Eucyclops defayeae, Mercado-Salas & Suárez-Morales & Silva-Briano, 2015

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 : 103-111

Eucyclops defayeae sp. nov. Mercado-Salas and Suárez-Morales ( Figures 48 – 54 )

Material examined

Holotype. Adult ♀ specimen dissected, mounted in glycerin, slides sealed with Entellan (ECO-CH-Z-05110).

Allotype. Adult ♂, dissected, mounted in glycerin, slides sealed with Entellan (ECO-CH- Z-05111).

Paratypes. Five adult ♀♀ undissected, ethanol-preserved (90%) (ECO-CH-Z-05112). Samples from type locality collected 12 March 1992 by Marcelo Silva-Briano.

Type locality

Pond at Villa Juárez, Asientos, Aguascalientes, Mexico.

Etymology

This species is warmly dedicated to Dr. Danielle Defaye (Museum National d ’ Histoire Naturelle, Paris) for her many contributions to the knowledge of the taxonomy and

systematics of freshwater copepods, and also for all her kind help and advice during the development of this work.

Distribution

Central and Northern part of Mexico (Aguascalientes, Zacatecas, San Luis Potosí) .

Description

Female. Habitus as in Figure 50A . Average length excluding caudal setae = 800 µm. Prosome representing 55% of total body length, symmetrical in dorsal view. Prosomal fringes finely serrate in dorsal view. Urosomal fringes strongly serrate. Genital double somite symmetrical ( Figure 50C ), representing 12.5% of total body length; anterior third of genital double somite expanded laterally. Seminal receptacle with rounded lateral arms on posterior margin, typical of the serrulatus -complex. Anal operculum slightly rounded and serrate ( Figure 50D ). Length/width of caudal rami = 4.6; inner margin of caudal ramus naked; strong spinules covering 53% with respect to the total length of ramus. Dorsal seta (VII) 0.5 times as long as caudal ramus and 0.9 times as long as outermost caudal seta (III). Ratio of innermost caudal seta (VI)/outermost caudal seta (III) = 1.2. Lateral caudal seta (II) inserted at 76% of caudal ramus.

Antennule ( Figures 48C–D , 50F , 51A ). Tip reaching posterior margin of second pediger. 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(8s). One transverse row of spinules on first segment. Spine on sixth segment reaching midlength of seventh antennular segment.

Antenna ( Figures 48E–F , 51B–D ). Coxa (unarmed), basis (2s+Exp), plus three-segmented Enp (1s, 9s, 7s, respectively). Basis with rows of spinules on frontal surface: N1(V), N2(VI), N3(7), N4(7), N5(6), N6(7), N15(5), N17(8), N18(3); on caudal surface: N7(5), N8(6),

N9+10(7), N11(7), N12(7), N14(4), N16(14). Caudal surface of Enp1 with B1(5), B2(7) and B3(3).

Leg 1 ( Figures 49A–C , 51F , 52A ). Frontal surface of intercoxal sclerite smooth (rows not observed), caudal surface with row II continuous, bearing 21 strong but small spinules, row I absent. Inner coxal seta biserially setulated, caudal coxal surface with spinule formula = A-B-C. Inner basal seta (basipodal spine) long exceeding apical margin of Enp3, 1.1 times as long as Enp. Length/width ratio Enp3 = 1.2, apical spine of Enp3 being 1.1 times as long as Enp3.

Leg 2 ( Figure 49D–G ). Frontal surface of intercoxal sclerite with row I bearing strong spinules arranged in a semicircular pattern; caudal surface with rows I and II continuous, row I with 14 minute spinules and row II with 23. 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 = 1.7, apical spine of Enp3 being 1.1 times as long as Enp3. No modified setae present.

Leg 3 ( Figures 49H , 52B–C ). Frontal surface of intercoxal sclerite with minute spinules arranged in a semicircular pattern on each side; caudal surface with row I bearing small,

strong spinules (gap in middle section), row II continuous, bearing small, slender spinules; row III continuous, with strong, long spinules (spinules adjacent to outer margins longer than those in middle section). 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. Length/width ratio of Enp = 2.0, apical spine of Enp3 being 1.1 times as long as Enp3. Modified setae present in Exp and Enp.

Leg 4 ( Figures 49I–J , 52D–F , 53A ). Distal margin of intercoxal sclerite with two low, rounded, chitinised projections. Frontal surface of sclerite with row I bearing minute spinules arranged in a semicircular pattern, caudal surface of sclerite with row I bearing long, strong spinules, row II continuous, with small spinules; row III with strong, slightly longer spinules, small gap in middle section. Frontal surface of coxa with row of small spinules at insertion of Bsp. Inner coxal spine with heterogeneous ornamentation; proximal inner margin with long hairs, distal margin with strong spinules, outer margin with two distal spinules, proximally setulated, gap in middle margin. Spinule formula on caudal surface = A-B-C + D-E-F-H-J. Length/width ratio Enp3 = 2.4, length ratio inner spine of Enp3/length Enp3 = 1.2; length ratio outer spine of Enp3/length Enp3 = 0.7; length ratio inner/outer spines Enp3 = 1.8. Lateral seta of Enp3 inserted at 64% of segment. Modified setae in Enp and Exp.

Leg 5 ( Figures 48B , 53B ). Free segment subrectangular, 1.8 times longer than wide, bearing one strong inner spine and two setae; medial seta 1.8 times longer than outer seta and 2.3 times longer than inner spine. Inner spine 1.4 times longer than segment.

Remarks. As mentioned in the remarks section of other species, E. defayeae sp. nov. shares with E. elegans and E. tziscao some characters like the rounded, serrate anal operculum, but differs from E. elegans in the body length and the length/width ratio of the caudal ramus; in this new species the ramus is 4.6 times longer than wide, vs a ratio of over 6.0 found in E. elegans . This new species can be easily distinguished from E. tziscao by the ornamentarion of the frontal surface of the antennal basis: row II bears long hairs in E. defayeae sp. nov., but in E. tziscao it has small, strong spinules.

Mexican records of E. bondi are now assignable to either E. tziscao or E. defayeae sp. nov. These three species share general morphometric values and the same armature of the caudal surface of the intercoxal sclerite of P4. Both Mexican species can be easily distinguished from E. bondi if males are available. The sixth leg in E. bondi differs from that of E. tziscao and E. defayeae sp. nov. in having a remarkably short inner spine and a medial seta as long as or slightly longer than the spine, and an outer seta longer than the inner spine. In both E. tziscao and E. defayeae sp. nov., the inner spine is always much longer than both the medial and the outer setae. Eucyclops tziscao and E. defayeae sp. nov. can be distinguished because in the former species the frontal surface of the antennal basis row N2 bears short spinules vs long hairs in E. defayeae sp. nov. Rows N6, N7, N14, N16 and N18 are present in E. defayeae sp. nov. but they are absent in E. tziscao ( Gutiérrez-Aguirre et al. 2013) . The ornamentation on the caudal surface of P1 and P2 intercoxal sclerites differs between these species: in E. defayeae sp. nov. row I of P1 is absent but it is present in E. tziscao , and row I of P2 is present in E. defayeae sp. nov. but it is absent in E. tziscao . The presence of caudal spinules on P3 row I is another distinctive character in E. defayeae sp. nov. Among the species distributed in Mexico, this character is shared with E. cuatrocienegas and E. mittmanni sp. nov.

The only other known congener sharing the presence of long hairs in row N2 with E. defayeae sp. nov. is E. wixarica , but N6 is absent in E. wixarica sp. nov.; in addition, rows N9 and N10 are separated in E. wixarica sp. nov. but fused in E. defayeae sp. nov. Additional differences between these two species include the ornamentation of the caudal surface of the P1 intercoxal sclerite: row I is present and bears minute spinules in E. wixarica but it is absent in E. defayeae sp. nov. The ratio of basipodal spine/length of Enp of P1 is 0.6 in E. wixarica , while in E. defayeae sp. nov. the spine is remarkably long (about 1.1). Also, modified setae were observed in P3 and P4 of E. defayeae sp. nov., while in E. wixarica all swimming setae are normal.

Figures

Figure 48. Eucyclops defaye sp. nov. Adult female. (A) Urosome, ventral; (B) P5; (C) antennule, segments 1–8; (D) antennule, segments 8–10; (E) antenna, frontal; (F) basis and Enp1 antenna; (G) maxilla; (H) maxilliped.

Figure 49. Eucyclops defaye sp. nov. Adult female. (A) P1, frontal; (B) exopod P1, (C) intercoxal sclerite P1, caudal; (D) exopod P2; (E) coxa, basis and endopod P2, frontal; (F) coxa and intercoxal sclerite P2, caudal; (G) intercoxal sclerite P2, frontal. (H) P3, frontal; (I) coxa, basis and endopod P4, frontal; (J) coxa and intercoxal sclerite P4, caudal; (K) exopod P4.

Figure 50. Eucyclops defaye sp. nov. Adult female. (A) Habitus, dorsal; (B) genital somite, dorsal; (C) genital somite, ventral; (D) anal operculum, dorsal; (E) caudal rami, ventral; (F) antennule.

Figure 51. Eucyclops defaye sp. nov. Adult female. (A) Antennule segment 9; (B) antenna, caudal; (C) antennal basis, caudal; (D) antennal basis and Enp1, frontal; (E) maxilla and maxilliped; (F) P1, caudal.

Figure 52. Eucyclops defaye sp. nov. Adult female. (A) Intercoxal sclerite P1, caudal; (B) P3, caudal; (C) intercoxal sclerite P3, caudal; (D) P4, caudal; (E) coxa P4, caudal; (F) intercoxal sclerite P4, caudal.

Figure 53. Eucyclops defaye sp. nov. 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 54. Eucyclops defaye sp. nov. Adult male. (A) Antenna, frontal; (B) antennal basis, frontal; (C) P1, frontal; (D) intercoxal sclerite P1, frontal; (E) intercoxal sclerite P3, caudal; (F) P4, frontal.