World Congress of Malacology Antwerp ... - Unitas Malacologica

First identification of mitochondrial M genome in males of Anodonta anatina and Unio
pictorum (Mollusca, Bivalvia, Unionidae)
Soroka, Marianna
Department of Genetics, University of Szczecin, Piastow 40b, 71-065 Szczecin, Poland,
Email: marianna.soroka@univ.szczecin.pl
Mitochondrial DNA (mtDNA), contrary to nuclear DNA, is inherited only maternally. This standard
maternal inheritance (SMI) occurs in a majority of eukaryotic organisms. However, in marine and
freshwater bivalves, another pattern of mtDNA inheritance takes place, which is named doubly
uniparental inheritance (DUI). In this case, we observe two types of mitochondrial DNA: the F-type,
which is inherited from the mother, and the M-type, inherited from the father. A male has both those
types: the mitochondrial M-type genome, which is located in male gonads and is transmited to male
progeny and the F-type of mtDNA in its somatic cells. Females usually have maternally inherited Ftype
mtDNA in all their cells. The fact that DUI was found in phylogenetically remote bivalves
families (Mytilidae, Veneritae, Unionidae) suggests that the phenomenon is widespread. Among
unionids DUI was found in 18 species. The taxonomic restriction of the phenomenon is difficult to
explain and not thoroughly studied. Many authors use somatic tissues as a source of DNA, thus
obtaining only F haplotype. In these studies DNA was isolated from the gonads of male unionid
specimens: Anodonta anatina and Unio pictorum. In both species the M-type mitochondrial DNA
was identified through sequence analyses of the mitochondrial cytochrome oxidase subunit I (cox1)
gene. Using the observed divergency method within the M-type of mtDNA, the level of inter-species
genetic divergence ranged from 0 to 0.2%. The parameter was higher, up to 18%, between A. anatina
and U. pictorum specimens. The sequence divergence between the M- and F-types within the cox1
gene region reached 29-32% for both species and, although very high, was still characteristic for the
bivalves in which DUI had been found. In homology and phylogenetic trees M and F types form
separate clades.
3D-anatomy of the rhipidoglossate heterobranchs Hyalogyrina depressa Hasegawa, 1997 and
Xenoskenea pellucida Monterosato, 1874 (Gastropoda, Ectobranchia)
Speimann, E.; Heß, M.; Haszprunar, G.
Department Biology I, Ludwig-Maximilians-Universität München, BioZentrum Martinsried,
Großhadernerstr. 2, 82152 Planegg-Martinsried, Germany,
Email: erika.speimann@gmx.de; hess@zi.biologie.uni-muenchen.de; haszi@zsm.mwn.de
The discovery of marine representatives of the Valvatoidea (Ectobranchia) by Ponder in 1990
established this clade as basal Heterobranchia, formerly known only from freshwater habitats. We
investigated the anatomy of two marine microgastropods originally classified as Skeneidae by shell
and radula characters and later transferred to the Valvatoidea as family Hyalogyrinidae: Hyalogyrina
depressa from deep waters off Japan and Xenoskenea pellucida from Mediterranean shallow water.
We applied computer aided 3D-reconstructions (software: AMIRA ) based on semithin section
series.
Both species have a tapered snout with a pair of tentacles, an anteriorly bifurcate foot, and a
metapodium with a large mass of calcium cells. The mantle cavity contains an osphradium, a
bipectinate, ciliated gill without bursicles or skeletal rods, and a left, pallial kidney. The rectum
bypasses the monotocardian heart and shows several loops in the pallial roof. A complex,
hermaphroditic genital system suggests internal fertilisation. The rhipidoglossate radula apparatus
lacks cartilages, the salivary glands are long and tubular, the stomach shows a gastric shield. The
nervous system is epiathroid and streptoneurous, each statocyst contains a single statolith. The eyeless
Hyalogyrina depressa has a ciliated pallial tentacle at the right side. Xenoskenea pellucida has a
small copulatory organ behind the right cephalic tentacle, a metapodial tentacle, and simple lens eyes.
These anatomical data and the hyperstrophic larval shells all reflect basal heterobranch conditions.
The metapodial calcium cells and the looped pallial rectum are interpreted as synapomorphies for the
212