Attheyella (Attheyella) tahoensis, Bang, Hyun Woo, Baguley, Jeffrey G. & Moon, Heejin, 2015

Bang, Hyun Woo, Baguley, Jeffrey G. & Moon, Heejin, 2015, First record of harpacticoid copepods from Lake Tahoe, United States: two new species of Attheyella (Harpacticoida, Canthocamptidae), ZooKeys 479, pp. 1-24 : 2-3

Taxon classification Animalia Harpacticoida Canthocamptidae

Attheyella (Attheyella) tahoensis sp. n. Figs 1, 2, 3, 4, 5, 6

Type locality.

The Lakeside littoral zone; 38°57'42"N, 119°57'14"W, 5 m water depth, of Lake Tahoe in California-Nevada, United States.

Material examined.

Holotype: 1♀ (USNM No: 1251801) dissected on 8 slides. Paratype 2♀♀ and 1♂ (USNM No’s listed in order presented in text: 1251802, 1251804, 1251803) each dissected on 6, 9 and 8 slides respectively, and 6♀♀ and 4♂♂ (USNM No’s for specimens in vials (female, male): 1251805, 1251806) in 70% ethanol, vial. All from the type locality, July 2013, leg. J.G. Baguley.

Description.

Female. Total body length 816 µm (n=6; range: 753-868 µm), measured from anterior margin of rostrum to posterior margin of caudal rami. Largest width measured at posterior margin of cephalic shield: 241 µm. Urosome narrower than prosome (Fig. 1A). Posterior and lateral margins on all somites except anal somite strongly serrated (Fig. 1 A–B).

Cephalothorax (Fig. 1A) bell-shaped, with saddle-shaped dorsal integumental window and some scattering sensillae on dorsal surface and along lateral margin (Fig. 1C). Pedigerous somites with sensillae on dorsal surface, serrate posteriorly as cephalothorax; pleural areas well developed. Urosome 5-segmented, comprising P5-bearing somite, genital double-somite and 3 free abdominal somites.

Genital somite and first abdominal somite partly fused forming double-somite, wider than long. Genital field as in Fig. 4B. Genital apertures located anteriorly, closely set together. Copulatory pore located anteriorly between genital apertures. Seminal receptacle well developed on each side. P6 with small protuberance bearing 2 pinnate setae.

Anal somite (Figs 1D, 4C) with pair of sensilla dorsally, with well-developed rounded operculum bearing row of setules. Caudal rami (Fig. 1 D–E) bottle-shaped, strongly tapering distally, about 2.5 times as long as wide, each ramus with 7 setae: setae I-II bare, short, of subequal lengths, closely set, seta III bipinnate, seta IV bare, seta V longest, seta VI bare and short, seta VII tri-articulate at base. Inner margin of each ramus with lateral concavity.

Antennule (Fig. 2A) 7-segmented. Segment 1 largest, with 1 spinular row and 1 seta. Segment 2 with 2 spinular rows around posterior and lateral margins. Segment 4 with aesthetasc fused basally to seta and set on pedestal. Armature formula: 1-[1], 2-[9], 3-[6], 4-[2+(1+ae)], 5-[1], 6-[4], 7-[8+acrothek]. Apical acrothek consisting of a small aesthetasc fused basally to 2 bare setae.

Antenna (Fig. 2B) 3-segmented, comprising coxa, allobasis and free 1-segmented endopod. Coxa small. Allobasis elongated; spinules on abexopodal margin; with 2 long abexopodal setae. Exopod 1-segmented; with 1 inner and 3 apical pinnate setae. Endopod elongated, with strong spinules along inner margin; lateral armature consisting of 2 pinnate spines and a minute seta; distal armature consisting of 2 apically curved pinnate spines and 3 geniculate setae, the outer-most bipinnate and basally fused to an additional short seta.

Mandible (Fig. 2 C–D) with well-developed gnathobase bearing 2 strong teeth and several smaller, multicuspidate teeth around distal margin and 1 pinnate spine at dorsal corner; spinules near base of palp. Palp 2-segmented, distal segment with 4 bare setae.

Maxillule (Fig. 2E). Praecoxal arthrite well developed, with 9 apical strong and transformed spines, 2 bare setae on anterior surface and, few spinules near outer margin. Coxa with cylindrical endite bearing 1 naked seta, and 1 curved spine. Basis with 2 geniculated setae and 1 bipinnate spine apically; with several spinules around inner distal margin and base of endopod. Endopod and exopod incorporated in basis and presented by 1 pinnate and 1 naked seta, and 2 naked setae, respectively.

Maxilla (Fig. 2F). Syncoxa with 2 endites each carrying apically 2 strong pinnate spines and 1 seta. Allobasis drawn out into strong, slightly curved, distally pinnate claw, accessory armature consisting of 2 bare setae with 1 tube pore. Endopod small, with 2 naked setae.

Maxilliped (Fig. 2G). Syncoxa with 1 plumose seta on inner distal corner. Basis with 1 row of spinules along palmar region. Endopodal segment produced into strong and distally pinnate curved claw; accessory armature consisting of 1 small seta at base.

Swimming legs 1-4 with wide intercoxal sclerite, biramous, endopods 2-segmented except for P1, exopods 3-segmented. Coxa and basis with row of spinules along outer margins as illustrated.

P1 (Fig. 3A). Preacoxa large, with longitudinal spinular row on anterior surface. Coxa large, with four spinular rows on anterior surface, and row of spinules along outer margin. Basis with strong bipinnate outer spine on outer margin and bipinnate spine on inner distal surface, with several spinules and setules as figured. Endopod 3-segmented; enp-1 about 2.1 times as long as enp-2; enp-1 with one small inner bipinnate seta on distal fourth; enp-2 with 1 bipinnate inner seta; enp-3 with 1 small pinnate seta and 2 long geniculate setae distally. Exopod 3-segmented, reaching middle of enp-2, exp-2 with 1 inner pinnate seta; exp-3 with 2 geniculate distal setae and 2 strong spinulose outer spines.

P2-P4. Coxa and basis with spinular rows along outer margin and anterior surface. Basis with pinnate spine (P2) or bare seta (P3-P4), each seta arising from a setophore.

P2 (Fig. 3B) with large coxa, ornamented with row of spinules on anterior surface, and with row of long spinules along outer margin; P2 enp-2 more than twice as long as enp-1; with 1 short, pinnate inner seta; enp-2 with 1 inner pinnate short seta, and 1 short apical seta and 1 bipinnate apical spine; exopod 3-segmented; each segment with row of spinules along outer margins; third segment about 1.8 times as long as second segment with 3 strong bipinnate outer spines, 2 apical pinnate spines, and 1 inner bipinnate seta.

P3 (Fig. 3C) with small praecoxa. Coxa nearly 1.5 times as wide as long, with 3 spinular rows on anterior surface and 2 rows of spinules along outer margin. Enp-2 about 3 times longer than enp-1; enp-2 with 2 small bare inner setae and 2 short distal naked setae and one pinnate spine.

P4 (Fig. 3D) with small and triangular praecoxa, with row of spinules on anterior surface along distal margin. Coxa with 1 row of small spinules on anterior surface and 1 spinular row along outer margin. Enp-2 2.5 times as long as enp-1; enp-2 with 1 naked seta, 1 pinnate seta and 1 spine. Spine and setal formulae as follows:

P 5 (Fig. 4A) with separate exopod and baseoendopod, each covered with spinules as illustrated. Baseoendopod longer than wide, forming short outer setophore bearing the basal seta. Endopodal lobe long and almost reaching distal margin of exopod, with 3 pinnate inner setae, 2 distal setae, and 1 pinnate outer seta. All setae pinnate and short. Secretory pore on anterior surface. Exopod elongated, 3.4 times as long as wide, with 1 short inner, 2 distal and 2 outer setae.

P6 (Fig. 4B) each with small protuberance bearing 2 plumose setae.

Description.

Male. Body slightly smaller and more slender than female, habitus as in Fig. 5A. Body length 784 µm (n=5; range: 765-821 µm), measured from anterior margin of rostrum to posterior margin of caudal rami. Largest width measured at P2-bearing somite: 214 µm. Sexual dimorphism in antennule, P3-P4 endopod, P5 and P6.

Prosome (Fig. 5A) posterior margin of cephalothorax and pedigerous somites with serrated process, with integumental sensilla.

Urosome (Fig. 5A, C) 6-segmented, comprised of P5-bearing somite, genital somite, and 4 free abdominal somites. Urosomite with serrated posterior margin dorsally and ventrally.

Caudal rami (Fig. 5D) slightly more elongated than female, about 3.3 times as long as wide, seta III bare, seta IV pinnate. Inner margin of each ramus with lateral concavity.

Antennule (Fig. 6A) 10-segmented; subchirocer with geniculation between segments 5 and 6, and between segment 7 and 8. Segment 1 with a row of spinules along anterior margin. Segment 4 and 6 represented by a small sclerite. Segment 5 swollen with large bump along posterior margin. Segment 7 and 8 with 3 spinular processes from modified setae on each segment. Armature formula: 1-[1], 2-[7], 3-[9], 4-[2], 5-[5 + (1 + ae)], 6-[2], 7-[2 + 3 modified] 8-[3 modified], 9-[1], 10-[7 + acrothek]. Apical acrothek consisting of a small aesthetasc fused basally to 2 bare setae.

P3 (Fig. 6B). Exopod as in female, except for outer spine on first and second exopodal segment of P3 proportionately stronger. Endopod modified, 3-segmented; enp-1 shortest with inner pinnate seta; enp-2 with well-developed inner apophysis; enp-3 with 1 pinnate apical seta and 1 long bare seta.

P4 (Fig. 6C). Setae and spines on exopod modified, outer spine on first and second exopodal segment proportionally stronger than female. Endopod 2 with 1 pinnate seta and 2 pinnate spines and longer than those in female.

Fifth pair of legs (P5) (Fig. 5B) smaller and much shorter than female and fused medially, with no spinules. Baseoendopod with outer setophore bearing the basal seta. Endopodal lobe with 2 distal pinnate setae with large pore on anterior surface. Exopod shorter than in female, as long as wide, with 1 inner bare seta, 2 distal pinnate setae and 1 pinnate spine, and 2 outer pinnate spines.

P6 (Fig. 5C) asymmetrical, bearing 2 naked seta on a cylindrical process. On left side a lobe with two setae, on the right side a small plate with two setae.

Variability.

Intraspecific variability was observed in the shape of caudal rami of female (about 20%; 6/30 observed individuals). Caudal rami (Fig. 4 D–F) lamelliform and elongate, about twice as long as wide, laterally compressed, inner margin of each ramus with lateral concavity. Each ramus with 7 setae: seta III bare, seta IV bipinnate, seta V extremely reduced, seta VI bare and longer than normal.

Etymology.

The species name refers to the type locality, Lake Tahoe. This is one of the largest alpine lakes in the world is known for its pristine waters and aesthetic beauty.