Mira Rosenberg

Comparative community genomics in the Dead Sea: an increasingly extreme environment

Owing to the extreme salinity (∼10 times saltier than the oceans), near toxic magnesium levels (∼2.0 M Mg2+), the dominance of divalent cations, acidic pH (6.0) and high-absorbed radiation flux rates, the Dead Sea represents a unique and harsh ecosystem. Measures of microbial presence (microscopy, pigments and lipids) indicate that during rare bloom events after exceptionally rainy seasons, the microbial communities can reach high densities. However, most of the time, when the Dead Sea level is declining and halite is precipitating from the water column, it is difficult to reliably measure the presence of microorganisms and their activities. Although a number of halophilic Archaea have been previously isolated from the Dead Sea, polar lipid analyses of biomass collected during Dead Sea blooms suggested that these isolates were not the major components of the microbial community of these blooms. In this study, in an effort to characterize the perennial microbial community of the Dead Sea and compare it with bloom assemblages, we performed metagenomic analyses of concentrated biomass from hundreds of liters of brine and of microbial material from the last massive Dead Sea bloom. The difference between the two conditions was reflected in community composition and diversity, in which the bloom was different and less diverse from the residual brine population. The distributional patterns of microbial genes suggested Dead Sea community trends in mono- and divalent cation metabolisms as well as in transposable elements. This may indicate possible mechanisms and pathways enabling these microbes to survive in such a harsh environment.

Cutaneous glands in the Australian hylid Litoria caerulea (Amphibia, Hylidae)

Ultrastructure of cutaneous glands is described in the Australian hylid Litoria caerulea. Three main types of glands could be distinguished in both ventral and dorsal skin: mucous, serous or granular, and lipid glands. Both mucous, and to some extent, serous glands show a PAS-positive reaction. Some of the granular-serous glands react to lipid staining. In addition, a very large gland confined to the dorsal skin of the head reacts to lipid staining. Apparently more than one type of dermal gland is involved in lipid secretion. The subject of skin lipid secretion is discussed in relation to the ecophysiological adaptations of this xeric-inhabiting frog.

BchY-Based Degenerate Primers Target All Types of Anoxygenic Photosynthetic Bacteria in a Single PCR

ABSTRACT To detect anoxygenic bacteria containing either type 1 or type 2 photosynthetic reaction centers in a single PCR, we designed a degenerate primer set based on the bchY gene. The new primers were validated in silico using the GenBank nucleotide database as well as by PCR on pure strains and environmental DNA.

Changes in structure of ventral epidermis of Rana ridibunda during metamorphosis

SummaryThe organisation of the ventral epidermis organisation was followed throughout ontogenesis in Rana ridibunda. Epidermis of tadpoles with 2–3 limbs was organised into two layers: a stratum germinativum consisting of elongated columnar cells, and an outer stratum corneum consisting of two types of cuboid cells. Two types of cells can be distinguished; they are a light (clear) cell and a dark (dense) cell. In the 4-legged tadpoles the stratum corneum cells start to flatten and a replacement layer appeared underneath. A well-defined stratum germinativum is found and within it, epidermal glands. Moulting took place for the first time in tadpoles just before metamorphosis, and a well-organised stratum granulosum was formed still containing the two main types of epidermal glands. The flask cells appear in the juveniles for the first time, greatly increasing in numbers in the adult epidermis.

Brood-pouch structures in terrestrial isopods

Summary The brood-pouch (marsupium) of the oniscid isopod species Armadillo officinalis Dumeril 1816 (see Vandel 1955) (Armadillidae), Schizidium tiberianum Verhoeff 1923 (Armadillidiidae), and Porcellio olivieri (Audouin 1825) (Porcellionidae) was examined during their marsupial (breeding) period. In the first two species eggs, embryos and mancas are contained inside sacs which are suspended by a chord from the marsupium roof, whereas in the last species, eggs are connected singly each by a cotyledon. The thin wall of these marsupial sacs is a monolayered, flat epithelium consisting of cells rich in rough endoplasmic reticulum (RER), infoldings, mitochondria, and secretion vesicles. In its structure it is similar to that of the cotyledons. Both structures are probably active in secreting nutrients to the developing embryos. The evolutionary significance of this structure is discussed.

‘Chloride-cell’ — like mitochondria-rich cells of salamander larva gill epithelium

Two types of mitochondria-rich cells (MRC) are described ultrastructurally in the gill epithelium of salamander larva. They resemble MRC found in larval ventral epidermis. Histochemical localization of carbonic anhydrase indicated numerous positive reacting cells, most of them flask-shaped. Morphological and functional similarities to fish ‘chloride cells’ are discussed.

THE FEMALE REPRODUCTIVE SYSTEM IN SCORPIO MAURUS FUSCUS (SCORPIONES; SCORPIONIDAE)

ABSTRACT The female reproductive system in Scorpio maurus fuscus (Scorpionidae) is described. Situated on the ventral side of the ovariuterus tubes are buds and diverticulae belonging to three developmental phases: 1. Bud-like, rudimentary diverticulae that will form future generations. 2. Embryonic diverticulae that house the present generation. 3. Degenerating (= postpartum) diverticulae that contained the previous generation of juveniles just bom. The smallest buds, as well as scars of the previous postpartum diverticulae, can be identified only by scanning electron microscopy, or in microscopic sections of the ovariuterus tube.

Ovariuterus and oocyte dimensions in the female buthid scorpion, Leiurus quinquestriatus, H. & E. (Scorpiones: Buthidae), and the effect of higher temperature

Summary The ovariuterus of the scorpion Leiurus quinquestriatus consists of three longitudinal tubes with five tubes interconnecting them. Oocytes of various sizes are situated on very short pedicles on the ventral side of the ovariuterus tubes. About 50 of either large or small oocytes could be observed under the dissecting microscope. Smaller ones (less than 50 pm in diameter) could only be recognized using a scanning electron microscope or in microscopic sections. Such means also allowed the identification of scars left by shrunken pedicles following parturition. The entire ovariuterus of a female was screened under SEM, and all visible oocytes were counted. In females kept at 25°C, growth and maturation of the small oocytes were accelerated, markedly increasing the number of large oocytes. Moreover, a large number of small, yellow, degenerated oocytes was noticed in these females.

Ultrastructural and ultracytochemical studies of the gill epithelium in the larvae of Salamandra salamandra (Amphibia, Urodela)

SummaryThe morphology of Salamandra salamandra (Linné, 1758) larva gills is described by scanning and transmission electron microscopy. Three main cell types comprising the surface of the gill epithelium are described: (a) pavement cell, (b) ciliary cell and (c) mitochondria-rich cell (MRC). Two subtypes of MRC were distinguished by their ultrastructural characteristics: a fibrillar cell and a tubulovesicular cell. Kü-dependent-nitrophenyl-phosphatase (K-NPPase) activity, indicative of Naü-Kü-ATPase activity was confined to the basolateral membranes of the pavement cells. MRC were devoid of such activity. Possible relationships between structure and function of the different cell types are discussed.

LIFE HISTORY OF A SEMELPAROUS ONISCID ISOPOD, SCHIZIDIUM TIBERIANUM VERHOEFF, INHABITING THE MEDITERRANEAN REGION OF NORTHERN ISRAEL

ABSTRACT The oniscid pillbug, Schizidium tiberianum Verhoeff (Armadillidiidae), inhabits the Mediterranean region of northern Israel. Its population structure was studied in a pine forest. Since no overlap in weight (age) groups was observed, Schizidium was inferred to have an annual cycle. Males were rarely found in the natural population, and the sex ratio in the population was 1M: 6F. The sex ratio in juvenile cohorts raised in the laboratory was 1:1. This indicates a possible higher mortality among males. Indeed, the laboratory males died sooner than females. Oogenesis and subsequent vitellogenesis are short, lasting 3 months. These are reflected in increased dimensions of both ovaries and oocytes. Vitellogenesis ends when the mature ova move into the marsupium. A loss in oocytes, partly due to oosorption, was noticeable at this stage. Eggs, embryos, and mancas can be found simultaneously in the marsupium. The females die soon after having released their mancas, and the latter feed on their mothers c...