The brain of Echiniscus viridissimus Peterfi, 1956 (Heterotardigrada): a key to understanding the phylogenetic position of tardigrades and the evolution of the arthropod head

The brain of Echiniscus viridissimus , Peterfi, 1956 is composed of a series of orthogonally arranged neuropils. The most anterior neuropils are rireumbuccal, positioned dorso-and ventrolateral to the buccal tube and are associated with ganglia for sensory receptors of the mouth cone. Posterior to these are neuropils and ganglia for the (1) internal cirri and (2) cephalic papillae, external cirri, cirri A and clavae. They are joined by two pairs of vertical tracts to neuropils lateral to the buccal tube. A model based on the postcephalic organization of the tardigrade nervous system is used to propose a transformation of segmental ganglia that gives an arrangement congruent with the pattern of neuropils in the brain. The analysis suggests that the brain is derived from nervous elements of four segments with the fourth segment having contributed paired dorsal ganglia and their connecting vertical tracts to the first trunk ganglia of the ventral chain. The organization of the head of tardigrades is compared with that of other lobopods and arthropods and several possible key evolutionary innovations are offered. In addition homologous characters for the heads of tardigrades and other lobopods and arthropods are proposed and the nomenclature for the tardigrade cephalic nervous system is discussed.     

Development of the compound eyes of the water stick insect, Ranatra linearis

ABSTRACT. Relationships between estimation of predator-prey distance prior to a capture attempt and some features of the compound eye are investigated at all stages of post-embryonic development. Interommatidial angles increase gradually from the anterior and the dorsal regions to the posterior and ventral regions. Facet diameters vary only slightly over the eye surface but increase with age. New ommatidia appear around the borders of eye after each moult. The older ommatidia are pushed away from the border. From one instar to another ommatidia change their direction of view from between 10 to 30 relative to the body axes. This change in direction far exceeds the calculated changes in direction that would be optimal if ommatidia were to continue viewing the same relative directions in space. This suggests a high degree of plasticity of the underlying neuronal networks.     

Growth of Bacillus cereus in Media Containing Plant Seed Materials and Ingredients Used in Chinese Cookery

Growth and sporulation of enterotoxigenic strains of Bacillus cereus in media containing 20 different plant seed flours and meals, with and without added infusions of beef, pork, chicken and shrimp, monosodium glutamate (MSG), and soy sauce, were studied. Suspensions (2%; pH 7–1) of seed flours and meals from diverse botanical origins were found to be excellent sources of nutrients for growth. No correlations could be made between composition of seed materials and rate of cell division. Mean generation times of B. cereus cultured in soy, peanut and rice flour media supplemented with animal flesh infusions were significantly faster ( P ≤ 0.05) than those of respective controls. Monosodium glutamate (1–2%) and soy sauce (5–10%) stimulated the rate of growth of B. cereus in rice flour medium. Test flours supporting slower growth rates appeared generally to support higher rates of sporulation.     

Role of mixed‐species flocks in the use of adjacent savannas by forest birds in the central Cerrado,Brazil

Abstract: We examined the role of mixed‐species flocks for forest birds during their breeding and non‐breeding seasons in the use of savannas adjacent to forests in central Cerrado, Brazil. Transect surveys (n = 64) were conducted in eight savanna patches. Distances of birds from forests were estimated. Recorded birds were classified as members or not of mixed‐species flocks. About half of the bird species recorded in savannas were found in at least one mixed‐species flock. As distance from the forest increased, the number of species in mixed‐species flocks tended not to vary, while the number of species foraging alone or in mono‐specific groups decreased. Thus, for some forest species, participation in mixed‐species flocks allowed a greater use of more distant savannas. This tendency of being in mixed‐species flocks at greater distances from forests also can be interpreted as a reluctance to forage alone or in mono‐specific groups due to higher predation risk in less protective vegetation distant from cover. There was strong seasonal variation in the participation of bird species in mixed‐species flocks. There were significantly more species in mixed‐species flocks than out of these associations in the non‐breeding season, while differences in the breeding season were not significant. These patterns occurred, in part because mixed‐species flocks tended to be more frequent, to have more species and to forage at greater distances from forests during the early non‐breeding season than in other periods. This study suggests that the formation of mixed‐species flocks plays an important role in promoting the use of adjacent savannas by forest birds at forest/savanna boundaries in Cerrado. It also pointed out a novel advantage gained by birds with participation in mixed‐species flocks – greater use of adjacent vegetation patches.     

Aspects of the Functional Morphology of the Lophophore in Articulate Brachiopods

Histologic studies made on three species of articulate brachiopodsprovide information on the structural integrity, epithelialspecialization and other cellular aspects of the lophophore.Similarities in staining properties of granular inclusions foundin the matrix with those found in epithelial modifications ofthe brachial trough and the bases of the filaments suggest movementbetween cells within the matrix and the epithelium. The natureof the granular inclusions raises the possibility of intracellulardigestion along the lophophore of these brachiopods.     

Springs in Swimming Animals

Animals can lower the metabolic cost of swimming by using appropriatelytuned, elastic springs. Jet-powered invertebrates use springsthat lie in functional parallel to their swimming muscles topower half the locomotor cycle. The parallel geometry constrainsthe spring to be non-linearly elastic; muscle power is divertedto load the spring only when swimming muscles are not capableof producing maximal hydrodynamic thrust. The springs of jellyfishand scallops are forced at or near their resonant frequency,producing large energy savings. Measuring the contribution ofelastic energy storage to jet-powered locomotion has been facilitatedby the relatively simple geometries of invertebrate locomotorsystems. In contrast, complex musculoskeletal systems and kinematicshave complicated the study of springs in swimming vertebrates.Skins, tendons and axial skeletons of some vertebrate swimmershave appropriate mechanical properties to act as springs. Todate, though, there exist just a handful of studies that haveinvestigated the mechanical behaviors of these locomotor structuresin swimming vertebrates, and these data have yet to be integratedwith measures of swimming power. Integrating mechanical, kinematic,hydrodynamic and metabolic data are required to understand morefully the role of elastic springs in vertebrate swimming energetics.     

STRUCTURE AND FORMATION OF THE BYSSUS COMPLEX IN MYTILUS (MOLLUSCA, BIVALVIA)

A review is presented of the mechanism of byssus productionin the genus Mytilus. The pedal glands which secrete the byssusmaterial are described, followed by an account of the morphology,structure and chemistry of the byssus itself. Finally, the releaseor shedding of the byssus from the pedal tissues is discussed. (Received 10 November 1981;     

Differential staining for live and dead sperm of honey bees

ABSTRACT Seven staining techniques were modified and tested for differentially staining the live and the dead sperm cells for the honey bee (Apis mellifera L.). The eosin Y staining method was found to be a simple technique by which the live cells stain bluish purple whereas the dead cells stain bright yellow to greenish yellow. Therefore, it produces a strong contrast between the dead and live sperm cells, and appears to be the most suitable supravital staining method for evaluating the viability of honey bee sperm cells. The significance of supravital staining techniques in assessing the quality of sperm cells during cryopreserving sperm cells is discussed.