HISTOLOGICAL CONDITIONS OF THE DIGESTIVE GLAND OF THE BLUE ABALONE (Haliotis fulgens) AND YELLOW ABALONE (Haliotis corrugata) UNINFECTED AND INFECTED BY THE RICKETTSIALES-LIKE ORGANISM Candidatus Xenohaliotis californiensis  

Jorge Cáceres-Martínez* and Montserrat Muñoz-Flores
Centro de Investigación Científica y Educación Superior de Ensenada, Km 107 Carretera Ensenada-Tijuana No. 3918, Zona Playitas, 22860. Ensenada, Baja California, México.
jcaceres@cicese.mx
 

Abalone species Haliotis sp from the West coast of North America are susceptible to an infection by the Rickettsiales-like organism Candidatus Xenohaliotis californiensis (RLO) which affect the digestive gland and produces Withering Syndrome (WS). Descriptions of the histological conditions of uninfected abalone are very few, while alterations associated to infection by RLO have been focused only in black and red abalone in the USA. To obtain data about the normal conditions of uninfected and infected blue abalone H. fulgens and yellow abalone H. corrugata, an analysis of blue abalone and yellow abalone was carried out. The digestive gland of each abalone was fixed in 10% neutral buffered formalin for conventional histology and tissues were observed by light microscopy. In uninfected abalones changes of digestive tubules suggest a constant regeneration and a junction of the duct with a tube was observed which do not represent a pathological condition. In infected abalones the intensity of infection was established by counting the relative number of inclusions formed by RLOs and these were associated with cell and tissue alterations of the digestive gland. Three degrees of infection intensity were established, degree of 1, (1 to 500 inclusions); degree of 2, (501 to 1000 inclusions) and a degree of 3 (more than 1000 inclusions). Cell and tissue alterations corresponding to an intensity of infection of a degree of 1 were light and they were comprised of hypertrophy of infected cells and compression of neighbor cells, while epithelial tissues maintained their integrity. In a degree of 2, in addition to cell hypertrophy, some areas of the epithelia show hyperplasia and dysplasia (Figure 1) to some degree.

Also, detachment of individual cells and fractions of epithelia with RLOs inclusions were observed. In a degree of 3, the alterations mentioned above were generalized and metaplasia in digestive tubules was observed; moreover, there is a loss of the digestive tubules and the spaces between tubules become occupied by connective tissue. The observed alterations indicate a gradual evolution of the disease that finally overcome animals with degree 3 of infection. This information constitutes the first comparison of uninfected epithelia in the digestive gland with infected epithelia which allows the differentiation between pathological alterations from a normal condition. Additionally, this agrees with the chronic nature of the disease and its slow evolution, suggesting that sudden massive mortalities of blue and yellow abalone from the study area can hardly be directly attribute to this disease.