TABLE CONTENTS

SESSION NINE – MORPHOLOGY AND DEVELOPMENT
CONVENORS: WILFRIDA DECRAEMER & VLADIMIR YUSHIN
Morphology in a DNA Barcoding World
Decraemer, W. (1, 2) & C. Neira (3)
(1) Royal Belgian Institute of Natural Sciences, Department of Invertebrates, Vautierstraat 29, 1000 Brussels,
Belgium; (2) Ghent University, Department of Biology, Ledeganckstraat 35, 9000 Ghent, Belgium, (3) Scripps
Institution of Oceanography, 9500 Gilman Drive, La Jolla, CA 92093-0218, USA.
In a changing DNA barcoding world we can question ourselves on the importance of
morphological studies, in particular, morphology based on light microscopic observations, for
identification and understanding relationships and functioning.
A case study will be presented based on a new genus found in bathyal oxygen minimum zone
sediments off Peru. The new taxon closely resembles a known genus Richtersia in habitus
and spiny ornamentations of body cuticle but differs in the structure of the buccal cavity. In
the past, the morphology of the buccal cavity and its cuticular structures played an important
role in determining relationships within the Chromadoroidea, more specifically with respect
to the position of the Selachinematidae. The interpretation of buccal morphology and
homology of its cuticular structures based upon light microscopy for unravelling relationships
will be discussed. Animal-sediment interaction and morphological adaptations will be shortly
addressed.
Male Reproductive System of Marine Nematodes: A Simple Tube?
Yushin, V.V.
Institute of Marine Biology FEB RAS, Vladivostok 690041, Russia
Extensive studies of spermatogenesis in many taxa of free-living marine nematodes now
allows presentation of much original data on the ultrastructure of male reproductive
system in a short review. The genital primordium of the first stage juveniles includes
two primordial germ cells accompanied by two somatic gonad precursor cells. This
close association of two cell lines persists in testes of adults. The somatic sells forms all
the cells of the testis epithelium which encircle totally a cluster of developing germ
cells. Three main parts may be detected easily in each testis: a distal tip cell (DTC), a
testis main part, and a seminal vesicle. In the chromadorians the DTC is a unicellular
gland which probably regulates conversion from mitotic to meiotic divisions of the germ
cells; in the enoplids this gland is multicellular. In both cases these cells protrude long
processes into the testis lumen to be in close contact with spermatogonia. The
epithelium of the main part of testis is extremely thin; sometimes the testis wall reduces
to a basal lamina. This weakness of the wall apparently favors a nutrient transfer from
the intestine to the developing germinal cells which usually have great synthetic activity.
The epithelium of the seminal-vesicle-encircling cluster of spermatozoa is thick and has
distinct synthetic activity; the cytoplasm of the epithelial cells usually contains
numerous secretory granules. The vas deferens of large enoplids is a real epithelial tube
which at the distal end is characterized by a well developed muscular sphincter. The vas
5 th International Congress of Nematology, 2008 34