Interrelations Among Water and Energy Relations of Reptilian Eggs, Embryos, and Hatchlings

Reptilian eggs previously categorized with respect to the flexibilityof eggshells appear to fall into two groups: endohydric eggsare those that are invested, by the female parent at the timeof oviposition, with all of the water necessary to completeembryogenesis; and ectohydric eggs which need to absorb waterfrom the nest medium tocomplete embryogenesis. Eggs of the Galapagosland iguana are unusual among most lepidosaurians by havingvery permeable parchment shells, but containing a large albumen(apparently serving as a reservoir of water for the embryo).It appears that the eggs of Galapagos land iguanas can exploitan endohydric habit without the rigid, impermeable shell seenin other endohydric eggs. This ability appears to be mediatedby two factors: eggs of Galapagos land iguanas are laid in drysoils which are essentially impermeable to water, and the verylarge eggs of land iguanas have a relatively small surface areatovolume ratio which results in a relatively small exchangeof water across the eggshell. It appears too that the waterrelations of Galapagos land iguana eggs will affect the energeticsof both the contained embryo and the subsequent hatchling. Withoutadequate water, land iguana eggs will produce hatchlings thatare both smaller and possess less fat to sustain thejuvenileduring the first year of life.     

Sperm competition and the evolution of the precopulatory passive phase behaviour in Locusta migratoria migratorioides

An account is given of sperm competition in Locusta migratoria, for cases where the competing ejaculates occur either as one per oviposition cycle or as two per cycle. These situations exert quite different sperm competition effects; evolutionary reasons for this are discussed. The adaptive value of the male precopulatory passive phase behaviour is considered in relation to sexual selection and sperm competition.     

IMPORTANCE OF SENSORY FACTORS IN PROCESSED SEAFOOD: METHODS AND RESULTS1

This paper considers “importance” of sensory attributes from the consumer point of view, with emphasis on processed seafood. There are three key measures of importance. Attitudinal importance measures what consumers think to be important and refers to general opinions about the category. Sensory system importance measures how strongly different sensory inputs (e.g., appearance, aroma, taste, texture) “drive” overall liking, and show the key sensory inputs to which consumers attend. Attribute level importance measures the relation between sensory intensity and overall liking for each attribute. It shows which specific attributes drive liking, how liking varies with the specific sensory attribute, and whether (and at what sensory level) there exists an optimal level.     

Morphogenesis of Mouse Mammary Epithelium In Vivo in Response to Biomatrix Prepared from a Stimulatory Fetal Mesenchyme

Insoluble "biomatrix" of mesenchyme is a stimulator of mammary cell differentiation in vitro , but its effect in the morphogenesis is unknown. Fetal salivary mesenchyme induces intense local duct formation when implanted into adult mammary gland. We have therefore tested whether biomatrix prepared from fetal salivary mesenchyme retains this abillity to stimulate duct formation in vivo . Salivary mesenchyme isolated from mouse fetuses at 13.5–14.0 days of gestation, extracted sequentially with water and with 1 M NaCl, then digested with DNAse and RNAse was implanted into mammary glands of female mice and left for periods of 1–35 days. In approximately 40% of recipients, the local epithelium either formed cyst like structures, or else "spikes" of mammary epithelium penetrated the matrix forming a simplified ductwork inside it. Similar responses were elicited by salivary mesenchyme killed by freezing and also by biomatrix prepared from fetal mammary fat pad precursor tissue, mesenchyme of fetal lung, and fetal heart, liver, and brain. However when mesenchyme was either fixed with glutaraldehyde or sonicated and embedded in polymer blocks before implantation, no epithelial response was noted. These observations suggest that the biomatrix provides a passive scaffolding that contributes to morphogenesis of mammary ducts, is insufficient to support normal morphogenesis.     

Breeding success and the question of clutch size of Northwestern Crows Corvus caurinus

The breeding biology of two island populations of the Northwestern Crow was studied in British Columbia over a period of five years. Both populations laid an average of four eggs per clutch, of which approximately 75% hatched. More young survived to fledge on Mandate than on Mitlenatch Island. The young from nests close (< 100 m) to the beach on Mitlenatch had a higher survival rate than those from further inland. The number of eggs lost or failing to hatch was lowest in clutches of four eggs. There was a non-significant trend for chick survival to be inversely related to clutch size. The net result was that clutches of five eggs produced no more young than did clutches of four eggs. It is suggested that the major limiting factor on clutch size is food availability but the decreased hatching success of any remaining eggs once hatching has started is also a contributing factor.