Brucerolis, Poore & Storey, 2009

Poore, Gary & Storey, Melissa, 2009, Brucerolis gen. n., and Acutiserolis Brandt, 1988, deep-water southern genera of isopods (Crustacea, Isopoda, Serolidae), ZooKeys 18 (18), pp. 143-160 : 151-153

Brucerolis gen. n.

urn:lsid:zoobank.org:act:FC4BEA04-0350-49E1-8FA3-01AF4DBB7186

Type species. Brucerolis nowra , sp. n. here designated.

Diagnosis. Body deeply incised between extremely long, attenuating, posteriorly directed coxal and epimeral plates; middorsal line without midposterior processes, not elevated in lateral view, or with short triangular middorsal processes on posterior margin of head, pereonites 2–4 and pleonites 1–3, evident in lateral view. Pereonite 6 to pleonite 1 fused middorsally and midventrally. Eyes contiguous with head margin posteriorly, twice as long as wide, reniform. Coxal dorsal plates 2–4 delimited from tergite by suture; coxal dorsal plates 2–6 with anterior blunt process slotting into groove on preceding coxae, isolating an oval aperture between coxae; coxal plate 5 with an intermediate anterior process meeting a similar posterior process on coxal plate 4, so subdividing intercoxal aperture. Pleotelson with horizontal obscure middorsal keel; dorsal surface with flattened plate-like ridges laterally, with rounded ends. Pereonal sternite 1 with sharp medial ridge anteriorly and saddle posteriorly; ventral coxal plates 2–4 meeting in midline, without pair of contiguous teeth on anteromesial corners of sternites 2, smaller pair on sternites 3; pleonal sternites 1–3 with acute posterior ridged margin. Antenna 2 article 5 about 10 times as long as wide. Mandible, incisor smooth, chitinised, hoof-like; left lacinia mobilis expanded, half as wide as mandibular incisor; right lacinia mobilis diverging, with obsolete apical dentition; spine simple; mandibular palp, article 2 with row of setae confined distally along mesial margin. Maxilla 1 inner lobe a simple expanded plate, outer lobe with ̴11 robust terminal setae. Maxilla 2 inner lobe broad, distally richly setose, middle and lateral lobes each with 2 apical setae. Maxilliped, endite with 2 strong distal robust setae; maxillipedal palp of 3 articles; palp article 2 distally dilated, distomesially lobed, with shallow indentation on mesial margin separating two clusters of setae; epipod more or less semicircular. Pereopod 1, palm of propodus with alternating flagellate cylindrical setae and flagellate plate-like setae. Pereopod 2 of male subchelate; palm of propodus with U-shaped row of robust setae; dactylus with small terminal unguis. Pereopod 7 of male sexually differentiated, propodus broader than in female, with felt of fine scale setae, dactylus simple, curved. Pleopod 4 endopod simply triangular, not bilobed. Uropod biramous, inserting sublaterally at about midpoint of pleotelson. Oostegites of female present on pereopods 1–4.

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) (ex. Acutiserolis ) comb. n. – Coral Sea, 891–

1491 m depth.

B. macdonnellae ( Menzies, 1962) (ex. Serolis ( Serolis )) comb. n. – South Atlantic,

2741 m depth.

? B. maryannae ( Menzies, 1962 (ex. Serolis ( Serolis )) comb. n. – South

Atlantic, 3839 m depth.

B. nowra sp. n. – south-eastern Tasman Sea, 450–1750 m depth.

Etymology. Named for Niel Bruce, Museum of Tropical Queensland, Townsville, formerly of National Institute of Water and Atmosphere, Wellington, in recognition of his extensive contribution to isopod taxonomy and his friendship.

Remarks. Acutiserolis is diagnosed above and Cuspidoserolis is placed in synonymy. Brucerolis differs 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 different from Acutiserolis and Cuspidoserolis .

Brandt (1988) listed five 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 definition of Brucerolis and are here transferred to join the type species. The illustrations of Serolis (Serolis) macdonnellae Menzies, 1962 show the coxal keys, pereonite 1 and pleotelson in suffi cient detail to be confident that this too belongs to Brucerolis . Serolis (Serolis) maryannae Menzies, 1962 has the general habitus, pleotelson sculpture, elongate bifid 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 superficially 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 differences. The 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 figures and our own examination of material of Serolis gracilis and S. neaera demonstrate many differences 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 confirmed 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 .