonomic descriptions.

Molecular data provided strong support for recognition of the eight new species with high posterior probability values for all clades and with congruent results between species delimitation analyses based on two mitochondrial and one nuclear marker. The Nothria otsuchiensis species complex clade ( Fig. 1 , clade C) showed conflicting delimitation results due to high divergence in sequences, missing sequence data for some specimens/markers and insufficient taxon sampling. If more specimens from this complex are analyzed in the future, it might result in splitting it into several well delimited species. The analysis of morphology has not revealed any obvious differences between the specimens within the complex. Thus, N. otsuchiensis may represent a complex of cryptic species, alternatively, such characters could be found after examination of a large amount of material containing various ontogenetic stages. Another delimitation conflict was recovered within Nothria orensanzi sp. nov. ( Fig. 1 , clade B) which contained one specimen delimited as a separate species in 16S and COI analyses. Adding more sequences may potentially lead to splitting this species into two. Nevertheless, here we recognize the whole clade B as a single species based on the data available at hand.

Three larger clades were highly supported in the analysis based on the combined dataset of three markers. Clade B+E+H showed no synapomorphic morphological characters. Clade F+A contains two sister species N. josae sp. nov. and N. lizae sp. nov. that share a similar distribution of simple and pseudocompound hooks on chaetigers 1–3, pectinate chaetae from chaetiger 3, have short protomandibles and maxilla IIL with a distal fang. Clade J+D+I comprising Nothria conchylega , N. delta sp. nov. and N. deltasigma sp. nov. is the only larger clade that showed synapomorphic characters. The latter three species shared the presence of robust unidentate simple hooks on chaetiger 1 and lacking a distal fang on maxilla II left. Nothria delta sp. nov. and N. deltasigma sp. nov. have long protomandibles, in contrast to the other new species described here.Although the protomandibles of N. conchylega do not surpass the lower end of the cutting plates, they are equal in length to those in Nothria delta sp. nov. and N. deltasigma sp. nov. Our tree represents only a third of species diversity in Nothria which might be even higher than is currently known. A better taxon coverage would be required to aid in understanding of phylogeny and evolution of morphological characters within the genus.

While we recognized that we might be dealing with eight new species, it was the certainty of the genetic results that substantiated it. As stated above, Nothria has 21 recognized species. To this number we are adding eight new deep-water species, almost half as many as the previously known diversity. This underscores that a large proportion of Nothria inhabit the deep oceanic waters that are still understudied. At the same time, it demonstrates the advantage of integrated studies. While presently we can only reconcile the clades D, I and J ( N. delta sp. nov., N. deltasigma sp. nov. and N. conchylega ) on genetic and morphological grounds, we feel certain that with future studies that can be extended to other clades as more known species are sequenced and included.

ACKNOWLEDGEMENTS. The authors wish to thank the CSIRO Marine National Facility (MNF) for its support in the form of sea time on RV Investigator , support personnel, scientific equipment, and data management. All data and samples acquired on the voyage are made publicly available in accordance with MNF Policy. We also thank all the scientific staff and crew who participated in the voyages. Project funding was provided by the Marine Biodiversity Hub, supported through the Australian Government’s National Environmental Science Program (NESP). We thank the collection staff at the Australian Museum Sydney for their generous assistance with material and associated queries. We are grateful to Sue Lindsay, Microscopy Unit, Macquarie University, for SEM imaging and some of the photography. Molecular work was done at the DNA laboratory of the University of Bergen with assistance of Louise Lindblom and supported by a Marie Curie postdoctoral Fellowship (Project PRODEEP “PROgenetic evolution of the DEEP-sea fauna”), and the Research Council of Norway (top-up financing of Marie Curie Fellows). This project was also funded by the Chadwick Biodiversity Fellowship from the Australian Museum, Deep-Sea Biology Society “Dive Deeper” grant, Linnean Society of New South Wales Joyce Vickery grant to LG. Comparative material of Nothria conchylega and Hyalinoecia tubicola used in the molecular analysis has been collected in a number of Norwegian and Russian expeditions and was made available by the University Museum of Bergen, University of Bergen and the Shirshov Institute of Oceanology, Russian Academy of Sciences. We thank Karen Gowlett-Holmes for the images of live specimens taken on board the expedition and Dr Joana Zanol, Dr Eivind Oug and Dr Victor Seixas for their careful reviews and valuable suggestions.

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 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.

Figure 8. Nothria deltasigmasp.nov.(A) photograph of tube ofAM W.53846. (B) map of distribution; red dot represents type locality.

Figure 9. Nothria digitata sp. nov. SEM micrographs of paratype AM W.49953. (A) anterior part, dorsal view; (B) same, ventral view; (C) parapodium of chaetiger 9, showing first branchia, dorsal view; (D) parapodium of chaetiger 12, showing fully developed branchia, dorsal view; br, branchia; dc, dorsal cirrus; ms, median section of ventral upper lip.

Figure 14. Nothria josae sp. nov. (A) photograph of tube AM W.51449; (B) map of distribution; red dot represents type locality, green dot other site of collection.

Figure 17. Nothria lizae sp. nov. (A) photograph of tube AM W.51446; (B) map of distribution; red dot represents type locality; green dots other sites of collection.

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

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.