Аннотация:This study re-examines in detail the microanatomy of the Arctic opisthobranch
Asperspina murmanica, the only acochlidian that was described as retaining a
well-developed mantle cavity, and evaluates its supposedly basal position
within the Acochlidia. Several specimens were recollected at the type locality
in Russia. Spicules and radulae were studied by scanning electron microscopy.
Semithin sections were prepared and a computer-based three-dimensional
reconstruction of all major organ systems was made using Amira software. Our
results show significant differences from the original description, e.g. the
nervous system shows paired rhinophoral and gastro-oesophageal ganglia and
large aggregations of precerebral accessory ganglia, whereas the presence of a
postulated posterior genital ganglion can be excluded; the radula is asymmetric;
the circulatory system includes a small heart; and the reproductive system
comprises a sac-like ampulla and three female glands. The most surprising
discrepancy to the original description refers to the complete absence of any
mantle cavity. The gonopore, anus and nephropore open separately to the
exterior. Instead of being aberrant or basal, A. murmanica fits well with other
Asperspina species and comes closest to the Mediterranean Asperspina rhopalotecta.
The monotypic genus/family Minicheviella/Minicheviellidae Starobogatov (1983)
is confirmed as a junior synonym of Asperspina/Asperspinidae Rankin (1979).