Growth kinetics of a bacteriophage in continuous culture

Lytic coliphage Qbeta was grown in continuously cultured host bacteria using a cascade of stirred flow reactors. The apparatus was constructed so that the steady stream of exponentially growing bacterial cells passing through the stirred flow reactors served to prevent coevolution brought about by host-parasite interactions. Wall growth was the primary cause for deviation from ideal continuous culture conditions and is largely dependent on the surface structure of the host bacteria. Using an Escherichia coli strain deficient in adhesive type I pili expression, the desynchronization of single burst events could easily be followed over the course of four infection latency periods. Computer simulations based on a two-stage model for the Qbeta infection cycle were in perfect agreement with the experimental data. Applications of the optimized system to strategies of molecular evolution are discussed. (c) 1996 John Wiley & Sons, Inc.     

Pollen Morphology of Asarum in China

The present paper describes the pollen morphology of 27 species, 4 varieties and 1 form of Asarum from China. The pollen grains were all examined under light microscope and scanning electron microscope. The apertures of pollen grains of Asarum are variable and so distinct as to allow the identification of individual subgenera and species. The exine ornamentation is compound and may be divided into two types: reticulate or cerebelloid under verrucae. The pollen grains of Subgen. Asarum and Subgen. Heterotropa are distinguishable, which supports the taxonomical subdivision based on the gross morphology. The differences in the pollen morphology between A. caulescens Maxim. and A. sieboldii Miq. in China and in Japan are discussed and some comparisons in the pollenmorphology between several species similar in the gross morphology are also made.     

Corrections and additions to the Dumontiidae Santos-Flores &; Dodson, 2003 (Crustacea: Branchiopoda: Anomopoda), and implications for anomopod phylogeny

The presumed sixth limb of Dumontia Santos-Flores & Dodson, 2003 is shown to correspond to the inner part of the fifth limb. Comparison of the latter structure within the order increases the similarity between the Dumontiidae and the Daphniidae (plus Moinidae), but important similarities with the Radopoda remain. The relationship between a ‘‘daphniid line’’ and radopods needs further attention. Handling editor: K. Martens     

Individual feeding specialisation in shorebirds: population consequences and conservation implications

Individual feeding specialisation in shorebirds is reviewed, and the possilble mechanisms involved in such specialisations. Any specialisation can he seen as an individual strategy, and the optimum strategy for any given individual will be conditional upon its specific priorities and constraints. Some specialisations are related to social status and some to individual skills. Some are also probably frequency-dependent. However, most shorebird specialisations are constrained to a large extent by individual morphology, particularly bill morphology. For example, larger birds are able to handle larger prey, and birds with longer bills are able to feed on more deeply buried prey. Sex differences in bill length are uncommon in the Charardriidae, which are surface peckers, but are common in the Scolopacidae, which feed by probing in soft substrates. Sex differences in bill morphology are frequently associated with sex differences in feeding specialisation. There is evidence that different feeding specialisations are associated with different payoffs, in which case the probability of failing to reproduce or of dying will not be distributed equally throughout the population. I consider the population consequences of such feeding specialisations, particularly the different risks and benefits associated with different habitats or diets. I also consider the way in which individuals may differ in their response to habitat loss or change. I suggest that population models designed to predict the effect of habitat loss or change on shorebirds should have the ability to investigate the differential response of certain sections of the population, particularly different ages or sexes, that specialise in different diets or feeding methods.     

Morphology and feeding in tadpoles of Ceratophrys cranwelli (Anura: Leptodactylidae)

This paper provides data on the skeleton, musculature, buccal apparatus, buccopharyngeal cavity and diet of Ceratophrys cranwelli tadpoles, and attempts to contribute to the knowledge of relations between morphology and ecology in anuran larvae. Both in morphological characters and feeding habits, these tadpoles are very similar to other species within the genus. They possess many of the structural features usually found in predaceous tadpoles: strong, keratinized jaw sheaths and keratodonts, reduced buccal papillation, high values of in‐lever arm proportion and buccal floor area, well‐developed ceratohyals, and hypertrophied jaw muscles. Food sources consist of other tadpoles, microcrustaceans, larvae of insects, plant fragments, as well as rotifers and microalgae. As facultative carnivores, they are likely to play an important role in regulating the aquatic communities of the ephemeral ponds where they develop.     

THE MORPHOLOGY OF HYOLITHIDS AND ITS FUNCTIONAL IMPLICATIONS

Abstract:  The exceptionally preserved hyolithids Gompholites striatulus , Maxilites robustus , Maxilites snajdri and Maxilites sp. are described with particular emphasis on helen and muscle scar morphology. These two aspects of hyolithid morphology have remained controversial. In life position, each helen curved ventrally. When the operculum closed the aperture of the conch, each helen was locked at the commissure slit with its dorsal edge tilted forward. Inside the conch, it was held in the dorsal apertural plane and clear of the inner surface of the operculum. Previously unidentified muscle scars are described from both the operculum and the conch. Dorsal scars on the conch aperture held muscles directed to the operculum. Comparative study of the muscle insertion pattern indicates that hyolithids did not have serially arranged muscles and that all hyolithids may have had a common skeleto-muscular system. The arrangement of the muscle scars with respect to the helens suggests that the latter were capable of relatively complex movements and could have been used to propel the organism over the substrate. The general morphology and orientation of the helens suggests that in addition they functioned to stabilize the organism on the sea-floor.     

General biology of Ostrinia palustralis memnialis (Walker), a potential biological control agent of Rumex spp. in Korea

Ostrinia palustralis memnialis is an oligophagous insect that feeds on the species of the genus Rumex. Continuous rearing of O. palustralis memnialis was carried out from 2004 to 2005, and its general biology was studied. The preliminary host specificity test showed a promising result for O. palustralis memnialis as a potential biological control agent for Rumex spp.     

LIGHT MICROSCOPY AND ELECTRON MICROSCOPY OF NEPHROSELMIS SPINOSA SP. NOV. (PRASINOPHYCEAE,CHLOROPHYTA)1

Nephroselmis spinosa Suda sp. nov. is described based on LM and EM observations. Two strains of N. spinosa (S222 and SD959‐3) were isolated from sand samples collected from the northwest coast of western Australia. The cells were remarkably right–left flattened and appeared ellipse or bean‐shaped when viewed from their right or left side. A single, parietal, crescent chloroplast was pale green to yellowish green and contained one conspicuous eyespot in its anterior ventral edge near the base of the short flagellum. A pyrenoid with three starch plates was located at the dorsal of the chloroplast. The cells divided by transverse binary cell division, as is common in other species of this genus. This alga possessed four types of body scales, and three scale types were similar to N. olivacea Stein and N. astigmatica Inouye & Pienaar. However, the fourth and outermost scale type was distinctive because although it was a spiny stellate scale with nine spines, one of them extended about 1 μm and was slightly curved with a hook at the end. This scale morphology, an important taxonomic characteristic, has never been described for the genus Nephroselmis. The cell's morphology, pyrenoid structure, hair scales, and cell size were distinctive from previously described Nephroselmis species, and its unique scale characteristic led me to name this newly proposed species “spinosa,” meaning spiny.     

Postcanine dental form in the mustelidae and viverridae (Carnivora: Mammalia)

This study investigates whether the gross morphology of mustelid and viverrid postcanine dentitions corresponds with differences in diet. For each species, the predominant foods ingested are used to form predictions of dental form and measurements of the carnassial and molar teeth determine the extent of shearing and crushing surfaces on the postcanine teeth. Principal components analysis distinguishes species according to morphological differences in the dentition and these differences are compared with predictions of dental form based on diet. Dietarily specialized species are more likely to be correspondingly specialized in the dentition and species with varied food sources are more likely to possess dental characteristics that are generalized in function. Consumers of foods with high fracture resistance, such as vertebrate tissue and hard-surfaced invertebrates, possess specialized shearing or crushing postcanine teeth. On the other hand, species that consume foods of lesser fracture resistance, such as fruit and soft invertebrates, differ greatly in dental form and are more generalized in dental function. A few species possess postcanine dentitions that do not correspond with diet; the absence of dental-dietary correlation in these species suggests that other factors, such as phylogeny, are important in determining dental form.     

Differential mesowear in occluding upper and lower molars: opening mesowear analysis for lower molars and premolars in hypsodont horses

A new approach of reconstructing ungulate diet, the mesowear method, was recently introduced by Fortelius and Solounias ([2000] Am Mus Novitat 3301:1-36). Mesowear is based on facet development on the occlusal surfaces of the teeth. Restricting mesowear investigation to maxillary cheek teeth would allow mesowear investigation only in assemblages of large numbers of individuals and therefore would generally restrict this method to relatively few assemblages of recent and fossil ungulates. Most of the fossil, subfossil, and recent ungulate osteological assemblages that may be assigned to a single taxon have smaller numbers of individuals. This results in a demand to extend the mesowear method to further tooth positions in order to obtain stable dietary classifications of fossil taxa. The focus of this article is to test if a consistent mesowear classification is obtainable for mandibular as well as for maxillary teeth. For statistical testing, large assemblages of isolated cheek teeth of the Vallesian hipparionine horse Hippotherium primigenium and of the recent zebra Equus burchelli were employed as models. The upper tooth positions P4, M1, M2, and M3 as suggested by Kaiser and Solounias (2003) as the model for the "extended" mesowear method and the lower tooth positions P4-M3 were tested for their consistency in classification of the mesowear variables. We found a considerable shift of the mesowear signature towards the grazing edge of the mesowear continuum in lower cheek teeth. In order to adjust the signal of lower teeth to the signal of the upper teeth, a calibration factor was introduced which allowed incorporation of lower cheek teeth into the same model of mesowear investigation together with upper cheek teeth. We propose that this model is particularly suited for the reconstruction of paleodiets in hypsodont hipparionine and equine equids. We further investigated the functional relation between the mesowear profiles and the distribution of dental tissues along the course of the occlusal contact. We therefore correlated mesowear profiles with enamel distribution profiles and found the mesowear profile to be strongly controlled by the attritional environment encountered by a given apex area. The differential signal observed in cusp apex morphology between upper and lower cheek teeth was found to be more closely related to attrition by the antagonistic tooth than to the distribution of dental tissues in the tooth under consideration. The results suggest a general extension of the mesowear method of paleodiet reconstruction and a basic scenario for the evolution of anisodont dentitions.