Investigation of echinoderid kinorhynchs described 90 years ago: redescription of Echinoderes capitatus (Zelinka, 1928) and Echinoderes ferrugineus Zelinka, 1928

Abstract

The two kinorhynch species Echinoderes capitatus (Zelinka, 1928) and Echinoderes ferrugineus Zelinka, 1928 are redescribed herein, based on specimens collected at different Mediterranean locations. Echinoderes capitatus is characterized by the presence of middorsal acicular spine on segment 4 and lateroventral acicular spines on segments 6–9; at least three pairs of tubes on segment 2 (subdorsal, midlateral, and ventrolateral); subdorsal tubes on segment 8; laterodorsal tubes on segment 10; lateral accessory tubes on segments 5 and 8; subdorsal sensory spots on segments 1 and 3–11; and ventromedial sensory spots on segments 2 and 5–7, often additionally on segment 8; occurrence of subdorsal tubes on segments 6 and 7, laterodorsal tubes on segment 2, midlateral tubes on segments 7 and 8, and ventromedial tubes on segment 8 showing intraspecific variation; and the absence of the type-2 gland cell outlets. The pattern of the additional tubes is relatively well-preserved within a population but differs among populations. Echinoderes ferrugineus is characterized by the presence of middorsal acicular spines on segment 4–8; lateroventral acicular spines on segments 6–9; lateral accessory tubes on segment 5; type-2 gland cell outlets in subdorsal, laterodorsal, sublateral, and ventrolateral position on segment 2, subdorsal and midlateral position on segment 4, midlateral position on segment 5, and midlateral position on segment 8; long lateral terminal spines (ca. 140–180 μm, 45–63% of trunk length). Comments are provided on the intraspecific variation in tube pattern in E. capitatus, and its potential importance in a speciation and evolutionary context.