Histopathological effects of the intramolluscan stages of Zygocotyle lunata, Echinostoma trivolvis, and Ribeiroia ondatrae on Helisoma trivolvis and observations on keratin in the trematode larvae

Abstract

The histopathological effects of Zygocotyle lunata, Echinostoma trivolvis, and Ribeiroia ondatrae in naturally infected Helisoma trivolvis were studied in hematoxylin and eosin sections of infected digestive glands fixed in 10% neutral buffered formalin. The larval stages of all three trematodes damaged the snail digestive gland. Most notable histopathology included disrupted digestive gland tubules, lysed cells, compressed tubules, and edematous spaces between tubules. Considerable damage was done by rediae ingesting digestive cells. There was a detectable hemocytic response by H. trivolvis in response to the rediae and cercariae of Z. lunata. Histochemical studies on sectioned material stained with the Ayoub-Shklar method for keratin detected the presence of this protein in the rediae and cercariae of Z. lunata and R. ondatrae. The presence of keratin is probably related to its role in cercarial encystment.

Histopathological Lesions Caused by a Digenean Trematode in a Pest Apple Snail, Pomacea canaliculata, in Its Native Geographic Distribution Area

“…Metacercariae (Figure 1E) Metacercarial cysts are usually spherical and 336.6 (300-376.6) in diameter. Cyst wall: 11.3 (9)(10)(11)(12)(13).…”

“…Intramolluscan stages (sporocysts and/or rediae) proliferate asexually in the snail when it acts as the first intermediate host; they migrate through blood spaces until reaching the tissues, from which they obtain nutrients [8,9]. These intra-molluscan stages can cause histological damage and structural alterations that may include the castration of the snail host [10][11][12][13][14]. Beyond providing energy for multiplication, infecting the host's gonad allows the parasites to improve conditions for survival without causing severe damage and to complete their life cycles [15][16][17].…”

Effects of Trematode Parasites on Snails and Northern Leopard Frogs (Lithobates pipiens) in Pesticide-Exposed Mesocosm Communities

“…By the end of the experiment, snail abundance in parasite-present mesocosms was 75% lower than that in parasite-absent mesocosms and likely reduced competition for periphyton algal resources between tadpoles and snails (Holomuzki and Hemphill, 1996;Rohr and Crumrine, 2005). The reduced abundance of snails in parasite-present mesocosms is likely driven by trematode-induced castration of snails (Huffman et al, 2009) as is evident from the (Ponder and Fried, 2004), which could further contribute to the lack of juvenile snails in parasite-present mesocosms. Reduced snail numbers in parasite mesocosms did not increase tadpole size early in development, but changes in food resources may have become more important later in the larval period (Leips and Travis, 1994), and competition between tadpoles and snails may have been limited early in the experiment when snail numbers were low.…”

Impact of Schistosoma sp., Infection on Biological, Feeding, Physiological, Histological, and Genotoxicological Aspects of Biomphalaria alexandrina and Bulinus truncatus Snails

“…These snails harbor various developmental stages, such as sporocysts, rediae, and cercariae. During their multiplication and growth, they obtain nutrients from infected tissues, such as the digestive gland and gonads, leading not only to diverse histopathological changes in the snails but also to physiological disturbances [ 19 , 21 – 24 ].…”