Sperchon, Kramer, 1877

Kolesnikov, Vasiliy B. & Stolbov, Vitaly A., 2025, Review of the genus Sperchon Kramer, 1877 (Acari, Hydrachnidia: Sperchontidae) from Russia, Zootaxa 5666 (1), pp. 53-73 : 69-70

Key to species of the Sperchon from Russia

1 P-4 with two greatly enlarged ventral peg-like setae, close to each other ( Palpisperchon Lundblad, 1941 ).............. 26

– P-4 with two small ventral peg-like setae................................................................... 2

2 Integument rugose or papillate ( Sperchon s. str.)............................................................. 3

– Integument reticulated (at least in localized areas) ( Hispidosperchon Thor, 1901 ).................................. 28

3 Claws of leg with 3 teeth; P-4 shorter than P-3.............................................................. 4

– Claws of leg with 2 teeth; P-4 longer than P-3............................................................... 5

4 Integument with muscle attachment sclerites; P-2 with 2 setae; P-3 is stockier, maximum height near middle of segment; leg claws with three unequal clawlets, lamella ventral margin concave......................... Sperchon (Sperchon) pesici

– Integument without muscle attachment sclerites; P-2 with 3 setae; P-3 more slender, maximum height in proximal quarter; leg claws with three subequal clawlets, lamella ventral margin straight..................... Sperchon (Sperchon) tridentatus

5 Acetabula small, rounded, distance between Ac-1 and Ac-2 is more than 3 times longer than the length of each acetabulum. 6

– Acetabula larger, rounded or elongated, distance between Ac-1 and Ac-2 is no more than 3 times longer than the length of each acetabulum.......................................................................................... 9

6 P-3 with setae on ventral side............................................................................ 7

– P-3 without setae on ventral side......................................................................... 8

7 Integument with large tubercles into which cuticular folds flow; P-2 with short conical ventrodistal process; P-4 with ventral peg-like setae of different size - distal seta is noticeably smaller than proxima setal; P-5 with 3 filiform setae (except bifurcated seta); length of genital plates female 285, male—265................................. Sperchon (Sperchon) prosperus

– Integument with small tubercles and ribs, without folds; P-2 with long conical ventrodistal process; P-5 with 4 filiform setae (except bifurcated seta); length of genital plates female 250–270, male—195–230........ Sperchon (Sperchon) prosperoides

8 P-5 short, length is approximately equal to its width; rostrum longer................... Sperchon (Sperchon) minutiporus

– P-5 longer, twice as long as it is wide; rostrum shorter............................... Sperchon (Sperchon) laurenticus

9 Acetabula Ac-1 and Ac-2 slightly elongated, not more than two times longer than their width........................ 10

– Acetabula Ac-1 and Ac-2 noticeably elongated, their length is more than two times longer than their width............. 16

10 Base of ventrodistal process on P-2 without spine-like seta.................... Sperchon (Hispidosperchon) kurilensis *

– Base of ventrodistal process on P-2 with 1 spine-like seta.................................................... 11

11 P-4 with one ventral peg-like seta............................................. Sperchon (Sperchon) monodentatus

– P-4 with two ventral peg-like setae...................................................................... 12

12 Length of P-5 longer than distance from distal ventral peg-like seta on P-4 to distal margin of P-4; distance between bases of distal and ventral filiform setae exceeds length of ventral setae................................................ 13

– Length of P-5 shorter than or approximately equal to distance from distal ventral peg-like seta on P-4 to distal margin of P-4; distance between bases of distal and ventral filiform setae shorter than length of ventral setae........................ 15

13 Integument with numerous rounded papillae connected to each other by short skin folds; ventral filiform seta on P-5 short. 14

– Integument with linear wavy folds, without rounded papillae; ventral filiform seta on P-5 of medium length............................................................................................ Sperchon (Sperchon) similis

14 P-4 longer than P-2+3; ventrodistal process on P-2 with 2 setae, clearly bifurcated........... Sperchon (Sperchon) questor

– P-4 not longer than P-2+3; ventrodistal process on P-2 with 3 setae, not bifurcated... Sperchon (Sperchon) uralensis sp. nov.

15 Length of P-5 shorter than distance of distal ventral peg-like seta on P-4 to distal margin of P-4; acetabula large, distance between Ac-1 and Ac-2 is 1/2 times less than their length; ridges of integument on dorsum and posterior to genital field are arranged in irregular rows; excretory pore without sclerotized ring...................... Sperchon (Sperchon) fluviatilis

– Length of P-5 approximately equal to distance of distal ventral peg-like seta on P-4 to distal edge of P-4; acetabula smaller, distance between Ac-1 and Ac-2 is 1-2 times greater than their length; ridges of idosoma covers on dosrum and posterior to genital opening are arranged in transverse rows; ecxretory pore with sclerotized ring................................................................................................ Sperchon (Sperchon) zhavoronkovae sp. nov.

16 Base of ventrodistal extension on P-2 with 2 spine-like setae, tip of ventrodistal extension with 1 seta............................................................................... Sperchon (Sperchon) monticolus Wainstein, 1981

– Base of ventrodistal extyension on P-2 with 1 spine-like seta or without spine-like seta, tip of ventrodistal process with 2-3 seta............................................................................................... 17

17 Base of ventrodistal process on P-2 without spine-like seta................................................... 18

– Base of ventrodistal process on P-2 with 1 spine-like seta.................................................... 20

18 Ventrodistal extension on P-2 long; P-2 and P-3 not shortened or widened; ventral peg-like setae on P-4 not close to each other, directed ventrally............................................................ Sperchon (Sperchon) squamosus

– Ventrodistal extension on P-2 short; P-2 and P-3 are greatly shortened and widened; ventral peg-like setae on P-4 closer to each other, directed proximally.............................................................................. 19

19 Р-2 higher than long, its distoventral projection narrow, finger-shaped; Р-4 distoventral peg-like seta located medially, closer to proximoventral peg seta than to distal segment margin................................. Sperchon (Sperchon) turgidus

– Р-2 as long as high, its distoventral projection short, forming а broad-based triangle; Р-4 distoventral peg-like seta located ventrally, closer to distal segment margin than to proximoventral peg seta................. Sperchon (Sperchon) resupinus

20 Ventrodistal extension on P-2 short, ventral spine seta longer that its length...................................... 21

– Ventrodistal extension on P-2 long, ventral spine seta not longer that its length.................................... 22

21 P-5 twice as long as wide, medial seta is located almost at same level as bifurcated seta; ventral peg-like setae on P-4 pointed, proximal peg-like seta situated near middle of ventral row P-4......................... Sperchon (Sperchon) ussuriensis

– P-5 2.5 times longer than wide, medial seta distinctly posterior to bifurcated seta; ventral peg-like setae on P-4 with flat tip, proximal peg-like seta does not reach 1/2 middle of ventral row P-4..................... Sperchon (Sperchon) kuluensis

22 Cx-I medially fused, completely surrounding gnathosomal base; ventral peg-like setae on P-4 very small; P-4 longer than P-2+3....................................................................... Sperchon (Sperchon) brevirostris

– Cx-I medially separated bу а fine strip of membranous integument; ventral peg-like setae on P-4 of normal size; P-4 not longer than P-2+3......................................................................................... 23

23 Plate with postocular seta greater than ocular capsule............................... Sperchon (Sperchon) glandulosus

– Plate with postocular seta smaller than ocular capsule....................................................... 24

24 Anus surrounded bу а sclerotized ring................................................................... 25

– Anus without sclerotized ring................................................. Sperchon (Sperchon) thienemanni

25 Seta Dgl-1 longer than diameter its chitinous plate; P-1 without seta; 17-19 medial genital setae in female; dorsal and ventral setae on tibia IV are indistinguishable from each other….............................. Sperchon (Sperchon) orientalis

– Seta Dgl-1 shorter than diameter its chitinous plate; P-1 with seta; 12 medial genital setae in female; dorsal setae on tibia IV slightly thinner and longer than ventral setae......................................... Sperchon (Sperchon) termalis

26 Integument with small papillae; ventral extension on P-3 is weakly expressed; acetabula Ac-1 and Ac-2 are elongated, their length is greater than distance between the acetabula........................... Sperchon (Palpisperchon) crassipalpis

– Integument fine lined or with strips and ribs; ventral protrusion on P-3 is distinct; acetabula Ac-1 and Ac-2 are rounded, their length is clearly less than distance between the acetabula..................................................... 27

27 Integument fine-lined; Cx-II and Cx-III close together, the distance less than their width; ventral peg-like seta on P-4 not expanded or slightly expanded at tip, not rhomboid................................ Sperchon (Palpisperchon) distans

– Integument with strips and ribs; Cx-II and Cx-III not close together, distance is greater than their width; ventral peg-like seta on P-4 weakly expanded at tip, rhomboid....................................... Sperchon (Palpisperchon) scopetsi

28 Well developed sexual dimorphism: mаles раlр stout, with inflated Р-2 and Р-3 distal margins forming strongly developed sheaths flanking base of subsequent segments, female раlр slender, ventral margin of Р-3 covered bу fine denticulation.......................................................... Sperchon (Hispidosperchon) denticulatus species group**

– Poorly developed sexual dimorphism, in both sexes, palp neither inflated, nor with а denticulate ventral margin of Р-3.... 29

29 Сх-III with а glandularium near medial margin............................................................. 30

– Сх-III without a glandularium near medial margin.......................................................... 33

30 Distance between Ac-1 and Ac-2 is shorter than their length.................................................. 31

– Distance between Ac-1 and Ac-2 is longer or approximately equal to their length… Sperchon (Hispidosperchon) levanidovae

31 Excretory pore located closer to Vgl-1 than to Vgl-3; male with 2 large dorsal shields. Sperchon (Hispidosperchon) nevelskoii

– xcretory pore located closer to Vgl-3 than to Vgl-1; male with 1 large dorsal shield or with several isolated plates........ 32

32 Excretory pore surrounded bу а sclerotized ring; IV-leg with densely plumose dorsal setae (> 6); in both sexes, dorsum with several isolated platelets................................................ Sperchon (Hispidosperchon) hispidus ***

– Excretory pore without sclerotized ring; IV-leg with less plumose dorsal setae (<6); males with а dorsal shield, females with several isolated plates.................................................... Sperchon (Hyspidosperchon) clupeifer

33 Р-3 without ventral setae............................................... Sperchon (Hispidosperchon) compactilis

– Р-3 with ventral setae................................................................................. 34

34 Р-3 with up to 2 ventral setae; integument sculpture made up of а network of fine denticles combined with additional larger papillae.............................................................. Sperchon (Hispidosperchon) papillosus

– Р-3 with four, rarely three ventral setae; integument sculpture formed exclusively bу fine denticles............... Sperchon (Hispidosperchon) setiger

Notes

* Due to limited data from the description, characters in the key based on the available information. The species requires re-examination.

** Since it is impossible to reliably determine to which species of the denticulatus species group the specimens from Russia belong (specimens and their images are missing), we use in the key only the definition of this group.

*** The male of Sperchon clupeifer anulatus Wainstein, 1981 is unknown, so it is impossible to compare the dorsal plates. It is similar to S. hispidus in the presence of a sclerotized ring around the anus and dense dorsal setae on tibia IV, but in the less plumose dorsal setae on tibia IV it is more reminiscent of S. clupeifer . This subspecies has the narrowest P-4 (~8.0). It is possible that this is a separate species