Evansula polaris, Huys & Conroy-Dalton, 2006
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publication ID |
https://doi.org/ 10.1111/j.1096-3642.2006.00227.x |
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persistent identifier |
https://treatment.plazi.org/id/03F487A0-FF84-FF88-FD49-F94BFD109637 |
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treatment provided by |
Felipe |
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scientific name |
Evansula polaris |
| status |
sp. nov. |
EVANSULA POLARIS SP. NOV.
Synonym: Evansula incerta (T. Scott, 1892) sensu Scott (1903b) .
Original description: Scott (1903b) did not provide any descriptive information.
Type locality: Norway, East Finmark, Laksefjord. Material examined: From type locality: holotype ♂ found among spirit-preserved ‘cotypes’ of E. incerta (reg. nos 44508–509) as part of the Cannon A. M. Norman collection (1911.11.8); coll. A. M. Norman, 30 June 1890; det. T. Scott and labelled Tetragoniceps incertus ; deposited in NHM (reg. no. 1995.427); dissected on eight slides.
Etymology: The species name is derived from the Latin polaris , meaning polar, and refers to the Arctic distribution of this species.
Description
Female: Unknown.
Male: Total body length: 435 µm. Body slender, cylindrical ( Fig. 33A View Figure 33 ), semitransparent, yellowish; no distinct separation between prosome and urosome. Anal somite only slightly longer than wide (46 × 41 µm), with two pairs of secretory pores laterally ( Fig. 33B View Figure 33 ); posterior margin with one short spinular row on either side of ventral midline ( Fig. 34D View Figure 34 ). Anal operculum weakly developed, unarmed ( Fig. 34B View Figure 34 ).
Caudal ramus short and conical ( Fig. 34B–D View Figure 34 ), proximal inner margin slightly convex, length (measured along outer margin) approximately 2.5 times the proximal width; dorsal surface without chitinous spur but with raised spinular row; with seven setae, setae I–VI in distal and seta VII in proximal half ( Fig. 34B View Figure 34 ); seta I diminutive; setae II–III long and bare; seta IV uniplumose, slightly longer than styliform part of V; seta V long, with distinct flexure zone between styliform part and long distal flagellate part, fused at base with seta IV; seta VI vestigial; seta VII tri-articulate at base and located along proximal inner margin, with conspicuous swelling in proximal quarter; ventral surface with one tube-pore near anterior margin ( Fig. 34D View Figure 34 ), lateral surface with two tube-pores ( Fig. 34C View Figure 34 ).
Rostrum elongate ( Fig. 33C View Figure 33 ), with slightly convex margins in proximal half, tapering distally; slightly shorter than first antennulary segment; with two long sensillae; median pore positioned dorsally near apex of rostrum.
Antennule distinctly nine-segmented ( Fig. 33C View Figure 33 ), geniculation between segments 7 and 8; segment 1 only slightly shorter than segment 2, with small sclerite around proximal posterior margin, with anterior pattern of spinular rows as illustrated for other species; segment 5 distinctly swollen, with a distal cylindrical process bearing a basally fused seta and large aesthetasc (52 µm); acrothek on segment 9 with slen- der aesthetasc (17 µm).
Antenna, mandible, maxillule, and maxilla as in E. incerta .
Maxilliped well developed, subchelate, directed inwards. Syncoxa well developed, without pinnate seta, with two spinular rows. Basis elongate, with two to three long spinules anteriorly and a posterior spinular row along inner margin. Endopod represented by strong, curved, bare claw.
P1 ( Fig. 34A View Figure 34 ). Praecoxa strongly developed. Coxa with four spinular rows. Basis with sparsely plumose inner seta and pinnate outer seta. Exopod threesegmented; with two spines and two geniculate setae on exp-3. P1 endopod prehensile, distinctly longer than exopod; proximal segment approximately ten times as long as average width, with pinnate inner seta being plumose in proximal third; distal segment short, with three spinular rows, a subdistal setule, and two geniculate spines distally.
Swimming legs P2–P4 ( Fig. 35A–D View Figure 35 ). Praecoxae well developed, with spinular row on anterior surface in P2–P4. Coxae with pattern of spinules as in Figure 35A, B, D View Figure 35 , with large tube-pore on anterior surface of P3. Bases with outer seta (short and pinnate in P2, long and plumose in P3, short and naked in P4); with spinular rows on anterior surface only. Exopods three-segmented, endopods one-segmented (P2, P4) or incompletely three-segmented (P3). Inner distal spine of P3–P4 shorter than outer distal one. Inner setae of P4 endopod and exp-3 serrate. Seta and spine formulae as for genus.
P2 ( Fig. 35A View Figure 35 ) with inner distal corner of basis not modified into spinous process but with well-chitinized lateral margin. Endopod with three spinular rows; apical seta pinnate and clearly extending beyond distal margin of exp-2; inner element setiform and naked. Exp-3 modified; outer distal seta very long; inner distal element transformed into slender claw, directed medially and posteriorly, and with middle third pinnate and distal third denticulate.
Spines of P3 exopodal segments with pinnate ornamentation ( Fig. 35B View Figure 35 ); exp-1 with reduced hyaline frill; exp-3 with secretory pore on anterior surface near joint with exp-2. P3 endopod ( Fig. 35B, C View Figure 35 ) indistinctly three-segmented with middle and distal segments partly fused along posterior surface; enp-1 small, without armature or ornamentation; enp-2 with serrate, posterior seta and rigid, slightly sigmoid apophysis arising from anterior surface; enp-3 with weakly chitinized inner margin and with one short pinnate seta apically.
Fifth legs ( Fig. 33B, D View Figure 33 ) with baseoendopod and exopod fused into a common elongate plate, tapering distally towards long, pinnate, spinous process, which is longer than the plate; inner margin with serrate spine; outer margin with small, pinnate spine, three naked setae and sparsely plumose seta derived from baseoendopod; anterior surface with three large tube-pores.
Sixth pair of legs ( Figs 33B View Figure 33 , 35E View Figure 35 ) asymmetrical, with one short, naked and two long, sparsely pinnate setae each. First postgenital somite with transverse spinular row near ventral anterior margin ( Fig. 35E View Figure 35 ).
Differential diagnosis: Evansula polaris is thus far the only species that possesses spinule rows on the ventral posterior margin of the anal somite in the male (the condition in E. pygmaea is unknown). The characteristic shape of the male P3 endopod is an additional differentiating feature. E. polaris is the smallest representative of the genus.
Distribution: Norway: Laksefjord ( Scott, 1903b). Perhaps also in Troldfjord inside the Lofoten Islands [one male recorded by Sars (1911) as E. incerta ].
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.