Novel Stages in the Life Cycles of Digeneans (Platyhelminthes: Trematoda)
Transcript of Novel Stages in the Life Cycles of Digeneans (Platyhelminthes: Trematoda)
NOVEL STAGES IN LIFE CYCLES OF DIGENEANS (PLATYHELMINTHES: TREMATODA)
DAVID BRUCE CONN & DENISE A. CONN
Berry College, Mount Berry, Georgia, 30149‐5036, U.S.A.OneWorld Scientific/NASCENT, Monteagle, Tennessee, U.S.A.
2nd InternationalCongress onInvertebrateMorphology
Exploration for New Life‐cycle Stages
• There is a great need to deepen our exploration of “known” life cycles to determine whether we are missing important aspects of the parasite’s overall life strategy.
• The period between cercaria and metacercaria is poorly known for many species, especially those that actively enter the host by lumenal migration or tissue penetration.
Metacercariae in Rana kidney
Adult inwaterfowl intestine
Echinostomatids:Entering metacercariae
Metacercariae inDreissenagonad
from Conn & Conn, 1995
Echinostomatidmetacercariae in Rana pipiens(Anura) kidneys
All are in lumen
FromMartin & Conn (1990)
Echinostoma trivolvis cercaria-metacercaria migration in mucus sloughed from Helisoma trivolvis(Gastropoda). (Conn, unpublished)
Echinostoma trivolviscercaria-metacercariamigration in mucus sloughed from Helisomatrivolvis (Gastropoda). (Conn, unpublished)
Migration of schistosomula of human schistosomes, Schistosoma spp.
Schistosoma mansoni schistosomule migrating through mouse blood vessel. Based on SEM observations. (from Crabtree and Wilson, 1980).
Parasite‐induced distortion of cranium
• A. Uninfected host.
• B. Infected host.
(from Sandland and Goater, 2001, J. Parasitol.)
Ornithodiplostomumptychocheilus
Histopathology: Transverse Sections
Bipartite body plan of diplostomulumduring site establishment phase
• opisthosoma – relatively non‐motile with long tegumental microvilli consistent with function of host cell disaggregation and nutrient absorption during the period up to day 28 PI (Goater, Bray, and Conn, 2005).
• prosoma – motile as eversible proboscis with distinctive tegumental spines that are shaped in such a way that would facilitate burrowing through host tissues (Conn, Goater, and Bray, 2008).
2>Prodiplostomulum
4>Mesodiplostomulum
7>Metadiplostomulum
Days PI
(from Goater, Bray, and Conn, 2005)
Days PI2, 4>pro‐
mesodiplostomulum
7, 14>meso‐
metadiplostomulum
28, 56>metacercaria
(from Goater, Bray, and Conn, 2005)
Names of four stages of development during invasion of the fish host (Conn et al., 2008)• 1) prodiplostomulum the penetrating and early migrating diplostomulum (described by Hendrickson, 1979)
• 2) mesodiplostomulum the site‐establishment stage described in the present study
• 3) metadiplostomulum the primary stage of diplostomulum growth and host tissue alteration in the final site of prolonged infection (described by Goater, Bray, and Conn, 2005)
• 4) metacercaria the encysted stage (described by So and Wittrock, 1982)