Photoperiod and delayed implantation in the northern fur seal (Callorhinus ursinus).
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An equation for determination of the photoperiod at any given latitude for any given date is presented and used in an analysis of reproductive timing in the northern fur seal in which there is an obligatory delay of implantation. Fur seals breeding on San Miguel Island, California (33 degrees N) displayed a mean date of parturition that was 14 days earlier (P less than 0.001) than that of the parent stock on the Pribilof Islands, Alaska (57 degrees N). Previous studies have shown that changes occur in the corpus luteum, in follicles in the ovary containing the corpus luteum, in concentrations of plasma progesterone and oestradiol-17 beta, and in the uterine lining when there is a mean photoperiod of 12.5 h/day. This photoperiod occurs at both locations at 62 days after the mean dates of parturition, and may act as a cue for the initiation of implantation in these seals. (+info)
Animal identification. II. Freeze branding of seals for laboratory identification.
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Five young seals and three mature seals were branded using liquid nitrogen cooled branding tools with xylol as a wetting agent. Preliminary results are encouraging as presented by photographic evidence. (+info)
Genic variability and strategies of adaptation in animals.
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Levels of genic heterozygosity, as measured by surveys of allozymic variation, are much lower in populations of large, mobile animals (most vertebrates) than in those of small, relatively immobile animals (most invertebrates). This difference is not consistent with theories relating variability to population size (species number) or dispersal ability (gene flow), but it is predicted by Levins' theory of adaptive strategies in relation to environmental uncertainty ("grain"). Mobility and degree of homeostatic control apparently are important factors influencing levels of genic heterozygosity in natural populations. The results argue indirectly that at least a major proportion of allozymic variation is maintained by natural selection. (+info)
Cytotoxicity of adenovirus-antibody aggregates: sensitivity to different cell strains, and inhibition by hexon antiserum and by complement.
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Adenovirus-antibody aggregates under defined conditions are cytotoxic in vitro. All members of adenovirus groups I, II, and III caused toxicity upon aggregation. The toxicity of the clusters is exerted by the virions. Toxicity is temperature dependent and may be caused by a mechanism similar to that used in viral penetration. Cells permitting direct viral penetration were all sensitive to the toxic aggregates. The toxicity seems to be related to hexon antigens on the surface of the virions since antihexon sera neutralized the toxicity. No evidence was obtained showing that pentons are required for this kind of cytotoxicity. Adenovirus types 3, 5, and 9 were used in the experiment. Cytotoxicity was estimated by the (51)Cr release assay. Complement factors could be excluded as mediators of the cytolytic reactions. Instead, complement was shown to prevent the formation of toxic aggregates or to neutralize the toxicity of preformed ones. (+info)
Circulating levels of oestradiol-17beta during early pregnancy in the Alaskan fur seal showing an oestrogen surge preceding implantation.(61/80)
Since 1919, in Canada, 62 authenticated outbreaks of human botulism have affected 181 persons, with 83 deaths, a fatality rate of 46%. Among these, 41 outbreaks were bacteriologically determined (31 in one laboratory) as six type A, four type B, one both A and B, and 30 type E. About two thirds of the total outbreaks, cases and deaths involved Eskimos and Pacific coast Indians consuming raw marine mammal products and salmon eggs, respectively. Other parts of Canada recorded seven occurrences due to miscellaneous vehicles, three being type B. Since January 1961 there have been 38 outbreaks, involving 94 cases with 33 deaths. These include 18 outbreaks among Eskimos, affecting 51 persons (of whom 24 died) in Labrador, southern Baffin Island, northern Quebec, and the Mackenzie area. Also, putrid salmon eggs caused 15 outbreaks among Pacific coast Indians, totalling 35 cases, of whom only six died, the low fatality rate reflecting the introduction of type E botulinus antitoxin during 1961. (+info)
Problems of toxicants in marine food products. 1. Marine biotoxins.
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The expansion of marine fisheries into tropical waters, which is now occurring, will increase the risks of widespread poisonings because of the abundance of biotoxins in warm-water organisms. However, toxic marine organisms are not only a health hazard but also a possible source of new pharmaceutical products.A classification of marine intoxicants is given in this paper with special reference to the oral biotoxins which will be of primary concern in the expansion of warm-water fisheries. The biotoxins are both invertebrate (e.g., molluscs, arthropods) and vertebrate (mostly fishes) in origin. Biotoxications of vertebrate origin may be caused by the muscles, the gonads or the blood of certain fishes or by special poison glands not equipped with traumagenic devices. (Venomous fishes, having poison glands and traumagenic spines, etc., are of no direct concern as oral intoxicants.)The ichthyosarcotoxic fishes, in which the flesh is poisonous, appear to constitute the most significant health hazard. A list of fishes reported as causing ciguatera poisoning (one of the most serious and widespread forms of ichthyosarcotoxism) is included in this paper. (+info)
Underwater audiogram of the California sea lion by the conditioned vocalization technique.
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Conditioning techniques were developed demonstrating that pure tone frequencies under water can exert nearly perfect control over the underwater click vocalizations of the California sea lion (Zalophus californianus). Conditioned vocalizations proved to be a reliable way of obtaining underwater sound detection thresholds in Zalophus at 13 different frequencies, covering a frequency range of 250 to 64,000 Hz. The audiogram generated by these threshold measurements suggests that under water, the range of maximal sensitivity for Zalophus lies between one and 28 kHz with best sensitivity at 16 kHz. Between 28 and 36 kHz there is a loss in sensitivity of 60 dB/octave. However, with relatively intense acoustic signals (> 38 dB re 1 mub underwater), Zalophus will respond to frequencies at least as high as 192 kHz. These results are compared with the underwater hearing of other marine mammals. (+info)