Haemoproteus danilewsky Kruse, 1890
Plate 1, Figs. 1–12

Members of the genus Haemoproteus Kruse, 1890, reproduce asexually in the endothelial cells of the blood vessels of the host. The only forms found in the blood are the gametocytes, which enter erythrocytes when young and develop within these cells. As the blood thus contains only sexual stages which must be taken up by an invertebrate host before further development can be undergone, it is impossible to investigate the susceptibility of various species of host to a particular species of Haemoproteus by means of inoculation (Wenyon, 1926). Thus many species have been described as new on the basis of their being found in a new host, although it is likely to prove eventually, by analogy with Plasmodium in birds, that many of these will fall as synonyms to some of the earlier described species of the genus.

Haemoproteus danilewsky was described by Kruse (1890) from the European grey crow Corvus comix. Parasites inseparable from H. danilewsky on morphological grounds have since been described from other hosts. Coatney and West (1938) record the species from the American eastern crow Corvus branchyrhynchos, page 4 and expand the original description, which was based on material stained with methylene blue, in the light of modern staining methods.

Doré's (1920) record of Haemoproteus (danilewsky) from Turdus ericetorum is now confirmed, after an examination of one of his preparations in the Victoria College collection and of fresh material. This latter material consists of a single lightly-infected preparation (averaging 1 parasite per 10,000 erythrocytes) from each of the species Turdus ericetorum (eight specimens examined) and Turdus merula (14 specimens examined). Both parasitized birds were shot at Mangere. 10 miles from Auckland, in July, 1947, and both had light infections of Plasmodium relictum (Grassi and Feletti, 1891). H. danilewsky is already known from Turdus merula in Europe (Cardamatis, 1909).

Doré (1920) recorded (Halteridium) = Haemoproteus from both the above hosts, the birds being shot at Kimihia, some 60 miles south of Auckland, in February, 1917. Approximately 5 per cent. of the birds examined were infected, the percentage of infected cells ranging from 5 to 12 per cent. Doré tentatively identified his Haemoproteus as H. danilewsky, and subsequently recorded what he considered to be the same species of parasite from Alauda arvensis. Of birds of this species shot at Kimihia in January, 1921, 3 per cent. were parasitized, some very lightly (fewer than 12 parasites per slide). Cardamatis (1909) recorded H. danilewsky from Alauda arvensis in Greece, while a further species, Haemoproteus alaudae (Celli and San Felice, 1891), had already been described from this host in Italy. Danilewsky (1889)^*, Wasielewsky (1908)^*, and Coles (1914) all list undesignated representatives of the genus Haemoproteus from Turdus ericetorum in various parts of Europe.

The younger gametocytes of H. danilewsky (Pl. 1, Fig. 2) have no pigment. Microgametocytes in my preparations range from 10.7 to 18.0μ in total length, and from 1.8 to 2.3μ (the approximate limit of the available space between the cell membrane and nuclear membrane of the host cell) in breadth at the nucleus. The cytoplasm is lightly vacuolated, and appears whitish-blue to pale blue with Giemsa, while the diffuse nucleus, usually central in position, stains pale pink. This latter structure may be ovoid (Pl. 1, Figs. 3 and 4) or irregular (Pl. 1, Fig. 6) in shape, but is more usually elongate, extending along one side of the parasite only (Pl. 1, Fig. 5) or occupying the full width of the body (Pl. 1, Figs. 7 and 8). The pigment granules are round to ovoid in shape and irregular in size, the number present ranging from 9 to 18 and averaging 14. Macrogametocytes range in total length from 10.2 to 23.0μ, and in breadth at the nucleus from 1.5 to 2.3μ. The cytoplasm is lightly vacuolated and stains deep blue, and the centrally placed nucleus is a compact structure round to ovoid in shape and staining deep page 5 pink. The pigment granules resemble those of the microgametocytes, and range in number from 11 to 20, with an average of 16.

Both microgametocytes and macrogametocyetes are typically C-shaped when fully developed (Pl. 1, Figs. 8 and 11). A few large macrogametocytes surround the host cell nucleus and almost completely fill the available space between the cell and nuclear membranes (Pl. 1, Fig. 12). The host erythrocyte does not show marked hypertrophy. Those cells appearing longer and thinner than the others in Pl. 1 (Figs. 7 and 9) are from a part of the preparation showing longitudinal distortion of erythrocytes as a result of the smearing process. The only case of double infection observed, in which the host cell contains a developing microgametocyte and a developing macrogametocyte, is illustrated in Pl. 1, Fig. 9.

H. danilewsky from Turdus ericetorum and T. merula agrees in all essentials of its morphology with the parasite described from Corvus by Kruse (1890) and Coatney and West (1938). In overall dimensions it is slighly smaller than the parasite studied by the latter authors, whose figure of 5.28μ for the greatest width of the microgametocyte I find hard to credit unless this is intended to represent the width of a large specimen clear across the host cell and not the true width of the body between the cell and nuclear membranes of the host erythrocyte. My average granule counts of 15 and 16 for microgametocytes and macrogametocytes respectively, compare favourably with those of Coatney and West, 17 and 15. It appeared from Doré's (1920) figure of 10μ for the average length of his Haemoproteus from Turdus ericetorum, and from his rough sketches of this parasite, that his measurements must have been made in a straight line between the end limits of the body instead of following the curving centre line. This was found to be the case on a re-examination of one of Doré's slides in the Victoria College collection.

No smears were obtained from Alauda arvensis during the survey, and none of Doré's slides of the Haemoproteus from this host could be found in the small collection of his material at the Dominion Museum, Wellington. There is nothing in Doré's (1921) description to separate this parasite from H. danilewsky, but opinion must be withheld until fresh material has been obtained and compared with the descriptions of H. danilewsky and of H. alaudae.