The method for egg counts is a modification of the Whitlock-Gordon technique for sheep strongyles and has been developed for low-plane infestations. It uses a three-gram faecal sample and an egg-counting slide of four 0.5-ml. cells. Satisfactory larval cultures are obtained by mixing dry, sterile cattle dung with the fresh faeces. A modified Baermann technique is used for recovering larvae from cultures.
A systematic study has been made of the species of Ixodes (Ixodidae) occurring in Australia. Nineteen species were recognized in the material available for examination, namely I. uriae, I. kohlsi, I. eudyptidis, I. pterodromae, I. simplex simplex, I. vespertilionis, I. ornithorhynchi, I. tasmani, I. hydromyidis, I. australiensis, I. victoriensis, I. fecialis, I. antechini, I. vestitus, I. holocyclus, I. confusus, I. cornuatus, I. hirsti, and I. trichosuri. Four of these, I. antechini, I. cornuatus, I, confusus, and I. trichosuri, are regarded as new species and I. simplex simplex and I. pterodromae are recorded from Australia for the first time. I. rothschildi recorded by Arthur (1953) from Western Australia was not encountered. A detailed description with appropriate figures is given for each species, including all known stages in the life cycle, together with data on host range and geographical distribution. Keys are supplied for the known males, females, nymphs, and larvae and a classified host list has been compiled.
The investigations reported in this paper were undertaken to determine whether Haemonchus contortus from sheep and H. contortus from cattle are identical or different species. The length of the spicules and the distances from the hooks to the tips of the spicules were found to be significantly greater in males from cattle. Differences were also seen in the shape and dimensions of the appendage of the genital cone in males from the two hosts, but these were not constant. A study of adult females showed at least 14 different types of vulva1 process. In the majority (88.9 per cent.) of females from sheep there was a long, linguiform process, whereas in the majority (93.5 per cent.) of females from cattle the process was short and rounded. In experimental infestations, despite a change of host, these two types maintained their characteristics in accordance with the host of origin. The progeny of single females from sheep and cattle, respectively, gave a distribution of types similar to that of natural infestations in these hosts. The infective larvae from the two hosts were found to be visually distinct. Measurements showed significant differences in total length, tail length, and in the ratio of total length to tail length, larvae from cattle having the greater measurements and smaller ratio. A change of host did not alter these difference and no association was apparent between the type of larva and the type of vulva1 process in the parent female. In an experiment to test the ability of the two populations to interbreed, mixed sheep and cattle larvae were given to the same host. The subsequent generation of larvae could be classified into sheep and cattle types without any difficulty and there was no evidence of any intermediate types. Evidence of this reluctance to interbreed was also seen under conditions favouring cross-infestation in the field, when both types of larvae maintain their respective characteristics. In accordance with the above findings and as there is also evidence of some degree of host specificity, it is concluded that the populations in sheep and cattle represent distinct species. The name Haemonchus contortus (Rud. 1803) is retained for the species defined in this paper as occurring in sheep and the name Haemonchus placei (Place 1893) is proposed for the species occurring in cattle.
A taxonomic study has been made of the species of Rhipicephalus Koch and Boophilus Curtice occurring in Australia. It was concluded that only one species of each genus is present and determination of these as R. sanguineus (Latreille) and B. microplus (Canestrini) respectively, was confirmed. A redescription is given of the male, female, nymph, and larva of each species based on Australian material, the morphological variations observed are noted, and the host range and geographical distribution are discussed.
The Editor, case was there any residual effect on sperm quality. THE AUSTRALIAN VETERINARY JOL'RNAL, Two of the three rams receiving 4.0 ml. doses re-Dear Sir, mained highly fertile. The semen of the third Being aware of the advantages of a simple ram showed a marked drop in quantity and quality method of producing teaser rams, a recent article Of the four receiving 6.0 ml. each, two by a German worker was read with interest. The remained unchanged and two exhibited a severe article, published as a n abstract i n J . Amer. vet.I n general the semen nied. Ass., 131: 288, dealt with the sterilising of picture of the affected rams was worst at the male ruminants using a sclero-therapeutic agent first test (one month after treatment), the final "1)ondren". This agent was injected into the test at eleven weeks showing some tendency to tail of the epididymus in doses ranging from 0.5-5.0 recovery. Manual palpation of the testes revealed nil.Sterilisation was achieved by the localised a n initial hardening and enlargement of the tails formation of connective tissue which completely of the epididymes in all cases, the degree of ensealed the ducts of the epididymus. largement being roughly proportional to the dose A supply of "Dondren" was kindly made avail-rate. By eleven weeks the epididymes of the 2.0 able by the manufacturers, Knoll Chemical Cornml. dose group had returned to normal size. pany, Ludwigshafen, Germany, and was injectedThe results of this investigation indicate that into eleven fertile rams i n doses ranging from up to a dose rate of 6.0 ml. per ram, Dondren" 2.0-6.0 ml. per ram. Semen was collected from is too unreliable in its action to have any value the rams by electro-ejaculation on four subsequent as a sterilisinE agent for producing teaser rams. occasions over a period of eleven weeks from the Yours, etc.. date of injection. Semen quality was estimated A. J. MORRANT, by recording the sperm density of each ejaculate, Livestock Research Officer. motility and per cent. abnormal sperm.
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