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Fine structure of egg envelopes in some viviparous goodeid fishes, with comments on the relation of envelope thinness to viviparity
The egg envelope (zona radiata) of the full-grown oocytes before fertilization was examined by electron microscope in eight viviparous species of Goodeidae (Cyprinodontiformes) from the MexicanExpand
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The 18S rDNA sequences support polyphyly of the Hypsibiidae (Eutardigrada)
To extend data on 18S rDNA gene phylogeny within the Eutardigrada and to provide additional information on unclear taxonomic status of a glacier tardigrade Hypsibius klebelsbergi, gene sequences fromExpand
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Comments on the eyes of tardigrades.
  • H. Greven
  • Biology, Medicine
  • Arthropod structure & development
  • 1 December 2007
A survey is given on the scarce information on the visual organs (eyes or ocelli) of Tardigrada. Many Eutardigrada and some Arthrotardigrada, namely the Echiniscidae, possess inverse pigment-cupExpand
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Mechanical properties of the skin of Xenopus laevis (Anura, Amphibia)
The skin of the aquatic pipid frog, Xenopus laevis, was examined for specific biomechanical features: (1) thickness, (2) maximal strain at break (εf), (3) tensile strength (σm), (4) modulus ofExpand
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Survey of the oviduct of salamandrids with special reference to the viviparous species.
  • H. Greven
  • Biology, Medicine
  • The Journal of experimental zoology
  • 1 November 1998
Urodeles include oviparous and a few obligately viviparous species that belong to one family, the Salamandridae. Oviducts of both groups have basically the same design, but some modifications becameExpand
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Genital structures in the entelegyne widow spider Latrodectus revivensis (Arachnida; Araneae; Theridiidae) indicate a low ability for cryptic female choice by sperm manipulation
The female genital structures of the entelegyne spider Latrodectus revivensis are described using semithin sections and scanning electron microscopy. Apart from the tactile hairs overhanging theExpand
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Maternal Adaptations to Reproductive Modes in Amphibians
Publisher Summary Amphibians typically lay eggs in water and from these eggs larvae hatch and undergo metamorphosis to finally live terrestrially. Various types of parental investment in offspringExpand
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Copulation and egg retention in an oviparous Caecilian (Amphibia: Gymnophiona)
Abstract Viviparity (i.e., the bearing of live young) has evolved from oviparity (egg laying) independently in various major vertebrate lineages, and several transitional stages have been described.Expand
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cDNA cloning of a cadmium-inducible mRNA encoding a novel cysteine-rich, non-metallothionein 25-kDa protein in an enchytraeid earthworm.
Cadmium accumulation and its effect on gene expression have been investigated at sublethal cadmium concentrations in the soil oligochaete Enchytraeus buchholzi. This worm is capable of accumulatingExpand
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Placental steroids in cattle: hormones, placental growth factors or by-products of trophoblast giant cell differentiation?
The bovine placenta produces large amounts of steroids, mainly estrone (E1) and progesterone (P4). Specific features of bovine placental steroidogenesis are 1) the expression of all enzymes neededExpand
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