Development of the hyaline layer around the planktonic embryos and larvae of the asteroid Patiriella calcar and the presence of associated bacteria

Summary

The hyaline layer (HL) around the embryos and larvae of Patiriella calcar is examined by transmission electron microscopy. P. calcar hatches at the gastrula stage and develops through a lecithotrophic planktonic brachiolaria. The hyaline layer of unhatched P. calcar is poorly developed and is comprised of wispy fibrils scattered among the epithelial microvilli. Fibrils are also occasionally seen associated with the inner surface of the fertilization envelope. By the hatched gastrula stage, the hyaline layer is organized into three strata: the intervillous layer, the supporting layer and the coarse outer meshwork layer. Seven-day-old brachiolaria also have a hyaline layer comprised of three strata. In these larvae the supporting layer elevates away from the epithelial surface due to the tuft-like organization of the underlying microvilli. This results in the formation of local outpockets giving the surface of the HL a lobed appearance. Bacteria are occassionally seen in the intervillous layer, particularly in association with the outpockets. These bacteria are phagocytosed by the epithelial cells and, in larvae that have bacteria, may play an augmentive role in larval nutrition. The structure of the hyaline layer of P. calcar is compared with that of the hyaline layer of other Patiriella species to determine if it is more similar to the external coats around its planktonic (P. regularis) or benthic (P. exigua) developing congeners. The comparison shows that the hyaline layer of P. calcar is virtually identical to that of P. regularis, a similarity that may reflect the pelagic life histories of these species.     

Inoculation and acquisition of maize bushy stunt mycoplasma by its leafhopper vector Dalbulus maidis

Maize bushy stunt mycoplasma (MBSM), a mycoplasma-like organism, is transmitted in a persistent manner by the corn leafhopper, Dalbulus maidis, to maize (Zea mays). The influence of the duration of acquisition access and inoculation access periods on the transmission of MBSM by D. maidis was investigated. The proportion of plants infected by D. maidis increased significantly from 0 to 0.51 as the inoculation access time to a plant increased from 10 min to 72 h (X²= 101.5, P < 0.001). Likewise, the proportion of insects acquiring MBSM from infected plants increased from 0 to 0.19 as the acquisition access time to the source plant increased from 10 min to 72 h (X²= 53.2, P < 0.001). The data were fitted to a loglinear regression model. No significant association was found between the sex of the insects and vector ability.     

The spider fauna of the Aladjagiola wetland complex (Nestos Delta,north‐east Greece): a reflection of a unique zoogeographical transition zone in Europe

In order to increase our arachnological knowledge of Greece, and in particular north‐east Greece, an investigation of the arachnofauna of the Aladjagiola wetland complex was conducted from April to July 2008. The study area is part of the Nestos Delta in north‐east Greece, and comprises an area of approximately 20 km². Spiders were collected from 28 sites using pitfall traps. In all, 6694 specimens were sampled, including 206 species from 31 families. Altogether, 30 and 74 species were new to the districts of Greece and Macedonia, respectively. A number of faunistically interesting species were recorded during the study: Brachythele denieri (Simon, 1916), Camillina metellus (Roewer, 1928), Zelotes cingarus (O.P.‐Cambridge, 1874), Zodarion blagoevi Bosmans, 2009, Zodarion epirense Brignoli, 1984, Zodarion hauseri Brignoli, 1985, and Zodarion pirini Drensky, 1921, are Balkan endemics; Tegenaria angustipalpis Levy, 1996 and Titanoeca turkmenia Wunderlich, 1995 were newly discovered in Europe. Widespread elements represented the largest share of the species inventory, although chorological analysis indicated that the study area, as well as the whole north‐eastern part of Greece, is a reflection of a transition zone from the European fauna towards the Mediterranean and eastern (or Ponto–Anatolian) elements. Taken in combination, these affect the local fauna. The Balkan endemics, although small in number of species, further underline the unique identity of the area. Based on comparisons with data sets from the country's southernmost island, i.e. Crete, Greece can be regarded as a zoogeographical gradient. Hereby, Aladjagiola represents the northern edge, with European and Anatolian elements dominating the species inventory, and Crete represents the southern edge, with widespread but also endemic Mediterranean and eastern elements creating a more local and insular zoogeographical character. In conclusion, Greece cannot be viewed as a uniform zoogeographical unit, but rather as a mosaic of various regional zoogeographical patterns. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 217–233.     

MICROTUBULES IN THE SHELL OF THE INVASIVE BIVALVE CORBICULA FLUMINEA (MULLER, 1774) (BIVALVIA: HETERODONTA)

Using scanning electron and histological techniques on specimensof the bivalve Corbicula fluminea a new relationship betweenmantle, shell and periostracum has been observed, apparentlyfor the first time. Here we demonstrate that several extensionsof the mantle epithelium pierce the shell to join the innerlayer of the two-layered periostracum. The mantle extensionsare confirmed as unicellular processes. We suggest that theycould serve the animal in the mobilization of calcium from theshell for buffering the extrapalhal fluid under anaerobic conditions,when organic acids accumulate or when an extra contributionof Ca²⁺ is required (Received 5 January 1994; accepted 30 March 1994)     

Comparison of TRPs From Murine and Human Malignant Melanocytes

Most of our knowledge of the mammalian tyrosinase related protein (TRP) activities is derived from studies using murine melanoma models, such as B16 or Cloudman S-91 melanocytes. Owing to the high degree of homology between the murine and human enzymes, it has been assumed that their kinetic behavior could be similar. However, the protein sequences at the metal binding sites of the murine and human enzymes show some differences of possible functional relevance. These differences are more significant in the metal-A site than in the metal-B site. By using three human melanoma cell lines (HBL, SCL, and BEU), we have studied the catalytic abilities of the human melanogenic enzymes in comparison to those obtained for the counterpart murine enzymes isolated from B16 melanoma. We have found that TRP2 extracted from all cell lines show dopachrome tautomerase activity, although the activity levels in human malignant melanocytes are much lower than in mouse cells. Reconstitution experiments of the human enzyme indicate that TRP2 has Zn at its metal binding-sites. Although mouse tyrosinase does not show DHICA oxidase activity, and this step of the melanogenesis pathway is specifically catalyzed by mouse TRP1, the human enzyme seems to recognize carboxylated indoles. Thus, human tyrosinase could display some residual DHICA oxidase activity, and the function of human TRP1 could differ from that of the murine protein. Attempts to clarify the nature of the metal cofactor in TRP1 were unsuccessful. The enzyme contains mostly Fe and Cu, but the reconstitution of the enzymatic activity from the apoprotein with these ions was not possible.     

Estrogen and Androgen Target Cells in the Brain of Fishes, Reptiles and Birds: Phylogeny and Ontogeny

The cellular and subcellular distribution of 3H estradiol inthe forebrain of goldfish, platyfish, lizard, turtle, and ringdove was studied by thaw-mount autoradiography. The topographicdistribution of estrogen target cells in these non-mammalianspecies corresponds to the general pattern established earlierin our laboratory for mammals. In all non-mammalians studied,accumulations of estrogen target cells exist in preoptic-septal,central hypothalamic and thalamic areas. While allocorticaldistribution of estrogen target cells is present in the avianand reptilian species, it appears to be absent in the teleosts.Differences in brain evolution probably account for it. Thisphylogenetically delayed acquisition of telencephalic steroidtarget sites seems paralleled by an ontogenetic delay, as observedin the chick embryo: early embryonic appearance of estrogenuptake (receptors) in preoptic and central hypothalamic regionsand late appearance of estrogen receptors in the amygdala. Androgendistribution in the forebrain of the dove and lizard overlapswith the estrogen distribution with some exceptions.     

Amplification of a New Region of DNA in an Unselected Laboratory Stock of L. tarentolae: The T Region

A new DNA amplification is described from an isolate of the lizard parasite Leishmania tarentolae . This DNA is present in up to 50 copies in the Trager line of this species and present but not amplified in all other lines tested. This amplification has been named the T amplification (for Tarentolae/Trager). Restriction enzyme digestion and electrophoresis of total DNA reveal amplified fragments totalling 19 kb following staining with ethidium bromide, a finding confirmed by the use of specific hybridization probes. Much of the amplified T DNA occurs as extra-chromosomal circular molecules. No cross-hybridization was observed between the T region and other amplified DNA of Leishmania , or the maxicircle of L. tarentolae , nor was resistance to methotrexate, chloroquine or primaquine detected in the T-amplified line. Combined with our previous results showing H region amplification in 2 other unselected lab stocks, these data demonstrate the prevalence of apparently spontaneous gene amplifications in L. tarentolae .