ABSTRACT
The review presents a topological interpretation of some morphogenetic events through the use of well-known mathematical concepts and theorems. Spatial organization of the biological fields is analyzable in topological terms. Topological singularities inevitably emerging in biological morphogenesis are retained and transformed during pattern formation. It is the topological language that can provide strict and adequate description of various phenomena in developmental and evolutionary transformations. The relationship between local and global orders in metazoan development, i.e., between local morphogenetic processes and integral developmental patterns, is established. A topological inevitability of some developmental events through the use of classical topological concepts is discussed. This methodology reveals a topological imperative as a certain set of topological rules that constrains and directs embryogenesis. A breaking of spatial symmetry of preexisting pattern plays a critical role in biological morphogenesis in development and evolution.
Subject(s)
Biological Evolution , Cell Polarity/physiology , Embryonic Development/physiology , Models, Biological , Morphogenesis/physiology , Animals , Fertilization/physiologyABSTRACT
vasa (vas)-related genes are members of the DEAD-box protein family and are expressed in the germ cells of many Metazoa. We cloned vasa-related genes (PpVLG, CpVLG) and other DEAD-box family related genes (PpDRH1, PpDRH2, CpDRH, AtDRHr) from the colonial parasitic rhizocephalan barnacle Polyascus polygenea, the non-colonial Clistosaccus paguri (Crustacea: Cirripedia: Rhizocephala), and the parasitic isopodan Athelgis takanoshimensis (Crustacea: Isopoda). The colonial Polyascus polygenea, a parasite of the coastal crabs Hemigrapsus sanguineus and Hemigrapsus longitarsis was used as a model object for further detailed investigations. Phylogenetic analysis suggested that PpVLG and CpVLG are closely related to vasa-like genes of other Arthropoda. The rest of the studied genes form their own separate branch on the phylogenetic tree and have a common ancestry with the p68 and PL10 subfamilies. We suppose this group may be a new subfamily of the DEAD-box RNA helicases that is specific for parasitic Crustacea. We found PpVLG and PpDRH1 expression products in stem cells from stolons and buds of internae, during asexual reproduction of colonial P. polygenea, and in germ cells from sexually reproducing externae, including male spermatogenic cells and female oogenic cells.
Subject(s)
DEAD-box RNA Helicases/genetics , Gene Expression Regulation , Parasites/cytology , Parasites/genetics , Stem Cells/metabolism , Thoracica/cytology , Thoracica/genetics , Amino Acid Sequence , Animals , DEAD-box RNA Helicases/chemistry , DEAD-box RNA Helicases/isolation & purification , DEAD-box RNA Helicases/metabolism , Life Cycle Stages , Molecular Sequence Data , Parasites/anatomy & histology , Parasites/growth & development , Phylogeny , RNA, Messenger/genetics , RNA, Messenger/metabolism , Sequence Alignment , Sequence Analysis, DNA , Thoracica/anatomy & histology , Thoracica/growth & developmentABSTRACT
Commercial crab populations off the Kamchatka coasts are infested to a considerable degree by the rhizocephalan parasite Briarosaccus callosus: of 769 Lithodes aequispina males examined, 43 (5.7%) were parasitized. Infestations result in the feminization of the crabs, a significant decrease in the cheliped length, and a significant decrease in the carapace length and width. We suggest that commercial selection of healthy males, and the returning of unsuitable crabs, including infested ones, back into the sea, results in an increase of the proportion of infested crabs in the population, their elimination from reproduction, and, eventually, the gradual degradation of a whole population. To minimize as far as possible the negative effects of commercial crab harvesting, all infested crab specimens caught must be destroyed, either aboard or elsewhere, instead of throwing them back into the sea.
