SENSILLAE OF THE CERCARIAE

SENSILLAE OF THE CERCARIAE

OF ECHINOSTOMA TRIVOLVIS (CORT, 1 9 1 4 ) (TREMATODA: ECHINOSTOMATIDAE)

DIMITROV V.*, KANEV I.*, FRIED B.** & RADEV V.*

S u m m a r y :

The precise location of sensillae of the cercaria of E. trivolvis is described. This study allows one to distinguish E. trivolvis from E. revolutum, E. echinatum, E. caproni, E.jurini and E. parvocirrus on the basis of the arrangement of the argentophilic structures of their cercariae. The arrangement of the tegumentary receptors of the circle AI dorsal (AID) complex allows for clear differentiation of the cercariae of E. trivolvis from the cercariae of all trematode species studied by silver nitrate staining in the genera

Ecbinoparyphium, Hypoderaeum, Moliniella, and Paryphostomum in the family Echinostomatidae.

K E Y W O R D S : Echinostoma trivolvis, cercariae, tegumentary papillae.

Résumé : PAPILLES ARGYROPHILES TÉGUMENTAIRES DE CERCAIRES DE ECHINOSTOMA TRIVOLVIS (CORT, 1914) (TREMATODA :

ECHINOSTOMATIDAE)

La localisation précise des papilles tégumentaires de cercaires d'E. trivolvis est décrite. Les études permettent de distinguer E. trivolvis de E. revolutum, E. echinatum, E. caproni, E. jurini et E. parvocirrus selon la disposition des papilles sensorielles de leurs cercaires. La disposition des récepteurs tégumentaires du complex AID permet une claire différenciation des cercaires d'E. trivolvis de celles de toutes les espèces de trématodes du genre

Echinoparyphium, Hypoderaeum, Moliniella et Paryphostomum de la famille des Echinostomatidae, étudiées par coloration au nitrate d'argent.

MOTS CLES : Echinostoma trivolvis, cercaires, papilles tégumentaires.

INTRODUCTION

T

h e identity and the life cycle o f Echinostoma trivolvis (Cort, 1 9 1 4 ) Kanev, 1 9 8 5 w e r e des- cribed and discussed by K a n e v ( 1 9 8 5 ) , Huff- m a n n & Fried ( 1 9 9 0 ) and K a n e v et al. ( 1 9 9 5 ) . T e g u - mentary papillae o f E. trivolvis cercariae w e r e not studied in detail and described according to the inter- nationally r e c o g n i s e d n o m e n c l a t u r e o f Richard ( 1 9 7 1 ) or that o f Bayssade-Dufour et al. ( 1 9 8 9 ) . Preliminary data for a total n u m b e r o f 2 5 3 papillae w e r e reported b y Fried & Fujino ( 1 9 8 7 ) . In that study, the organism w a s referred to as E. revolutum (Froelich, 1 8 0 2 ) . This p a p e r presents a detailed study o n the argento- philic structures o f E. trivolvis cercariae described in a c c o r d with internationally a c c e p t e d nomenclature.

* Institute of Experimental Pathology and Parasitology, Bulgarian Aca- demy of Sciences, BL. 25, Sofia, 1113.

** Department of Biology, Lafayette College, Easton, Pennsylvania, USA.

Correspondence: Prof. Dr. Sc. Ivan Kanev, Institute of Experimental Pathology and Parasitology, Bulgarian Academy of Sciences, Bl. 25, Sofia 1113, Bulgaria. Tel: (003592) 713 23 26 - Fax: (003592) 71 01 07 - e-mail: kanevi@bgearn.acad.bg - ikanev@bgearn.bitnet.

MATERIALS AND METHODS

E trivolvis cercariae were obtained from naturally infected snails Helisoma trivolvis (Say) collected from N o r t h a m p t o n C o u n t r y , P e n n s y l v a n i a (USA). O v e r 100 cercariae w e r e impregnated by the m e t h o d o f C o m b e s et al. ( 1 9 7 6 ) . T h e arrangement o f the papillae was described according to the n o m e n - clature o f Bayssade-Dufour et al. ( 1 9 8 9 ) . Examination, drawings and pictures w e r e m a d e with an « O p t o n » m i c r o s c o p e supplied with c a m e r a lucida, videomat and automatic p h o t o c a m e r a .

RESULTS

T h e arrangement o f the tegumentary papillae o f E. tri- volvis cercariae is as follows:

1. Cephalic region (Figs. 1A, 2A) CI = lCI1, 3 C I3

CII = lCII1, 2CII², 4-7CII,, about 7-12CII,

CIII = 1CIII,, 2-3CIII,,

4-5CIII

³

,

5-7CIII⁴, 2 + 2CIII, CIV = 5CIV1, 2-3CIV2, 3 C I V ,

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Article available athttp://www.parasite-journal.orgorhttp://dx.doi.org/10.1051/parasite/1997042153

2. B o d y (Figs. 1B, C; 2 B ) a) ventral papillae 1-3AIV, 3-4AIIV, 1-2AIIIV 2MIV

3PIIIV

b) dorsal papillae 9AID = 2 + 3 + 4 3-4AIID, 2-3AIIID 2MID

1PID

c) acetabular papillae 1SI, 2SII, 2SIII d) lateral papillae

about 3 5 - 4 0 for e a c h lateral area 3. Tail papillae (Fig. 2 C )

a) ventral

a + b = 2 + 0 - 2 = 2 - 4 b) dorsolateral

x + y + 1 = 9 - 11 + 8 - 12 + 1 = 18 - 22

T h e tegumentary papillae o f the c e p h a l i c region are arranged in four circles; lCI1 and s o m e o f the 3 C I³ group are invaginated. It is difficult to determine the e x a c t n u m b e r o f the receptors from the C I I⁴ groups.

In addition to the described papillae o f the first type (Lie, 1966), there are also s e c o n d type papillae in the groups C I I⁴ and CIII⁴, as well as at the level o f the CIV circle. Their total n u m b e r in the c e p h a l i c region is about 16. O n e o f the argentophilic structures in e a c h CIII3 g r o u p is s e e n b e l o w t h e o t h e r o n e s , a n d is stained m o r e intensely than the papillae. T h e s e struc­

tures s e e m to b e orifices o f the paraesophageal glands.

T h e typical a r r a n g e m e n t o f the ventral papillae is 2AIV, 3AIIV, 2AIIIV, 2MIV and 3PHIV. Only the groups MIV and PIIIV have a constant n u m b e r o f papillae.

T h e formula o f the circle AI dorsal ( A I D ) papillae is 4 + 3 + 4 + 3 + 4. In s o m e cercariae a m o n g these papillae there are structures with smaller dimensions than those o f the papillae, and they are s e e n as small dots (Fig. 2 A ) . T w o variants are o b s e r v e d in t h e n u m b e r o f papillae from the groups AIID (3AIID and 4AIID) and AIIID (2AIIID and 3AIIID). T h e groups MID and PID have a constant n u m b e r and arrangement.

No c h a n g e s w e r e found in the n u m b e r and arrange­

ment o f the acetabular papillae.

Each lateral region o f the b o d y has 3 5 - 4 0 o f the first type o f papillae and 2 o f the s e c o n d type o f papillae.

All lateral papillae are differentiated a l o n g 4 a x e s (L and L').

T h e tail papillae have ventral and dorsolateral posi­

tions. T h e ventral tail papillae are differentiated in groups a + b, with the following three variants in their arrangement: a + 6 - 2 + 1 , 2 + 2 and 2 + 0. At P(t) > 9 9 9 the average total n u m b e r o f these papillae

is M = 3-37 ± 0.11 and the coefficient o f variation CV = 1 8 . 5 1 . T h e dorsolateral tail papillae are arranged in three groups x + y + 1. T h e following arrangements are identified: x +y + 1 = 1 0 + 1 0 + 1, 1 0 + 8 + 1, 11 + 8 + 1, 10 + 9 +1, 11 + 9 + 1, 10 + 11 + 1, 9 + 8 + 1, 9 + 10 + 1, 9 + 11 + 1, 11 + 10 + 1, 9 + 12 + 1. T h e average total n u m b e r and the coefficient o f variation o f t h e s e papillae at P(t) > 99-9 is: M = 2 0 . 5 1 ± 0.17;

CV = 5 . 2 1 . T h e e x c r e t o r y pores, w h i c h are usually at the level b e t w e e n the third and fourth papillae from g r o u p x, a r e s t a i n e d t o g e t h e r w i t h t h e p a p i l l a e (Fig. 2 C ) .

DISCUSSION

A

total n u m b e r o f 3 1 2 t e g u m e n t a r y papillae w e r e found in E. trivolvis c e r c a r i a e . T h e i r n u m b e r and arrangement w e r e c o m p a r e d to those o f closely related 37-collar-spined s p e c i e s o f the g e n u s Echinostoma, d e s c r i b e d b y R i c h a r d ( 1 9 7 1 ) , Kanev et al. ( 1 9 8 7 ) , Dimitrov ( 1 9 8 7 ) , Nassi & D u p o u y ( 1 9 8 8 ) and Dimitrov & K a n e v ( 1 9 9 2 a ) as: E. caproni (Richard, 1 9 6 4 ) , E. revolutum, E. ecbinatum (Zeder, 1 8 0 3 ) , E. jurini (Skvortsov, 1 9 2 4 ) and E. parvocirrus (Nassi & Dupouy, 1 9 8 8 ) . T h e comparative evaluations are presented in T a b l e s I and II.

T h e data in T a b l e I s h o w that the main differences bet­

w e e n the cercariae o f E. trivolvis o n the o n e hand, and those o f E. caproni and E ecbinatum o n the other, are illustrated b y the n u m b e r and arrangement o f the papillae in the CIII5 (= StDL by Richard, 1 9 7 1 ) group.

T h e cercariae o f E. revolutum differ from t h o s e o f the other trematode s p e c i e s b y the p r e s e n c e o f t w o c l o ­ sely related argentophilic structures with medioventral position at the level AIV. In the majority o f E. trivolvis cercariae the CIII2 groups consist o f three papillae each, w h e r e a s all E. jurini cercariae in these groups have two papillae e a c h .

In addition to the tegumentary papillae, s o m e o f the cercariae stained with silver s h o w e d the p r e s e n c e o f the orifices o f the p a r a e s o p h a g e a l glands. T h e orifices are located in the c e p h a l i c region and o n the body, or only in the c e p h a l i c region and w h e n impregnated with silver a p p e a r as papillae. According to K a n e v ( 1 9 8 5 ) and K a n e v et al. ( 1 9 9 4 ) their total n u m b e r in the cercariae o f E. ecbinatum varies from 6 0 to 6 4 ; in E. parvocirrus over 32 ; in E. revolutum from 16 to 2 0 ; in E jurini from 8 to 10 ; and in E. trivolvis from 4 to 6. No p a r a e s o p h a g e a l glands have b e e n identified in the cercariae o f E. caproni.

Differences w e r e also o b s e r v e d b e t w e e n the cercariae o f E. trivolvis and the cercariae o f the o t h e r c o m p a r e d s p e c i e s with respect to the total n u m b e r o f the tail papillae from the groups a + b and x + y + 1 ( T a b l e II).

154 Parasite, 1997, 2, 153-158

MÉMOIRE

Parasite, 1997, 2, 153-158 _{1 5 5} TEGUMENTARY PAPILLAE OF ECHINOSTOMA TRIVOLVIS

Pig. 1. — Arrangement of the tegumentary papillae of E. trivolvis cercariae: A - on the ventral surface of the head region. B - on the ven­

tral surface of the body and the acetabulum. C - on the lateral area of the body. Scale bars = 10 micrometers.

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156 Parasite, 1997, 2, 153-158

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TEGUMENTARY PAPILLAE OF ECHINOSTOMA TRIVOLVIS

Table I. — Comparative data on the number and arrangement of papillae on the cephalic region and body of closely related 37-collar- spined cercariae of the genus Echinostoma.

Table II. — Comparative data on the number and arrangement of the tail papillae of closely related 37-collar-spined cercariae of the genus Echinostoma.

T h e difference b e t w e e n the m e a n values ( M ) o f the total n u m b e r o f the dorsolateral tail papillae in the cer­

cariae o f E. trivolvis, E. revolutum, E. echinatum and E. jurini are statistically significant ( P ( t ) > 9 9 . 9 ) .

T h e arrangement o f the b a s i c groups o f the papillae from the circle AI dorsally ( A I D ) c o m p l e x ( 3 + 4 + 3 ) can serve as a basis for distinguishing the cercariae o f E. trivolvis from the cercariae b e l o n g i n g to the g e n e r a Echinoparyphium (AID = 5 + 6 + 5 ) , Hypoderaeum (5 + 8 + 5 ) , Moliniella ( 4 + 4 + 4 ) and Paryphostomum ( 6 - 7 + 4 + 6 - 7 ) .

ACKNOWLEDGEMENT

T

his work was carried aut with the financial sup­

port from the Bulgarian A c a d e m y o f S c i e n c e s , - Scientific R e s e a r c h » National F u n d grant Parasite, 1997, 2, 153-158

Nr NI B - 2 3 1 and B - 5 2 6 and Lafayette College, Easton, Pennsylvania, USA. Mrs I. Petkova and Mr D. Vlaev are also gratefully a c k n o w l e d g e d for their e x c e l l e n t tech­

nical assistance.

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1 5 7

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Reçu le 18 novembre 1996 Accepté le 20 mars 1997

158 Parasite, 1997, 2, 153-158

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