Edaxiella rubra Fosshagen, Boxshall and Iliffe, 2001

Edaxiella rubra Fosshagen, Boxshall and Iliffe, 2001 View in CoL

( Figs. 2–3)

Material. One adult female (ECO-CHZ-11621) and one adult male (ECO-CHZ-11622), Mexico, Quintana Roo, Cozumel Island, Cenote Tres Potrillos (20°27´3.2˝N 86°59´14.4˝W);halocline at 11 m depth; mounted on separate semi-permanent slides with glycerol, sealed with Entellan ®; 16 Sep 2022, coll. LM. Mejía-Ortiz and CO. Cortés-Gandara GoogleMaps .

Description of female. Total body length, including caudal rami = 1.93mm.Body surface ornamented with minute scale-like spinules ( Fig.2K).A1 27-segmented, reaching 3rd pediger, with segments 10-11 partially fused, segment 24 with two setae ( Fig. 2A). Urosome 4-segmented, genital double-somite with well-developed gonopore, produced ventrally. Caudal rami with 5 setae. A2 with Exp almost twice as long as Enp ( Fig. 2C). Md gnathobase with 5 paired teeth, with 14 accessory spines and pinnate dorsal seta ( Fig. 2E), Md palp ( Fig. 2D) and other appendages as originally described for the species ( Fosshagen et al. 2001). P1 ( Fig. 2F) Enp lacking small, pointed outer process as originally described, with row of setules on terminal segment (arrow, Fig. 2F). P2 – 4 Bs with distal spinous process ( Figs. 2G–I), P4 with small, rounded lamella on Bs ( Fig. 2I). Segmentation and armature as shown in Tab. 1.

P5( Fig.2J, K). Enp and Exp segments ornamented with minute scale-like spinules. Bs with short, slender outer seta. Exp and Enp 2-segmented. Exp1 with outer spine, armed with patterns of scale-like spines as shown in the closer view of Figure 2K; Exp2 with 3 spines, apical spine and 5 inner setae. Enp1 with inner seta, Enp2 with 3,2,2 setal formula.

Description of male. Total body length, including caudal rami = 1.91 mm ( Fig. 3A). Body surface ornamented with tiny scale-like spinules. Prosome, left A1, P1 – 4 and all oral appendages as described for female. Urosome 5-segmented, caudal rami with 5 caudal setae. Right A1 23-segmented, segment 2 partially fused; geniculate at segments 19-20 ( Fig.3B).

P5 ( Fig. 3C). Cx subtrapezoid. Bs broader than long, with seta inserted middle-distally. Exp and Enp 3-segmented and covered with scale-like spinule integumental patches. Exp rami modified, asymmetrical, Enp2 and 3 with row of setules on inner margin.Right P5Exp3 with3 elements:inner proximal seta, long pointed terminal process ornamented with spinules, and short outer spiniform process. Left P5 with elongate Exp2, with concave inner margin furnished with setules, and outer distal spine; Exp3 short, armed with 3 elements: inner medial spine, terminal pointed process with row of spinules, and outer spine.

Distribution. This species was originally described from Airstrip Caves, Discovery Bay, Jamaica, and it is the second cave-dwelling calanoid copepod recorded from anchialine systems of the YP, after Stephos fernandoi Suárez-Morales, Gutiérrez-Aguirre, Cervantes-Martínez and Illife, 2017 ( Suárez-Morales et al. 2017b), and the third calanoid copepod found in Cozumel Island, where an epigean freshwater diaptomid Mastigodiaptomus ha Cervantes, 2020 was also reported ( Cervantes-Martínez et al. 2021).

Remarks. We identified this species as E. rubra by possession of the following structures that agree with its original description: both female and male individuals had a reddish color before fixation; rostrum with long filaments near distal tip of rostral base; the antenna has exopod segments compressed; mandible with raptorial gnathobase, mandibular palp with unarmed triangle-shaped basis, and small unsegmented endopod distally placed to basis, with two unequal setae; maxilla and maxilliped with long basis; armature of thoracic legs as originally described. Male fifth legs with 3rd exopods and left fifth leg 2nd exopod, partially modified. Female P5 unmodified, but with 2-segmented exopods and endopods in both rami, based on a single specimen.

In addition, we found some morphological differences of the YP E. rubra with respect to the original description, including: (1) the integument of all body parts is covered with minute scale-like spinules, a character not reported before; (2) rostrum with relatively shorter filaments with a patch of setulae like elements ( Fig. 2B), instead of the large pores described for the Jamaican specimens ( Fosshagen et al., 2001: Figs. 1C, 14A); and (3) female fifth leg with 2-segmentedramus.Weidentifiedsomeornamentation details that were not recorded previously, like: (1) the accessory spines on the proximal area of the mandibular gnathobase; and (2) male left fifth leg Exp2 with inner setules.