Testechiniscus Kristensen, 1987

Gąsiorek, Piotr, Stec, Daniel, Zawierucha, Krzysztof, Kristensen, Reinhardt Møbjerg & Michalczyk, Łukasz, 2018, Revision of Testechiniscus Kristensen, 1987 (Heterotardigrada: Echiniscidae) refutes the polar-temperate distribution of the genus, Zootaxa 4472 (2), pp. 261-297 : 265-266

Genus: Testechiniscus Kristensen, 1987

Amended genus diagnosis: Medium-sized echiniscids with black, crystalline eyes. Rigid buccal tube with large cuticular stylet supports. Appendaged, i.e. having both cephalic and trunk cirri. Two pairs of segmental plates, unpaired scapular and caudal plates. Three median plates. Cuticular sculpture composed of large true round or polygonal pores that gradually become reticulum. Incisions (notches) on caudal (terminal) plate. Eight rows of ventral plates. No pseudosegmental plates.

Differential diagnosis. Phenotypic. Testechiniscus differs from Bryodelphax , Bryochoerus Marcus, 1936 and Echiniscus in having black eyes. Moreover, Testechiniscus can be separated from Bryodelphax and Bryochoerus by the presence of incisions on the caudal plate and cirri in positions other than A, and from Echiniscus by the presence of ventral armature covering the entire venter. Furthermore, Diploechiniscus has only two rows of ventral plates (subcephalic and genital) and double cuticular sculpture absent in Testechiniscus . Finally, Hypechiniscus Thulin, 1928 lacks trunk cirri (sometimes only an autapomorphic mediodorsal cirrus is present) and ventral plates; dorsal armature is very weakly sclerotised compared to large and strongly sclerotised plates in Testechiniscus .

Genotypic. Based on the currently available sequences, the 18S rRNA p-distances within the genus Testechiniscus vary from 0.2% to 0.8%, and between Testechiniscus spp. and other currently recognised echiniscid genera they vary from 4.6% ( E. granulatus ( Doyère, 1840) , MG016454 ) to 15.7% ( Bryodelphax parvulus Thulin, 1928 , HM193371 , and B. maculatus Gąsiorek et al., 2017 , KY609137 ). The corresponding comparisons for the 28S rRNA fragment yield higher minimal but lower maximal p-values between genera; respectively from 6.3% ( E. trisetosus Cuénot, 1932 and E. canadensis Murray, 1910 , FJ435781 and FJ435784 , FJ435786 ) to 13.9% ( Pseudechiniscus facettalis Petersen, 1951 , FJ435788 ). Full p-distance matrices are provided in the Supplementary Materials (SM.2).

Composition: Testechiniscus sensu stricto: T. spitsbergensis spitsbergensis , T. spitsbergensis tropicalis ssp. nov . and T. laterculus . Testechiniscus sensu lato includes T. macronyx and T. meridionalis (our analyses described below show that the two last species do not belong to the genus. However, their taxonomic status remains unchanged, pending formal taxonomic designations).

Etymology: From Latin testa = shell, armour. The name refers to well-developed plates covering both dorsum and venter of animals ( Kristensen 1987).