Pseudotanais Sars, 1882 (Crustacea: Tanaidacea) From the SE Australian Slope: A Gap in Our Knowledge

In the current paper, we present the description of five new species of pseudotanaids sampled off the Bass Strait during two campaigns (SLOPE), which took place in 1986/8 and 1994 from the upper continental margin (slope) at depths 200–1550 m, hopefully starting to fill a gap in the knowledge of this major habitat. From five species, two occurred off eastern coast between Gippsland and Jervis Point and three others on the southern coast between Great Otway (Otway Point) and Kangaroo Island. These five species bring the total number of described pseudotanaid species 94 and to six in Australian waters.


INTRODUCTION
are small tanaidaceans from the superfamily Paratanaoidea Lang (1949), characterized by their compact (short) body, enlarged chelipeds and a brood pouch composed of one pair of oostegites (Lang, 1949;Sieg, 1977). Currently, the Pseudotanaidae is the third most species-rich family of Paratanaoidea after Leptocheliidae Lang, 1973 andTyphlotanaidae Sieg (1976) (with 132 and 116 nominal species, respectively) 1 . They are probably epifaunal or shallow sediment burrowers (infauna), and some are unselective predators and hosts for nematode parasites .
Pseudotanaids are often numerous and a frequent element in macrobenthic communities, an example being the 36% contribution to the tanaid abundance (7% of macrofauna) on the bathyal Chatham Rise, SW Pacific (Bird and Holdich, 1984;Pabis et al., 2014Pabis et al., , 2015Kaiser et al., 2018). They are present in a variety of marine habitats (Bird and Holdich, 1989b;Bird, 1999;Bamber et al., 2009;Błażewicz-Paszkowycz and Bamber, 2011;Jakiel et al., 2015Jakiel et al., , 2019Stȩpień et al., 2018) and are recorded over a wide bathymetric range. The shallowest record of the family belongs to Akanthinotanais pedecerritulus Tzeng and Hsueh, 2021 present in the intertidal of Taiwan, while the deepest record was recorded for Pseudotanais longisetosus Sieg (1977) and P. nordenskioldi Sieg (1977), which were recorded at 6050 m (Kudinova-Pasternak, 1993). Although a few large publications have focused specifically on the diversity of Pseudotanaidae (Sieg, 1977;Bird and Holdich, 1989b;Jakiel et al., 2018Jakiel et al., , 2019Jakiel et al., , 2020, knowledge about their diversity, community structure and spatial distribution is still severely limited. Peracarid pseudotanaids, as with other brooders, are assumed to have limited dispersal ability and narrow zoographical ranges. This was tentatively confirmed with employment of morphometric and molecular methods (Jakiel et al., 2018(Jakiel et al., , 2019 for investigation of their distribution in the deep North Atlantic and the abyssal of Central and NW Pacific (Bird and Holdich, 1989b;Jakiel et al., 2019Jakiel et al., , 2020. For this reason, pseudotanaids are possibly good indicators for effective environmental impact assessment, habitat resilience and its potential for reconstruction (Bird and Holdich, 1989b;O'Hara et al., 2020;Francesca et al., 2021).
The continental margins (continental slope) are a narrow oceanic zone covering 11% of the surface (Menot et al., 2010) and the huge extent of Australia's slopes are relatively understudied. Complicated geomorphology, chemistry and hydrodynamic processes augmented by the steep gradient of temperature, hydrostatic pressure, and oxygen levels make them the most complex and heterogenic zone of the oceanic floor. The steep slope, and often hard and unstable sediments are logistically demanding for sampling and hamper benthic faunal investigations. Analyzing the zoogeographical ranges, natural biodiversity, and factors determining their character makes a baseline for understanding the evolutionary processes and distribution patterns critical for management regimes and conservation reserves (Zardus et al., 2006;Jennings et al., 2013;Poore et al., 2015). In the current paper, we present the description of five new species of pseudotanaids sampled off the Bass Strait during two campaigns (SLOPE), which took place in 1986/8 and 1994 from the upper continental margin (slope) at depths 200-1550 m, hopefully starting to fill a gap in the knowledge of this major habitat.

Stations and Collection
Pseudotanaids were recovered from a series of the samples collected at depths greater than 200 m, perpendicular to the East and South coasts of Australia during three campaigns of the O.R.V. Franklin 1986Franklin -1988Franklin and 1994. Altogether, 213 samples were collected with different devices, e.g., Woods Hole Oceanographic Institute epibenthic sled, Reineck box-corer, Beam trawl (Poore et al., 1994;unpublished data). Pseudotanaids were recovered only at six stations (Table 1).

Morphological Analyses and Taxonomical Identification
Specimens were dissected with chemically sharpened tungsten needles and the dissected appendages mounted on slides with glycerine as a medium and sealed with paraffin-wax . Drawings were prepared using a light microscope (Nikon Eclipse 50i) equipped with a camera lucida. Digital drawings were inked and arranged with Photoshop.
Morphological terminology is largely as in Jakiel et al. (2019Jakiel et al. ( , 2020; -the unique blade-like spine, if present, located at the ventrodistal part of the pereopod carpus is characteristic of most pseudotanaids. It is categorized as "long" when is at least 0.6x propodus, "intermediate" when it is 0.5x propodus, and "short" when it is at most 0.3x the propodus; -setal types are recognized as: (1) simple setae (= without ornamentation), (2) serrate -with serration or denticulation, (3) plumose -with any type of plumose or delicate setulae distributed along the main axis, (4) penicillate -with a tuft of setules located distally and with a small knob on which a seta is fixed to the tegument and (5) rod setae -slightly inflated distally and with a pore; and -the dorsodistal seta occurring on the carpus of pereopods 4-6 has a chemosensory function -("rod seta" Jakiel et al., 2019); it is categorized as "long" when it is at least 0.8x propodus, "intermediate" when it is 0.5x propodus, and "short" when it is at most 0.25x propodus.

Measurements, Developmental and Stage Identification
Total body length (BL) was measured along the main axis of symmetry from the rostrum to the end of the telson. Body width (BW) was measured at the widest point along the main axis of symmetry. The length was measured along the axis of symmetry, and the width perpendicular to the axis of symmetry at the widest spot. To simplify species descriptions, the expression "Nx" replaces "N times longer than/as long as" and "N L:W" replaces "N times longer than wide." The measurements were made with a camera connected to the microscope (Nikon Eclipse Ci-L) and NIS-Elements View software. 2 The body width and the length of the cephalothorax, pereonites, pleonites, and pleotelson were measured on whole specimens.
All individuals, developmental stages were identified. We refer to the following stages: -two stages of manca, i.e., "manca-2" and "manca-3" which refer to specimens without or with buds of pereopod-6, respectively; -preparatory female characterized by undeveloped oostegites ('buds') (Bird and Holdich, 1989b) and brooding female (with fully developed oostegites) were not recovered in the studied material; -neuter -a stage that is morphologically like the juvenile female, but lacking oostegites buds; and -'juvenile male' that shows incompletely developed sexual dimorphic characters, i.e., resembling the neuter but has thicker antennules (equivalent to 'preparatory male' sensu Bird and Holdich, 1989b).
In our collection sexually mature males ("swimming" male) and brooding females were not recovered.

RESULTS
Nine individuals belonging to Pseudotanaidae were examined in the current paper. All of them were classified to the genus 2 www.nikoninstruments.com Pseudotanais: two of them represented "affinis + longisetosus" morphogroup (Pseudotanais chardonnayi n. sp. and P. caberneti n. sp.) and two "denticulatus + abathagastor" group: (P. barossai n. sp. and P. coonawarrai n. sp.). The fifth of described species P. shirazi is not assigned to any of the Pseudotanais groups.
Description of juvenile male. Similar to female, but antennule thicker (Figures 1C,D).
Distribution. The species is known only from the type locality: SE Australia (off Gippsland), at the depth 400 m.
Remarks. Pseudotanais chardonnayi sp. nov. has a dorsodistal spine on antenna articles 2-3, a relatively long propodal distal seta on pereopods 2-3, and a long dorsodistal seta on carpus of pereopods 5-6, that allow classification of the species to the "affinis + longisetosus" morpho-group (Bird and Holdich, 1989b;Jakiel et al., 2019), although the relatively short dorsodistal seta on the pereopod merus (rather long in "affinis + longisetosus" group) is anomalous we have decided to deposit P. chardonnayi in this group as this seta is still longer than in members of other groups where it is minute or absent.
The short dorsodistal seta on the pereopod-4 carpus distinguishes P. chardonnayi from P. chanelae, P. curieae and P. longisetosus, where this seta is long. The combination of a spine and seta on the pereopods 4-6 merus and carpal long rod seta of P. chardonnayi is similar to P. romeo, but it can be separated by the uropod exopod that is 0.7x endopod in P. chardonnayi and 0.9x in P. romeo. Additionally, the blade-like spine on the carpus of pereopod-3 is 0.7x propodus in P. chardonnayi, while P. romeo it is slightly longer (0.8x propodus). Finally, both species can be distinguished by the setation of ischium of pereopods 4-6, with two setae in P. chardonnayi and naked in P. romeo.
Etymology. The species name is after one of most widely distributed and best-known wine grape varieties grown in SE Australia, as genitive.
Maxilliped ( Figure 4J) palp article-1 naked, article-2 1.3 L:W, with fine outer and three inner setae (two long and one short); article-3 1.3 L:W with one shorter and three longer inner setae; article-4 1.4 L:W with six distal and subdistal setae. Maxilliped endite, basis not dissected.
Distribution: Species known from SE Australia, off Cape Otway, from the depth 209 m.
Key for identification of Pseudotanais females of the "affinis + longisetosus" morpho-group.
Etymology. From the Barossa Valley in South Australia, a premium wine-growing region, as genitive.
Distribution. Species known only from type locality, off Kangaroo Island (SE Australia) at depth 1548 m.
Remarks. Pseudotanais barossai sp. nov. has a thin spine on antenna article-2 and with this it can be separated from P. abathagastor and P. mariae which have a weaker seta at this position, and P. barnesi that lacks any seta. Furthermore, a thin spine on antennal article-3 also distinguishes P. barossai from P. amundseni, which has a weaker seta. In addition, a single spine on the pereopods 2-6 merus differentiates P. barossai from all other congeners that have a combination of spine and seta, two setae or being naked at this position.
Etymology. In the Bindjali Aboriginal language, coonawarra is honeysuckle and a wine region from southern Australia, as genitive.
Distribution. Species known only from the type locality off Cape Otway (SE Australia) at depth 1021 m.
Remarks. The combination of antenna articles 2-3 with spines, coronal mandible molar, short ventrodistal setae on the pereopod-1 merus and carpus, and slender uropods places P. coonawarrai sp. nov. in the "denticulatus + abathagastor" group. A spine on the antenna article-2 distinguishes the new species from P. abathagastor and P. mariae, which have a seta on this article, and from P. barnesi, which has this article naked. The uropod exopod, shorter than the endopod (0.8x), separates P. coonawarrai from P. chaplini and P. oloughlini, where exopod is 1.1x endopod, and from P. palmeri where the exopod and endopod are equal. The presence of a spine and seta on the merus of pereopods 4-6 separates P. coonawarrai from P. biopearli, P. barossai, P. corollatus, P. georgesandae and P. locueloae, which have a spine or two setae in this position. Finely, the absence of wide-based spines on pereopods 2-3 in P. coonawarrai is similar to P. denticulatus and P. kitsoni although it can be distinguished by a short pereopod-2 with an overall proportion of 9.6 L:W compared to > 13 L:W in P. denticulatus and P. kitsoni.
Key for the identification of Pseudotanais females of the "denticulatus + abathagastor" morpho-group.
Etymology. Shiraz is a grape varied, mostly used in Australia and South Africa, as genitive.
Maxilliped endites mostly fused but with distinct central cleft, each with small middle seta and two gustatory cusps. Epignath (Figure 10K) linguiform, simple distally rounded.
Remarks. Pseudotanais shirazi sp. nov., with short conical blade like-spines on the carpus of pereopods 2-6, is the second species after P. intortus with this shape. Its maxilliped endites with a distinct medial cleft and each with one simple seta and two tubercles, distinguish it from P. intortus where the maxilliped endites are fused and each have only one tubercle. Additionally, the blade-like spine in pereopod-2 in P. shirazi is conical while, in P. intortus pereopod-2 is more flattened, with the cavity in the central part. A short propodal seta on pereopods 2-3 (0.2x dactylus and unguis combined length) in P. shirazi is different from P. intortus, where this spine is almost as long as dactylus and unguis combined length (0.8x). Finally, the pereopods 4-6 unguis is simple in contrast to P. intortus with a bifurcated unguis.

DISCUSSION
The present study provides for the first time information about Pseudotanaidae species from the continental margin of SE Australia near Bass Strait. From five species, two occurred off eastern coast between Gippsland and Jervis Point (P. shirazi and P. chardonnayi), and three on the southern coast between Great Otway (Otway Point) and Kangaroo Island (P. caberneti, P. barossai and P. coonawarrai) (Figure 12). These five species bring the total number of described pseudotanaid species to 94. Until now the family was represented in Australian waters by only one species -the shallow-water Akanthinotanais scrappi (Bamber, 2005). Remarkably, the family is apparently absent in the well sampled Bass Strait (Błażewicz-Paszkowycz and Bamber, 2012;Bamber and Błażewicz-Paszkowycz, 2013), but they were recorded at the deeper shelf (around 100 m) and at the slope of West Australia (Bamber, 2005;McCallum et al., 2015;Poore et al., 2015); also, it was recorded in two locations of Great Barrier Reef e.g., Lizard and Heron Is; . Unfortunately, these collections were not identified to species level.
The Pseudotanaidae is cosmopolitan family that encompass all biogeographic zones (Watling et al., 2013). Collated literature date on the distribution of currently recognized pseudotanaid genera and the morpho-groups, allow to group pseudotanaids into few categories (Table 2 and Figure 13): -Akanthinotanais and "forcipatus" can be common on the shelf from the tropics to polar regions and have been only occasionally recorded below the continental margin (Sieg, 1977;Bird and Holdich, 1989a,b) or the abyssal (Jakiel et al., 2019). The former is still relatively understudied because of its relative scarcity, and exhibits a range of morphologies that may encompass several genera, even in a separate family; -"denticulatus + abathagastor" and "affinis + longisetosus" represent deep-sea fauna, but several species have been recorded on the shelf of polar regions. This distribution supports a polar emergence phenomenon observed for several taxa (Wilson, 1998;Berkman et al., 2004;Błażewicz-Paszkowycz, 2005;Raupach et al., 2012). With some probability, this group could also be represented by Beksitanais, although this assumption could be revised when more records become available; -"spicatus" is recorded on the upper, lower slope and in the abyss; -Parapseudotanais is recorded only from the abyss; -Mystriocentrus is known from lower slope and the abyss.
To confirm that Parapseudotanais and Mystriocentrus are deep-water genera requires more data. The species provisionally classified to the "colonus" group does not reveal a clear distribution pattern that suggest an artificial (non-monophyletic) character of the group.
Apart from the Pseudotanaidae, in general, the peracarid fauna of Australian coast is very diverse (Poore et al., 1994;Lowry and Stoddard, 2003;Poore and Bruce, 2012). With that background, tanaids are represented by 162 species in 66 genera (Edgar, 1997(Edgar, , 2008(Edgar, , 2012Bamber, 2005Bamber, , 2008Błażewicz-Paszkowycz and Bamber, 2007, 2012Jóźwiak and Błażewicz, 2021). This situation is apparently worse at the shelf break where only nine species from seven genera and FIGURE 12 | Distribution of Pseudotanaidae (described in this study) on the coast of SE Australia.  Bird and Holdich (1989b) and McLelland (2007  The zoogeographical and bathymetrical classification according to Spalding et al. (2007) and Watling et al. (2013).
four families (Apseudidae: one species; Agathotanaidae: two species, Anarthruridae six species, Paratanaidae: one species) are formally described (three species were described from SE Australia) (Larsen and Heard, 2001;Jóźwiak and Jakiel, 2012;Bamber and Błażewicz-Paszkowycz, 2013;Gellert and Błażewicz, 2018). For this reason tanaids are regarded as a comparatively non-diverse group, especially when compared to the other well studied taxa as Isopoda being represented in SE Australia by 51 families (Poore et al., 1994). However, exploration of the deeper shelf and slope of W Australia (McCallum et al., 2015;Poore et al., 2015) proves that tanaids below the continental break are diverse and the perceived lack of diversity mentioned above may be an illusion. The collection of Pseudotanaidae that we studied here is too limited to draw a conclusion about zoogeographical relationships and their link to the complex geological/tectonic history of SE Australia.
FIGURE 13 | Distribution of pseudotanaid genera and morpho-groups according to Bird and Holdich (1989b) and McLelland (2007) (for details see Table 2). The zoogeographical and bathymetrical classification according to Spalding et al. (2007) and Watling et al. (2013). The size of the pies corresponds to the number of species recorded.

AUTHOR CONTRIBUTIONS
MB did the general concept and identification of the material. MB and AJ did the species, description, manuscript editing and figures editing. GB did the discussion and manuscript editing. All authors contributed to the article and approved the submitted version.