Makarasphaera, Bruce, 2005

Bruce, Niel L., 2005, New sphaeromatids (Crustacea: Isopoda: Sphaeromatidea) from coastal and freshwater habitats in New Zealand, Zootaxa 1002 (1002), pp. 1-20 : 10-12

Makarasphaera gen. nov.

Type species. Makarasphaera amnicosa sp. nov., here designated.

Diagnosis: Head deeply immersed in pereonite 1; pereonite 1 lateral margins ventrally thickened and flat; pleonite 1 medially fused to remainder of pleon; single short suture running to posterior of pleon. Pleotelson posterior margin simple, entire. Antennule peduncle not flattened or expanded; article collinear. Pereopods secondary unguis simple; inferior margins without setulose fringe, superior margins of ischium without long setae. Penial processes long, extending to pleopod rami, entirely separate, basally in contact. Pleopods lamellar, all rami membranous, without thickened ridges; appendix masculina basal, flask­shaped, distally abruptly narrowed.

Description. Body vaulted, dorsal surfaces smooth, without setae, with ability to conglobate; not or weakly sexually dimorphic. Head with rostral point present, simple, not separating antennular bases; anterior margin simple, without incision, lateral margins not laterally extended to body outline. Eyes lateral, simple. Pereonites all smooth; 2–7 with posterior margin not raised; pereonite 1 lateral margins anteriorly produced, laterally enclosing head, anteriorly without keys. Sternite 1 without cuticular mesial extensions. Pereonite 6 simple, without bosses, processes or marginal extensions. Pereonite 7 as wide as pereonite 6, forming part of body outline, dorsally without bosses, processes or marginal extensions. Coxae ventrally wide, those of pereonites 2–7 overlapping anterior over posterior, rectilinear, coxae without ventral ‘lock and key’ processes, with grooved articulation; those of pereonite 6 not large, not overlapping those of pereonite 7. Pleon consisting of 2 visible segments (as determined by lateral sutures); pleonite 1 medially fused to pleonite 2; posterior margin even, as wide as remainder of pleon, extending to pleon lateral margins; pleonal sternite absent; single short suture running to posterior margin; dorsal surface without process; posterior margin even, with 'keys'. Pleotelson vaulted, anteriorly as wide as pleon, without dorsal process; posterior margin entire, simple, arcuate; lateral margins simple.

Membrana cingula absent.

Antennule peduncle with basal articles mesially not in contact, articles 1 and 2 robust, article 3 slender; article 1 not anteriorly produced, without anterior lobe; article 2 short, less than 0.4 times as long as article 1, without anterodistal lobe; articles 1 and 2 not flattened; with articles 2 and 3 collinear, article 3 longer than article 2; flagellum shorter than peduncle, longer than peduncular article 3. Antenna peduncle articles all collinear, articles less robust than antennule, peduncular articles all of sub­similar thickness.

Epistome anteriorly acute, without median constriction, anteriorly flush with head, not projecting, anteriorly not prominently extended, elongate, posteriorly enclosing labrum.

Mandible incisor wide, multicuspid; lacinia mobilis present, tri­cuspid; spine row normal; molar process gnathal surface with transverse ridges, rounded. Maxillule lateral lobe robust setae with some or all serrate, medial lobe with 4 major robust setae, these setae

being strongly plumose. Maxilla with setae on middle and lateral lobes serrate and nodular. Maxilliped palp articles 2–4 medial margins lobate, article 2 not expanded.

Pereopod 1 ambulatory; dactylus secondary unguis slender, simple. Pereopod 2 simi­

lar in proportion to pereopod 3; dactylus with secondary unguis slender and simple. Pereopods 3–7 dactylus with secondary unguis simple. Pereopods with inferior margins of ischium to carpus not bearing dense setulose fringe, ischium superior margin with sinuate acute robust seta(e), 1–3 or 4 ischium superior margin without long stiff slender setae. Penial processes entirely separate, basally in contact, long (extending to pleopod rami), tapering smoothly from base, apex acute.

Pleopod 1 rami not operculate; exopod lamellar; exopod with longitudinal axis weakly oblique; endopod of similar proportions to exopod, medial margin lamellar, distally triangular, endopod proximomedial heel absent; exopod distally truncate, exopod distal margins not serrate. Pleopod 2 endopod about as long as pleopod 1; exopod distal margins not deeply serrate; appendix masculina inserted basally, proximal lobe absent, basally swollen (‘flask­shaped’ or ‘distally abruptly narrowed’), about as long as endopod, distally acute. Pleopod 3 exopod transverse suture absent, endopod of similar proportions to exopod. Pleopod 4 rami with PMS (endopod with 1 plumose seta); exopod transverse suture absent, exopod thickened transverse ridges absent, exopod lateral margin not thickened, exopod lateral margin with short simple marginal setae; endopod thickened transverse ridges absent; mesial margin without deep distal notch; without proximomedial lobe. Pleopod 5 exopod transverse suture absent, thickened transverse ridges absent, lateral margin without short simple setae, lateral margin not thickened, scale patches 2 discrete patches (scarcely evident); endopod with thickened transverse ridges absent, endopod without proximomedial lobe.

Uropod rami not strongly flattened, not forming part of continuous body outline; exopod lamellar, exopod reduced, mobile, inserted at anterolateral angle, lateral margin simple, smooth, distally narrowly rounded; endopod lamellar, distally acute.

Female: No ovigerous females present in the material examined. Non­ovigerous females similar to males except for sexual characters.

Remarks: The simple arcuate pleotelson with no trace of an exit channel or ventral excavation, anterior pereopods with a simple secondary unguis, and lamellar uropods suggest a similarity with genera such as Exosphaeroma Stebbing, 1900 (see Bruce 2003 for recent diagnosis and discussion of the genus) and the recently described endemic New Zealand genus Bilistra Sket & Bruce, 2004 . In contrast to those and other related genera, including the Northern Hemisphere freshwater and estuarine genus Gnorimosphaeroma Menzies, 1954 , Makarasphaera gen. nov. has the pleon reduced to a single segment with only a weak indication of a single suture on the posterior margin. Makarasphaera has elongate penial processes, and the shape of the endopod and peduncle of pleopod 1 are more similar to those of Dynamenella Hansen, 1905 rather than to Exosphaeroma , as is the shape of the appendix masculina; the short pleonal suture running to the posterior margin

of the pleon is further character shared with such genera as Dynamenella and Paradella Harrison & Holdich, 1982 (see Harrison & Holdich 1982 for figures).

The endemic and potentially sympatric genus Bilistra (the genus is known only from the northern South Island), which has a similar body and uropod shape, can be easily distinguished by its larger size (6.8–10.6 mm, compared to under 3 mm for Makarasphaera ), the head extending clear of pereonite 1 (vs. deeply immersed in pereonite 1), dense setulose fringe on the inferior margins of the pereopods and prominent, long sutures on the pleon; in addition the shape of the peduncle and endopod of pleopod 1 are dissimilar, and the appendix masculina of Bilistra is slender and straight sided, extending well beyond the distal margin of the ramus (the penial processes for Bilistra have not been described).

Taberner (1988b) redescribed the species Pseudosphaeroma platense ( Giambiagi, 1922) , recorded from freshwater river beaches in Argentina. Harrison (1984) excluded the species from Pseudosphaeroma Chilton, 1909 , commenting that a new genus would likely be necessary to contain the South American species. Pseudosphaeroma platense is similar in body form to Makarasphaera , but the morphology of pleopod 1 and 2, the shape of the appendix masculina and the penial processes all differ substantially, and that species is not likely to belong in Makarasphaera . Pseudosphaeroma differs from Makarasphaera in having the posterior margin of the pleotelson upturned, two pleonal sutures running the lateral margins, both rami of pleopods 4 and 5 with thickened ridges, and short penial processes; all species of Pseudosphaeroma show some dorsal nodular ornamentation. The genus Pseudosphaeroma is represented in marine habitats around New Zealand, but is not known from freshwater.

Etymology. The type locality name is used in combination with the ending – sphaera to indicate the family affinity; gender feminine.