Eucyclops prionophorus Kiefer, 1931b

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 : 43-49

Eucyclops prionophorus Kiefer, 1931b

( Figures 9 – 13 )

Description

Female. Habitus as in Figure 11A . Average length excluding caudal setae = 688 µm. Prosome representing 58% of total body length, symmetrical in dorsal view. Prosomal fringes finely serrate in dorsal view. Urosomal fringes strongly serrate. Genital double somite symmetrical ( Figures 9A , 11B ), representing 11.3% of total body length; proximal third of genital somite expanded laterally. Seminal receptacle with rounded lateral arms, posterior margin with sinuous sac ( Figure 9A ). Anal operculum slightly rounded, smooth ( Figure 9B ). Length/width of caudal rami = 3.9; inner margin of caudal ramus naked; outer margin with strong spinules covering 55% 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) = 1.1. Lateral caudal seta (II) inserted at 74% of caudal ramus.

Antennule ( Figures 9C , 11E–F ). Tip reaching posterior margin of fourth 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(8s). Two transversal rows of spinules on first segment, first with strong spinules of different sizes

and second row with minute spinules. Spine on sixth segment not reaching medial margin of seventh segment.

Antenna ( Figures 9D–E , 12A–B ). Coxa (unarmed), basis (2s+Exp), plus three-segmented Enp (1s, 9s, 7s, respectively). Basis with rows of spinules on frontal surface: N1(IV), N2(4), N3(5), N4(12), N5(6), N15(4), N17(5), N18(5) and on caudal surface: N7(13), N8(5),

N9 + 10(6), N11(7), N12(6), N14(4), N16(7), N22(11). Frontal surface of Enp1 with B1(9) and caudal surface with B2(8).

Leg 1 ( Figures 10A , 12D–E ). Frontal surface of intercoxal sclerite with row of hair-like elements arranged in a semicircular pattern on each side, caudal surface with row I bearing 10 minute spinules and row II with 24 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 = 1.6, apical spine of Enp3 as long as Enp3 (1.0).

Leg 2 ( Figure 10B–C ). Frontal surface of intercoxal sclerite with row I bearing hair-like spinules arranged in a circular pattern; caudal surface with rows I and II close to each other, forming a group in a position where group II is usually found, with minute 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 = 2.4, apical spine of Enp3 1.2 times as long as Enp3. No modified setae present.

Leg 3 ( Figures 10D–F , 12F , 13A–B ). Frontal surface of intercoxal sclerite ornamented with hair-like spinules arranged in circular pattern on each side; caudal surface with row I bearing long hair-like elements (small gap in the middle), row II continuous, bearing 25 strong spinules, those near outer margins longer than medial ones. Row III continuous, with 15 strong spinules, spinules on outer margins longer than medial ones. Distal margin with two rounded, chitinised projections. Coxa with strong, biserially setulated inner coxal seta ornamented with long hairs proximally and with strong spinules distally along both margins. Caudal coxal surface with spinule formula = A-B-C. Length/width ratio of Enp = 2.4, apical spine of Enp3 as long as Enp3. Modified setae present in both Exp and Enp.

Leg 4 ( Figures 10G–H , 13C–E ). Distal margin of intercoxal sclerite with two low, rounded, chitinised projections. Frontal surface of sclerite with row I bearing small spinules arranged in circular pattern, caudal surface of intercoxal sclerite with row I bearing long, strong spinules, row II with long slender spinules near outer margins and row III with long, slender spinules. 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 and distal section with strong spinules. Outer margin with one distal spinule and proximal section with hairs, gap in middle margin. Spinule formula on the caudal surface of coxa: A-B-C + D-E-F-H-J. Length/width ratio Enp3 = 2.6, length ratio inner spine of Enp3/ Enp3 = 1.1; length ratio outer spine of Enp3/length Enp3 = 0.8; length ratio inner/outer spines Enp3 = 1.4. Lateral seta of Enp3 inserted at 66% of segment. Modified setae in Enp and Exp.

Leg 5 ( Figures 9A , 13F ). Free segment subrectangular, 1.5 times longer than wide, bearing one strong inner spine and two setae; medial seta 1.4 times longer than outer seta and 1.6 times longer than inner spine. Inner spine 1.9 times longer than segment.

Male. Not found.

Remarks. In Kiefer ’ s (1931a) original description, the ornamentation of the outer margin of the caudal rami, with spinules increasing in size distally, and the remarkably strong spine of the fifth leg were advanced as the main characteristics to distinguish this species. Both characters were found in the Mexican specimens identified as E. prionophorus . This species was studied by Einsle (1992) based on type material and additional records deposited in Kiefer ’ s collection and recently also by Mercado-Salas and Suárez- Morales (2014b). This species differs from its congeners by the possession of a dorsal caudal seta shorther than both the innermost and outermost caudal setae, a P1 basipodal seta reaching the middle margin of Enp3, and the modified setae of Exp of P3 and P4, which are heavily chitinised and distally blunt. This species differs from E. bondi and E. conrowae by its possession of a relatively smaller caudal dorsal seta and in the ornamentation of the fourth coxal plate, in which row I is represented by long and strong spinules, whereas it is formed by small and stronger spinules in the other two species. There are additional differences in rows I and II; in the former two species these rows are always continuous, with short and strong spinules, but in in E. prionophorus both rows are present only adjacent to the outer margins and are represented by long hair-like spinules. As stated by Alekseev and Defaye (2011), E. prionophorus belongs to the serrulatus -group, a notion that we are able to support with the additional data on the ornamentation of the antennal basis. In addition, we observed that in some of the Mexican specimens the seminal receptacle differs from that observed in specimens from Kiefer ’ s collection but also from those depicted by Einsle (1992) and Mercado-Salas and Suárez-Morales (2014a). These specimens have a typical seminal receptacle of the serrulatus -group, but in some Mexican specimens the posterior margin has a sinuous sac. Another difference between the Mexican E. prionophorus and the type material was the length/width proportion of Enp3 of all swimming legs, which is slightly longer in the Mexican material. Eucyclops prionophorus can be easily distinguished from E. serrulatus by the possession of small spinules on row N2 on the frontal surface of the antennal basis and also by the presence of rows N18 (frontal surface), N10, N16 and N22 (caudal surface), absent in E. serrulatus . It differs from E. pectinifer by the absence of N6 and the presence of N22 (absent in E. pectinifer ); both species share the absence of N13 and the presence of row N1. Spinules of row N12 have the same size in E. prionophorus while some spinules are clearly longer than the others in E. pectinifer . The ornamentation patterns of the caudal surface of the intercoxal sclerites of E. prionophorus differ from those of both E. pectinifer and E. serrulatus . In P1, rows I and II of E. prionophorus bear minute spinules whereas row I is absent and row II bears long hair-spinules in the other two species. In P2 of E. prionophorus rows I and II has minute spinules and both are closer to each other than in other related species. In E. serrulatus and E. pectinifer row I is absent and row II is, as in P1, formed by long spinules. The caudal surface of the intercoxal sclerite of P3 has some additional differences among these three species. In E. pectinifer row I bears long hairs and a gap at the middle margin, row II and III are continuous and armed with long hair-spinules; in E. serrulatus row I bears long hair spinules and a gap in the middle margin as well, row II is continuous, with small spinules, row III bears long, strong spinules only in the outer margins (gap in middle section); and in E. prionophorus row I bears long hairs with a small gap at middle margin, row II is continuous and bears strong spinules, those adjacent to the outer margins are longer than those in the middle, and row III is continuous, with strong spinules, while the spinules on the outer margins are longer. The fourth leg sclerite ornamentation differs among these species: in E. pectinifer and E. serrulatus row I bears remarkably long spinules while in E. prionophorus these spinules are long but shorter than in the other species, rows II and III fit well in the variation pattern described by Alekseev et al. (2006) and Alekseev and Defaye (2011) for E. serrulatus and E. pectinifer . In E. prionophorus row F is present in the coxal surface, like in E. pectinifer , but this row is absent in E. serrulatus .

Figures

Figure 9. Eucyclops prionophorus Kiefer, 1931a. Adult female. (A) Urosome, ventral; (B) anal operculum, dorsal; (C) antennule; (D) Enp1–3 antenna; (E) antennal basis, frontal; (F) maxilla; (G) maxilliped.

Figure 10. Eucyclops prionophorus Kiefer, 1931a. Adult female. (A) P1, frontal; (B) P2, frontal; (C) intercoxal sclerite P2, caudal; (D) P3, frontal; (E) exopod P3; (F) intercoxal sclerite P3, caudal; (G) P4, frontal; (H) coxa and intercoxal sclerite P4, caudal.

Figure 11. Eucyclops prionophorus Kiefer, 1931a. Adult female. (A) Habitus, dorsal; (B) genital somite, ventral; (C) anal operculum, dorsal; (D) caudal rami, dorsal; (E) antennule; (F) antennule segment 9.

Figure 12. Eucyclops prionophorus Kiefer, 1931a. Adult female. (A) Antenna, caudal; (B) antennal basis, caudal; (C) mandible; (D) P1, caudal; (E) intercoxal sclerite P1, caudal; (F) P3, caudal.

Figure 13. Eucyclops prionophorus Kiefer, 1931a. Adult female. (A) Coxa, basis and intercoxal sclerite P3, caudal; (B) intercoxal sclerite P3, caudal; (C) P4; (D) coxa, basis and intercoxal sclerite P4, frontal; (E) coxa P4, frontal; (F) P5.