Caecidotea zacapuensis García-Vázquez & Pedraza-Lara & Rodríguez-Almaraz 2021, sp. nov

Caecidotea zacapuensis sp. nov. (Figs 22–25) Material examined: Holotype, male (CNCR 35522), length 7.5 mm, Laguna de Zacapu, 19°49’37.00”N, 101°47’23.00”W, elev. 1993 m, Municipality Zacapu, Michoacan, Mexico, 20 March 2018, coll. L. García-Vázquez and C. Pedraza-Lara. Paratypes, male (CNCR 35523), length 7.6 mm; same data of collection and collectors as holotype; dissected parts left pereiopod I, left pereiopod IV, pleopod II; dissected structures for right pleopod drawings I, III, IV and V in the specimen tube. 20 Males and 15 females (CNCR 35524). Diagnosis. Male body length 3.4 width. Head trapezoidal, width 2.4 length, anterior margin concave; eyes length 3.8 width. Pleopod III with 36 plumose marginal setae. Exopod pleopod IV with proximal incomplete transverse suture. Uropods length 0.7 pleotelson length. Description. Male (CNCR 35522) 7.5 mm (Fig. 22A); head trapezoidal, width 2.4 length, anterior margin concave; eyes present, oval, dark pigmented, length 3.8 width. Postmandibular lobes not produced. Subrectangular pereionites lateral margins with simple setae, pereionites 1–5 straight, pereionites 6–7 rounded. Pereionite 1 length 1.2 pereionite 2 length; pereionite 1 1.1 pereionite 3 length; pereionites 6–7 with lateral margins rounded, widening posterior. Antennula flagellum with 10 articles, longer than distal antenna podomere middle; last four segments with aestetascs in formula 1–0–1–1. Antenna flagellum with 65 articles; proximal article width 1.2 length; following articles decreasing in length. Pereiopod I (Figs 22B, 23A – B) dactylus outer edge with 10 simple setae; dactylus longer than palm; palmar margin with row simple setae; proximal process with 3 robust spines; mesial process acute, as wide as dactylus; distal process small acute triangular. Pereiopods II–III (Fig. 22C–D) similar length. Pereiopod IV (Figs 22E, 23C) propodus with spine in dactylus, dactylus length 0.6 propodus length, dactylus with 4 slender spines on lower margin. Pereiopod V (Fig. 22F) basis length 1.2 propodus length. Pereiopod VI (Fig. 22G) similar length to pereiopod VII, basis length 1.3 propodus length. Pereiopod VII (Fig. 22H) length 0.6 body length. Pleopod I (Fig. 24A) length 2.2 pleopod III length; basal segment oval, proximal margin straight, length 1.4 width, inner margin with 6 retinacula, distal segment oval, external margin medially straight, length 1.9 width, margins with 20 simple setae. Pleopod II (Fig. 25A–F), protopod subrectangular, proximal edge rounded, internal margin with 2 simple spines; exopod oval with small cuticular scales on inner and outer margin, exopod margin with 22 plumose setae; endopod slender, curved mesial surface, length 3.2 width, length 0.9 exopod length, length 0.7 protopod length, internal and external processes prominent; endopod apex with 3 processes: cannula short subcylindrical surpassing caudal process, like a semi-rolled sheet; mesial process evident; caudal process robust, subconical, with rounded apex, armed on subapical dorsal surface with 2–17 cuticular scales. Pleopod III (Fig. 24B), exopod oval, length 1.5 width, width 1.6 endopod length, transverse suture in proximal half, 36 plumose setae in distal and proximal margins; endopod subrectangular, length 0.9 exopod length. Pleopod IV (Fig. 24C), exopod length 1.6 width, external proximal margin with incomplete transverse suture, close to pleopod joint; endopod length 0.8 exopod length. Pleopod V (Fig. 24D), exopod oval, length 1.8 width, transverse suture not evident; endopod length 0.9 exopod length, width 0.8 exopod width. Pleotelson (Fig. 24E), subsquare, length 1.0 width, lateral margins parallel, with simple marginal setae, caudomedial lobe produced subacute. Uropods (Fig. 24E), length 0.7 pleotelson length, armed with robust marginal setae, apical endopod setae, exopod length 1.2 endopod length; protopod length 1.1 exopod length. Habitat. This species was located on the shore of the Zacapu lake, between the roots of the aquatic vegetation, in the water lily Eichornia crassipes. Distribution. Known only from the type locality. Etymology. This species is named after the municipality Zacapu, where it inhabits. Remarks. The pleopod IV of Caecidotea zacapuensis sp. nov. is similar to the one of Caecidotea buzwilsoni sp. nov. from Yuriria Lagoon. Both can be differentiated using the transverse suture in pleopod IV: incomplete in Caecidotea zacapuensis sp. nov., and complete in Caecidotea buzwilsoni sp. nov.