Responses of the Toad Bufo bufo (L.) to Stationary Prey Stimuli1

In the present work toads (Bufo bufo) are shown to respond with prey catching to stationary dummies without previous or accompanying visual or olfactory stimulation. The subjects very rarely showed jerky head movements which, therefore, cannot be necessary for perception of stationary objects. Size preference with respect to stationary stimuli is about the same as in experiments with moving stimuli. However, differences exist between the effects of stationary and moving stimuli with respect to shape and orientation. If a square measuring 10 times 10 mm and a rectangle measuring 5 times 20 mm, oriented either horizontally or vertically, are presented within the frontal-vertical plane, the square is preferred to the rectangles, and among these the horizontal rectangle is to the vertical one. This latter preference is due to the negative effect of the vertical extension: If the vertical rectangle is reduced in length, it becomes more effective as compared to the horizontal rectangle. In the horizontal (X-Z) plane the square and the rectangle oriented parallel to the Z-axis are equally superior to the bar oriented parallel to the X-axis. At presentation of a pair of stimuli in both planes, the one in the frontal-vertical plane is always preferred to that in the horizontal plane. Correspondences and differences of these results to those from experiments with moving prey dummies are discussed.     

Miniaturization in plethodontid salamanders (Gaudata: Plethodontidae) and its consequences for the brain and visual system

In seven species of plethodontid salamanders (Desmognathus ochrophaeus, Eurycea bislineata, Plethodon cinereus, Batrachoseps attenuatus, Hydromantes italicus, Thorius narisovalis and Bolitoglossa subpalmata), absolute and relative volumes of the eye, the brain, major regions of the brain, and regions containing the major visual and visuomotor centres (i.e. thalamus, praetectum, tectum and tegmentum mesencephali), and the density and number of neurons in these regions were determined. The seven species range from moderately large to extremely small in body size and from the smallest to the largest genome sizes found in terrestrial salamanders. The following processes were observed in miniaturized salamanders with intermediate to large genome and cell sizes (Batrachoseps, Thorius) as compared to small and medium-sized salamanders with small genome and cell sizes: (1) increase in the relative size of the brain, from 3.9 to 12.4% of head volume; (2) reduction in relative size of the ventricles from 10.9 to 5.8% of brain volume; (3) increase in relative volume of those brain regions containing the major visual and visuomotor centres from 29.2 to 37% of brain volume; (4) increase in volume of grey matter relative to white matter, from 33.2 to 44.4% of midbrain volume; (5) increase in volume of tectal relative to tegmental grey matter, from 54.8 to 76.8% of total midbrain volume; (6) increase in neuron packing density in the regions containing the visual centres, from 16 to 31.5%. Because of these compensatory processes, Thorius, the smallest species with a head 1/27 and a brain 1/9 the size of that of the largest one, Hydromantes, has 1/3 as many central visual neurons (58 000 vs. 187 000). Some of these processes found in miniaturized salamanders, such as increase in tectal cell density, also occur in large salamanders with very large genome and cell sizes, viz. in Bolitoglossa (25%) and Hydromantes (29%). Thus, increase in genome size and cell size seem to pose functional problems similar to miniaturization; both cases involve an increase in cell size relative to overall organismal structure.     

Xhosa Beer Drinking Rituals: Power, Practice and Performance in the South African Rural Periphery

Xhosa Beer Drinking Rituals: Power, Practice and Performance in the South African Rural Periphery . Patrick A. McAllister. Durham, NC: Carolina Academic Press, 2006. 355 pp.     

Proteins in Intercellular Washing Fluids from Leaves of Barley (Hordeum vulgare L.)

Primary leaves of barley were detached, infiltrated with variousbuffers, and centrifuged to yield ‘intercellular washingfluid’ (IWF). Effective pH control of the IWF was obtainedonly with Tris, among all buffers tried. In these liquids, upto 30 proteins were detected by gradient gel electrophoresis.Intracellular protein from injured cells at the cut ends ofleaves was present in IWF but did not contribute significantlyto the total protein recovered in this liquid. The yield ofprotein in the IWF depended on the buffer used for infiltrationand on the concentration of the buffer. Higher concentrationsof buffer yielded more protein. In other experiments leaves were infiltrated with Tris, centrifuged,and then infiltrated a second time with this buffer containingvarious concentrations of the zwitterionic detergent CHAPS,a sulphobetaine derivative of cholate. Gel electrophoresis ofthe IWF obtained after the second centrifugation revealed protein‘bands’ not detected when the detergent had beenomitted from the infiltration buffer. The electrophoretic patternsof protein ‘bands’ in the gels differed dependingon the CHAPS concentration used for infiltration. The effect of CHAPS on plasmalemma integrity was studied byobserving infiltrated tissue with the electron microscope andby treating isolated protoplasts with the detergent. After infiltrationwith CHAPS at 0.6 mM or 2.0 mM no plasmalemma breaks were detectedin leaves, and isolated protoplasts survived exposure to CHAPSat these concentrations for 2 h without bursting. Evidently,CHAPS at these low concentrations did not destroy the integrityof the plasmalemma; the additional protein recovered in theIWF under these conditions probably originated in the cell wall.Infiltration of leaves with 6.0 mM CHAPS resulted in breaksof the plasmalemma, in tissue collapse and leaf tip necrosis.Isolated protoplasts burst within minutes after being exposedto CHAPS at this concentration. Key words: Cell wall permeability, Intercellular space, Detergent, CHAPS, Protoplasts     

Sequence Diversity and Linkage Disequilibrium within the Merozoite Surface Protein-1 (Msp-1) Locus of Plasmodium falciparum: A Longitudinal Study in Brazil

ABSTRACT. The merozoite surface protein‐1 (MSP‐1) is a major vaccine candidate for the asexual blood stage of malaria. We examined both the extent of sequence diversity in block 17, the 3′end of Msp‐1 gene coding for a 19‐kDa polypeptide (MSP‐1₁₉) putatively involved in red blood cell binding, and the patterns of linkage disequilibrium between polymorphic sites throughout the Msp‐1 locus. The parasite population sample consisted of Plasmodium falciparum isolates collected between 1985 and 1998 in Rondônia. an area of hypoendemic malaria transmission in the southwestern Brazilian Amazon. Results were summarized as follows. (I) Seven block‐17 sequence variants or haplotypes were found among 130 isolates, including two new haplotypes (novel combinations of previously reported amino acid replacements), here named Brazil‐1 (E‐TSR‐F) and Brazil‐2 (Q‐TSR‐F). (2) As previously shown for other Msp‐1 polymorphisms, frequencies of block‐17 haplotypes displayed significant temporal variation. (3) Extensive linkage disequilibrium was demonstrated between neighboring dimorphic sites within block 17, as well as between polymorphisms at the 5′and 3′ends of Msp‐1 (map distance range: 3.83–4.99 kb). (4) The overall patterns of linkage disequilibrium within Msp‐1 remained stable over a period of nearly one decade, and examples of possible ‘epidemic’ expansion of parasites carrying particular Msp‐1 alleles were found in the 1980s and 1990s. These results are discussed in relation to the population biology of P. falciparum and the development of malaria vaccines based on MSP‐1.     

THE ORGANISATION OF THE PEDAL MUSCULATURE AND ITS CONNECTION TO THE DORSOVENTRAL MUSCULATURE IN SCAPHOPODA

Scaphopoda possess one or two pairs of dorsoventral muscles.At the level of the diaphragm between the intestinal and theperianal sinus these muscles divide into a latero-dorsal portionand a medio-ventral portion. The entire medio-ventral portionand the ventral parts of the latero-dorsal portion form thepedal longitudinal musculature. This is the general patternin both orders, Dentaliida and Gadilida. In Gadilida exceptthe family Entalinidae, these muscle portions are reduced comparedto an additional pair of central pedal retractor muscles. Themusculature of the pedal wall is four-layered: outer circularmuscles, two layers of helical muscles, and inner longitudinalmuscles. Because of differences in the organization of the musculature,the foot consists of three functional units: a pedal base, amiddle piece, and an anchoring organ. In the dentalud foot,all of the longitudinal muscles are in contact with the pedalwall. In the Entalinidae, three or four pairs of central retractormuscles become free of the pedal wall at the base of the middlepiece. In all other Gadilida the two central retractors arecontinuous from the dorsoventral muscles into the anchoringorgan. The elongation of the foot is purely hydraulic in Gadilida.In Dentaliida, however, the principles of hydraulic and muscular-hydrostatsare combined. (Received 17 July 1991; accepted 28 October 1991)     

The deciduous dentition and dental replacement in the Eocene bat Palaeochiropteryx tupaiodon from Messel: The primitive condition and beginning of specialization of milk teeth among Chiroptera

The deciduous dentition and tooth replacement pattern of Palaeochiropteryx tupaiodon from the early Middle Eocene of Messel, near Frankfurt, Germany, are described. Ontogenetic states include fetuses to subadults. The posterior portion of the deciduous dentition (dP3-4) still shows the primitive eutherian condition of molarization, while the anterior part (dI-dC) was already engaged in the evolution of the highly derived condition found in living bats for clinging to the mother's fur. A styliform and sharp anterior dentition is considered a prerequisite in earliest chiropteran evolution. The greatly modified milk teeth of all living bats developed in different clades by parallel evolution under high selective pressure. The tiny and, at initial stages, poorly calcified teeth are substantiated by a newly developed microradiographic technique which is described in detail.     

HYDRAULIC BURROWING IN THE BIVALVE MYA ARENARIA LINNAEUS (MYOIDEA) AND ASSOCIATED LIGAMENTAL ADAPTATIONS

The burrowing behaviour of the bivalve Mya arenaria from tidalflats of the Dutch Wadden Sea has been observed and recorded.Compared to other bivalves, M. arenaria is a very slow burrower,its burrowing behaviour being unique among bivalves since itis based essentially on the ejection of water through the pedalgape, with little assistance by the foot, which performs onlyan anchoring function. Water ejection is specially powerfuland individual jets may last several seconds, thus constitutingan effective means of removing sand from below the animal duringdigging. This hydraulic burrowing is more effective in loosesandy than in cohesive muddy substrates. Water ejection is providedby the ability of the bivalve to rock its valves across a dorsoventralaxis. This rocking motion implies special modifications of theligamental area. The ligament is conical in appearance and runsdorso-ventrally between the two chondrophores which are placedin two planes parallel to the cardinal axis. During rockingthe whole ligament acts in torsion and the lamellar layer ofthe ligament opposes closing of the anterior part of the valves.During normal adduction of the valves the ligament acts in bending,the axis of motion being placed internally with respect to thecardinal axis. This leads to approaching of the umbones withcomplete adduction and to resorption of the left umbo. Fromthe adaptive point of view, the slow hydraulic mode of burrowingis sufficient to cope with the slow sedimentation and erosionrates of the tidal flats in which M. arenaria lives. This burrowingmode implies the existence of a tiny foot, which leaves roomfor other organs within the mantle cavity. This, together withanterior divarication of the valves permits a large volume ofwater to be ejected from the mantle cavity, but, in the caseof M. arenaria, also the existence of an enormous stomach, possiblyas an adaptation for food processing. (Received 12 April 1996; accepted 2 October 1996)