Eucyclops edytae, Tang & Knott, 2009

Tang, Danny & Knott, Brenton, 2009, Freshwater cyclopoids and harpacticoids (Crustacea: Copepoda) from the Gnangara Mound region of Western Australia, Zootaxa 2029, pp. 1-70 : 7-13

Eucyclops edytae sp. nov.

( Figs 2–6)

Type material. Holotype ♀ ( AM P.78707), allotype ♂ ( AM P.78708) and 32 paratypes (3 ♀, 3 ♂ and 22 copepodids in alcohol; 2 ♀ and 2 ♂ dissected and mounted on one slide each) ( AM P.78709–P.78713), Egerton spring, Ellenbrook, Western Australia (31°46'18''S, 115°58'51''E), 20 December , 1994.

Other material examined. Cabaret Cave ( YN 30), Yanchep National Park, Western Australia (31°32'31''S, 115°41'24''E): 1 ♀, 9 October, 2007; Bevan Peters’ spring, Ellenbrook , Western Australia (31°35'14''S, 115°57'47''E) : 1 ♀, 2 August , 1992 ; 4 ♀, 4 ♂ and 10 copepodids ( AM P.78714), 21 December, 1992; Egerton spring, Ellenbrook , Western Australia (31°46'18''S, 115°58'51''E) : 2 ♀, 1995; 1 ♀, 2 ♂ and 12 copepodids, 7 November , 2005 ; 5 ♀ (1 dissected and mounted on slide) and 1 ♂, 9 October , 2006 ; 32 ♀ and 17 ♂, 9 October , 2007 ; 14 ♀, 4 ♂ and 1 copepodid, 22 August, 2008; Mrs. King’s tumulus spring, Bullsbrook , Western Australia (31°39'04''S, 115°57'11''E) : 2 ♀, 8 May , 1996 ; 1 ♀ dissected and mounted on slide ( DEC collection), 5 December, 2002; Sue’s spring (South), Bullsbrook , Western Australia (31°38'42''S, 115°58'17''E) : 1 damaged ♀, 1 February , 2008 ; 1 ♀, 22 August , 2008 .

Description of female. Total body length (measured from anterior margin of cephalothorax to posterior margin of caudal rami), based on 10 specimens, 610–760 µm, mean 690.5 µm; body width 220–270 µm,

mean 243 µm. Prosome ( Fig. 2A) composed of cephalothorax and 3 free pedigerous somites. Urosome ( Figs 2A–B) comprised of fifth pedigerous somite, genital double-somite and 3 free abdominal somites. Fourth and fifth pedigerous somites each furnished with setules along posterolateral corners. Genital double-somite subequal in length, mean 88.5 × 88 µm; seminal receptacle not observed. Posterior margin of urosomites 2–4 slightly uneven dorsally and serrate ventrally. Anal somite ( Figs 2B–C) with posterior spinular row dorsally and ventrally; anal cleft with longitudinal rows of setules.

Caudal ramus ( Figs 2C–D) longer (35–45 µm; mean 42.5 µm) than wide (20–25 µm; mean 23 µm); bears 6 setae (seta I absent), 4 groups of spinules on ventral surface and spinular row at base of setae II and III. Setae II and VII inserted at posterior ⅔ of ramus. Seta VII setulate; seta II with few spinules apically; remaining setae spinulate. Seta VI twice as long as seta III. Setae IV and V with proximal breaking plane.

Antennule ( Fig. 3A) 12-segmented, with armature and ancestral segmentation pattern in brackets as follows: 8 (I–V), 4 (VI–VII), 2 (VIII), 6 (IX–XI), 4 (XII–XIII), 1+spine (XIV), 2 (XV–XVI), 3 (XVII–XX), 2+ae (XXI–XXIII), 2 (XXIV), 2+ae (XXV), and 7+ae (XXVI–XXVIII). First segment with proximoventral spinular rows. Finely serrate hyaline membrane present on segments 10 and 12.

Antenna ( Figs 3B–C) 4-segmented, comprising coxobasis and 3-segmented endopod. Coxobasis with long distolateral exopodal seta, 2 distomedial barbed setae and complex ornamentation on frontal and caudal surfaces as figured. Proximal endopodal segment with inner naked seta and lateral spinular patch. Middle endopodal segment bears 9 inner setae and spinules along outer margin. Terminal endopodal segment with usual proximal and distal spinules and 7 distal setae.

Labrum ( Fig. 3D) with 2 teeth on each lateral corner, 15 teeth along medial margin, and long setules on anterior surface.

Mandible ( Fig. 3E) composed of coxa and reduced palp. Distal end of coxal gnathobase with outer quadridentate tooth, 2 central bicuspidate teeth, 2 inner unicuspidate teeth, spinulate seta and row of strong spinules. Palp with row of spinules near base and 3 distal setae (2 long and plumose, 1 short and naked).

Maxillule ( Fig. 4A) comprising praecoxa and 2-segmented palp. Praecoxal arthrite bears 7 elements (of which 4 are unornamented) along medial margin and spinulate seta and 3 large unicuspidate teeth distally. Coxobasis with proximal seta and 3 terminal setae. Endopod 1-segmented, armed with 3 setae.

Maxilla ( Fig. 4B) 5-segmented, composed of praecoxa, coxa, basis and 2-segmented endopod. Praecoxal endite armed with 2 spinulate setae. Proximal and distal coxal endites with 1 and 2 spinulate setae, respectively; few spinules present proximally on outer margin of coxa. Basis drawn out into large claw furnished with large teeth along middle part of inner margin; accessory armature composed of spinulate spine and seta. Proximal endopodal segment with 2 setae; distal endopodal segment with 3 setae.

Maxilliped ( Fig. 4C) 4-segmented, comprising syncoxa, basis and 2-segmented endopod. Syncoxa with 3 medial spinulate setae and row of stout spinules. Basis with 2 large patches of spinules along outer margin, several long spinules on antero-medial surface and 2 medial spinulate setae. Proximal endopodal segment with long spinules on anterior surface and long, inner spinulate seta. Terminal endopodal segment with largest element fused to segment, claw-like, and furnished with long spinules; middle and lateral setae unilaterally spinulate.

Legs 1–4 biramous ( Figs 4D, 5A–D), with 3-segmented rami. Armature on rami of legs 1 to 4 as follows (Roman numerals = spines; Arabic numerals = setae):

Leg 1 ( Fig. 4D) intercoxal sclerite with spinular row on anterior surface; posterior surface with 2 spinular rows. Coxa with fine spinules along distal margin of anterior surface and well developed spinules laterally and medially on posterior surface. Basis with small, mediodistal triangular process, setules along inner margin and spinules at insertion point of rami and inner spine. Outer seta setulate; inner spinulate spine reaches to proximal ½ of terminal endopodal segment. Anterior surface of endopodal segments and posterior surface of first two exopodal segments and middle endopodal segment with distal spinular row. Inner margin of exopodal segments and outer margin of endopodal segments with setules; outer margin of middle exopodal segment also with setules. Outermost seta on terminal exopodal segment heterogeneously ornamented, with lateral row of denticles and inner row of setules; all other setae on rami plumose. All spines on rami denticulate; small spinules present at insertion point of each spine.

Leg 2 ( Fig. 5A) intercoxal sclerite and coxa similar to those of leg 1, except coxa with additional row of setules along lateral margin and more prominent spinular row along distal margin. Basis with mediodistal triangular process, inner corner produced into large acute process and spinules at insertion point of endopod and along outer and inner margins. Exopod ornamented as in leg 1, except with additional distal spinular row on anterior surface of proximal segment and 1–2 minute denticles on proximolateral margin of middle and terminal segments. Proximal outer spine on terminal exopodal segment ⅔ length of other outer spines. All setae on rami plumose. Endopod ornamented as in leg 1, except with more developed spinules on anterior surface and additional spinular row on posterior surface of first segment and few proximomedial setules on distal segment.

Leg 3 ( Fig. 5B) similar to leg 2, except for additional spinular row along posterior margin of intercoxal sclerite, relatively shorter outer seta on basis, absence of mediodistal triangular process on basis, naked outer margin of middle exopodal segment and naked inner margin on distal endopodal segment.

Leg 4 ( Figs 5C–D) intercoxal sclerite with fewer spinules than those of preceding legs. Coxa with highly complex ornamentation on posterior surface as figured. Basis structured as in leg 2. Rami ornamented as in leg 3. Inner apical spine two times longer than outer apical spine on terminal endopodal segment.

Leg 5 ( Figs 2B, 6A) 1-segmented, armed with 3 elements; outer and middle setae setulate; base of middle seta strongly produced. Inner spine longest of 3 elements, curves slightly inward at distal half, reaches to proximal ⅔ of genital double-somite and furnished with spinules at base.

Leg 6 ( Fig. 6B) rudimentary, represented by long, weakly spinulate seta and 2 short naked spines on genital operculum.

Male. Mean body length (measured from anterior margin of cephalothorax to posterior margin of caudal rami), based on 10 specimens, 569 µm (480–620 µm); mean body width 181 µm (170–190 µm) at posterior margin of cephalothorax. Prosome ( Fig. 6C) composed of cephalothorax and 3 free pedigerous somites; posterior margin of prosomites smooth. Urosome ( Fig. 6C) comprised of fifth pedigerous somite, genital somite and 4 free abdominal somites. Fourth and fifth pedigerous somites without setules on posterolateral corners. Posterior margin of urosomites 2–5 uneven dorsally and serrate ventrally. Genital somite ( Figs 6C, F) wider than long (mean 50 × 62 µm). Caudal ramus ( Fig. 6C) longer than wide (mean 34 × 19 µm), armed and ornamented as in female.

Antennule ( Fig. 6D) 15-segmented, digeniculate, with armature and ancestral segmentation pattern as follows: 8+ae (I–V), 4 (VI–VII), 2 (VIII), 2+ae (IX), 2 (X), 2 (XI), 2 (XII), 2 (XIII), 2+ae (XIV), 2 (XV), 2 (XVI), 2 (XVII), 6 (XVIII-XX), 4 (XXI-XXIII), and 11+ae (XXIV–XXVIII). Apically blunt, setulose seta(e) present on segments 1–5. Short, spinulate seta present on segments 11 and 13. Short, highly chitinized spine present on segment 12. Two very short, blunt setae present on segment 13; similar element on segment 14. Modified ridged element(s) present on segments 13 and 14.

Leg 3 basis ( Fig. 6E) with small acute process between rami.

Leg 5 ( Fig. 6F) with inner spine extending to proximal margin of leg 6.

Leg 6 ( Fig. 6F) represented by 3 elements on genital operculum; outer seta with sparse setules; middle seta unilaterally spinulate; inner spine slightly shorter than outer and middle setae, with spinules at base.

Etymology. This species is named in honour of Dr. Edyta J. Jasinska, for her pioneering studies on the root mat communities of the Yanchep National Park Caves in Western Australia.

Remarks. Among the 11 Eucyclopinae genera, the new species conforms to the genus Eucyclops sens. lat. by having setules on the distolateral margins of the fifth pedigerous somite, a 12-segmented antennule that bears a hyaline membrane on the distal segments, maxilliped with the innermost element on the terminal endopodal segment fused basally to the segment, the inner corner of the basis of legs 2 to 4 produced into a large acute process and a 1-segmented leg 5 armed with two setae and one spine ( Morton 1990; Dussart & Defaye 1995).

Most Eucyclops species possess spinules along either a small portion or almost the entire length of the lateral margin of each caudal ramus. The absence of this feature, as exhibited by the new species, is shared with 13 species: E. teras (Graeter, 1907) , E. angustus (G. O. Sars, 1909) , E. dubius (G. O. Sars, 1909) , E. laevimargo (G. O. Sars, 1909) , E. indicus ( Kiefer, 1927) , E. glaber Kiefer, 1935 , E. nudus Kiefer, 1935 , E. caparti Lindberg, 1951 , E. congolensis Lindberg, 1951 , E. orthostylis Lindberg, 1952 , E. miurai Itô, 1952 , E. persistens Monchenko, 1978 , E. puteincola Kiefer, 1981 , E. neocaledoniensis Dussart, 1984 and E. bathanalicola Boxshall & Strong, 2004 . Of these, E. edytae sp. nov. is most similar to E. puteincola in having caudal rami that are less than three times as long as wide, caudal seta VI at least two times longer than seta III and the inner spine on leg 5 that is at least two times as long as the free exopodal segment.

Eucyclops edytae sp. nov. can be easily distinguished from E. puteincola , and all other congeners, by the unique spinulation pattern on the mid-ventral surface of the caudal rami. In other Eucyclops species , the midventral surface of each caudal ramus is devoid of integumental structures. The new species differs further from E. puteincola with respect to the relative length of the inner spine on leg 1 basis, relative lengths of the apical spines on the terminal endopodal segment of leg 4 and insertion point of the outer seta and the relative length of the middle seta on leg 5. The inner spine on leg 1 basis extends to the proximal half of the terminal endopodal segment in the new species, whereas it reaches to the distal margin of same limb segment in E. puteincola . The outer apical spine on the terminal endopodal segment of leg 4 is half as long as the inner apical spine in the new species. In E. puteincola this outer apical spine is about two-thirds as long as the adjacent spine. The outer seta and inner spine on leg 5 are inserted at the same level in the new species, but these elements are each inserted at a different level in E. puteincola . The middle seta on leg 5 is shorter than the inner spine in the new species, but longer than the inner spine in E. puteincola .

Eucyclops edytae sp. nov. is the sixth member of the genus to be reported from Australia. The other five species recorded previously from this continent are: E. ruttneri Kiefer, 1933 , E. nichollsi Brehm, 1950 , E. australiensis Morton, 1990 , E. baylyi Morton, 1990 and E. spatulatus Morton, 1990 [see Morton 1990]. Of these, E. spatulatus and E. australiensis are also known to occur in Western Australia. These two taxa are, unlike E. edytae sp. nov., strictly lacustrine species and distributed in other states, such as South Australia, Victoria, Tasmania and New South Wales ( Morton 1990). Although E. edytae sp. nov. is currently known to exist exclusively in ground waters, extensive sampling of surface water habitats in Western Australia is required to determine whether it is a truly stygobitic or stygophilic species.