ATTHABOON WATTHAMMAWUT, MONSICHA SOMRIT, ASSIST. PROF. SOMLUCK
ASUVAPONGPATTANA, ASSOC. PROF. WATTANA WEERACHATYANUL,
MORPHOLOGICAL AND BIOLOGICAL CHARACTERIZATIONS OF THE ACROSOMELIKE STRUCTURE IN SPERM AND THE PROCESS OF THE SPERM-EGG
INTERACTIONS IN THE GIANT FRESHWATER PRAWN, MACROBRACHIUM
ROSENBERGII
ABSTRACT:
In the great freshwater prawn Macrobrachium rosenbergii, mature sperm are similar to
other palaemonid decapods in that they appear to have an everted umbrella-shaped cell while
similar to natatians in general by possessing a single (unistellate), immotile anterior projection
called the spike. In contrast to other species of prawn such as unistellates Sicyonidae and
Penaeidae along with other invertebrates, no acrosomal region or any structures related to the
acrosomal process have been identified in M. rosenbergii sperm has even been suggested to not
be present at all.
However, past studies in M. rosenbergii and in related unistellates have shown that after
the passive contact between sperm and egg, the base of the sperm adheres to the vitelline
envelope, and is followed by the bending of the spike to penetrate the egg envelope. This
suggests that the sperm may possess structures that may function as an acrosome that may
contain associating hydrolytic enzymes to allow for the successful penetration of the tough layer
of the egg vitelline envelope.
Therefore, in this study, the existence of an acrosomal region was examined in the mature
sperm of M. rosenbergii by a correlative approach using fluorometric enzyme assays, enzyme
localization under light microscope, immunocytochemical localization of acrosomal enzymes
under confocal microscope for spatial-3D reconstruction, scanning and transmission electron
microscopy (SEM and TEM) for a molecular level of detail to observe morphology.
In addition, as a purported acrosome region must undergo structural modifications in
order to either release hydrolytic acrosomal enzymes or cause a mechanical penetration of the
egg envelope, modifications of associated structures such as the cytoskeletal proteins and protein
phosphorylations will also be investigated.
Moreover, the functional aspect of a purported acrosomal region in M. rosenbergii sperm
will be investigated through assays determining the enzymatic activities on the egg vitelline
envelope proteins, and live sperm-egg assays, with high fidelity visualization of the interaction
using spatial and temporal reconstruction.
In conclusion, this study will allow for the better understanding of the distinctive sperm
of M. rosenbergii, and through the study of its acrosomal region and reaction upon contact with
the egg may lead to the development of methods and techniques for future in vitro fertilization
studies. This could also lead to the successful selection of males for the better yields and superior
quality of off-spring.