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  • 1
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    Springer
    In:  Journal of Materials Science, 18 (7). pp. 2081-2086.
    Publication Date: 2021-08-02
    Description: The internal shell of the cuttlefish, which acts as a rigid buoyancy tank, is structured to combine high compressive strength — since it must withstand the external hydrostatic pressure — with minimum weighT. The micro-architecture of cuttlebone has been examined by electron microscopy and the relevance of the structure to the mechanical duties required of the shellin vivo are briefly discussed. The inorganic calcareous structure is associated with an organic component which may act as a template for mineralization.
    Type: Article , PeerReviewed
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  • 2
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    Springer
    In:  Marine Biology, 65 (1). pp. 1-12.
    Publication Date: 2021-05-05
    Description: The biology of Octopus vulgaris Cuvier inhabiting subtropical littoral reefs off the east coast of South Africa was investigated. Analyses of stomach contents and lair middens revealed that the mussel Perna perna was the dominant food organism. Growth rate of captive individuals was higher than has previously been recorded but food conversion was lower. Females became sexually mature at 900 g which is estimated to be attained in 3.6 months. Males became sexually mature at 400 g, which is estimated to be attained after 3 months. Results indicate that females live for 9–12 months and have the potential to reach 4 000 g in 240 d while males live for about 12–15 months and have the potential to achieve 4 000 g in 290 d. Mating and breeding occurred throughout the year although evidence for the seasonal migration of females is presented and discussed in relation to breeding and feeding behaviour.
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  • 3
    Publication Date: 2020-11-04
    Description: The identity of substrate-inhibitor specificity with respect to several choline esters and organophosphorus compunds was demonstrated for the cholinesterases of the optical ganglion of the squid Ommastrephes bartrami, inhabiting the South Atlantic and the Great Australian Bight. Two cholinesterases with different properties were found in optical ganglia of these squid.
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  • 4
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    Springer
    In:  Cell and Tissue Research, 167 (2). pp. 229-241.
    Publication Date: 2020-07-24
    Description: A single layer of cells secretes the hard cephalopod beaks. The beccublasts are tall columnar cells that separate the beak from the surrounding buccal muscles, and must serve to attach these muscles to the beak. Within the cell layer there are three types of cells. The first, and most frequently found contain cell-long fibrils. These fibrils may have contractile and tensile properties. Complex trabeculae extend from the beccublasts into the matrix of the beak. The fibrils are attached to these trabeculae and at the other end of the cells they are anchored near to the beccublast-muscle cell interface, closely associated with the muscles that move the beak. The second group of cells contain masses of endoplasmic reticulum the cysternae of which are arranged along the long axis of the cell. These cells also contain dense granules and are probably the major source of beak hard tissue. It is probable that each cell secretes its own column of beak hard tissue. The third group of cells contains a mixture of fibrils and secretory tissue. In the beccublast layer there are changes in the proportion of the three types of cells depending upon the region sampled. In the region where growth is most active there are mostly secretory cells, whereas near the biting and wearing tip there are mainly anchoring type cells.
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  • 5
    Publication Date: 2020-07-14
    Description: The luminescent flashing capabilities and swimming behavior were examined for two species of small midwater squids (Pterygioteuthis microlampas and P. giardi). Recently captured squid were placed in a small aquarium, where their movements and luminescent flashes could be recorded with an image intensifier, a photomultiplier tube and associated equipment. Flashing behavior was initiated by disturbing the squid with an electrical shock. The following 4 behaviors were observed: (1) a short flash and a rapid departure from the electrode; (2) a short flash and a delayed, slow departure from the electrode; (3) a longer flash persisting after a rapid departure from the electrode; (4) a longer flash when departure was prevented by continuing the shock. Luminescent flashes probably have a general defensive function, discouraging or disrupting an attack by potential predators, and within this context there may exist numerous strategies involving flashes.
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  • 6
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    Springer
    In:  Marine Biology, 76 (1). pp. 47-54.
    Publication Date: 2020-07-14
    Description: Statoliths of the short-finned squid Illex illecebrosus were chemically analyzed to define their chemical composition and surveyed by scanning electron microscope to differentiate internal structural patterns. X-ray diffraction data demonstrated that L Illecebrosus statoliths were composed principally of CaCQ in the aragonite crystal form. The crystals occurred in a protein matrix to form incremental patterns which radiated from the nucleus to the edge of the statoliths. The protein matrix comprised approximately 5% of the statolith by weight. The protein was principally composed of acidic amino acids. A high abundance of aspartic acid in the protein matrix indicated that the matrix would function as a template in the initiation and acceleration of the crystal growth of CaCO. The rhythmic microstructural patterns, constructed of aragonite crystals in the protein matrix, wer e suggested to be daily in formation and subsequent growth estimations were in agreement with known life history information. The stable isotopic composition of the carbonate of L illecebrosus statoliths suggested that oxygen may be deposited in isotopic equilibrium with the surrounding environment while carbon appeared to be related to biological processes. The information recorded in the statotiths as incremental growth and stable isotopic composition could provide valuable insights into the ecological history of squid.
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  • 7
    Publication Date: 2020-07-14
    Description: Several tissues (e.g. kidney, blood, digestive gland) in oceanic cephalopods which do not exhibit in vivo bioluminescence, luminesce when homogenized in the presence of air or when simply exposed to air in a vial (blood). The source of the luminescence appears to be a luciferin: treatment of kidney homogenates and blood with a photophore extract presumably containing luciferase resulted in a 20-fold increase in light production. Luminescence was also found in the renal fluid, which may be the source of luminescent clouds produced by squids. The variability in luminescence found in some tissues of cephalopods appeared to be related to feeding. Luminescence was also detected in the digestive glands of midwater octopods.
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  • 8
    Publication Date: 2020-07-14
    Description: The means of detecting downwelling light for counterillumination in several midwater animals has been examined. Eyes and extraocular photoreceptors (drosal photosensitive vesicles in the enoploteuthid squid Abraliopsis sp. B and pineal organs in the myctophid fish Myctophum spinosum) were alternately exposed to overhead light or covered by a small opaque shield above the animal and the bioluminescent response of the animal was monitored. Covering either the eyes or the extraocular photoreceptors resulted in a reduction in the intensity of counterillumination. Preliminary experiments examining the bioluminescent feedback mechanism for monitoring intensity of bioluminescence during counterillumination in the midwater squid Abralia trigonura indicated that the ventral photosensitive vesicles are responsible for bioluminescent feedback.
    Type: Article , PeerReviewed
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  • 9
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    Springer
    In:  Clays and Clay Minerals, 27 . pp. 63-71.
    Publication Date: 2020-05-18
    Description: Infrared and Mössbauer spectroscopy show that the extent of the reduction of nontronite is dependent on the chemical composition of the nontronite and on the nature of the reducing agent. Hydrazine reversibly reduces about 10% of the iron in all of the nontronites studied irrespective of composition and it is suggested that the resulting ferrous iron occurs only in distorted octahedral sites. Similar conclusions are reached for the dithionite reduction of the nontronites containing little tetrahedral iron, but for those with more than one in eight silicons replaced by iron, changes brought about by dithionite treatment are irreversible due to dissolution of appreciable quantities of iron. Results from both spectroscopic techniques suggest that iron in tetrahedral sites is preferentially dissolved and that up to 80% of the structural iron can be reduced. Evidence is presented for the formation in these extensively reduced nontronites of a small amount of a mica-like phase resembling celadonite or glauconite, and, as dithionite is used for the pretreatment of soils, the implication of this observation is briefly discussed. The use of deuterated hydrazine as a reducing agent has enabled the nontronite absorption band near 850 cm-1 to be assigned to a Si-O (apical) stretching vibration, which is inactive in the infrared for perfect hexagonal symmetry, but which is activated by distortions in the tetrahedral layer
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  • 10
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    Springer
    In:  Deutsche Hydrographische Zeitschrift, 37 (2). pp. 57-69.
    Publication Date: 2019-09-23
    Description: Radiative transfer modelling for a coupled ocean-atmosphere system near 685 nm indicates a sufficiently high fluorescence signal of the chlorophyll a transmitted to the top of the atmosphere. However, only the shortwave half is seen at the top of the atmosphere, the longwave half is fully masked by atmospheric oxygen and water vapour absorption. The impact of atmospheric aerosol extinction on the signal transmission is almost negligible. The Hα line of the sun, atmospheric water vapour absorption, and chlorophyll absorption near 670 nm influence radiative transfer in the shortwave tail of the fluorescence line making the search for a baseline in order to eliminate the background radiation a difficult task.
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