World Congress of Malacology Antwerp ... - Unitas Malacologica

Motivation to resist sex in a simultaneous hermaphrodite
Hoffer, Jeroen N.A.; Koene, Joris M.
Vrije Universiteit, de Boelelaan 1085, 1081HV Amsterdam, The Netherlands,
Email: jeroen.hoffer@falw.vu.nl, joris.koene@falw.vu.nl
Sexual encounters are usually accompanied by conflicts of interest between mating partners.
Theoretical modeling indicates that these conflicts may be more severe in hermaphrodites than in
gonochorists. Using the simultaneous hermaphrodite Lymnaea stagnalis (Gastropoda, Pulmonata) we
investigated behavioral aspects of sexual conflict.
It has been shown that the motivation of individuals to mate in the male role (conditional reciprocal
insemination does not occur) is dependent on the amount of fluid present in the prostate gland. When
an animal has not donated sperm for more than a week, the male sex drive is at a maximum. It is
usually assumed that sperm recipients are passive during sexual encounters. However, female-acting
copulants receive a sizeable amount of hormones together with the sperm, which interferes with their
ability to optimally allocate resources to male and female functions and growth. Receiving an
ejaculate may thus not be in the interest of an individual.
We focused on female resistance against insemination in behavioral experiments. Specifically, we
examined the behavior of animals that 1) were isolated or grouped, 2) were satiated or starved, 3) had
laid eggs or not and 4) were virgin or recently inseminated. These animals were all paired with
individuals with maximal male-drive. By monitoring the behavior of the focal (treatment) animal, we
attempt to dissect the motivation or resistance to accept an ejaculate.
Tag-team approach: Mitochondrial DNA and morphological assessment of Vietnamese
freshwater gastropods (Caenogastropoda: Pachychilidae)
Holford, Mande 1 ; Do, Van Tu 2 ; Ho, Thanh Hai 2 ; Köhler, Frank 3
1. University of Utah, Salt Lake City, Utah, 84112, USA,
Email: mande.holford@gmail.com
2. Vietnamese Academy of Science and Technology, Institute of Ecology and Bio-Resources, 18
Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam,
3. Museum für Naturkunde, Humboldt-Universität Berlin, Invalidenstr. 43, 10115 Berlin, Germany,
Email: frank.koehler@rz.hu-berlin.de
The DNA Barcoding Initiative (DBI) has led to a lively debate on the utility of DNA sequences to
assess the world’s biota and identify species by the sequence of certain reference genes.
Mitochondrial sequences, already instrumental for the inference of phylogenetic relationships of
organisms, are increasingly being used by barcoders for the recognition and delineation of species.
Generally it is not disputed that sequences contain taxonomically relevant information, but claims
that barcode data should exclusively or preferential be used in taxonomic work are not widely
accepted. In the present study we compared the degrees of morphological and mitochondrial
differentiation of Vietnamese freshwater gastropods (Caenogastropoda: Pachychilidae), in order to
determine whether analyses of reference sequences alone provide accurate species level
identifications. For this purpose, fragments of two mitochondrial genes (COI, 16S) were analysed
independently by reconstructing Maximum Likelihood phylograms. If species indeed can be
recognized and delineated only by means of their mitochondrial sequences, then conspecific
individuals should cluster together in well- individualized clades. Our observations were only partly
consistent with this precondition: The trees produced a clear separation between several different
sequence clusters, indicating the representation of individual species. However, various specimens
clustered together in a loose group, making it impossible to unambiguously differentiate species. In
addition, we found no correlation between genetic and morphological differentiation. By contrast, we
observed high degrees of morphological differentiation in genetically rather homogeneous groups
and vice versa. We conclude that mitochondrial genes are useful to explore the diversity of a given
group, but reliable taxonomic decision should always be based on thorough analysis of both genetic
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