Phreatipontia, Sak & Karaytuğ & Huys, 2024

Sak, Serdar, Karaytuğ, Süphan & Huys, Rony, 2024, Review of Neoleptastacus Nicholls, 1945 (Harpacticoida, Arenopontiidae), including an updated key to species and proposal of Phreatipontia gen. nov., Zootaxa 5525 (1), pp. 1-66 : 47-48

Genus Phreatipontia gen. nov.

https://zoobank.org/ 90EF26CD-AACB-474A-BA67-1D246C2F5E75

Diagnosis. Arenopontiidae . Urosomites without conspicuous surface ornamentation. Anal somite without paired dorsolateral spinous processes. Anal operculum not modified. Hyaline frills of abdominal somites with rectangular digitate lappets. Caudal ramus without dorsolateral spur or raised spinular row near medial margin; seta IV with long setule on outer margin. P1 exopod three-segmented; exp-1 with outer spine; exp-3 with two spines and two geniculate setae. P1 endopod not prehensile, slightly longer than exopod; enp-2 with two geniculate setae. P2–P4 endopods two-segmented. P2–P3 endopods with one apical seta. P4 endopod with well developed outer distal element. Armature formula as follows:

	Exopod	Endopod
P2	0.0.021	0.110
P3	0.0.021	0.010
P4	0.0.121	0.020

P3 endopod ♂ not sexually dimorphic, two-segmented. P5 with outer basal seta and four discrete elements; innermost element fused to segment forming spinous process; length of process sometimes sexually dimorphic. P 6 ♂ with two setae/spines.

Type species. Arenopontia (Neoleptastacus) speluncae Cottarelli, Bruno & Venanzetti, 1994 [by original designation].

Other species. Arenopontia (Neoleptastacus) phreatica Cottarelli, Bruno & Venanzetti, 1994 = Phreatipontia phreatica ( Cottarelli, Bruno & Venanzetti, 1994) comb. nov.

Etymology. The genus name is derived from the Greek φρέαρ (phréar), meaning well, spring, and πόντος (pόntos), meaning sea, and refers to the low salinity habitat preference of its members. Gender: feminine.

Remarks. The two members included in this genus, P. phreatica comb. nov. and P. speluncae comb. nov., differ from all Neoleptastacus species in the presence of two geniculate setae on the distal segment of the P1 endopod (instead of an outer spine and an inner geniculate seta). This character state is shared with two other genera in the Arenopontiidae , Psammoleptastacus and Onychopontia , both of which display sexual dimorphism on the P3 endopod which is not expressed in Phreatipontia gen. nov. Psammoleptastacus additionally differs from the new genus in (1) the presence of a dorsolateral spur on the inner margin of the caudal ramus, (2) P1 endopod being distinctly shorter than the exopod, (3) the presence of two distal elements on P2–P3 enp-2, and (4) the absence of an inner spinous process on the P 5 in both sexes. Onychopontia can be differentiated from Phreatipontia gen. nov. by (1) the characteristic deeply incised hyaline frills on the abdominal somites, (2) the absence of the inner serrate seta on P2 enp-2, (3) the very short P2–P3 enp-2, and (4) the absence of an inner spinous process on the female P5. Both species of Phreatipontia gen. nov. display a reduced armature on P2–P3 endopods with only one apical seta on the distal segment. This condition is shared with members of the trisetosus -group of Neoleptastacus , however in this lineage the endopods are only 1-segmented ( Table 2 ). Finally, both P. phreatica comb. nov. and P. speluncae comb. nov. exhibit a characteristic caudal ramus seta IV which has a long setule on the outer margin (indicated by arrows in Figs 12C ; 16C ) which can be considered an autapomorphy for the genus. Current records suggest that, unlike most arenopontiids, both species favour low salinity environments, including phreatic and water table habitats ( Cottarelli et al. 1994, 1996; Bruno et al. 1998; this study).

Within the family, only Arenopontia cf. subterranea was previously recorded from habitats with a strong freshwater influence in various localities in Abruzzi, Lazio and Tuscany in Italy ( Cottarelli 1969; Cottarelli et al. 1994; Cottarelli & Venanzetti 1989), representing a second but independent incursion into low salinity environments.

Figures

FIGURE 12. Phreatipontia phreatica (Cottarelli, Bruno & Venanzetti, 1994) comb. nov. (♀): (A) habitus, lateral; (B) habitus, dorsal; (C) anal somite and caudal rami, dorsal [arrow indicating modified seta IV]: (D) anal somite and right caudal ramus, lateral.

FIGURE 16. Phreatipontia speluncae (Cottarelli, Bruno & Venanzetti, 1994) comb. nov. (♀): (A) habitus, dorsal; (B) habitus, lateral; (C) anal somite and caudal rami, dorsal [arrow indicating modified seta IV]; (D) anal somite and right caudal ramus, lateral.