The extent and differences in mitotic activity of the root tip ofVicia faba L.

Mitotic activity does not stop for different meristematic cells of the root apex at the same distance from the initials. The differences are connected with the functional heterogeneity of the apical meristem of the root. The arrangement of vascular bundles,i.e. the alternation of independent xylem and phloem groups, is of major importance. In broad bean roots, the protophloem sieve elements stop dividing first. The centre of the stelei. e. late metaxylem elements stop dividing next. Division in the stele gradually ceases centrifugally, while it ceases centripetally in the peripheral part of the root. The cylindrical region with prolonged cell division includes internal layers of the cortex including endodermis, pericycle and adjoining cells of the stele. Proximally apical meristem is reduced to isolated strands of cells adjacent to the protoxylem poles. Pericycle cells stop dividing last at a distance of approx. 9–10 mm from the initials. The number of the division cycles is limited and is specific for individual cell types. Epidermal and cortical cells divide in broad bean roots transversely approximately seven times, cells of late metaxylem approximately five times. Root apical meristem is an asynchronous cell population with a different duration of the mitotic cycle. We determined local variations in the duration of the mitotic cycle in the apical meristem of broad bean root by means of colchicine-induced polyploidy. The cells of the quiescent centre had the longest mitotic cycle after colchicine treatment. The region of the proper root adjacent to the quiescent centre was mixoploid (2n and 4n). Isolated cells with a long cycle occurred also in the cortex and in the central cylinder. Cells with a division cycle of 18h were found in the root cap, in the epidermis, in the cortex and in the central cylinder. Relatively numerous cells with the shortest division cycle, approx. 12 h, occurred farther of the quiescent centre in the epidermis, in the cortex, in the pericycle, and in adjacent layers of the stele through-out the entire meristematic region. The results derived from the analysis of the apical meristem are discussed in connection with the ontogenesis of different types of cells taking part in the primary structure of the root.     

Storage Polysaccharide in Coccidial Sporozites after Excystation and Penetration of Cells

SYNOPSIS. Eimeria acervulina, E. necatrix , and E. meleagrimitis sporozoites were examined for carbohydrates by cytochemical methods during dormancy, after excystation, and after penetration of cells. The only carbohydrate found was amylopectin, a homogeneous polymer of glucose. It was distributed in 3 regions: (a) in front of the anterior refractile globule, (b) around the nucleus, and (c) behind the posterior refractile globule. The relative amounts decreased after excystation and penetration of cells until only small amounts remained around the nucleus. The quantity of amylopectin decreased following excystation from 30.0-36.7 to 9.4-13.3 μg glucose/10⁶ oocysts. Over a 6 yr period of storage at 4 C, there was a decrease in the quantity of amylopectin in dormant sporozoites of E. acervulina from 33.3 μg glucose/10⁶ oocysts at 3 mos to 1.5 μg at 6 years. Coincidentally, 3 month- and 1 year-old oocysts of E. acervulina produced patent infections in chicks with a dosage of 5 × 10⁴ oocysts, but only a few of the oocysts that had been stored for 2 years were infective; a dosage of 2 × 10⁶ oocysts was necessary to produce a patent infection. Oocysts which had been stored 6 years did not produce a patent infection.
It was concluded that amylopectin is the energy source for excystation and subsequent penetration of cells. Small amounts of amylopectin are used during dormancy and, when the content in the sporozoite falls below a certain level, the sporozoites lack sufficient energy to infect cells.     

The Polyunsaturated Fatty Acids of Marine and Freshwater Cryptomonads1

SYNOPSIS Fatty acids were examined of photosynthetic and non-photosynthetic marine and freshwater cryptomonads cultured as photoauxotrophs, photoheterotrophs and heterotrophs at various incubation temperatures and constant light intensity. Photo-synthetic marine and freshwater forms contained octadecatrienoic, octadecatetraenoic, eicosapentaenoic and docosahexaenoic (all-cis, ω3 acids) as the major polyunsaturates, and a freshwater heterotroph contained mostly the octadecatrienoic acid. The polar lipids of a marine, photosynthetic form, Cryptomonas sp., included the usual thylakoid membrane lipids of the chloroplasts of eukaryotic, photosynthetic cells: galactosyl diglycerides, phosphatidyl glycerol and a sulfolipid. Also present were 2 choline-containing phospholipids: phosphatidyl choline and an unknown. Ninhydrin-positive and inositol-containing lipids were not detected. Octadecatetraenoic acid comprised 75% of the total fatty acids of the monogalactosyl diglyceride fraction. The phosphatidyl glycerol was acylated mostly by ω13 trans-hexadecaenoic acid and the eicosapentaenoic acid. Evolutionary relationships of cryptomonads as mirrored in lipid composition are discussed.     

Serial Passage of Trypanosoma lewisi in the Heterologous Mouse Host. I. Development in Calorically-restricted Hosts.

SYNOPSIS. Two isolates ("A" and "B") of Trypanosoma lewisi from the same rat stock source were serially transferred in calorically-restricted mice supplemented daily with normal rat serum. The "A" strain was transferred consecutively through 300 mice over a period of more than 3 years and was voluntarily discontinued. The "B" strain died out spontaneously after 43 consecutive passages in mice. The developmental histories of these 2 isolates were analyzed and compared with respect to duration of the parasitemic period, interval to the next subsequent passage in mice, day of death of each host animal, proportion of host animals that died, intensity of parasitemia in mouse tail blood, interval required for development of the observed maximal parasitemia, and duration of maximal parasitemia.
"A" appeared to have become progressively adapted to the mouse as judged by a decrease in parasitemic period with successive transfer associated with a progressive increase in trypanosome population, and declines in the interval required for development of the observed maximal parasitemia and in the duration of this maximal response. There did not appear to be any correlation of the percentage of animals that died with any other factor. The "B" strain did not appear to have adapted itself to mice as judged by the foregoing criteria.     

Radio-Tracking Timber Wolves in Ontario

Miniature collar-type transmitters originally designed by W.W. Cochran, Illinois, were adapted for use on timber wolves(Canis lupus sp.) in east-central Ontario. Wild timber wolveswere captured in steel traps, restrained with a forked stick,fitted with radio-collars and released at point of capture.Receivers were adapted for use in trucks, airplanes, and forwalking in rough bush country. Maximum ranges were 3.2 km withground and 9.6 km with aircraft receivers. A preadult femaletagged in July, 1964, and a lactating adult female tagged inJune, 1965, were tracked intermittently for 5.5 and 2.5 months,respectively. Tracking periods for six other animals of bothsexes, ranging in age from pups to adults, varied from 2 daysto 4 months. The lactating female and her associated pack regularlyreturned to three preferred "resting sites" for various periodsduring July and August. Preferred areas were well drained, semi-open,mixed conifer-hardwood stands in close proximity to swamps orbeaver ponds. The preadult female ranged in an area frequentedby a pack, but frequently remained independent of it. A preadultmale, tagged in the same region, wandered over a slightly largerarea than the female. Tagged animals were active throughoutall periods of the day or night. Activity increased slightlyduring the early evening hours. There was a slight correlationbetween weather conditions and patterns of behavior and activity.Apparently, tagged individuals were quickly accepted by othermembers of the pack.     

Consequences of differences in body mass,wing length and leg morphology for nectar-feeding birds

Nectar-feeding birds are prominent in many parts of the world, and vary with respect to body size. Despite the availability of considerable morphometric data, few concerted efforts have been made to assess the influence of attributes such as mass, wing length and leg morphology upon the speed, acceleration, mode and energetic cost of movement by birds between flowers when foraging for nectar. This review attempts to consolidate and interpret available data and highlight areas where further investigations appear warranted. Australian honeyeaters are generally larger, and American hummingbirds smaller, than Hawaiian honeycreepers and sunbirds of Africa or Asia. Sunbirds, honeyeaters and honeycreepers generally perch while extracting nectar from flowers. Hummingbirds usually hover, apparently because suitable perches close to flowers are lacking, and not because hovering increases the speed at which flowers can be visited. Honeyeaters move from one flower to another at speeds that are at least as great as those for hummingbirds. Most passerine nectarivores need to ingest more nectar per day than hummingbirds in order to maintain energy balance, some species devoting more than 60% of the day to foraging. The major consequence of reduced foraging activity by hummingbirds, which spend only 5–30% of the day in this manner, appears to be male emancipation from nest construction and care of offspring. Large nectarivores have a greater capacity to store surplus food and to fast than smaller birds, and so can take advantage of short-lived peaks in nectar abundance. Nectarivores such as honeyeaters should therefore be favoured by the rapid diurnal changes in nectar availability which are characteristic of many Australian and African habitats. Body mass also determines the likely access to rich sources of nectar through size-related interspecific dominance hierarchies. In all families, larger species tend to monopolize the most rewarding nectar supplies, forcing smaller subordinate species to use poorer, more scattered sources. Within particular species, males usually have longer wings and greater masses than females. These variations imply that the two sexes differ with regard to their foraging ecology, although few supporting data are currently available.     

FACTORS INFLUENCING THE EFFICIENCY OF INCOMPLETE BLOCK DESIGNS IN SENSORY EVALUATION EXPERIMENTS

The efficiencies of incomplete block designs were investigated by comparing two hundred and twenty eight analyses from eleven trials using hedonic scales with corresponding randomized complete block analyses. Of the ten explanatory factors examined, only the panelist, the product type, the number of samples per session and the average score of the data had an effect on the efficiency of incomplete block designs. The effect of product type was attributed to influences of produce consumed outside the trial, and the effect of the data mean reflected decreased conscientiousness with products the panelists disliked. With three and four samples per session, incomplete block designs were 31 % and 2 % more efficient, respectively, than randomized complete block designs. When five or more samples were tested, the incomplete block designs were markedly less efficient. The practical implications of all these effects on experimental design are discussed.     

The function of the intramaxillary joint in the Round Island boa, Casarea dussumieri

The bolyeriid snakes Casarea dussumieri and Bolyeria multocarinata are unique among vertebrates in possessing an intramaxillary joint that separates the maxilla into anterior and posterior segments. In contrast to previous studies, which suggest that this joint permits enhanced elevation of the anterior maxillary teeth, our films of live Casarea show that the snout and anterior maxillary teeth are actively depressed 15° 20° below rest position through bilateral retraction of the palatomaxillary arches. Patterns of bone movement in living Casarea support the hypothesis that a caudally directed force is transmitted to the snout via the medial bones of the palatomaxillary arch, suggesting functional affinities between Casarea and higher henophidians.
The intramaxillary joint, in conjunction with the curvature of the mandibles, allows the jaws of Casarea to encircle hard, cylindrical prey held transversely in the mouth. Because the Mauritian terrestrial vertebrate fauna lacks mammals and is dominated by skinks and geckos, which Casarea is known to consume, we suggest that the intramaxillary joint functions in a manner analogous to that achieved by quite different maxillary modifications in colubrid scincivores. Although the origin of the bolyeriid intramaxillary joint remains unclear, its structural refinement and evolutionary stability may be due to selection pressures arising from limited prey diversity.