Mexicophria, Boxshall, Geoff A., Zylinski, Sarah, Jaume, Damià, Iliffe, Thomas M. & Suárez-Morales, Eduardo, 2014

Boxshall, Geoff A., Zylinski, Sarah, Jaume, Damià, Iliffe, Thomas M. & Suárez-Morales, Eduardo, 2014, A new genus of speleophriid copepod (Copepoda: Misophrioida) from a cenote in the Yucatan, Mexico with a phylogenetic analysis at the species level, Zootaxa 3821 (3), pp. 321-336 : 324-325

Mexicophria gen. nov.

Diagnosis. Cephalosome not produced posteriorly into carapace-like extension. First pedigerous somite free. Female urosome 5-segmented, with genital and first abdominal somites fused to form genital double-somite; single copulatory pore opening mid-ventrally. Free abdominal somites separated by extensive arthrodial membrane allowing telescoping of adjacent somites. Caudal rami armed with 6 setae. Antennules 27-segmented in female, with compound apical segment derived from ancestral segments XXVII–XXVIII. Proximal segment swollen dorsolaterally, forming bulbous lobe: segments II–X and XI–XII not completely separated along posterior margin; elongate aesthetascs on segments XI and XVI. Antennule 23-segmented in male; geniculate between segments 19 (XIX–XX) and 20 (XXI–XXIII); segment 21 (XXIV) free, segment 22 (XXV–XXVI) and apical segment (XXVII–XXVIII) double. Antenna with 1 seta on basis; exopod 7-segmented bearing 1, 1, 1, 1, 1, 1, 4 setae; endopod indistinctly 3-segmented bearing 2, 5, 7 setae. Mandible with 2 setae on basis, endopod with 4, 7 setae; exopod with 1, 1, 1, 3 setae. Maxillulary basal exite absent. Allobasis of maxilla with armature formula 4, 2. Maxilliped syncoxa lacking praecoxal seta; endopod 6-segmented, setal formula 2, 2, 2, 2, 2+1, 4. Swimming legs 1–4 biramous with 3-segmented rami except for 2-segmented endopod of leg 1; spine and seta formula as below for type species. Fifth legs uniramous in both sexes, located immediately adjacent to ventral midline, lacking intercoxal sclerite; segmentation sexually dimorphic, 2-segmented, with unsegmented protopodal segment and single exopodal segment in female, 3-segmented, with separate coxa and basis plus single exopodal segment in male.

Type species. Mexicophria cenoticola gen. et sp. nov., by original designation.

Etymology. The generic name is based on the name of the country where it is found, Mexico, combined with the ending – ophria, which is commonly used within the family.

Remarks. The fifth legs of the new genus are located immediately adjacent to the ventral midline of the somite and lack an intercoxal sclerite, as in several other speleophriid genera, but they are more strongly reduced than in most other genera. Speleophriopsis , Speleophria , Boxshallia , Archimisophria , Huysia and Protospeleophria all have a fifth leg in the female consisting of at least three segments. The enigmatic genus Dimisophria has a 2- segmented fifth leg ( Boxshall & Iliffe 1987), but this genus can be distinguished from Mexicophria n. gen. by the lack of a bulbous lobe on the proximal segment of the antennule, and by mouthpart characters, such as the reduced setation on the mandibular endopod and the maxillulary exopod. Expansophria species vary in the form of the female fifth leg. In female E. dimorpha Boxshall & Iliffe, 1987 the fifth leg is 3-segmented, comprising an unarmed coxa, the basis with a single outer seta and a 1-segmented exopod with 2 apical setae but in E. apoda Boxshall & Iliffe, 1987 , the female fifth leg is lacking. Within the family, this 3-segmented state is the most similar to that found in the new genus. However, the male fifth legs differ markedly between the new genus and Expansophria : in the former they are 3-segmented with 1-segmented exopod whereas known males of the latter genus have a 5-segmented fifth leg with a 3-segmented exopod ( Boxshall & Iliffe 1987, Jaume & Boxshall 1996b).

The new genus exhibits reduced leg setation. The second endopodal segment of legs 2 to 4 bears only 1 inner seta and this is a unique character state for the family. The third exopodal segment of legs 1 to 4 carries 3, 4, 4, 3 inner margin setae, respectively, as in Boxshallia , Huysia , and Protospeleophria ( Huys 1988, Jaume et al. 1998) and 3, 4, 4, 3 outer and distal spines. These other genera do not share the latter formula: in Boxshallia and Protospeleophria it is 4, 4, 4, 4, while in Huysia it is 3, 4, 4, 4. The presence of flagellated tips on the outer spines of exopodal segments 2 and 3 of leg 1 is a fine scale similarity shared only with Boxshallia out of these three genera. Boxshallia and the new genus also share the possession of the conspicuous bulbous lobe on the proximal segment of the antennule.

The new genus can be distinguished from Boxshallia by its derived 2-segmented endopod of leg 1 since this ramus retains a 3-segmented state in Boxshallia . Another major difference between these two genera is the fifth leg. In Boxshallia the intercoxal sclerite is retained, the coxa and basis are separate in both sexes and the exopod is 2-segmented, plus the endopod is represented by an inner seta on the basis, so the leg is biramous ( Huys 1988). In contrast, in the new genus the leg is uniramous, the exopod is 1-segmented in both sexes and the intercoxal sclerite is lacking.