Eucyclops festivus Lindberg, 1955

Mercado-Salas, Nancy F., Suárez-Morales, Eduardo & Silva-Briano, Marcelo, 2015, Taxonomic revision of the Mexican Eucyclops (Copepoda: Cyclopoida) with comments on the biogeography of the genus, Journal of Natural History 50, pp. 25-147 : 50-59

Eucyclops festivus Lindberg, 1955

( Figures 14 – 21 )

Description

Female. Habitus as in Figure 16A . Average body length excluding caudal setae = 866 µm. Body surface (including caudal rami) ornamented with small pits. Prosome representing 59% of total body length. Prosomal fringes serrate dorsally. Urosomal fringes strongly serrate. Genital double somite symmetrical ( Figure 16B ), representing 10.8% of total body length; proximal third of genital double somite slightly expanded laterally. Seminal receptacle with rounded lateral arms on posterior margin, typical of the serrulatus -complex. Length/width of caudal rami = 4.6; inner margin of caudal ramus smooth; outer margin with strong spinules covering 61% with respect to the total length of ramus. Dorsal seta (VII) 0.5 times as long as caudal ramus and 0.6 times as long as outermost caudal seta (III). Ratio of innermost caudal seta (VI)/outermost caudal seta (III) = 1.0. Lateral caudal seta (II) inserted at 74% of caudal ramus.

Antennule ( Figures 14B , 16E–F , 17A ). Tip reaching second pediger, antennules ornamented with pits. Armature per segment as follows: 1(8s), 2(4s), 3(2s), 4(6s), 5(4s), 6(1s+1sp), 7(2s), 8(3s), 9(2s+1ae), 10(2s), 11(3s), 12(7s+1ae). Transverse rows of spinules on first segment not observed. Spine on sixth segment reaching midlength of seventh antennular segment.

Antenna ( Figures 14C–D , 17B–D ). Coxa (unarmed), basis (2s+Exp), plus threesegmented Enp (1s, 9s, 7s, respectively). Basis with rows of spinules on frontal surface:

N1(V), N2(3), N3(5), N4(5), N5(8), N6(10), N15(4), N17 (12), N18(3) and on caudal surface: N7(4), N8(5), N9 + 10(8), N11(4), N12(6), N13(5), N14(8), N16(5), N22(10). Caudal surface of first Enp with B2 (5).

Leg 1 ( Figures 15A–B , 17F ). Frontal surface of intercoxal sclerite with row I armed with hair-like elements arranged in semicircular pattern, caudal surface with rows I and II bearing minute spinules. Inner coxal seta biserially setulated, caudal coxal surface with spinule formula = A-B-C. Inner basal seta (basipodal spine) reaching middle margin of

Enp3, 0.8 times as long as Enp. Length/width ratio Enp3 = 1.4, apical spine of Enp3 being 1.2 times as long as Enp3.

Leg 2 ( Figures 15C–D , 18A–B ). Frontal surface of intercoxal sclerite with row I bearing hair-like elements arranged in a circular pattern; caudal surface with row I discontinuous, bearing 7 – 9 small spinules on each side, row II continuous with 24 – 30 small spinules. Distal margin of intercoxal sclerite with two rounded, chitinised projections. Inner coxal seta biserially setulated, caudal coxal surface with spinule formula A-B-C-D.

Length/width ratio of Enp3 = 2, apical spine of Enp3 1.2 times as long as Enp3. No modified setae present.

Leg 3 ( Figures 15E–F , 18C–D ). Frontal surface of intercoxal sclerite armed with group of long hairs on each side; caudal surface with row I bearing long hairs and with a small gap in the middle, row II continuous bearing 30 – 32 small spinules and row III continuous bearing 32 – 37 spinules. Distal margin with two rounded, chitinised projections. Coxa with strong, biserially setulated inner coxal seta, basally with long hairs and distally with

strong spinules along both margins. Caudal coxal surface with spinule formula = A-B-C. Length/width ratio of Enp3 = 1.9, apical spine of Enp3 as long as segment (Enp3). No modified setae present.

Leg 4 ( Figures 15G–H , 18F , 19A ). Distal margin of intercoxal sclerite with two low, rounded, chitinised projections. Frontal surface of sclerite with row I bearing long slender spinules arranged in a semicircular pattern on both sides of surface. Caudal surface of intercoxal sclerite with row I with seven strong spinules on each side and with a small gap in the middle margin; row II continuous, with strong spinules, outer margins bearing more spinules than medial margin; and row III divided into three sections, two on outer margins with strong and long spinules and medial margin with 3 – 4 long spinules. Frontal surface of coxa with row of small spinules at insertion of Bsp. Inner coxal spine with heterogeneous ornamentation; inner margin with long hairs on proximal section and strong spinules distally; outer edge with one distal spinule and proximal hair-like elements, gap in the middle margin. Length/width ratio Enp3 = 2.5, length ratio inner spine of Enp3/length Enp3 = 1.2; length ratio outer spine of Enp3/ length Enp3 = 0.9; proportion inner/outer spines Enp3 = 1.3. Lateral seta of Enp3 inserted at 68% of segment. No modified setae in Enp and Exp.

Leg 5 ( Figure 19B ). Free segment subrectangular, 2.1 times longer than wide, bearing one strong inner spine and two setae; medial seta 1.8 times longer than outer seta and 1.6 times longer than inner spine. Inner spine twice longer than segment.

Remarks. As mentioned by Gutiérrez-Aguirre et al. (2013), E. festivus has been recorded in north and central Mexico and recently also from a pond in the state of Chiapas in southeast Mexico. This species appears to be related to E. estherae sp. nov. and E. wixarica sp. nov., both described herein. Differences among these species are presented in the remarks sections of E. wixarica sp. nov. and E. estherae sp. nov.

Figures

Figure 14. Eucyclops festivus Lindberg, 1955. Adult female. (A) Urosome, ventral; (B) antennule; (C) antennal basis, frontal; (D) basis and Enp1 antenna, caudal, (E) Enp2 and Enp3 antenna.

Figure 15. Eucyclops festivus Lindberg, 1955. Adult female. (A) P1, frontal; (B) coxa and intercoxal sclerite P1, caudal; (C) P2, frontal; (D) coxa and intercoxal sclerite P2, caudal; (E) endopod P3; (F) coxa, basis, intercoxal sclerite and exopodite P3, frontal; (G) P4, frontal; (H) coxaP4, caudal.

Figure 16. Eucyclops festivus Lindberg, 1955. Adult female. (A) Habitus, dorsal; (B) genital somite, ventral; (C) anal operculum, dorsal; (D) caudal rami, ventral; (E) antennule; (F) antennule segments 1–5.

Figure 17. Eucyclops festivus Lindberg, 1955. Adult female. (A) Antennule segment 9; (B) antenna, caudal; (C) antennal basis, frontal; (D) antennal basis, caudal; (E) maxillule, maxilla and maxiliped, (F) P1, frontal.

Figure 18. Eucyclops festivus Lindberg, 1955. Adult female. (A) P2, frontal; (B) intercoxal sclerite P2, frontal; (C) P3, caudal; (D) intercoxal sclerite P3, caudal; (E) P4, frontal; (F) intercoxal sclerite P4, frontal.

Figure 19. Eucyclops festivus Lindberg, 1955. Adult female, A–B; adult male, C–F. (A) Coxal spine P4; (B) P5; (C) P5 and P6; (D) caudal rami, ventral; (E) antennule; (F) antennule.

Figure 20. Eucyclops festivus Lindberg, 1955. Adult male. (A) Antennule; (B) antennule; (C) antenna, caudal; (D) basis and Enp1 antenna, caudal; (E) maxillule; (F) maxilla and maxilliped.

Figure 21. Eucyclops festivus Lindberg, 1955. Adult male. (A) P2, frontal; (B) intercoxal sclerite P2, frontal; (C) P3, frontal; (D) P4, caudal; (E) coxa P4, caudal; (F) coxa and intercoxal sclerite P4, caudal.