Isolation of haemolytic bacilli from field‐collected Culicoides oxystoma and Culicoides peregrinus: potential vectors of bluetongue virus in West Bengal,India

Two haemolytic bacterial strains of Bacillus pumilus (CU1A, CU1B) and one blood‐utilizing strain of Bacillus licheniformis (CU2B) were isolated from relatively low numbers of field‐collected females of Culicoides oxystoma and Culicoides peregrinus (Diptera: Ceratopogonidae). A total of 36 females, including 18 of each of C. oxystoma and C. peregrinus (consisting of one and a pool of eight blood‐engorged specimens, and one and a pool of eight non‐engorged specimens for each species), were tested. In C. oxystoma, all three strains of bacteria were isolated from the one non‐engorged, the pool of non‐engorged and the pool of blood‐engorged females tested, but CU1A and CU2B were not found in the one blood‐engorged female tested. In C. peregrinus, all three strains were present in the pool of blood‐engorged females. However, the strain CU2B was not found in the pool of non‐engorged females. In the one blood‐engorged and one non‐engorged female tested, CU1A and CU2B were detected. The bacterial strains were identified based on Gram staining, enzyme activity (amylase and protease) and alignment of the 16S rRNA partial gene sequence to that available in the National Center for Biotechnology Information (NCBI) database GenBank. The functional role and significance of these haemolytic and blood‐digesting bacteria within the genus Culicoides remain to be determined.     

Structure and Cytochemistry of the Stigma and Pollen--Pistil Interaction in Zephyranthes

The stigma in Zephyranthes candida and Z. citrina is of thedry type with a continuous cuticle—pellicle. In some papillae,however, the terminal portion of the cuticle—pellicleis lifted upwards and occasionally even disrupted by the accumulationof a secretion product below it. Both non-specific esterasesand acid phosphatases are present on the stigma surface. Thestyle is solid with a central core of transmitting tissue whichhas conspicuous intercellular spaces containing a matrix thatincludes proteins, polysaccharides and pectic substances. Zephyranthes citrina is self-compatible while Z. candida isself-incompatible. Followng incompatible pollination in Z. candida,pollen germination is normal but pollen tube growth is inhibitedat the junction of the stigma and style. Self-incompatibilitycan be overcome by bud pollination. Protein synthesis is necessaryfor pollen germination in both species. Concanavalin A bindsto the stigma surface of both species, but does not affect pollentube penetration in Z. candida. In crosses between the two speciestypical unilateral incompatibility is observed when Z. candidais used as the pistillate parent. Zephyranthes, stigma-surface enzymes, dry stigma, pollen-pistil interaction, self-incompatibility, unilateral-incompatibility