Chapter 27 

 Subclass 2 Acnidosporidia Cepede 



THE sporozoa which are grouped here are mostly incompletely 

 known, although some of them are widely distributed. They pro- 

 duce spores which are simple in structure, being composed of a spore 

 membrane and a sporoplasm. 



Order 1 Haplosporidia Caullery and Mesnil 



This order includes those sporozoans which produce simple 

 spores. In some species the spores may resemble superficially those 

 of Microsporidia, but do not possess any polar filament. In this re- 

 gard, Haplosporidia may be considered a more primitive group than 

 Cnidosporidia (p. 643). 



The Haplosporidia are cytozoic, histozoic, or coelozoic parasites 

 of invertebrates and lower vertebrates. The spore is spherical or 

 ellipsoidal in form and covered by a resistant membrane which may 

 possess ridges or may be prolonged into a more or less long tail-like 

 projection. In a few species the spore membrane possesses a lid 

 which, when opened, will enable the sporoplasm to emerge as an 

 amoebula. The sporoplasm is uninucleate and fills the intrasporal 

 cavity. 



The development of a haplosporidian, Ichthyosporidium gigan- 

 teum, as worked out by Swarczewsky, is as follows (Fig. 271): The 

 spores germinate in the alimentary canal of the host fish and the 

 emerged amoebulae make their way to the connective tissue of vari- 

 ous organs (a). These amoebulae grow and their nuclei multiply in 

 number, thus forming plasmodia. The plasmodia divide into smaller 

 bodies, while the nuclei continue to divide (b-e). Presently the nuclei 

 become paired (/, g) and the nuclear membranes disappear (Ji). The 

 plasmodia now break up into numerous small bodies, each of which 

 contains one set of the paired nuclei (i, j). This is the sporont (j) 

 which develops into 2 spores by further differentiation (k-o). 



Genus Haplosporidium Caullery and Mesnil. After growing into 

 a large form, Plasmodium divides into uninucleate bodies, each of 

 which develops into a spore; spore truncate with a lid at one end; 

 envelope sometimes prolonged into processes; in aquatic annelids 

 and molluscs. 



H. chitonis (Lankester) (Fig. 272, a, b). In liver and connective 

 tissue of Craspidochilus cinereus; spores oval, 10m by 6m; envelope 

 with 2 prolonged projections. 



635 



