Brucerolis gen . n . , and Acutiserolis Brandt , 1988 , deep-water southern genera of isopods ( Crustacea , Isopoda , Serolidae )

Acutiserolis Brandt is rediagnosed (coxal dorsal plates 2–5 slot into each other with no aperture between; coxal plate 6 has a blunt process on its anterior margin slotting into a groove on coxa 5 and isolating an oval aperture; with prominent middorsal pereonal and pleonal spines; pleotelson with a sharp middorsal keel, upturned posteriorly; and sharply defi ned longitudinal sublateral keels ending acutely) and confi ned to the type species, Serolis spinosa Kussakin, 1967, and two species of Cuspidoserolis Brandt, 1988 syn. n. Brucerolis gen. n., (type species Brucerolis nowra sp. n.) is erected for species previously assigned to Acutiserolis but from which it diff ers in having the coxal dorsal plates 2–6 interacting only by means of key-like lobes, coxal plate 6 exceeding the pleotelson by at least the pleotelson length, middorsal spines being absent or obscure, and the pleotelson lacking ridges and keels. Four other species are included: Brucerolis bromleyana (Willemöes-Suhm, 1876); B. cidaris (Poore & Brandt, 1997); B. macdonnellae (Menzies, 1962); and possibly B. maryannae (Menzies, 1962).

During preparation of descriptions of numerous new species of "Acutiserolis" with extremely long, attenuating, posteriorly directed coxae and epimera, Niel Bruce suggested to us that substantial diff erences existed between these and the type species of Acutiserolis, S. spinosa.Brandt (1988) did not examine the type material of S. spinosa during her revision, nor did others who have adopted her revision (e.g., Wägele 1994;Poore and Brandt 1997;Held 2000).Topotypical specimens of Acutiserolis spinosa have been recently collected by New Zealand's National Institute of Water and Atmosphere (NIWA) in the Ross Sea, Antarctica.Th ese were made available to us by Niel Bruce and the diff erences between this and the other species are clearly apparent.
In this contribution, Acutiserolis and a new genus and species, Brucerolis nowra, are diagnosed.A supplementary description and illustrations of A. spinosa are presented.Th e diagnosis is modelled on the characters used for example by Wägele (1994) and Poore and Brandt (1997).In a subsequent paper we describe fi ve more species of Brucerolis (Storey and Poore in press) from southeastern Australia.
Th e mouthparts, pereopods and pleopods of the two genera are very much alike, diff ering only slightly in proportions.Salient features that distinguish Brucerolis from Acutiserolis and from other genera are included in the generic diagnoses.Th e diagnoses and descriptions were prepared using a DELTA database (Dallwitz et al. 1993).Type material is lodged in Museum Victoria, Melbourne (NMV) and the National Institute of Water and Atmosphere, Wellington, New Zealand (NIWA).
Included species (all originally described in Serolis).Acutiserolis spinosa (Kussakin 1967) -Ross Sea, Antarctica, 500-900 m A. gerlachei (Monod, 1925) comb. n. -Bellingshausen Sea, Antarctica, 400 m (Monod 1926).A. johnsoni (Hale 1952) comb. n. -Eastern Antarctica, 540-2267m (Kussakin 1967).A. luethjei (Wägele 1986) new combination -Weddell Sea, 189-481 m.Remarks.Th e most signifi cant features of Acutiserolis are: coxal dorsal plates 2-5 slot into each other with no aperture between; coxal plate 6 has a blunt process on its anterior margin slotting into a groove on coxa 5 and isolating an oval aperture; prominent middorsal pereonal and pleonal spines; pleotelson with a sharp middorsal keel, upturned posteriorly; and sharply defi ned longitudinal sublateral pleotelson keels ending acutely.Brandt (1988) relied on the extreme length of the coxal plates and pleonal epimera to characterise Acutiserolis but in our opinion this was unwarranted.Coxal plate 6 of Acutiserolis spinosa exceeds the pleotelson by one-third its length whereas in the remaining species included, the overlap of coxa 6 is at least as great as the pleotelson length and usually much greater.Acutiserolis spinosa is more similar to species of Cuspidoserolis Brandt, 1988 in this and other features than to the other species in-cluded by Brandt (1988) and Wägele (1994) in Acutiserolis.Brandt (1988) agreed that the two genera were similar in having long coxal dorsal plates and pleonal epimera although none overlap the pleotelson in Cuspidoserolis.Th e distinguishing feature of Cuspidoserolis, according to Brandt, is the elongate spine on the posterior margin of the head but this is found also in A. spinosa (fi g. 1).She treated the two genera as sister taxa sharing a middorsal spine on the head in a phylogenetic analysis (Brandt, 1991) but this is not true of the species we remove to Brucerolis.Th e type species of Cuspidoserolis, Serolis luethjei Wägele, 1986, diff ers from A. spinosa only in having a more rugose surface and more compact coxal plates and epimera.It shares prominent middorsal spines, ridges on pereonite 1, medial and sublateral keels on the pleotelson, and similar male pereopods 2 and 7. Brandt (1988) also included in Cuspidoserolis, Serolis gerlachei Monod, 1925(illustrated by Monod 1926) and S. johnsoni Hale, 1952.Th ey too have a long middorsal posterior spine on head, coxal plates contiguous proximally, middorsal pleotelson keel and similar sublateral keels on the pleo telson.All three diff er from A. spinosa only in having coxal plate 6 not reaching beyond the end of the pleotelson.Other authors have remarked on these similarities: Hale (1952) remarked on similarities between his S. johnsoni and S. gerlachei; Kussakin (1967) likened S. spinosa to S. johnsoni.Brandt remarked on the extreme length of the pleotelson of Cuspidoserolis, being about as long as wide, but this is true too of all species of Acutiserolis and Brucerolis.
In his phylogenetic analysis of the family, Wägele (1994) placed Cuspidoserolis and what he called Serolis (Acutiserolis) in sister-clades.Th e clade containing Cuspidoserolis was characterised by a sexually dimorphic pereopod 7, the male having broader and fi nely setose articles than the female.However, this is true too of Acutiserolis and Brucerolis.Th e apomorphies of the sister clade (dealing with male pereopod 2, pleopod 4 and coxal plates) are equally unconvincing.Held's molecular analysis placed two species of Cuspidoserolis (C.luethjei and C. johnsoni) close together and close to "Acutiserolis bromleyana".
We conclude that Cuspidoserolis is a junior synonym of Acutiserolis which now includes its type species plus the three species of Cuspidoserolis.We assign other species previously included in Acutiserolis to Brucerolis.

Acutiserolis spinosa (Kussakin, 1967) Figs 1a-f; 2-4
Serolis spinosa Kussakin 1967Kussakin (1968))  Type material.Region of Scott Island, East Antarctica, 500-900 m (Ob stn 377), Zoological Institute, St Petersburg, Russia, 1/46416 (holotype, male, 32 mm), plus 2 female paratypes (none examined).Description.Body length of fi gured male 34 mm.Body 1.2 times as long as greatest width (at coxae 3).Dorsal surface smooth.Head, anterolateral margins convex and continuous with anterior margin of pereonite 1; maximum width between anterolateral corners 1.1 times as wide as span between lateral margins of eyes; head without paired processes on transverse ridge at bases of antennae 1, with pair of bilobed tubercles between anterior part of eyes, with acute median posterior tubercle extending past pereonite 1, with obscure lobes lateral to median posterior tubercle.Pereonite 1 of male, lateral margin gently sinuous, 1, lateral margin upturned over anterior half, with sharply-crested submarginal ridge parallel to margin, dorsal surface with oblique transverse ridge reaching near margin.Coxal dorsal plate 2 of male 0.5 times as long as half pereonal tergite 2 width (following plates increasing in length); plate 4 of male as long as half pereonal tergite 4 width; plate 6 of male extending beyond tip of pleotelson by 0.3 times middorsal length of pleotelson; pleonal epimeron 2 of male 0.9 times length of pleotelson; pleonal epimeron 3 of male 0.8 times length of pleotelson; pleonal epimera 2 and 3 with acute apices.Antenna 1 peduncle articles 3+4 as long as article 2 (anterior margin); fl agellum with about 54 articles, at least 3 times as long as peduncle article 3+4 (in male), reaching anterior margin on pereonite 4. Antenna 2 peduncle article 5 1.25 times as long as article 4; fl agellum of 18 articles, at least 1.2 times as long as peduncle article 5.
Pereopod 1 propodus 2.2 times as long as greatest width.Pereopod 2 palm dorsal length 2.2 times greatest width, straight, sharply angled at free proximal margin, with 28 spiniform setae surrounding an oval palm.Pereopod 5 of male basis 5 times as long as greatest width, with a keel on the extensor margin, more prominent proximally; merus without setae; carpus 5.5 times as long as greatest width; propodus 6.5 times as long as greatest width; dactylus curved, 0.3 times as long as propodus.Pereopod 6 of male merus sparsely setose, carpus 7 times as long as greatest width; propodus 10 times as long as greatest width; dactylus curved, 0.25 times as long as propodus.Pereopod 7 of male carpus 4 times as long as greatest width (at distal end); propodus 4.5 times as long as greatest width, propodus tapering from base, lower margin gently convex; dactylus curved, 0.15 times as long as propodus.
Pleopod 2 endopod with evenly tapering distal angle bearing appendix masculina; appendix masculina 3.8 times as long as straight margin of endopod.Uropodal rami with rounded apices; exopod 0.7 length of endopod.Female.Pereonite 1, lateral margin of female as in male.Coxal dorsal plate 2 of female 0.5 times as long as half pereonal tergite 2 width; plate 4 of female 0.7 times as long as half pereonal tergite 4 width (following plates increasing in length); plate 6 of female extending beyond tip of pleotelson by 0.3 times middorsal length of pleotelson.
Remarks.Th e new material is clearly referable to Kussakin's species but illustrates some variability, mostly attributed to diff erences between sexes.Males, in diff erent stages of development, range in size from 25 to 34 mm long (fi gs 1a, b, e).All possess diff erentiated pereopods 2 and 7 and the smallest lacks an appendix masculina.In the 29-mm specimen, the appendix masculina is only half the length of that in the 34-mm specimen.In all males, the posterolateral oblique rugosity on the pleotelson is poorly developed.Th e head spine of males reaches about half the length of pereonite 2. Th e 28-mm female has oostegite buds whereas the others, 30-32 mm, are ovigerous.Dorsal coxal plates are slightly shorter in females.In females, the posterolateral oblique rugosity on the pleotelson is a more well-defi ned ridge than in the male.In two of the females (fi gs 1c, d), the posterior spine on the head barely reaches the posterior margin of pereonite 1 whereas in the other (fi g. 1d) it reaches the posterior margin of pereonite 2. Kussakin's illustration (1968: fi g. 15) of the male holotype shows a slightly longer coxal plate 6 than in the male fi gured here.
Remarks.A single male collected at a much lower latitude than A. spinosa is similar to the Ross Sea specimens.Key features of the coxal plates, middorsal and pleotelson sculpture, and armature of coxal ventral plates 2 and 3 and pleonal sternites are for all practical purposes indistinguishable.However, the spine on the head is considerably longer than in A. spinosa, reaching to the posterior margin of pereonite 3. Coxal plate 6 exceeds the pleotelson by slightly more than its length, further than in A. spinosa.Pleonal epimera 2 and 3 are similarly longer.While the male pereopod 2 propodus of the two species has similar numbers of robust palmar setae, the propodus of the New Zealand specimen is more elongated than in A. spinosa (fi g. 2d).In the absence of a larger sample and specimens from intermediate localities we are reluctant to describe this as a new species.

Included species (see too Remarks below).
Brucerolis bromleyana (Willemöes-Suhm, 1876) (ex.Serolis) comb.n. -Southern Ocean (Indian Ocean sector), 3614 m depth.B. cidaris (Poore & Brandt, 1997)  Remarks.Acutiserolis is diagnosed above and Cuspidoserolis is placed in synonymy.Brucerolis diff ers from Acutiserolis in having the coxal dorsal plates 2-6 interacting only by means of key-like lobes, coxal plate 6 exceeding the pleotelson by at least the pleotelson length, middorsal spines absent or obscure, and the pleotelson lacking ridges and keels.All are clearly distinctive autapomorphies diff erent from Acutiserolis and Cuspidoserolis.Brandt (1988) listed fi ve species and Wägele (1994) seven in Acutiserolis; another has been described since (Poore and Brandt 1997).All except the type species are excluded from Acutiserolis above and are candidates for inclusion in the new genus, Brucerolis.
Serolis bromleyana Willemöes-Suhm, 1876 and Acutiserolis cidaris Poore and Brandt, 1997, both illustrated in detail by Poore and Brandt (1997), conform well to the generic defi nition of Brucerolis and are here transferred to join the type species.Th e illustrations of Serolis (Serolis) macdonnellae Menzies, 1962 show the coxal keys, pereonite 1 and pleotelson in suffi cient detail to be confi dent that this too belongs to Brucerolis.Serolis (Serolis) maryannae Menzies, 1962 has the general habitus, pleotelson sculpture, elongate bifi d pleonal epimera, and acute coxal dorsal plates of Brucerolis and pereonite 1 like B. bromleyana, but coxal keys were not shown in the illustration.If this is an oversight by Menzies or a juvenile feature, the 18.8-mm female would be the smallest individual of the genus known.Th e species is a possible member of Brucerolis.All others listed previously in Acutiserolis are not.
Serolis gracilis Beddard, 1884 and S. neaera Beddard, 1884 are similar to each other (Beddard, 1884b) and superfi cially to species of Brucerolis, sharing acute tapering coxae, elongate coxa 6, prominent interacting coxal keys and notched article 2 of the maxillipedal palp, but there are several important diff erences.Th e anterolateral margin of the head is concave in species of Brucerolis, but in Serolis gracilis and S. neaera the anterior margin of the head is strongly convex and the anterolateral corners of the head extend much further laterally than the eyes.Th e pleotelson of S. gracilis and S. neaera are as in Acanthoserolis Brandt, 1988 (type species: Serolis polaris Richardson, 1911) with a proximal, acute spine middorsally and a median transverse ridge produced into acute spines middorsally and midlaterally, and uropods that insert on the pleotelson terminally and point mesially.We examined S. schythei Lütken, 1858 (included in Acanthoserolis by Brandt and Wägele and similar to S. polaris) from the collections of Museum Victoria.Both species lack elongate coxal plates and share a bilobed endopod on pleopod 4. Beddard's (1884b) descriptions and fi gures and our own examination of material of Serolis gracilis and S. neaera demonstrate many diff erences from Acutiserolis, Brucerolis and Acanthoserolis.Serolis neaera and S. gracilis have a dense mat of plumose setae on the male pereopod 2 whereas the three genera are scarcely setose.Th e endopod of pleopod 4 is bilobed in Serolis paradoxa Fabricius, 1775, Acanthoserolis schythei, A. polaris, Serolis neaera (Nordenstam, 1933) and S. gracilis (Beddard, 1884b), earlier observations confi rmed by us.Th e endopod of pleopod 4 is not bilobed in Acutiserolis or Brucerolis.Moreira (1977) discussed the resemblance of his species, S. insignis, included in Acanthoserolis by Wägele (1994), to Serolis gracilis.Th ese two and S. neaera are clearly related but their generic placement remains problematic.
Serolis margaretae Menzies, 1962 was included in Acutiserolis by Brandt (1991) and Wägele (1994).We agree with Poore and Brandt's (1997) conclusion that the very small (8.4 mm and smaller) type specimens without elongate coxal plates and epimera could not be assigned to Acutiserolis.Nor do they conform to Brucerolis.
Held's (Held 2000;Held and Wägele 2000;Held 2001) observations on the relationships of Acutiserolis derived from molecular analyses (using the species A. bromleyana) refer to Brucerolis.Description.Body length 31 mm (holotype).Body as long as greatest width (at coxae 3).Middorsal line with short triangular middorsal processes on posterior mar- gin of head, pereonites 2-4 and pleonites 1-3, evident in lateral view; dorsal surface punctate.Head, anterolateral margins concave, lateral corners acute and strongly projecting anteriorly and dorsally; maximum width between anterolateral corners 1.1 times as wide as span between lateral margins of eyes; head without paired processes on transverse ridge at bases of antennae 1, with obsolete paired tubercles between eyes, without median posterior tubercle, with obscure lobes lateral to median posterior tubercle.Pereonite 1 of male, lateral margin convex anteriorly, straight over most of length, lateral margin upturned over anterior half, with sharply-crested submarginal ridge parallel to margin, dorsal surface with oblique-transverse ridge reaching near margin, otherwise unornamented.Coxal dorsal plate 2 of male 0.8 times as long as half pereonal tergite 2 width (following plates increasing in length); plate 4 of male as long as half pereonal tergite 4 width; plate 6 of male extending beyond tip of pleotelson by 2.3 times middorsal length of pleotelson, the pair diverging over entire length, curving evenly; pleonal epimeron 2 of male 1.5 times length of pleotelson; pleonal epimeron 3 of male length of pleotelson; pleonal epimera 2 and 3 with assymetrically emarginate apices.Ventral coxal plates 2-4 with transverse ridges on mesial, anterior and posterior margins outlining a transverse depression.
Antenna 1 peduncle articles 3+4 2.1 times as long as article 2 (anterior margin); fl agellum with about 45 articles, 3.5 times as long as articles 3+4, reaching back to Pereopod 1 propodus 2.1 times as long as greatest width.Pereopod 2 palm dorsal length 1.8 times greatest width, gently continuous, with free proximal margin, with 18 spiniform setae arranged in an oval over the proximal two-thirds of the palm.Pere-  opod 5 of male basis 5.2 times as long as greatest width, of even width; merus with marginal setae; carpus 6 times as long as greatest width; propodus 7 times as long as greatest width; dactylus curved, half as long as propodus.Pereopod 6 of male merus setose, carpus 8 times as long as greatest width; propodus 11 times as long as greatest width; dactylus curved, 0.4 times as long as propodus.Pereopod 7 of male carpus 4.4 times as long as greatest width (near distal end); propodus 6.5 times as long as greatest width, propodus tapering from near base, lower margin straight; dactylus curved, 0.45 times as long as propodus.Pleopod 2 endopod with convex distal margin, sharply tapering to base of appendix masculina; appendix masculina 3.6 times as long as straight margin of endopod.Uropodal rami with rounded apices; exopod 0.8 length of endopod.
Female.Pereonite 1, lateral margin of female sinuous anteriorly, straight posteriorly.Coxal dorsal plate 2 of female 0.5 times as long as half pereonal tergite 2 width; plate 4 of female 0.8 times as long as half pereonal tergite 4 width (following plates increasing in length); plate 6 of female extending beyond tip of pleotelson by 1.1 times middorsal length of pleotelson (in juvenile female), the pair diverging and then converging slightly apically, curving evenly.
Etymology.Nowra, a coastal town near the type locality; noun in apposition.Distribution.Off southern NSW, Australia, south-eastern Tasman Sea; 450-1750 m.
Remarks.Coxal plates and epimera tend to become relatively longer in larger animals.Females are distinguished from males by the absence of modifi ed pereopods 2 and 7 and in the sinuous lateral margin of pereonite 1. Brucerolis nowra is distinguished by the strongly upturned and produced anterolateral lobes on the head (fi g. 6e) from others in the genus (already described and yet to be described by us in another work) where these lobes are obsolete or not upturned.