Comparative Observations on Cercariae and Metacercariae of Echinostoma trivolvis and Echinoparyphium sp.

Abstract

Comparative observations were made on cercariae of Echinoparyphium sp. from Physa gyrina in Charlie's pond, Stokes County, North Carolina and cercariae of Echinostoma trivolvis from Helisoma trivolvis in Northampton County, Pennsylvania. The cercaria of Echinoparyphium sp. has 43 collar spines, lacks penetration and paraesophageal glands, and has a conical tail without fin folds. The cercaria of E. trivolvis has 37 collar spines, penetration and paraesophageal glands, a finger-like process at the tip of the tail and fin folds. The length of the cercarial body and tail of E. trivolvis was significantly greater than that of Echinoparyphium sp. Cercariae of both species encysted in Biomphalaria glabrata snails in single and concurrent infections. In concurrent infections with a single cercaria of each species, 2 encysted metacercariae were adjacent to each other in the saccular kidney of the snail at 24 hr postinfection. The diameter of encysted metacercariae of E. trivolvis was significantly greater than that of Echinoparyphium sp. Echinoparyphium sp. metacercariae excysted at 39 C in an alkaline trypsin-bile salts medium used previously to excyst E. trivolvis. The length of excysted metacercariae of E. trivolvis was significantly greater than that of Echinoparyphium sp.

Parasite predators exhibit a rapid numerical response to increased parasite abundance and reduce transmission to hosts

“…Cercariae from each snail were morphologically identified as E. trivolvis (Fried et al. ), and were genetically identified as E. trivolvis lineage “a” (see below). Cercariae used in experiments were obtained by placing first intermediate infected snails under incandescent lights for up to 3 h (=maximum age of cercariae used).…”

“…Echinostoma trivolvis cercariae for experiments were obtained from naturally infected first intermediate host H. trivolvis snails collected from a private pond in Montgomery County, Virginia. Cercariae from each snail were morphologically identified as E. trivolvis (Fried et al 1998), and were genetically identified as E. trivolvis lineage "a" (see below). Cercariae used in experiments were obtained by placing first intermediate infected snails under incandescent lights for up to 3 h (=maximum age of cercariae used).…”

Effects of environmental change on helminth infections in amphibians: exploring the emergence of Ribeiroia and Echinostoma infections in North America.

“…Both molecular and morphological data support Echinostoma and Echinoparyphium as being distinct genera (Kostadinova et al 2003) . However, because they have relatively few recognizable features to separate them, especially as metacercariae, some workers believe that misidentification may be common (Sorensen et al 1997 ;Fried et al 1998) . Echinostoma revolutum has a more prevalent distribution in Europe, Asia, and Africa but has been confirmed in the midwestern USA by Sorensen et al (1997) using morphological traits and in Connecticut by Holland et al (2007) using molecular techniques.…”

Identification problems with species in the Echinoparyphium recurvatum complex from physid snails in the USA

“…To help colleagues requesting aid with identification of these cercariae, Fried et al (1998) and Kanev et al (1998) described morphological characteristics and biological features of 43-collar-spined echinostomes in the genus Echinoparyphium from physid snails in the USA. This report is concerned with the identity of 45-collar-spined echinostomes of the Echinoparyphium recurvatum complex from physid snails in the USA.…”