Echiniscus quadrispinosus Richters, 1902

Gąsiorek, Piotr & Vončina, Katarzyna, 2023, Atlas of the Echiniscidae (Heterotardigrada) of the World-part I: West Palaearctic Echiniscus species, Zootaxa 5344 (1), pp. 1-72 : 40-42

15. Echiniscus quadrispinosus Richters, 1902

Figures 22–25 , Supplementary Materials 5–8

Synonyms

E. creplini C.A.S. Schultze, 1861 : Cuénot (1932)

Echiniscus quadrispinosus brachyspinosus Bartoš, 1934 : Kaczmarek et al. (2022)

Echiniscus quadrispinosus cribrosus Murray, 1907 : Kaczmarek et al. (2022)

Echiniscus quadrispinosus fissispinosus Murray, 1907 : Kaczmarek et al. (2022)

E. scrofa Richters, 1902 : Ramazzotti & Maucci (1983)

Terra typica : Germany, Taunus Mountains.

New type locality: 50°11’49’’N, 8°27’15’’E, 485 m asl: Germany, Hesse, Taunus Mountains, vicinity of Königstein im Taunus .

Additional localities: See Table 1 for all sequenced populations. Comparative material embraced numerous populations of E. quadrispinosus from France, Germany, Italy, Russia, Scotland, and Spain, which has already been recorded from all these countries ( McInnes 1994).

Etymology: From Latin quattuor = four + spinosus = spiny, underlining the presence of dorsal spines Cd and Dd. An adjective in nominative singular.

Shortened description. Medium-sized (ca. 190–310 μm). Body appendage configuration A-B-C-Cd- D-Dd- E, usually stable and with rare asymmetries. Dorsal appendages always spiniform, whereas lateral ones developed as long filamentous cirri ( Figs 22–23A ). Dorsal plate sculpturing includes (1) dominant large pores ( Figs 24A, C ) overlapping with (2) densely arranged endocuticular pillars ( Fig. 24B ). Caudal plate often with unsculptured epicuticular ridges forming a cross. Subcephalic ( Fig. 24D ) and genital ( Fig. 25D ) plates present. Dentate collar IV with numerous, long irregular teeth. Claws of a moderate size with respect to the body length, with small primary spurs closely positioned to claw bases ( Figs 25A–C ). Juveniles with somewhat fainter dorsal sculpturing and body appendage formula A-C-Cd- D-Dd- E; clearly smaller than sexually mature individuals ( Fig. 23B ). Larvae much smaller than juveniles, with a pronounced layer of endocuticular pillars and large pores arranged mainly at the posterior margins of plates; body appendage formula A-Cd- Dd- E ( Fig. 23C ).

Phylogenetic position: Echiniscus quadrispinosus is a sister species of the clade E. granulatus + E. militaris (Figs 1–2). The genetic diversity between sequenced populations was low and evinced in a shallow phylogenetic structure.

Remarks: The biogeographic range of E. quadrispinosus is difficult to assess due to amassed misidentifications throughout the globe ( McInnes 1994). The well-documented and trustworthy records of E. quadrispinosus extend from Macaronesia and Spain in Western Palaearctic to the Caucasus in Central Palaearctic ( da Cunha & do Nascimento Ribeiro 1962; Biserov 1991; Guil 2002; present study). We do not exclude the possibility that this species inhabits Eastern Palaearctic and the Nearctic region, making it a Holarctic element, but the current data do not allow for claiming that with certainty. Reports from other zoogeographic regions are highly dubious as based mostly on chaetotaxy.

Figures

FIGURE 22. Echiniscus quadrispinosus from Germany (females): A—dorsal view (PCM), B—dorsal view (SEM), C— dorsolateral view (PCM), D—lateral view (SEM). Scale bars = 50 μm.

FIGURE 23. Echiniscus quadrispinosus from Germany (PCM): A—male in dorsolateral view, B—juvenile in dorsolateral view, C—larva in dorsal view. Scale bars = 50 μm.

FIGURE 24. Echiniscus quadrispinosus from Germany—cephalic region:A—scapular plate sculpturing in upper magnification (PCM), B—scapular plate sculpturing in lower magnification (PCM), C—scapular plate sculpturing (SEM), D—cephalic appendages and subcephalic plates (SEM). Scale bars = 20 μm.

FIGURE 25. Echiniscus quadrispinosus from Germany—morphological details: A—claws III (PCM), B —claws III (SEM), C—claws IV (SEM), D—genital plates and gonopore (SEM). Scale bars = 10 μm.