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  • 1
    ISSN: 1573-3297
    Keywords: Drosophila melanogaster ; courtship ; crowding ; prestimulation ; evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract The mating times of single males and pairs of males were increased by crowding with virgin females but only at very high densities. Mating times were decreased by the presence of a second male. Quantitative analysis of courtship showed that prestimulation of females in crowded conditions influences mating. The pattern of male courtship was highly consistent across moderate levels of crowding. This suggests thatDrosophila courtships evolved in crowded conditions.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 147 (1987), S. 141-155 
    ISSN: 1573-5117
    Keywords: Rotifera ; colony behavior ; feeding ; clearance rate ; predator-prey ; evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Coloniality in the phylum Rotifera is defined and reviewed. Only two families of rotifers contain truly colonial forms: Flosculariidae and Conochilidae (order Gnesiotrocha, suborder Flosculariacea). Most species form intraspecific colonies ranging in size from a few to about 200 individuals, but species that produce enormous colonies (〉 1000 individuals) are also known. All seven genera of the Flosculariidae contain species that form colonies to widely varying degrees (Beauchampia, Floscularia, Lacinularia, Limnias, Octotrocha, Ptygura, Sinantherina). All four species of the monogenetic Conochilidae (Conochilus) are colonial, but two species form colonies of only an adult and a few young. At least one other family (Philodinidae; Bdelloida) contains a species that exhibits a form of coloniality (Philodina megalotrocha). Two hypotheses that attempt to explain the adaptive significance of coloniality (Energetic Advantage and Predatory Avoidance) are reviewed and new information concerning the former is presented. Evolution of coloniality is discussed briefly.
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  • 3
    ISSN: 1573-5117
    Keywords: Acanthocephala ; aschelminthes ; cladistics ; evolution ; Gnathostomulida ; phylogeny ; pseudocoelomates ; Rotifera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We investigated phylogenetic relationships of phylum Rotifera using cladistic analysis to uncover all most-parsimonious trees from a data set comprising 60 morphological characters of nine taxa: one Acanthocephala, six Rotifera, and two outgroups (Turbellaria, Gnathostomulida). Analysis of our matrix yielded a single most-parsimonious tree. From our analysis we conclude the following: (1) Class Digononta is paraphyletic; (2) it is still premature to reject rotiferan monophyly; (3) the classification hierarchy that best conforms to this morphologically based, cladistic analysis is similar to several traditional schemes. In spite of these results, it is significant that this analysis yielded a tree that is incongruent with those trees developed from molecular data or by using the principles of evolutionary taxonomy.
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  • 4
    ISSN: 1573-5117
    Keywords: cladistics ; computers ; evolution ; evolutionary trees ; Notholca ; orders ; phylogeny ; Rotifera ; synapomorphies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We investigated evolutionary relationships among orders in phylum Rotifera and among species in genus Notholca (Rotifera) by computing parsimonious cladograms. All of the most-parsimonious cladograms generated for the ordinal level confirm the view that class Monogononta, superclass Eurotatoria, and phylum Rotifera are monophyletic. Species within the genus Notholca were separated into six groups (clades), but some species have been defined based on highly variable characters not reliably studied using cladistics. Therefore, phenetic studies are warranted, especially for species possessing caudal processes.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 255-256 (1993), S. 491-493 
    ISSN: 1573-5117
    Keywords: Acanthocephala ; evolution ; phylogeny ; Rotifera ; systematics ; taxonomy ; workshop
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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  • 6
    ISSN: 1573-5117
    Keywords: Acanthocephala ; aschelminthes ; cladistics ; evolution ; Gnathostomulida ; phylogeny ; pseudocoelomates ; Rotifera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We investigated phylogenetic relationships of phylum Rotifera using cladistic analysis to uncover all most-parsimonious trees from a data set comprising 60 morphological characters of nine taxa: one Acanthocephala, six Rotifera, and two outgroups (Turbellaria, Gnathostomulida). Analysis of our matrix yielded a single most-parsimonious tree. From our analysis we conclude the following: (1) Class Digononta is paraphyletic; (2) it is still premature to reject rotiferan monophyly; (3) the classification hierarchy that best conforms to this morphologically based, cladistic analysis is similar to several traditional schemes. In spite of these results, it is significant that this analysis yielded a tree that is incongruent with those trees developed from molecular data or by using the principles of evolutionary taxonomy.
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  • 7
    ISSN: 1573-6830
    Keywords: tyrosine hydroxylase immunocytochemistry ; spinal cord ; chick embryo ; dopamine immunocytochemistry ; evolution ; CSF-contacting neurons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. The development of tyrosine hydroxylase-immunoreactive (TH-IR) neurons was examined in the spinal cord of the chick embryo and hatchling. 2. Two groups of TH-IR cells are described, both of which appear to reach their full complement in number relatively late in embryonic development. One group is comprised of numerous cells located ventral to the central canal which make direct contact with the lumen of the canal. The other group consists of large multipolar neurons that reside in the dorsal horn, more commonly along the outer margin of the gray matter within lamina I and II, and less frequently deeper in the dorsal horn within medial portions of laminae V, VI or VII. 3. TH-IR cells ventral to the central canal in the chick are comparable in location to dopamine (DA)-containing spinal cord cells in lower vertebrate species. In contrast, the dorsally-suited TH-IR cells in the chick are known only to occur in similar positions in higher vertebrates. Therefore, the chick is novel in that the presence ofboth groups of TH-IR cells appearing together in significant numbers within the spinal cord has not been shown in any other species studied to date. 4. The TH-containing cells in the chick cord do not appear to contain the catecholamine biosynthesis enzymes, DBH or PNMT. Moreover, using anti-DA immunocytochemistry, neither group of TH-IR cells demonstrated detectable levels of DA in control animals nor in animals pretreated with inhibitors of MAO (MAO-I). 5. However, a difference was noted though between the two TH-IR cell groups in terms of their responses to exogenously supplied L-DOPA, the immediate precursor to DA. With the administration of L-DOPA and a MAO-I to chick hatchlings, cells in the region ventral to the central canal stained intensely for DA. In contrast, the same treatment failed to produce DA-immunoreactive cells in the dorsal horn. 6. One reasonable hypothesis for these results is that the TH-IR cells ventral to the central canal contain an active form of AADC, the enzyme that converts L-DOPA to DA. With this interpretation, if these cells can produce DA from L-DOPA, yet do not appear to synthesize DA endogenously, it would appear that the TH enzyme contained in these cells occurs in aninactive form. Whether the TH enzyme in the dorsally located immunoreactive cells is also inactive is uncertain since it remains unclear whether they contain AADC.
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