Adult Cestodes from the Coelomic Cavity of the Teid Lizard, \u3ci\u3eCnemidophorus sexlineatus\u3c/i\u3e

In a survey of 64 Cnemidophorus sexlineatus, adult cestodes identified as Oochoristica bivitellobata with gravid proglottids were found in the coelomic cavity of two hand caught specimens at Cedar Point Biological Station, Ogallala, Nebraska, during June and July 1977. Two O. bivitellobata were found free in the coelom of a male lizard, whereas four were found in the coelom and one in the intestine of a female. No ruptures were found in the walls of the intestines of all lizards examined. In addition, 61 O. bivitellobata were found in the intestine of nine (14%) of the C. sexlineatus with an average of 5.8 (1-18) worms per infected host. This is the first report of O. bivitellobata occurring extraintestinally. Active adults found in both the coelom and intestine suggest that both of these environments contain essential nutrients and osmotic characteristics that enable the worm to mature and carry out all differentiations leading to gravid proglottids. It is possible that the invasion of the coelom is accidental; however, these worms still possess an avenue of distribution by route of a predator

Evidence of multiple mechanisms of avermectin resistance in haemonchus contortus--comparison of selection protocols

Three isolates of Haemonchus contortus selected for avermectin resistance in sheep were compared in three in vitro pharmacological tests previously shown to discriminate between field isolates of H. contortus resistant and susceptible to the avermectins. Two isolates, F7-A and IVC, were selected for avermectin resistance in the laboratory from a reference susceptible isolate using suboptimal doses of ivermectin (LD95) for 7 and 16 generations, respectively. In these isolates avermectin resistance was not associated with a decreased sensitivity to avermectin inhibition of larval development or L3 motility but was associated with an increased sensitivity to paraherquamide. The third isolate, Warren, was derived from an overwhelmingly avermectin-susceptible, mixed species field isolate in a single generation by propagating the small number of survivors of a 0.2 mg/kg ivermectin treatment (i.e. 10 x LD95). This isolate, like previously characterised avermectin-resistant H. contortus isolates derived from the field in South Africa and Australia, showed a markedly reduced sensitivity to avermectin inhibition of larval development and L3 motility, as well as an increased sensitivity to paraherquamide. These results suggest that avermectin resistance can manifest itself in different ways and that the two selection protocols used to generate the F7-A, IVC and Warren isolates have resulted in the selection of different resistance phenotypes

\u3ci\u3eDrosophila\u3c/i\u3e Muller F Elements Maintain a Distinct Set of Genomic Properties Over 40 Million Years of Evolution

The Muller F element (4.2 Mb, ~80 protein-coding genes) is an unusual autosome of Drosophila melanogaster; it is mostly heterochromatic with a low recombination rate. To investigate how these properties impact the evolution of repeats and genes, we manually improved the sequence and annotated the genes on the D. erecta, D. mojavensis, and D. grimshawi F elements and euchromatic domains from the Muller D element. We find that F elements have greater transposon density (25–50%) than euchromatic reference regions (3–11%). Among the F elements, D. grimshawi has the lowest transposon density (particularly DINE-1: 2% vs. 11–27%). F element genes have larger coding spans, more coding exons, larger introns, and lower codon bias. Comparison of the Effective Number of Codons with the Codon Adaptation Index shows that, in contrast to the other species, codon bias in D. grimshawi F element genes can be attributed primarily to selection instead of mutational biases, suggesting that density and types of transposons affect the degree of local heterochromatin formation. F element genes have lower estimated DNA melting temperatures than D element genes, potentially facilitating transcription through heterochromatin. Most F element genes (~90%) have remained on that element, but the F element has smaller syntenic blocks than genome averages (3.4–3.6 vs. 8.4–8.8 genes per block), indicating greater rates of inversion despite lower rates of recombination. Overall, the F element has maintained characteristics that are distinct from other autosomes in the Drosophila lineage, illuminating the constraints imposed by a heterochromatic milieu