Morphology of the compound eye of the giant deep-sea isopod Bathynomus giganteus

The structural organization of the compound eye of the largest known isopod, Bathynomus giganteus, is described from four specimens maintained in the laboratory for as long as two months. Living specimens have not previously been available for study. The two triangular compound eyes measure about 18 mm on the dorsal edge and are separated by an interocular distance of 25 mm. They face forward and slightly downward and may have significant overlap in visual fields. Each eye contains about 3,500 ommatidia in animals of body lengths from 22.5 cm to 37.5 cm. The packing of ommatidia is not uniform across the retina, but is nearly hexagonal in the dorsal central region and nearly square in the ventral and lateral periphery. The dioptric elements in each ommatidium consist of a laminar cornea, which is flat externally and convex internally, and a bipartite crystalline cone. Sometimes seven and sometimes eight retinular cells closely appose the proximal tip of the cone and bear the microvilli of the rhabdom. Proximal to the rhabdom the retinular cells form thin pillars near the periphery of the ommatidium, and the central portion along the optic axis at this level is occupied by interstitial cells that contain massive arrays of clear vesicles thought to serve as reflective elements. The arhabdomeral segments of the retinular cells and the interstitial cells rest on a basement membrane. Within each ommatidium the basement membrane has two extensions with cylindrical cores and thin sheets of dense material and collagen-like filaments. These sheets occupy spaces between adjacent interstitial cells up to the level of the rhabdomeral segments of the retinular cells. Arrays of pigment cells with relatively weak light-screening properties separate adjacent ommatidia. Animals were fixed both in light within a week of being brought from depth into daylight, and after 2 months of maintenance in constant darkness following such daylight exposure. In both cases, microvilli of the rhabdom were severely disrupted and the retinular cytoplasm contained numerous multivesicular bodies. Exposure to natural daylight appears to cause irreversible structural damage to the photoreceptors of these animals.     

Volatiles identified from five stages of embryo development separated from a heterogeneous suspension culture of Daucus carota

Five stages of embryo development were fractionated from a mature culture of Daucus carota (Gelbe Rheinsche), using a series of metal sieves. The composition of the population of embryos in each fraction was determined quantitatively from microscopic investigations. Volatiles from samples of tissue from six stages of development were trapped on activated charcoal cartridges. These volatiles, some of which may play a significant role in the interaction of the plant with the carrot root fly (Psila rosae), were analysed using gas chromatography/mass spectroscopy. The resulting chromatograms are arranged in order of embryo development. The progressive elaboration of the volatile profile reflects the increased biosynthetic capacity of the developing embryo.Abbreviations 2,4-D (2,4-Dichlorophenoxy)acetic acid - NAA 1-Naphthaleneacetic acid     

Associations of garden birds with gradients in garden habitat and local habitat

Habitat associations of 40 bird species were analysed using data from a survey of 12892 garden sites throughout the United Kingdom between 1995 and 2002. Gradients in 20 garden habitat variables and 25 variables describing the surrounding local habitat were derived from Detrended Correspondence Analysis. The main garden axis explained 13.3% of variation in the data and described a gradient from sites containing and bounded by high levels of vegetation cover to open sites bounded by walls and fences. The main local axis explained 29.9% of variation in the data and described a gradient from rural to urban habitats. Higher probability of occurrence was detected in larger sites in 25 species and in smaller sites in four (urban-associated) species. Many species (22 out of 40) were significantly associated with the local gradient: seven species showed the highest probability of occurrence in sites within more urbanised habitats. Other species were most likely to occur in sites within rural or suburban habitats. Only five species showed a significant association with garden habitat gradient, four of these being most likely to occur in sites with highest vegetation cover. These associations were similar when controlling for garden size and for food provision in gardens. The results imply that the likelihood of many species occurring in gardens is dependent on the surrounding local habitat rather than the garden habitat. However, survey participants were likely to have "bird-friendly" gardens which may have reduced the variation in garden habitat across the sample. An assessment of the representativeness of survey sites is needed to further understand habitat associations of garden birds.