Dactylobiotus cf. octavi

Dactylobiotus cf. octavi View in CoL

( Figs. 11–12 View Fig View Fig )

Material examined: Four animals and 50 eggs were extracted from the sample collected in Greenland. The DNA sequences were obtained from one embryonated egg ( Table 2). Fifteen eggs were prepared and examined under SEM (SEM stub: TAR.19), while the remaining specimens were mounted on microscope slides in Hoyer’s medium (Slides: GL.004.01–05).

Material depositories: All specimens are deposited at the Institute of Systematics and Evolution of Animals, Polish Academy of Sciences, Sławkowska 17, 31-016, Kraków, Poland.

Remarks: The specimens and eggs found in this sample resemble those of D. ampullaceus ( Thulin, 1911) and D. octavi . Although the eggs of D. ampullaceus exhibit processes similar to those observed in the newly discovered Greenlandic population, they lack the pores around the process bases ( Thulin 1911) that are clearly visible under light microscopy in our population as well as in D. octavi . Consequently, the examination of the prepared specimens allowed their identification as D. cf. octavi , as all observed characteristics matched the original description of animals and eggs, except for some details in egg ornamentation. Guidetti et al. (2006) noted that the egg processes in D. octavi are crater-like, often featuring a small elevation at the center. Specifically, most processes are conical with introverted apices, while only a few are fully conical. In contrast, the eggs from the newly discovered population analyzed in this study are distinctly conical in shape ( Figs. 11 View Fig and 12 View Fig ). Their distal parts form a broad cone, tapering proximally into a short, slender tip ( Figs. 11 View Fig and 12 View Fig ). Notably, some processes appeared not fully extended, giving the impression of introverted apices ( Fig. 12A, C View Fig ).

Other investigated taxa: The examination of the type material for D. caldarellai and D. lombardoi , along with their original descriptions, revealed no reliable characters to differentiate these species from their congeners. Furthermore, as eggs are unknown for these species and the type specimens are in very poor condition (SM. 3), we designate them as nomina dubia with the following combinations: Dactylobiotus caldarellai Pilato and Binda, 1994 nom. dub., and Dactylobiotus lombardoi Binda and Pilato, 1999 nom. dub. The challenges surrounding the identification of these three Dactylobiotus taxa are further elaborated and discussed in detail in the corresponding discussion section below.