APOCREADIUM GALAICUS S P . N . (DIGENEA : APOCREADIIDAE), A PARASITE OF T H E THICKBACK SOLE MICROCHIRUS VARIEGATUS
(SOLEIDAE, OSTEICHTHYES) FROM N . W . S P A I N
SANMARTÍN ML.*, ALVAREZ F.*, QUINTEIRO P.* & PANIAGUA E.*
S u m m a r y :
A new species of digenetic trematode, Apocreadium galaicus (Apocreadiidae), parasitic in the intestine and occasionally the sto- mach of the thickback sole Microchirus variegatus (Soleidae, Osteichthyes), is described. To date, Apocreadium has been reported only from American and Asian coastal waters; this is the first report of a species from European coastal waters. The most similar taxa to the new species are A. foliatum, A. mexicanum, A.
synagris and A. balistis. A. galaicus can be distinguished a) from A. foliatum, because the oral sucker of this species is larger than the acetabulum, while in A. galaicus it is smaller; b| from A. mexi- canum by the simple (not sphincter-like) structure of the anterior quarter of its pharynx and by its larger eggs, c) from A. synagris by the position of the oral sucker and the restriction of cuticular spines to the pretesticular region in A. galaicus and d) from A.
balistis by its longer post-testicular region (55.3 - 69.6% of body length), by the densely spiny cuticle of the acetabular region and its larger eggs. In the study area, prevalence of infection by A.
galaicus showed a clear peak between November and January, and dropped to zero in May / June.
KEY W O R D S : Apocreadium galaicus sp. n. Microchirus variegatus. Galicia.
Spoin.
INTRODUCTION
T
h e g e n u s Apocreadium w a serected
b yM a n t e r ( 1 9 3 7 ) t o a c c o m m o d a t e A. mexica- num a n d A. longisinosum. T h i s author origi- n a l l y i n c l u d e d t h e g e n u s in t h e s u b f a m i l y M e g a s o l e n i n a e in v i e w o f t h e p r e s e n c e o f a w e l l - d e v e l o p e d l y m p h a t i c system, although it differs from t h e o t h e r g e n e r a o f this s u b f a m i l y in not h a v i n g a h e r m a p h r o d i t i c s a c . O v e r t h e s u b s e q u e n t 2 0 y e a r s , s e v e n s p e c i e s w e r e a s s i g n e d t o Apocreadium : A.
balistis Manter, 1 9 4 7 , A. synagris Y a m a g u t i , 1 9 5 3 , A.
caballeroi B r a v o , 1 9 5 3 , a n d A. coili, A. angustum, A.
uroproctoferum a n d A. bravoi, d e s c r i b e d b y S o g a n d a r e s - B e r n a l ( 1 9 5 9 ) . T h e latter a u t h o r p r o p o s e d
* Instituto de Investigacíon y Análisis Alimentarios. Laboratorio de Parasitología, Facultad de Farmacia. Universidad de Santiago de Compostela, Spain.
C o r r e s p o n d i n g a u t h o r : Dr. M.L. S a n m a r t í n , I n s t i t u t o d e Investigación y Análisis Alimentarios. Laboratorio de Parasitología, Facultad de Farmacia, Avenida de Vigo, s.n., 15706 Santiago de Compostela, Spain. Tel. : (986) 563100, ext. 4893 - Fax : (986) 593316.
Résumé : APOCREADIUM GAIAICUS SP. N. (DIGENEA : APOCREADIIDAE), UN PARASITE DE MICROCHIRUS VARIEGATUS (SOLEIDAE, OSTEICHTHYES) DANS LE NORD-OUEST DE L'ESPAGNE
Une nouvelle espèce de trématode (Digenea) est décrite, Aprocreadium galaicus (Apocreadiidae!. Elle parasite l'intestin et occasionnellement l'estomac de Microchirus variegatus (Soleidae : Osteichthyes). Jusqu'à présent le genre Apocreadium n'a été trouvé que dans les eaux des côtes américaines et asiatiques. Les taxons les plus proches de la nouvelle espèce sont A. foliatum, A. mexica- num, A. synagris et A. balistis. On peut les distinguer de A.
galaicus : A. foliatum, parce que dans cette espèce la ventouse orale est plus grande que l'acetabulum, au contraire de ce qui arrive chez A. galaicus ; A. mexicanum par la structure simple du quart antérieur de son pharynx et par la taille des oeufs qui sont plus grands ; A. synagris par la position de la ventouse orale et par les épines cuticulaires qui sont restreintes à la région pretesticulaire ; A. balistis par la longue région post-testiculaire (55,3 - 69, 1% de la longueur du corps), par la cuticule de la région de la ventouse ventrale, qui a des épines très serrées, et par les œufs qui sont plus grands. Dans la zone étudiée la prévalence de l'infestation par A.
galaicus montre un pic évident entre les mois de novembre et jan- vier et cette prévalence tombe à zéro les mois de mai et juin.
MOTS CLES : Apocreadium galaicus sp. n. Microchirus variegatus. Galice.
Espagne.
the following subclassification o f the g e n u s :
a ) O r a l s u c k e r w i t h t w o l a t e r a l l o b e s ; v i t e l l a r i a c o n f l u e n t anterior to a c e t a b u l u m - A. coili, A. angus- tum, A. bravoi.
b ) Oral s u c k e r without l o b e s ; vitellaria not confluent anterior t o a c e t a b u l u m .
i) without u r o p r o c t - A. mexicanum, A. longisinosum, A. synagris, A.caballeroi, A. balistis.
ii) with u r o p r o c t - A. uroproctoferum.
S i d d i q i a n d
Cable (1960) erected
t h e g e n u s Neoapocreadium to a c c o m m o d a t e t h e s p e c i e s o f the first g r o u p ( w h i c h thus b e c a m e N. coili, N. angustum a n d N. bravoi). F o u r s p e c i e s h a v e s u b s e q u e n t l y b e e n a s s i g n e d t o Apocreadium : A. cryptum O v e r s t r e e t , 1 9 6 9 , A. manteri O v e r s t r e e t , 1 9 7 0 , A. viguerasi Z h u k o v , 1 9 8 3 and A. vinodae A h m a d , 1 9 8 5 . In addi- t i o n , O v e r s t r e e t ( 1 9 6 9 ) t r a n s f e r r e d Homalometron foliatum Siddiqi et C a b l e , 1 9 6 0 to Apocreadium, s i n c ethis s p e c i e s has a l y m p h a t i c system. A. viguerasi has r e c e n t l y b e e n t r a n s f e r r e d b y A h m a d ( 1 9 8 7 ) t o Neoapocreadium.
Parasite, 1995, 2, 211-216
Mémoire
211Article available athttp://www.parasite-journal.orgorhttp://dx.doi.org/10.1051/parasite/199502s2211
SANMARTÍN M.L., ALVAREZ F., QUINTEIRO P. & PANIAGUA E.
T a b l e I. - M e a s u r e m e n t s o f Apocreadium galaicus s p . n. (in µm)
*Specimens with no eggs forming were considered sexually immature.
**Means ( X ) and Standard deviations (SO) are for both the holotype and paratypes.
Dimensions : I ) = distance; L= length; W= width. Parts of body : Acetab = acetabulum; Anterior E = anterior end of body; Mehlis G = Mehlis gland; O Sucker = oral sucker; PT Region = post-testicular region; Sem Rec = seminal receptacle; Sem Ves = seminal vesicle; Testis A = anterior testis; Testis P = poste
rior testis.
T h e g e n u s Apocreadium as currently r e c o g n i z e d thus contains 10 s p e c i e s . O n Yamaguti's ( 1 9 7 1 ) classifica
tion, Apocreadium forms part o f the family Apocrea- diidae, alongside Choanodera, Neoapocreadium and Neomegasolen a.
Here w e report a n e w s p e c i e s o f this genus, infecting t h e t h i c k b a c k s o l e (Microcbirus variegatus) from coastal waters o f the northwest Iberian Peninsula.
MATERIALS AND METHODS
W
e e x a m i n e d 1 5 0 i n d i v i d u a l s o f Microchirus variegatus c a u g h t b e t w e e n O c t o b e r 1987 and S e p t e m b e r 1 9 8 8 , and a further 183 individuals caught b e t w e e n O c t o b e r 1 9 9 3 and March 1 9 9 4 , in the Ria de Arousa (an estuarine bay in Galicia, northwest Spain). In all c a s e s e x a m i nation consisted o f careful observation o f the viscera under a s t e r e o m i c r o s c o p e . All trematodes found w e r e extracted, w a s h e d in physiological saline, relaxed and killed in Berland's fluid, fixed in B o u i n ' s fluid ( 2 4 h m i n i m u m ) and c o n s e r v e d in ethanol ( 7 0 % ) until prep a r a t i o n for m i c r o s c o p y . S p e c i m e n s w e r e s t a i n e d
with iron a c e t o c a r m i n e ( G e o r g i e v et al., 1 9 8 6 ) cleared in a 1:1 mixture o f b e e c h c r e o s o t e and ethanol ( 9 6 ° ) a n d m o u n t e d in C a n a d a b a l s a m . Additional s p e c i m e n s w e r e m o u n t e d in Hoyer's fluid to allow reliable m e a s u r e m e n t o f eggs, o r stained (in transverse, longi
tudinal and sagittal s e c t i o n s ) with 1% Mayer's h a e m a - toxylin-eosin o r Wheatley's T r i c h r o m e stain to allow e x a m i n a t i o n o f t h e l y m p h a t i c s y s t e m a n d o t h e r organs.
RESULTS
DESCRIPTION OF APOCREADIUM GALAICUS SP. N.
(APOCREADIIDAE) Measurements in table I.
B
o d y e l o n g a t e and slender, dorsoventrally flatt e n e d e x c e p t in the acetabular region, w h e r e it is m o r e cylindrical. Cuticle d e n s e l y spiny b e t w e e n the anterior e n d o f the b o d y and the aceta
bulum, sparsely spiny b e t w e e n the a c e t a b u l u m a n d the ovary or anterior testis; otherwise smooth.
212 Mémoire P a r a s i t e , 1995, 2, 211-216
APOCREADIUM GALAICUS SP. N. FROM M. VARIEGATUS
Fig. 1. - Apocreadium galaicus. a) Paratype. b) Eggs.
Oral s u c k e r ventral, slightly separated from the ante
rior e n d (Fig. l a ) . Acetabulum located in the anterior quarter o f the b o d y , postbifurcal; s u c k e r area ratio 1:1.4 - 1:2.3 ( o b t a i n e d as indicated by Mas-Coma et al., 1 9 8 4 ) (table I ) . B o t h suckers b e a r several papil
lae. Prepharynx short, pharynx longer than it is wide.
O e s o p h a g u s s h o r t , b i f u r c a t i n g to form t w o c a e c a w h i c h e x t e n d almost to the posterior e n d o f the b o d y (Fig. 1 a ) .
L y m p h a t i c s y s t e m c o m p r i s i n g four v e s s e l s running anteroposteriorly, branching in the hindbody, difficult to s e e in adults, e x c e p t in s p e c i m e n s in w h i c h the posterior ramifications are particularly well d e v e l o p e d and in very young, sexually inactive s p e c i m e n s . T e s t e s t a n d e m , p o s t a c e t a b u l a r , oval to rectangular, located in the anterior half o f the b o d y (Fig. l a ) , pos
terior testis generally slightly greater than anterior tes
tis. Post-testicular region 5 5 . 3 - 6 9 . 6 % o f b o d y length in mature (i.e. egg-bearing) s p e c i m e n s and in imma
ture s p e c i m e n s longer than 2.9 mm, and 4 7 . 5 - 4 9 % o f b o d y length in shorter s p e c i m e n s .
Cirrus and cirrus p o u c h absent. Seminal vesicle pyri- form, dorsal to acetabulum, with prostatic wall sur
rounded by glandular cells, fusing with the distal part o f the uterus anterior to the acetabulum, giving rise to a genital sinus. Genital pore located c l o s e to the ante
rior e d g e o f the acetabulum.
Ovary globular, smaller than and anterior to testes, generally slightly to the left o f the midline (Fig. l a ) , though median in s o m e immature s p e c i m e n s . Seminal r e c e p t a c l e g l o b u l a r , dorsal to ovary. M e h l i s ' gland l o c a t e d b e t w e e n ovary a n d anterior testis. Laurer's canal o p e n i n g to surface dorsally, just posterior to the acetabulum. Uterus with a single ascending branch, folded several times (Fig. l a ) , extending from about the level o f the ovary to that o f the acetabulum. Eggs large, operculate, with a protuberance or spine at the anopercular p o l e (Fig. 1 b ) .
Vitellarium follicular, l o c a t e d t h r o u g h o u t t h e hind- b o d y , laterally and b e t w e e n c a e c a , e x t e n d i n g ante
riorly as far as the anterior testis or, in s o m e cases, t h e p o s t e r i o r e d g e o f t h e ovary, f e e d i n g into t w o ducts w h i c h run intracaecally through the post-ova
rian r e g i o n and fuse to form a vitelline reservoir, w h i c h is confluent with Mehlis' gland, b e t w e e n the levels o f the ovary and the anterior testis (Fig. l a ) . E x c r e t o r y v e s i c l e I-shaped, terminating just b e h i n d the posterior testis; e x c r e t o r y pore at posterior e n d o f b o d y (Fig. 1 a ) .
OTHER INFORMATION ON TYPE SPECIMENS
T y p e host : Microchirus variegatus ( D o n o v a n , 1 8 0 8 ) (Soleidae, O s t e i c h t h y e s )
Site : Intestine, occasionally stomach.
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Mémoire 213
VNMARTÍN M.L., ALVAREZ F., QUINTEIRO P. & PANIAGUA E.
O c t Nov D e c J a n F e b Mar Apr May J u n J u l Aug S e p MONTHS
Fig. 2. - Prevalence and intensity of parasitation by A. galaicus.
S p e c i m e n s e x a m i n e d :
- H o l o t y p e : D e p o s i t e d in t h e M u s e o N a c i o n a l d e Historia Natural, Madrid, n° 4 0 2 / 7 .
- Paratypes : 24 s p e c i m e n s deposited in the M u s e o Nacional d e Historia Natural, Madrid, n° 4 0 2 / 8 - 1 5 . - O t h e r s p e c i m e n s d e p o s i t e d in t h e L a b o r a t o r y o f P a r a s i t o l o g y , F a c u l t y o f P h a r m a c y , S a n t i a g o d e Compostela, Spain.
T y p e l o c a t i o n : Ria d e A r o s a , G a l i c i a , n o r t h w e s t Spain. T h e specific n a m e refers to the region, Galicia, w h e r e the host s p e c i m e n s w e r e caught.
SEASONAL VARIATION IN PREVALENCE AND INTENSITY OF INFECTION
A. galaicus was detected in 3 3 % o f the 150 s p e c i m e n s o f M. variegatus caught b e t w e e n O c t o b e r 1987 and S e p t e m b e r 1 9 8 8 , and in 3 4 % o f t h e 1 8 3 s p e c i m e n s c a u g h t b e t w e e n O c t o b e r 1 9 9 3 a n d M a r c h 1 9 9 4 . Overall m e a n p r e v a l e n c e w a s 3 4 % . B r e a k i n g d o w n t h e data b y m o n t h s (Fig. 2 ) , m e a n p r e v a l e n c e w a s h i g h e s t in N o v e m b e r , D e c e m b e r a n d J a n u a r y a n d l o w e s t ( z e r o ) in May and J u n e ; from J u l y o n w a r d s p r e v a l e n c e b e g i n s to rise again, presumably reflecting reinfection b y larvae. M e a n intensity o f infection p e a k e d ( 2 3 parasites per h o s t ) in January.
DISCUSSION
P
art o f t h e e x a m i n e d material c o r r e s p o n d s to that m e n t i o n e d b y Q u i n t e i r o et al. ( 1 9 8 8 ) in the s a m e host. W e b e l i e v e that the s p e c i m e n s m e n t i o n e d b y these authors in S. lascaris also b e l o n g to the s a m e s p e c i e s , but this will b e the object o f further studies.
O n the basis o f published descriptions o f the m e m bers o f Apocreadium, the most similar s p e c i e s to A.
galaicus are A. foliatum, A. mexicanum, A. synagris and A. balistis. A. galaicus can b e distinguished from A. foliatum (Siddiqi et Cable, I 9 6 0 ) b e c a u s e in this s p e c i e s the oral s u c k e r is larger than the acetabulum, while in A. galaicus it is smaller. It differs from A.
mexicanum (Manter, 1 9 3 7 ) b y its larger e g g s and b y the simple structure o f its pharynx; the anterior quar
ter o f the pharynx o f A. mexicanum is formed b y a sphincter-like, circular muscle.
A. galaicus differs from A. synagris (Yamaguti, 1 9 5 3 ) in the position o f the oral sucker, which is completely ventral (slightly separated from the anterior e n d ) in the first species, and subterminal in the second, and in the cuticle being spiny only anterior to the testes, not over the w h o l e body. Finally, A. galaicus can b e distingui-
9 1 4 Parasite, 1995, 2, 211-216
APOCREADIUM GALAICOS SP. N. FROM M. VARIEGATI®
shed from A. balistis (Manter, 1 9 4 7 ) by its longer post- testicular region, by its larger eggs and by its cuticle;
that o f A. balistis is densely spiny only from the ante- rior end o f the body to the posterior e d g e o f the pha- rynx, and sparsely spiny in the acetabular region.
T h e m e m b e r s o f the g e n u s Apocreadium, including A. galaicus, can b e distinguished with the aid o f the following k e y :
1. a) Oral sucker terminal, more or less conical 2 b) Oral sucker usually subterminal or ventral, spherical or
subspherical 3 2. a) Oral sucker much larger than acetabulum (sucker ratio
1:0.4 - 1:0.5); post-testicular region about 30 - 40 % of body length A. cryptum b) Acetabulum and oral sucker of similar size (sucker ratio 1:1 - 1:1.2); post-testicular region very short (about 18 - 19 % of body length) A. vinodae 3. a) Cuticle with neither scales nor spines A. longisinosum b) Cuticle more or less covered with scales, each bearing 1 - 6 spines. Oral sucker smaller than acetabulum (sucker ratio 1:1.3 - 1:1.5); vitellarium extending to posterior edge of ace- tabulum; post-testicular region 26 - 35% of body length.
A. manteri c) Cuticle entirely or partially covered with simple spines 4 4. a) With uroproct. A. uroproctoferum
b) Without uroproct 5 5. a) Testes deeply lobulate A. caballeroi
b) Testes more or less irregular or oval in outline, not deeply
lobulate 6 6. a) Oral sucker subterminal; cuticle more densely spiny in
forebody than in hindbody. A. synagris b) Oral sucker ventral, slightly separated from the anterior
end. Only forebody cuticle spiny 7 7. a) Anterior quarter of pharynx formed by a sphincter-like,
circular muscle A. tnexicanutn
b) Anterior quarter of pharynx not sphincter-like 8 8. a) Post-testicular region near or over 50% of body length 9
b) Post-testicular region less than 50% of body length; cuticle densely spiny anterior to the posterior edge of the pharynx, sparsely spiny in the acetabular region A. balistis 9. a) Oral sucker smaller than acetabulum (sucker area ratio
1:1.4-1:2.2: width ratio 1:1.1-1:1.5 in mature specimens) A. galaicus b) Oral sucker larger than acetabulum (sucker width ratio
1:0.76). A.foliatum As regards distribution, all s p e c i e s o f Apocreadium
d e s c r i b e d to date are from American coastal waters ( P a c i f i c , C a r i b b e a n , G u l f o f M e x i c o a n d A t l a n t i c ) , e x c e p t A. synagris ( r e p o r t e d o n l y from I n d o n e s i a ; Yamaguti, 1 9 5 3 ; S o g a n d a r e s Bernal, 1 9 5 9 ) , A. vinodai ( r e p o r t e d only from the Arabian Sea n e a r B o m b a y ; Ahmad, 1 9 8 5 ) and A. balistis (reported from the Gulf o f M e x i c o , t h e C a r i b b e a n a n d t h e I n d i a n O c e a n ; T o m a n , 1 9 9 2 ) . A. galaicus is the first s p e c i e s to b e reported from European waters.
P r e v a l e n c e o f infection o f M. variegatus b y A. galai- cus p e a k s o v e r t h e p e r i o d N o v e m b e r - J a n u a r y a n d r e a c h e s a minimum in May and J u n e . Although the life cycles o f the s p e c i e s o f this g e n u s have not b e e n
determined yet, it is possible that this variation is rela- ted with the a b s e n c e o f the appropriate intermediate hosts in the diet o f the t h i c k b a c k sole in the spring m o n t h s , s o w h e n t h e a d u l t s d i e out, p r e v a l e n c e b e c o m e s zero. If w e have in mind that all the other s p e c i e s o f Apocreadium live in warm, tropical waters, it would s e e m that A. galaicus s h o w s a surprisingly m a r k e d p r e f e r e n c e for c o l d w a t e r , b u t w e m u s t r e m e m b e r t h a t t h e A t l a n t i c c o a s t o f S p a i n a n d Portugal are o n the course o f the Gulf Stream, which m a k e s the temperature o f its waters much milder in winter than would b e s u s p e c t e d according to its lati- tude. No information is available o n p r e v a l e n c e o f infection o f other m e m b e r s o f the genus.
ACKNOWLEDGEMENTS
his study was financially supported b y grant n u m b e r X U G A 2 0 3 10 B 9 3 o f the Xunta de Galicia.
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