Spinilimnesiinae, Smit & Batista-Ribeiro, 2025

Smit, Harry & Batista-Ribeiro, Dante, 2025, A new subfamily of the water mite family Limnesiidae, with the description of Spinilimnesia insolitipes n. gen. n. sp. from Brazil (Acari: Hydrachnidia), Ecologica Montenegrina 81, pp. 22-26 : 23

Family Limnesiidae Thor

Spinilimnesiinae n. subfam.

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Diagnosis. Male (female unknown): Integument soft. Dorsum with a pair of platelets bearing the postocularia and a larger posterodorsal platelet, lateral eyes small, lying below the integument. Coxae in four groups, Cxgl-4 absent. Posterior to the genital field a large plate with the excretory pore and Vgl- 2 and Vgl-4. Genital field with a small pregenital sclerite and paired genital flaps bearing five pairs of acetabula. Palp five-segmented, P-2 without a ventral projection, distoventrally a seta normal in shape., P-4 nearly equal in H from base to tip, with a blunt projection bearing a long seta in distal half and a further longer seta near P-5 insertion. Legs without swimming setae. IV-leg-1 strongly thickened, with rounded dorsal margin, IV-leg-5 with four extremely enlarged, stout ventral setae at regular distance, IV-leg-6 without claws inserted subdistally, short and narrow, with a short subterminal seta.

Type genus: Spinilimnesia n. gen.

Remarks. Based on the acetabula lying on the genital flaps, and IV-leg-6 without a claw, we assigned the new subfamily to Limnesiidae , a family embracing a wide variety of taxa with diverging adaptations, and thus difficult to define. The presence of movable genital flaps in males is rarely found in this family, as general feature in members of the subfamilies Epallagopodinae, Tyrrelliinae and Rheolimnesiinae ( Smit 2020), but as an exceptional case also in a subspecies of Limnesia (Limnesiinae, Gerecke 1991) . Absence of Cxgl-4 is reported for the Rheolimnesiinae which differ from the new taxon described here in the male sex in acetabula located not on, but between the genital flaps. In Tyrrelliinae, Cxgl-4 are present and the acetabula are lying on the genital flaps in both sexes (see Goldschmidt 2004). In Epallagopodinae the acetabula are also on movable flaps in the male, but differ in the presence of Cxgl- 4 and a very long P5. Males of all species of these three subfamilies do not have the unusual fourth leg as described below.