Eucyclops tziscao Mercado-Salas

Gutierrez-Aguirre, Martha Angelica, Mercado-Salas, Nancy Fabiola & Cervantes-Martinez, Adrian, 2013, Description of Eucyclops tziscao sp. n., E. angeli sp. n., and a new record of E. festivus Lindberg, 1955 (Cyclopoida, Cyclopidae, Eucyclopinae) in Chiapas, Mexico, ZooKeys 351, pp. 1-30 : 3-8

Eucyclops tziscao Mercado-Salas sp. n. Figs 2-4

Synonym.

Eucyclops bondi : Gutiérrez-Aguirre and Cervantes-Martínez (2013), Table 1.

Material examined.

Holotype: Adult ♀ specimen dissected, mounted in glycerin sealed with Entellan (ECO-CH-Z-08970). Allotype: Adult ♂, dissected, mounted in glycerin sealed with Entellan (ECO-CH-Z-08971). Paratypes: Eight adult ♀♀, one adult ♂ and two copepodites undissected ethanol-preserved (90%) (ECO-CH-Z-08972); three adult ♀♀, undissected, ethanol-preserved (90%) (CNCR-27840). The types were collected at 15.April.2000 by A. Cervantes-Martínez, M. A. Gutiérrez-Aguirre and M. Elías-Gutiérrez.

Comparative material.

To complement the morphological analysis, we also examined the type specimens of Eucyclops bondi deposited in the Staatliches Museum für Naturkunde Karlsruhe (SMNK) from Kiefer’s collection, and the type specimens of Eucyclops conrowae deposited in the National Museum of Natural History Smithsonian Institution, in Washington D. C. (USNM) (Table 1).

Type locality.

Laguna Tziscao, Chiapas, México (16°05'19"N, 91°40'10"W). At sampling the maximum depth was 74.5 m, the water temperature 22°C, and the dissolved oxygen 6.6 mg L-1. The system is considered as one of the deepest, oligotrophic lagoons in the southern Mexico, with karstic origin, located in Lagunas de Montebello National Park which belongs to the Usumacinta biogeographic province.

Etymology.

The species name is a noun in apposition that makes reference to the Lagoon where the species was collected from. Tziscao ( Tz’isk’a’aw) is a term composed by two words in the chuj local language (one of the Mayan languages), and it refers to the stone bridge made by hand by the first settlers of the community.

Description.

Female: Habitus as in Fig. 2A. 620 µm of total body length excluding caudal setae. Prosome expanded at first and second somite, representing 61% of total body length symmetrical in dorsal view. Five-segmented urosome relatively elongated, urosomal fringes strongly serrated (Fig. 2B); posterior margin of anal somite with one row of long spinules. Genital double-somite (Fig. 2C) symmetrical, carrying paired egg sacs. Lateral arms of seminal receptacle rounded on posterior margin. Genital double-somite 1.3 times as long as wide. Anal somite with hair-setae in anal opening, anal operculum serrated (Fig. 2D). Caudal ramus 4.0 times as long as width; inner margin naked, strong spines on the lateral margin (serra) extending 40% of ramus length (Fig. 2D). Dorsal seta (VII) short: 0.65 times the length of caudal ramus, and 1.1 times as long as outermost caudal seta (III). Ratio of innermost caudal seta (VI)/outermost caudal seta (III) is 1.2. Lateral caudal seta (II) inserted at 71% of caudal ramus. All the terminal caudal setae plumose.

Antennule (Figs 2E, F): 12-segmented, reaching from middle to distal margin of third prosomite; last three segments with finely denticulate hyaline membrane at distal margin. Armament per segment as follows (s= seta, ae= aesthetasc, sp= spine):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 rows of spines on first segment, first row with small spinules and second row with stronger and longer spinules. Spine on sixth segment reaching middle of seventh antennular segment.

Antenna (Figs 2G, H): Coxa (no seta), basis (2s + 1 seta representing Exp), plus 3-segmented Enp (first to third Enp with 1, 9 and 7 setae, respectively). Basis ornamented with: N1 (3-4 hair-setae), N2 (5 small spinules), N3, N4, N5, N15, and N17 on frontal surface (Fig. 2H); and N8, N9+10, N11, and N12 on caudal surface (Fig. 2G). First to third endopodites with dense rows of spinules along lateral margins; Enp1 with an additional row of 5 spinules along medial margin below seta (arrowed in Fig. 2H).

Labrum: Distal margin toothed.

Mandible (Fig. 2I): With seven teeth on gnathobase. Innermost margin with one spinulose seta. Row of 6 spinules in middle, below gnatobase. Palp with two long and one short seta, group of spinules near to palp (arrowed in Fig. 2I).

Maxillule (Fig. 2J): Precoxal arthrite with naked surface, with three strong chitinized distal claws and one spiniform seta on caudal side. Palp unarmed, Enp with three setae (two smooth setae subequal in size, and one plumose shorter seta), Exp with three setae and Bsp with one plumose seta.

Maxilla (Fig. 2K): Praecoxa and coxa partially fused. Praecoxa with endite bearing two setae and a transverse row of small spinules on frontal surface. Coxa naked, bearing one biserially plumose seta. Distal coxal endite well developed, with two apical setae, one strong and furnished with spinules and other one noticeably thicker and longer. Claw-like basal endite with one row of spinules on inner margin, one chitinized armed seta inserted in front of basal “claw” and one seta inserted at base of claw-like endite on caudal surface. Endopod with a single segment bearing five setae.

Maxilliped (Fig. 2L): Syncoxa with three setae. Basis with two sub equal setae, plus 8 long spinules on frontal surface. Two transverse rows of small spinules, each with 6-8 elements arranged in semi-circular pattern on caudal surface. Endopod two-segmented: Enp1 with one long seta and one transverse row of 5 spinules on frontal surface. Enp2 with three setae, the longest fused to Enp2 and biserially plumose on the proximal half, the distal half ornamented with small spinules in caudal surface (arrowed in Fig. 2L).

Legs 1-4: Endopods and exopods of all swimming legs three-segmented. Armature formula of swimming legs as in Table 2.

Leg 1 (Figs 3A, B): Intercoxal sclerite with one row of spinules arranged in a semi-circle on each side of frontal surface (Fig. 3A); caudal surface with two transversal rows of tiny spinules, distal margin with two rounded chitinized projections (Fig. 3B). Coxa with strong biserially plumose inner coxal seta. Coxa with one row of hair-setae on outer margin and one transverse row of hair-setae next medial margin (arrowed in Fig. 3A). Inner basal seta reaching middle of Enp3, 0.76 times as long as Enp.

Leg 2 (Fig. 3C, D): Intercoxal sclerite with two groups of small spinules arranged in semi-circle on each side of frontal surface (Fig. 3C), and one transverse row of spinules in middle on caudal surface (Fig. 3D). Distal margin of intercoxal sclerite with two rounded chitinized projections. Coxa with strong biserially plumose inner coxal seta. Coxa with one row of hair-setae along outer margin on frontal surface (arrowed in Fig. 3C) small spines next insertion of Enp.

Leg 3 (Fig. 3E, F): Intercoxal sclerite with two groups of small spinules on frontal surface (Fig. 3E) caudal surface of intercoxal sclerite with three rows of spinules: distal row bearing long hair-like spinules at each side (arrowed in Fig. 3F), middle and proximal rows with tiny spinules. Distal margin with two slightly rounded projections. Coxa bearing strong biserially plumose inner coxal seta, frontal surface with one row of tiny spinules along outer (lateral) margin, and one transverse row of spinules on caudal surface (arrowed in Fig. 3E). Modified setae on Enp3 and Exp3 (arrowed in Fig. 3E). Tiny spinules at insertion of all setae of Enp and all spines of Exp.

Leg 4 (Figs 3 G–I): Intercoxal sclerite with rows I, II, and III on caudal surface. Row I with strong spinules on each side and a small gap. Row II with small spinules divided into three sections with small gaps between them. Row III divided into three sections, the first section with 5 long spinules, the middle section with 6 small strong spinules, and the third section with 5 long spinules (Fig. 3G). Frontal surface of intercoxal sclerite with two groups of tiny spinules arranged in semi-circle on each side (Fig. 3H). Caudal surface of coxa with spinules groups A-C, and E-F-H-J. Inner coxal spine (seta) with heteronomous setulation: proximally with long hair-like setules, distally with spinule-like setules; outer edge of coxal spine with three spinule-like setules distally, naked proximally (arrowed in Fig. 3I). Enp3P4 3.0 times as long as wide; inner spine 1.4 times as long as outer spine and 1.1 times as long as segment; outer spine 0.70 times as long as segment. Lateral seta of Enp3P4 inserted at 66% of the total length of segment. Modified setae on Enp3 and Exp3 (arrowed in Fig. 3G). All setae of exopod with tiny spinules at insertion.

Leg 5 (Fig. 3J): One free segment subrectangular, 2.1 times longer than wide; bearing one inner spine and two setae; median seta about 1.3 times longer than outer seta and 1.8 times longer than inner spine. Inner spine 1.7 times as long as segment.

Male: Habitus as in Fig. 4A; 509 µm of total body length excluding caudal setae. Body more slender than in female. Prosome symmetrical in dorsal view, representing 65% of total body length. Urosome short, representing 35% of total body length. Anal operculum slightly rounded and smooth. Caudal ramus 3.5 times longer than width; medial margin naked, strong spinules at insertion of lateral caudal seta (II) and outermost terminal caudal seta (III). Dorsal seta (VII) short 0.35 times the length of caudal ramus, and 0.75 times as long as outermost caudal seta (III). Ratio of innermost caudal seta (VI)/outermost caudal seta (III) is 1.6. Lateral caudal seta (II) inserted at 70% of caudal ramus. All the terminal caudal setae plumose.

Antennule: 16-segmented (Figs 4C, D), armament per segment as follows (s= seta, ms= modified seta, ae= aesthetasc, sp= spine): 1(7s+2ms); 2(3s+1ms); 3(1s+2ms); 4(1s+1ms+1ae); 5(0); 6(2s); 7(1s); 8(1s); 9(0); 10(3s); 11(2s); 12(0); 13(0); 14(0); 15(3s); 16(8s).

Antenna (Fig. 4E, F): Coxa (no seta), basis (2s + 1 seta representing Exp) plus 3-segmented Enp (first to third Enp with 1, 8, and 7 setae respectively). Basis ornamented with: N1 (4 hair-setae), N2 (4 small spinules), N3, N4, N5, N15, and N17 on frontal surface (Fig. 4E); and N9+10, and N12 on caudal surface (Fig. 4F).

Legs 1-4: Endopods and exopods of all swimming legs three-segmented (Table 2); P1-P3 as described in females.

Leg 4 (Fig. 4G): Coxa, Bsp, and intercoxal sclerite as described in female, except for the distal row of spinules of intercoxal sclerite, which consists of 9 spinules longer and slender than in female (arrow of row I, in Fig. 4G). Enp3P4: 2.6 times as long as width; inner spine 1.2 times as long as outer spine, and 1.2 times as long as segment. No modified setae on fourth leg. Lateral seta of Enp3P4 inserted at 64.7% of segment length, lateral seta reaching the middle of outer spine.

Leg 5 (Fig. 4B): One free segment subrectangular, 1.5 times longer than wide;

bearing one inner spine and two setae: outer seta subequal to median seta and 1.3 times longer than inner spine. Inner spine 1.8 times as long as segment.

Leg 6 (Fig. 4B): Represented by small, low plate near lateral margin of genital somite with one strong and long inner spine and two unequal setae. Inner spine reaching the distal margin of fourth urosomite. Inner spine about 2.3 times longer than median seta and about 1.6 longer than outer seta.