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Haemogregarina salariasi n.sp.
(Text-figure 1, Figs. 37–39)

This haemogregarine is described from an 8 cm. example of the blenny Salarias periophthalmus Val., collected from a coral pool at Makuluva Island on 11th June, 1949. Twelve other examples of this species, also 17 of Salarias fasciatus (Bloch) captured at the same place and time, were negative for haematozoa. The single infection recorded was an exceedingly light one, only three parasitized erythrocytes being present in the smear.

One of the infected erythrocytes contains a single haemogregarine, unfortunately damaged during the preparation of the smear. This parasite measures 8.1μ by 2.1μ in its greatest dimensions. It has a subcentral nucleus staining deep red, and light blue staining cytoplasm. There is no indication of the presence of a capsule. In both other cases (Figs. 38 and 39) two haemogregarines occupy each host cell. Those seen in Fig. 38 are recent products of schizogony. Longitudinal cytoplasmic cleavage has taken place, but the adjacent sides of the haemogregarines are still in contact except for a short distance at one end. The parasites are crescentic in shape, tapering to a point at either extremity, and at their greatest dimensions they measure 8.3μ by 1.0μ and 9.9μ by 1.3μ respectively. In both cases the cytoplasm is hyaline, and the nuclear chromatin is diffuse and scattered. The host cell is not distorted, and falls within the size range of normal erythrocytes (Fig. 37). Its nucleus is only very slightly displaced in a lateral direction.

The erythrocyte seen in Fig. 39 owes its distortion to the pressure of adjacent blood cells in the smear. It holds two gametocytes, which are enclosed in a reniform clear space in the host cell cytoplasm. This space possibly indicates the presence of a capsule, although a capsular wall is not in evidence. Each gametocyte is curved in shape, narrowed towards the end near which the nucleus is situated, and swollen towards the other. The cytoplasm, which is hyaline towards the swollen end of the body, is stained light blue on the proximal side of the nucleus. This latter structure is stained deep red, with blackish-red aggregations of chromatin. At the bluntly rounded narrow end of one parasite there are three intensely stained granules of extranuclear chromatin, while at that of the other there are two such granules. The gametocytes measure 7.7μ by 1.0μ and 8.3μ by 1.0μ respectively, at their greatest dimensions. Their nuclei measure 2.3μ by 0.8μ and 2.3μ by 0.6μ respectively, in each case occupying the full width of the body.

The haemogregarine of Salarias periophthalmus is systematically close to members of its genus already known from blennies in other parts of the world. It resembles Haemogregarina bigemina, described from the European Blennius pholis and B. gattorugine by Laveran and Mesnil (1901), in its general morphology and twinning habit, although the size of the mature gametocytes of H. bigemina (12μ by 1.5μ to 2.0μ) is greater than that of the equivalent stages of the haemogregarine under consideration. The study of further material may, of course, disclose a greater size range for the gametocytes of the latter parasite. Kohl-Yakimoff and Yakimoff (1915) described Haemogregarina londoni from Blennius trigloides at Naples. These authors figured two intraerythrocytic gametocytes of H. londoni which were surrounded by a cyst-like structure (their Plate IV, Fig. 7). Such a structure has not been recorded for H. bigemina, although, as mentioned above, there is a possibility that the gametocytes of the haemogregarine of Salarias periophthalmus may be encapsuled. This parasite, being known from so little material, may ultimately page 4 prove to be identical with one of the previously described blenny haemogregarines. The possibility is enhanced by the fact that a variety of H. bigemina recently recorded from four New Zealand species of blennies (an account of this parasite being in course of preparation) shows considerable diversity in gametocyte morphology and size. There is, indeed, a possibility that all blenny haemogregarines may eventually prove to be merely races or host-induced morphological variants of H. bigemina. Nevertheless, in the absence of copious material enabling full and satisfactory comparisons to be made with previously described species, it is considered the wisest course to assign specific rank, temporary though this may be, to haemogregarines from new blenny hosts in new localities. For this reason, the parasite of Salarias periophthalmus discussed above is designated Haemogregarina salariasi n.sp.

The type slide has been deposited in the collection of the Dominion Museum, Wellington (catalogue number Z16).