Novel Stages in the Life Cycles of Digeneans (Platyhelminthes: Trematoda)

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NOVEL STAGES IN LIFE CYCLES OF DIGENEANS (PLATYHELMINTHES: TREMATODA) D AVID BRUCE CONN &DENISE A. CONN Berry College, Mount Berry, Georgia, 301495036, U.S.A. OneWorld Scientific/NASCENT, Monteagle, Tennessee, U.S.A. 2 nd International Congress on Invertebrate Morphology

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

Many details for intramolluscan stages, but not for stages in second intermediate host

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.

Echinostoma trivolvis

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 (Conn, unpublished)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 (Conn, unpublished)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).

Life cycle of a diplostomatid(from Olsen, 1972)

Parasite‐induced distortion of cranium

• A. Uninfected host.

• B. Infected host.

(from Sandland and Goater, 2001, J. Parasitol.)

Ornithodiplostomumptychocheilus

Histopathology: Transverse Sections

Diplostomatidjuvenile stages

(from Olsen, 1972)

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).

Light microscopy – Days 2 and 4 PIProdiplostomulum to Mesodiplostomulum

Light microscopy: Days 7 and 28 PIMetadiplostomulum to Metacercaria

2 Days PI:Prodiplostomulum to

early Mesodiplostomulum

4 Days PI:Mesodiplostomulum

2>Prodiplostomulum

4>Mesodiplostomulum

7>Metadiplostomulum

Days PI

(from Goater, Bray, and Conn, 2005)

14 days PIMetadiplostomulum

(from Goater, Bray, and Conn, 2005)

Days PI2, 4>pro‐

mesodiplostomulum

7, 14>meso‐

metadiplostomulum

28, 56>metacercaria

(from Goater, Bray, and Conn, 2005)

Mesodiplostomulum: 5 days PI

SEM – Day 5 PI, Mesodiplostomulum(Conn et al., 2008)

SEM of prosoma ‐ 5 days PI, Mesodiplostomulum (Conn et al., 2008)

TEM of prosoma ‐ 5 days PIMesodiplostomulum (Conn et al., 2008)

Confocal microscopy – Days 5 and 8 PIMesodiplostomulum (Conn et al., 2008)

Prosoma regression: MetadiplostomulumDay 10  >>  Day 14 (Conn et al., 2008)

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)