The Influence of Changes in Magnetic Variations and Light–Dark Cycle on Life-History Traits of Daphnia magna

Day–night cycle is the main zeitgeber (time giver) for biological circadian rhythms. Recently, it was suggested that natural diurnal geomagnetic variation may also be utilized by organisms for the synchronization of these rhythms. In this study, life-history traits in Daphnia magna were evaluated after short-term and multigenerational exposure to 16 h day/8 h night cycle, 32 h day/16 h night cycle, diurnal geomagnetic variation of 24 h, simulated magnetic variation of 48 h, and combinations of these conditions. With short-term exposure, the lighting mode substantially influenced the brood to brood period and the lifespan in daphnids. The brood to brood period, brood size, and body length of crustaceans similarly depended on the lighting mode during the multigenerational exposure. At the same time, an interaction of lighting mode and magnetic variations affected to a lesser extent brood to brood period, brood size, and newborn's body length. The influence of simulated diurnal variation on life-history traits in daphnids appeared distinctly as effects of synchronization between periods of lighting mode and magnetic variations during the multigenerational exposure. Newborn's body length significantly depended on the lighting regime when the periods of both studied zeitgebers were unsynchronized, or on the interaction of light regime with magnetic variations when the periods were synchronized. These results confirm the hypothesis that diurnal geomagnetic variation is an additional zeitgeber for biological circadian rhythms. Possible mechanisms for these observed effects are discussed. Bioelectromagnetics. © 2020 Bioelectromagnetics Society     

A Rich and Highly Endemic Decapod Crustacean Fauna from the Middle Jurassic of North-east France

Decapod crustaceans are relatively widespread in Jurassic deposits of Europe and a small number have been collected from the north-east of France. A new fossil of a macrurous decapod assigned to Eryma burgundiaca sp. nov., an erymid lobster, is described from this area and comparisons are made with closely allied species from Europe. Probable pagurid anomurous decapods are represented by Orhomalus magnificus sp. nov., Palaeopagurus acutus sp. nov. and Palaeopagurus neraudeaui sp. nov. No brachyurous decapods are presently known from the fauna. Based on the associated ammonites, the material is considered to be Callovian in age.     

Copepods of the Juréia ecological reserve,state of São Paulo,Brazil. II. The genera Hesperocyclops,Muscocyclops, and Bryocyclops (Cyclopoida,Cyclopidae)

Cyclopid copepods collected mainly in aquatic microcosms and semiterrestrial habitats in the Juréia Ecological Reserve are studied. Hesperocyclops herbsti and Bryocyclops campaneri are described as new species and their taxonomical relationships discussed. Females of Muscocyclops operculatus (Chappuis) are redescribed and the males described for the first time. An emended diagnosis for Muscocyclops is proposed.     

Functional bioassays utilizing zooplankton: a comparison

Functional zooplankton bioassays based on ingestion, reproduction and respiration are described, with methods for a new ingestion bioassay included. All bioassays are compared using three indices, including the variability of controls, the range of experimental responses, and a listing of contaminants causing inhibition/stimulation of response. The ingestion bioassay showed the greatest range of response, and was sensitive to pesticides, PCBs and heavy metals. It was also commonly characterized by a hormesis response. The reproduction bioassay showed the lowest variability, illustrated a reduced range of response, and was sensitive to nutrients and heavy metals. In one study, the respiration bioassay was sensitive only to PCBs.     

Immunocytochemical demonstration of the neurosecretory systems containing putative moult-inhibiting hormone and hyperglycemic hormone in the eyestalk of brachyuran crustaceans

Summary By use of antisera raised against purified moultinhibiting (MIH) and crustacean hyperglycemic hormone (CHH) from Carcinus maenas, complete and distinct neurosecretory pathways for both hormones were demonstrated with the PAP and immunofluorescence technique. By double staining, employing a combination of silver-enhanced immunogold labelling and PAP, both antigens could be visualized in the same section. Immunoreactive structures were studied in Carcinus maenas, Liocarcinus puber, Cancer pagurus, Uca pugilator and Maja squinado. They were only observed in the X-organ sinus gland (SG) system of the eyestalks and consisted of MIH-positive perikarya, which were dispersed among the more numerous CHH-positive perikarya of the medulla terminalis X-organ (XO). The MIH-positive neurons form branching collateral plexuses adjacent to the XO and axons that are arranged around the CHH-positive central axon bundle of the principal XO-SG tract. In the SG, MIH-positive axon profiles and terminals, clustered around hemolymph lacunae, are distributed between the more abundant CHH-positive axon profiles and terminals. Colocalisation of MIH and CHH was never observed. The gross morphology of both neurosecretory systems was similar in all species examined, however, in U. pugilator and M. squinado immunostaining for MIH was relatively faint unless higher concentrations of antiserum were used. Possible reasons for this phenomenon as well as observed moult cycle-related differences in immunostaining are discussed.     

Allergy against chironomids (non biting midges) in adult atopic patients

Summary The aim of this investigation was to evaluate the prevalence of atopic sensitization to chironomids (CHI) in patients with asthma and/or rhinitis (A/R), and to study concomitant sensitization to CHI and other allergens. Skin prick tests were performed with 3 different CHI extracts as well as with common inhalant allergens in 600 consecutive patients, 495 of which had A/R. Allergen specific IgE antibodies in the sera against CHI, shell fish and cockroaches were analyzed with Magic Lite.59 (12%) of the patients with A/R had a positive skin test with CHI. Positive skin tests with house dust mites and a storage mite were more common in CHI allergic patients than in other atopic patients. Nasal or conjunctival provocation tests, performed on 23 of the patients with positive skin test with CHI, were clearly positive in 7 cases (30%), questionable in 8 (35%) and negative in 8 cases (35%).Magic Lite, performed on sera from 50 of the patients with positive skin test against CHI, was positive with CHI in 39 cases (78%), with crayfish in 33 (66%), shrimp 20 (40%), cockroach 21 (40%) and with crab in 3 cases (6%).It is concluded that sensitization against CHI is common in patients with A/R. The clinical relevance of the positive test results is, however, unknown. Concomitant sensitization with CHI, crustaceans and cockroach is common.     

Long-term changes in the rotifer fauna after biomanipulation in Haussee (Feldberg,Germany, Mecklenburg-Vorpommern) and its relationship to the crustacean and phytoplankton communities

In Feldberg Haussee, an anthropogenic eutrophicated lake, biomanipulation was executed for restoration. To increase the biomass of crustaceans, fish grazing on zooplankton was reduced by catching small fishes and introducing pike-perch. After biomanipulation rotifer biomass from a wide range of species decreased to a small spring maximum with three dominant species. The development of food in spring and food competition between crustaceans probably controlled the rotifer development.     

Introductions, spread and colonization of new localities by fish helminth and crustacean parasites in the British Isles: a perspective and appraisal

Most parasites are disseminated by movements of infected hosts. The increasing extent and rapidity of anthropochore fish movements are causing increased concern related to awareness of their potential and known capacity for disseminating parasites. This paper puts these data in perspective by examining examples of actual and potential translocations of fish helminthes and crustaceans by anthropochore movements offish into and throughout the British Isles, and by distinguishing the processes of dissemination and invasiveness from those of colonization and establishment. An investigation of the British fish and helminth parasite fauna suggests that: (1) the range of many species is not well known, many are local in distribution and appearances beyond the range may reflect detection and patchiness, not translocation; (2) taxonomic problems in many groups hinder detection and determination of range; (3) most parasites possess the attributes of good colonizers so the natural expansion and contraction of ranges are often not noticed or recognized as such and the importance of parasite introductions by natural movements of fish or avian hosts is generally underestimated; (4) invasions are far commoner than colonizations, since conditions for establishment may be very restricted and transmission windows very narrow in time and space; (5) successful colonizations and translocations tend to be documented and attract attention whereas invasions resulting in failed colonizations are seldom observed and more seldom documented, thus biasing our perception. Given the extensive history of fish introductions to, and translocations within, the British Isles it is surprising how few fish helminths and crustaceans have invaded the country successfully (16 species: 11·4%) and how many still show restricted distributions. The majority (68·7%) of introduced helminths are associated with fish having ornamental varieties. Barriers of colonization are more effective than those to invasion and it is clear that most translocations and invasions fail. It is right to be concerned about the dangers, but it is also important to put anthropochore factors in perspective.     

The eyes of mesopelagic crustaceans

Summary In Streetsia challengeri left and right eyes have fused and become a single cylindrical photoreceptor, which occupies the basal half of a forward directed head projection. This unusual compound eye consists of approximately 2500 ommatidia, which are arranged in such a way that the animal has almost circumferential vision, but cannot look ahead or behind. It is thought that the eye operates on light-guide principles, and that the crystalline cones are the major dioptric component. Ommatidia in anterior-posterior rows show a greater overlap of visual fields than dorso-ventrally arranged ommatidia. Cone layer and retinula are separated by a 4 m thick screen-membrane, which contains tiny pigment granules of 0.15 m diameter. Cells of unknown function and origin, containing unusual multitubular organelles, are regularly found near the proximal ends of the crystalline cone threads. The twisted rhabdoms measure 18–20 m in diameter, and consist of microvilli 0.05 m in width, which belong to five retinula cells and which show no trace of disintegration. The position of interommatidial screening pigment, the density of retinula cell vesicles and inclusions, and the narrowness of the perirhabdomal space all suggest that the eyes have been light-adapted at the time of fixation for electron microscopy. The retinula cell nuclei lie on the proximal side of the heavily pigmented basement membrane. A tapetum or basal retinula cells are not developed. It is concluded that the eye optimally combines acuity with sensitivity, and that for distance estimation parallax may be important.Address until January 25th 1978: Scott Base, Ross Dependency, Antarctica (C/-Chief Post Office, Christchurch, New Zealand)     

The structure and distribution of satellite cells of cardiac muscles in decapod crustaceans

Summary The structure and distribution of satellite cells of cardiac muscles were examined in twenty-one species of animals chosen from each tribe within the order Decapoda (Arthropoda, Crustacea). The satellite cells were found in all animals observed. Most of them are morphologically identical with those described in different striated muscles of other species, but some cells have unusual features. The decapod satellite cell occasionally lies right over the region corresponding to the intercalated disc between the apposed cardiac muscle cells. The cell sends cytoplasmic processes into the adjacent muscle cells, enabling the plasma membrane to make close contact with the cleft opening of the intercalated disc, and with the myofibril at the level of the Z-line. Another characteristic feature is the presence of paired cells. Such cells are clearly separated from each other over most of the contact area by the respective plasma membranes, which are smooth in appearance and devoid of specialized regions. The significance of the presence of satellite cells in decapod cardiac muscle and its possible role are discussed and compared with those described for other species.