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  • 1
    Online Resource
    Online Resource
    Specialization for rapid excitation in fast squid tentacle muscle involves action potentials absent in slow arm muscle
    The Company of Biologists ; 2020
    In:  Journal of Experimental Biology
    Details
    In: Journal of Experimental Biology, The Company of Biologists
    Abstract: An important aspect of the performance of many fast muscle fiber types is rapid excitation. Previous research on the cross-striated muscle fibers responsible for the rapid tentacle strike in squid has revealed the specializations responsible for high shortening velocity, but little is known about excitation of these fibers. Conventional whole-cell patch recordings were made from tentacle fibers and the slower obliquely striated muscle fibers of the arms. The fast-contracting tentacle fibers show an approximately tenfold greater sodium conductance than that of the arm fibers and, unlike the arm fibers, the tentacle muscle fibers produce action potentials. In situ hybridization using an antisense probe to the voltage-dependent sodium channel present in this squid genus shows prominent expression of sodium channel mRNA in tentacle fibers but undetectable expression in arm fibers. Production of action potentials by tentacle muscle fibers and their absence in arm fibers is likely responsible for the previously reported greater twitch-tetanus ratio in the tentacle versus the arm fibers. During the rapid tentacle strike a few closely spaced action potentials would result in maximal activation of transverse tentacle muscle. Activation of the slower transverse muscle fibers in the arms would require summation of excitatory postsynaptic potentials over a longer time, allowing the precise modulation of force required for supporting slower movements of the arms.
    Type of Medium: Online Resource
    ISSN: 1477-9145 , 0022-0949
    URL: Article
    DOI: 10.1242/jeb.218081
    Language: English
    Publisher: The Company of Biologists
    Publication Date: 2020
    detail.hit.zdb_id: 1482461-9
    SSG: 12
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  • 2
    Online Resource
    Online Resource
    Effects of salinity on the growth and morphology of the invasive, euryhaline hydroid Cordylophora (Phylum Cnidaria, Class Hydrozoa)
    Wiley ; 2018
    In:  Invertebrate Biology Vol. 137, No. 1 ( 2018-03), p. 78-90
    Details
    In: Invertebrate Biology, Wiley, Vol. 137, No. 1 ( 2018-03), p. 78-90
    Abstract: The invasive, euryhaline hydroid Cordylophora sp. is a colonial cnidarian present in both freshwater and brackish water habitats. Individuals contend with osmotic stress at the tissue and cellular level. It has been suggested that this hydroid's ability to expand its range of distribution by invading new habitats is due in large part to an ability to acclimate to new salinities. The purpose of this study was to assess colony growth and morphological changes at various salinities in freshwater and brackish genotypes of Cordylophora sp. Single genotypes from a known freshwater clade (0.5 psu; Des Plaines River) and a known brackish clade (16 psu; Napa River) were cultured and gradually transitioned to 12 different salinities ranging 0.5–22 psu, and we characterized the growth rates and hydranth morphological features at each salinity. Colony growth was optimal at 0.5 psu for the freshwater genotype and 10 psu for the brackish genotype. Changes in hydranth morphology in the freshwater genotype were primarily observed at higher salinities, while morphological changes in the brackish genotype primarily occurred at lower salinities. Our results for the brackish genotype generally concur with previous work, but this study is the first to document the response of a freshwater genotype of Cordylophora sp. to various salinities. Differences in growth between these two genotypes strongly support the previously proposed existence of multiple cryptic species. Furthermore, because this hydroid is quite prevalent in freshwater and brackish systems as a fouling organism, understanding the effects of various salinities on the successful establishment of Cordylophora sp. is an important contribution to the understanding of the ecophysiology and management of this invasive hydroid.
    Type of Medium: Online Resource
    ISSN: 1077-8306 , 1744-7410
    URL: Issue
    URL: Article
    DOI: 10.1111/ivb.2018.137.issue-1
    DOI: 10.1111/ivb.12207
    Language: English
    Publisher: Wiley
    Publication Date: 2018
    detail.hit.zdb_id: 2092932-8
    SSG: 12
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