Echiniscus militaris Murray, 1911

Gąsiorek, Piotr & Degma, Peter, 2018, Three Echiniscidae species (Tardigrada: Heterotardigrada) new to the Polish fauna, with the description of a new gonochoristic Bryodelphax Thulin, 1928, Zootaxa 4410 (1), pp. 77-96 : 88-89

Echiniscus militaris Murray, 1911

( Figs 28–29 )

Locus typicus. Castlebar, Ireland.

Material examined: One four-clawed juvenile, found together with very numerous Echiniscus granulatus ( Doyère, 1840) , E. reticulatus Murray, 1905 , Pseudechiniscus suillus , Testechiniscus spitsbergensis , and Richtersius coronifer ( Richters, 1903) (sample PL.273; Kobylarzowy Coulouir).

Description: Very small (162 µm), conspicuously pink coloured. Cirrus internus / externus length ratio 67%. Cirrus A 48 µm long and very thick, lateral appendages B and E of equal lengths (20 µm), lateral cirri C and D markedly longer (60 and 76 µm, respectively). All dorsal appendages present, of which C d are the longest (44 µm vs B d 18 µm long and D d 33 µm long). In general, cirri in all B-positions are visibly thinner than other appendages. The difference is especially evident in the width of the dorsal appendage bases (1.9 µm in B d, 2.8 µm in C d, and 4.9 µm in D d, respectively). Plates with well-marked borders, lacking cervical (neck) and third median plates. Sculpture composed of polygons (blumi-canadensis type), with the largest polygons found on the small median plates and the central part of the caudal plate. Ventral cuticle smooth, except for the genital zone, where two large, trapezoid plates, in line with legs IV, occur ( Fig. 29 ). Pedal (leg) plates invisible in PCM. Dentate collar on legs IV comprises seven long, parallel teeth. Large, slender claws; claws I–III markedly shorter than claws IV (11.9–13.1 µm, 32.5–35.8% vs 16.6 µm, 45.4%). Small spurs (2.1 µm, 5.7%) positioned very close to the internal claw bases, and almost perpendicular to the claw branch.

Remarks: New record for Poland. E. militaris is without doubt one of the most elusive Palaearctic echiniscid species ( Ramazzotti & Maucci 1983). Since its original description in 1911, it has been recorded only a few times and in very small numbers from various European countries ( McInnes 1994). Pilato (1977) suppressed all subspecies after analysing different populations of the species. As there is a very high variability among recorded specimens, it is very likely that a number of independent species are captured under the one specific name. Unfortunately, difficulties in obtaining an adequate number of specimens for a detailed taxonomic study, including DNA sequencing, will hinder clarification of the taxonomic status of this species and resolving whether this is a single species exhibiting considerable intraspecific variability or a group of morphologically similar species.

Figures

FIGURES 28–29. First Polish record—Echiniscus militaris Murray, 1911 (PCM): 28—dorsal view; 29—ventral view, asterisks indicate genital plates with minute intracuticular pillars. Scale bars in µm.