Integrative studies of the Greenlandic kinorhynchs Krakenella greenlandica and Cristaphyes cryopygus (Kinorhyncha: Pycnophyidae) indicate conspecificity with species from Svalbard

The Greenlandic kinorhynchs Cristaphyes cryopygus and Krakenella greenlandica were collected at their type localities in Greenland. DNA was extracted for barcoding, and the specimens were prepared for morphological examination. Information from this newly obtained material was combined with re-examinations of type material and conspecific specimens from other localities in Greenland, and was used as the basis for redescriptions of the two species. The redescriptions revealed several significant shortcomings in the original descriptions of the species, and led to amended species diagnoses, and reassignment of K. greenlandica to Pycnophyes, under the name P. greenlandicus. In addition, specimens of Cryopygus scatha and Pycnophyes ancalagon were collected at and near their type localities at Svalbard, and made subject for similar barcoding and examinations. This information, together with information from the type specimens of the Svalbard species, was compared with the Greenlandic specimens, and based on similarities in morphology, and molecular distances below 0.01 or even 0.00 between several geographically distant specimens, it was concluded that C. scatha is a junior synonym of C. cryopygus, and likewise that P. ancalagon is a junior synonym of P. greenlandicus. In addition, examination of +50 specimens of each species revealed a surprisingly high level of intraspecific morphological variation in both species, mostly expressed in the order of sensory spots and setae on the tergal plates. In addition, C. cryopygus showed variation in regard to seta positions on the sternal plate of segment 7, and P. greenlandicus in regard to absence or presence of paradorsal setae on segments 4, 6 and 8. The latter represents a taxonomic challenge, since the presence of paradorsal setae is a key characteristic to identify P. greenlandicus morphologically. The present study stresses that even though application of molecular barcoding in kinorhynch taxonomy is still in its infancy, it might prove to become a pivotal tool to understand species boundaries and intraspecific morphological variation.