Observations on the ephippia of certain maerothricid cladocerans

Ephippia of four maerothricid cladocerans are described, that of Opbryoxus gracilis (perhaps the most primitive anomopod ephippium) for the first time. All are attached to substrata, but each in a different way, in a manner that must inhibit rather than encourage dispersal. Notwithstanding the drought-resistant properties of the eggs of at least two of these species, it has evidently been a more successful evolutionary stratagem to ensure continuity of an already established colony than to face the hazards of dispersal in the dried condition. Although proven only for Streblocerus serricaudatus it is almost certain that drying of the resting eggs is not obligatory before hatching for any of these species. Hatching of the resting eggs of S. serricaudatus and Acantholeberis curvirostris is described.     

STUDIES ON THE MORPHOLOGY AND CROSSBREEDING ABILITY OF TWO POPULATIONS OF BULINUS GLOBOSUS FROM NORTHERN NIGERIA

The general appearance and dimensions of the shells and copulatoryorgans of two populations of Bulinus globosus (Lake Chad andNgala) from the area of the South Chad Irrigation Project, Nigeria,were compared using samples bred in laboratory cultures. The body tissues of Lake Chad snails were darker than thoseof individuals from the Ngala sample, and lacked the distinctblack patches seen on the mantle of the latter. Significant differences in the occurrence of copulatory organeversion on relaxation in menthol were observed between thesamples. Both the total length and relative dimensions of preputiumand penis sheath also differed significantly between the LakeChad and Ngala populations. Crossbreeding experiments using enzymes (GPI and HBDH) as geneticmarkers showed that cross-fertilisation between Lake Chad andNgala snails is possible. The observed physical differencessprobably resulting from the ecological separation of these twopopulations have not resulted in their reproductive isolation. ^*Present address: Department of Zoology, Oregon State University,Coroallis, Oregon 97331, USA. (Received 14 October 1986;     

The feeding mechanisms of Lynceus (Crustacea: Branchiopoda: Laevicaudata), with special reference to L. simiaefacies Harding

Although generally assumed to be filter feeders, branchiopod crustaceans of the laevicaudatan genus Lynceus O.F. Müller, 1776 possess no filters and do not collect food by filtration. Investigated species of these bivalved, multi‐limbed animals have basically benthic habits and collect particulate food, mostly detritus, by scraping or sweeping it from surfaces with suitably armed trunk limbs. L. simiaefacies Harding, 1941, known only from a desert pool in Yemen, has trunk limbs that are armed with particularly robust scrapers and much of the complexity of these limbs and their armature is related to the collection and manipulation of detrital food by mechanical means. Material collected by scrapers borne distally on the more anterior limbs – although the anteriormost is very lightly armed – is swept posteriorly and dorsally, assisted by the armature of the more proximal endites, towards the posterior end of a deep food groove, whence it is passed anteriorly by the substantial gnathobases of the trunk limbs. The necessary movements of the trunk limbs are facilitated by a system of intrinsic muscles that enable individual endites to be moved independently – a remarkable specialized feature of a phyllopodial appendage. Before it enters the food groove, collected material is at all times confined to a narrow median chamber, or cage, between the two sets of opposed trunk limbs that extends over most of the anterior limbs – which are the largest. Each cage wall serves as a screen, covering the limbs of its side and is made up of long setose screening setae that superficially resemble coarse filter setae, and arise from the more proximal endites of most of the anterior trunk limbs. The screens prevent collected material from entering the inter‐limb spaces into which water flows during each cycle of trunk limb movements, where its presence would be disastrous. They do not interfere with the spines of the proximal endites that can protrude between them. The screens do not extend to the extreme posterior end of the trunk limb series where a complex and dense array of specialized spines of the short posterior trunk limbs completes the task of sweeping food material into the food groove. Material is passed anteriorly along the food groove by the trunk limb gnathobases and the small but robustly armed maxillules to the mandibles. Although constructed on the basic, boat‐like, branchiopod plan, in contrast to those of most particle‐feeding branchiopods whose mandibles have a broad masticatory surface, those of Lynceus have a masticatory surface that is narrow and elongate in the antero‐posterior plane. Interestingly, while the number of ‘teeth’ into which this surface is elaborated is few in most species of the genus, inviting comparison with a similar attribute in the Notostraca, L. simiaefacies has more numerous, smaller teeth. Although following the branchiopod plan, the mandibular musculature appears to have its own distinctive features but remains to be investigated in properly fixed material. At its distal extremity the oesophagus is differentiated into a small but complex gizzard, of which there appears to be no parallel in any other branchiopod order. This is described for the first time. Although provided with natatory antennae, species of Lynceus also employ their trunk limbs as organs of propulsion. In L. gracilicornis (Packard, 1871) the carapace valves can gape to more than 90°, which allows the trunk limbs to make a contribution to propulsion in a manner akin to that of the Anostraca. In this respect the Laevicaudata appears to stand in contrast to the Spinicaudata, in most species of which the trunk limbs contribute little or nothing to locomotion. More information is needed on representatives of both orders, which have received little study as living animals. Brief comments are made on the systematic position of the Laevicaudata, about which much remains to be resolved. © 2009 The Natural History Museum. Journal compilation © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 155 , 513–541.     

Development, Characterization, and Use of Monoclonal and Polyclonal Antibodies against the Myxosporean, Ceratomyxa shasta

Both monoclonal and polyclonal antisera were produced against Ceratomyxa shasta. Ascites containing trophozoites of the parasite was collected from infected fish and used as antigen for immunization of mice. The resulting monoclonal antibodies reacted specifically with trophozoite and sporoblast stages but did not react with C. shasta spores by either indirect fluorescent antibody techniques or in Western blots. This indicates that some C. shasta antigens are specific to certain life stages of the parasite. Polyclonal antiserum was produced in a rabbit by injecting a spore protein electro-eluted from an SDS-polyacrylamide gel. This antiserum reacted with both trophozoites and spores by indirect fluorescent antibody techniques and in Western blots. All antisera were tested for cross-reactivity to trout white blood cells, a contaminant of the ascites, and to other myxosporea. Two monoclonal antibodies reacted with white blood cells and myxosporea of the genera Sphaerospora and Myxobilatus. One hybridoma produced antibodies of high specificity for C. shasta pre-spore stages. This is the first report of a monoclonal antibody produced against a myxosporean parasite.     

The antioxidant effects of thylakoid Vitamin E (α-tocopherol)

Vitamin E (α-tocopherol) is essential for the prevention of photo-oxidative deterioration of biomembranes. The occurrence, relative biological activity and distribution of tocopherols in photosynthetic membranes is considered together with the possible biochemical and biophysical mechanisms by which tocopherols confer protection upon illuminated membranes. The common protective effects of Vitamin E in photo-synthetic membranes and in medically important light-induced diseases and conditions of the skin and eye in animal cell membranes are discussed. The importance of the Vitamin E-Vitamin C thylakoid antioxidant system is also examined, in terms of susceptibility to photo-oxidative damage under stress conditions including chilling, ageing and senescence, drought, atmospheric pollutants, herbicides and photosensitizing fungal toxins.     

Development of a Selective Medium for the Isolation of Clostridium sporogenes and Related Organisms

An attempt was made to develop a selective isolation medium for Clostridium sporogenes and related organisms based on the ability of these organisms to obtain their energy for growth by means of coupled oxidation-reduction reactions between appropriate pairs of amino acids (Stickland reaction). Using a semi-defined basal medium containing various combinations of amino acids, it was found that Cl. sporogenes utilized a wider range of amino acid pairs than strains of five other species of clostridia known to carry out a Stickland-type fermentation.
With alanine and proline as the principal energy sources and the medium solidified with agar. it was shown that reference strains of Cl. sporogenes and proteolytic Cl. botulinum types A, B and F could be recovered almost quantitatively, with or without prior heating at 80 °C for 10 min. By contrast, growth of test strains of Streptococcus faecalis, Strep. faecium , 'saccharolytic' Cl. botulinum types B, C, D, E and F and 'proteolytic' strains of types C and D was suppressed on this medium, as were strains of 26 other species of clostridia.
Addition of 50 μg/ml of polymyxin to the agar medium had no detectable effect on the recovery of Cl. sporogenes or Cl. botulinum. When samples of soil and mud were plated on the antibiotic-containing medium, 63.1% of 225 isolates thus obtained were identified as Cl. sporogenes/botulinum.