TRICHOSTRONGYLINA (NEMATODA) FROM MALAGASY M U R I D A E .
I - DESCRIPTION O F T W O N E W SPECIES O F HELIGMONELLIDAE I N NESOMYS SPP.
D U R E T T E - D E S S E T M.C.*, L E T H O N E N J . T * * & H A U K I S A L M I V.***
Summary:
Two new species of Heligmonellidae, Heligmonina wrightae n.sp.
(Nippostrongylinae) and Nesomystrongylus fissicauda n.gen., n.
sp. (Brevistriatinae) are described from Madagascar in Nesomys rufus and N. audeberti (Muridae]. In Nesomys audeberti, the species are coparasites. Heligmonina wrightae is differentiated from all the other species of the genus, except H. malacomysi Sakka & Durette-Desset, 1 9 8 8 , by the ratio of the length of the spicules on the length of the body (25-27.8 % versus 9,5-7 %). It differs from H. malacomysi by the pattern of the caudal bursa and by the angle of the axis of orientation of the cuticular ridges on the sagittal axis. Nesomystrongylus fissicauda Is related to the genus Fissicauda Durette-Desset & Krlshnasamy, 1 9 7 6 , by the absence of the carene, by the ridges discontinuous on all the sides of the body and by the deeply divided dorsal ray. It differs from this genus by a different structure of the ridges, by the pattern of the caudal bursa, (very tiny rays 2 and strongly developed rays 3, rays 8 arising from common trunk of rays 2 to 6] and by the presence of a caudal tip in the female.
KEY WORDS : Heligmonina wrightae n. sp., Nesomystrongylus fissicauda n.
gen., n. sp. Trichostrongylina, Heligmonellidae, Brevistriatinae,
Nippostrongylinae, Nesomys audeberti, Nesomys rufus, Muridae, Madagascar.
INTRODUCTION
T
h e p r e s e n t study is part o f a project o n the potential effects o f endoparasites introduced b y t h e n o n - n a t i v e b l a c k rat Rattus rattus o n the e n d e m i c small m a m m a l s in M a d a g a s c a r . T h e authors carry put the project in c o l l a b o r a t i o n with J . P . Hugot ( M u s e u m National d'Histoire Naturelle, F r a n c e ) , J . Laak- k o n e n (University o f California, USA) a n d H. Ramia- rinjanahary (University o f Diantananarivo, Madagascar).W e h a v e found several n e w , h o s t - s p e c i f i c s p e c i e s o f n e m a t o d e s from native r o d e n t s w h i c h b e l o n g to the
* Laboratoire de Biologie parasitaire, Protistologie, Helminthologie et CNRS FR3, Muséum National d'Histoire Naturelle, 61, rue Buffon.
75231 Paris cedex 05, France.
** Department of Ecology and Systematics. Division of Population Ecology, PO B O X 17 (Arkadiankatu 7), FIN-00014 University of Hel- sinki, Finland.
*** Finnish Forest of Research Institute, Vantaa Research Center, PO Box 18, FIN-01301 Vantaa, Finland.
Correspondence: M.C. Durette-Desset. E-mail: mcdd@cimrs1.mnhn.fr Fax: 33 (0) 1 46 07 34 99
Résumé : TRICHOSTRONGYLINA (NEMATODA) PARASITES DE MURIDÉS MALGACHES. I - DESCRIPTION DE DEUX NOUVELLES ESPÈCES
D'HELIGMONELLIDAE CHEZ NESOMYS SPP.
Deux nouveaux Heligmonellidae, Heligmonina wrightae n. sp.
INippostrongylinael el Nesomystrongylus fissicauda n. gen., n. sp.
(Brevistriatinae) sont décrits à Madagascar chez Nesomys rufus et N. audeberti. Les deux espèces sont coparasites chez Nesomys audeberti. Heligmonina wrightae se différencie de toutes les espèces du genre, à l'excepion d'H. malacomysi Sakka et Durette-Desset, 1988, par le rapport de la longueur des spicules sur la longueur du corps (25-27.8 % contre 9.5-17 %). Elle se distingue d'H. malacomysi par le type de bourse caudale et par l'inclinaison de l'axe d'orientation des crêtes cuticulaires sur l'axe sagittal. Nesomystrongylus fissicauda se rapproche du genre Fissicauda Durette-Desset et Krishnasamy, 1976, par l'absence de la carène, par des crêtes interrompues sur toute les faces du corps et par la profonde division de la côte dorsale. Elle s'éloigne de ce genre par la structure particulière des crêtes cuticulaires, par le type de la bourse caudale (côtes 2 grêles et côtes 3 très
développées, côtes 8 naissant sur le tronc commun aux côtes 2 à 6) et par la présence d'une pointe caudale chez la femelle.
R
o d e n t hosts w e r e c o l l e c t e d in V e v e m b e forest in s o u t h e a s t e r n M a d a g a s c a r b e t w e e n 12 a n d 1 5 D e c e m b e r , 1 9 9 5 a n d in R a n o m a f a n a MOTS CLES : Heligmonina wrightae n. sp., Nesomystrongylus fissicauda n.gen., n. sp., Trichostrongylina, Heligmonellidae, Brevistriatinae, Nippostrongylinae, Nesomys audeberti, Nesomys rufus, Muridae, Madagascar.
sub-family Nesomyinae (Muridae) as defined b y Musser
& Carleton ( 1 9 9 3 ) .
Previously gastrointestinal helminths w e r e studied from four s p e c i e s o f n e s o m y i n e rodents, i.e. Hypogeomys antimena, Gymnuromys roberti, Bracbyuromys rami- rohitra a n d B. betsiloensis ( C h a b a u d et al., 1 9 6 7 ; Q u e n t i n & D u r e t t e - D e s s e t , 1 9 7 4 ; D u r e t t e - D e s s e t &
C h a b a u d , 1 9 9 2 ) , but not from the g e n e r a Nesomys and Eliurus. T h e aim o f this w o r k is to d e s c r i b e t w o n e w s p e c i e s o f Trichostrongylina found in Nesomys spp. T h e c o n c l u s i o n s c o n c e r n i n g the T r i c h o s t r o n g y l i n a will b e p r e s e n t e d w h e n the t a x o n o m i c a l analysis o f the tri- chostrongylid fauna is c o m p l e t e d . G e n e r a l c o n c l u s i o n s a n d the s u m m a r y o f the project will b e p u b l i s h e d e l s e w h e r e w h e n all the parasitic fauna is a n a ly se d.
MATERIAL AND METHODS
Article available athttp://www.parasite-journal.orgorhttp://dx.doi.org/10.1051/parasite/200209129
DURETTE-DESSET M.C., LETHONEN J.T & HAUKISALMI V.
National Park in southeastern Madagascar b e t w e e n 15 S e p t e m b e r and 3 D e c e m b e r 1 9 9 8 . T h e gastrointes
tinal tract was preserved in 7 0 % ethanol or buffered 1 0 % formalin in the field. Later the stomach, small intestine, c a e c u m and rectum w e r e e x a m i n e d for hel
minths. T h e small intestine was divided in ten sections o f equivalent length, n u m b e r e d SI 1 to SI 10 from the pyloric valve to the ileo-caecal junction. T h e helminths w e r e stored in 7 0 % ethanol.
T h e n o m e n c l a t u r e used a b o v e the family-group is that o f Durette-Desset & Chabaud ( 1 9 9 3 ) . T h e synlophe was studied following the method o f Durette-Desset ( 1 9 8 5 ) , and the n o m e n c l a t u r e used for the study o f the caudal bursa is that o f Durette-Desset & C h a b a u d ( 1 9 8 1 ) . Measurements are in micrometres e x c e p t w h e r e stated otherwise. T y p e s p e c i m e n s w e r e deposited in the Hel- m i n t h o l o g i c a l C o l l e c t i o n s o f t h e M u s e u m national d'Histoire naturelle, Paris, F r a n c e (MNHN).
HELIGMONINA WRIGHTAE N. SP.
Material studied : h o l o t y p e m a l e , a l l o t y p e f e m a l e MNHN 194 MQa, 19 male, 23 female paratypes, MNHN 194 M Q b .
Host: Nesomys rufus Peters, 1 8 7 0 (Muridae) immature male.
Site: small intestine (SI 1-SI 6).
Geographical origin: Ranomafana National Park, Mada
gascar; 11 N o v e m b e r 1 9 9 8 , coll: J . T. Lehtonen.
O t h e r material: o n e male, s e v e n females, a posterior part o f female, MNHN 196 MQa, parasites o f the small intestine (SI 1- SI 4 ) o f Nesomys audeberti (Jentink, 1 8 7 9 ) male in V e v e m b e , Madagascar; 13 D e c e m b e r 1995, coll: J . Jernvall, coparasites o f Nesomystrongylus fissicauda n. gen., n. sp.
DESCRIPTION
Very small n e m a t o d e s with b o d y uncoiled or coiled only in its anterior part. Excretory pore within third p o s t e r i o r part o f o e s o p h a g u s o n a v e r a g e . Deirids situated at s a m e level as e x c r e t o r y pore.
Head: Cephalic vesicle present. In apical view, rounded b u c c a l o p e n i n g s u r r o u n d e d b y t w o amphids, four e x t e r n o labial papillae and four c e p h a l i c papillae (Fig. I B ) .
Synlophe: (studied in o n e male and o n e female para- t y p e ) (Fig. 1C-H). In b o t h s e x e s , cuticle bears longi
tudinally c o n t i n u o u s ridges. Ridges appearing at dif
f e r e n t l e v e l s p o s t e r i o r t o c e p h a l i c v e s i c l e a n d disappearing at about 100 anterior to caudal bursa in male and anterior to vulva in female.
P r e s e n c e o f c a r e n e m a d e up o f hypertrophied left ridge and well d e v e l o p e d right ridge ( c o m p a r e d to the o t h e r ridges) j o i n e d by a chitinoid bridge. In posterior part o f female, bridge disappears and right ridges
d e c r e a s e in size (Fig. I F ) . N u m b e r o f ridges: at level o f oesophago-intestinal junction, 12 ( c a r e n e , 3 strongly d e v e l o p e d left v e n t r a l , 2 right v e n t r a l , 5 d o r s a l ) (Fig. 1C). At mid-body in male, 12 ( c a r e n e , 2 strongly d e v e l o p e d left v e n t r a l , 3 right v e n t r a l , 5 d o r s a l ) (Fig. 1 G ) ; in female, 11 ( c a r e n e , 2 strongly d e v e l o p e d left ventral, 2 right ventral, 5 dorsal) (Fig. I D ) . In pos
terior part o f b o d y in both s e x e s , 13 ( c a r e n e , 6 ven
tral, 5 dorsal) with progressive decreasing o f size o f 2 left ventral ridges a n d a p p e a r a n c e o f 1 ( m a l e ) , 2 (female) ventral ridges (Fig. I E , H). Just a b o v e vulvar opening, 13 (left ala, 5 ventral, 7 dorsal) with a p p e a rance o f o n e n e w dorsal ridge (Fig. I F ) . Ridges o f une
qual size. At mid-body, right dorsal ridges m o r e d e v e loped than left o n e s .
At mid-body, ridges orientated at 6 0 ° on sagittal axis a n d directed from right ventral to left dorsal side (Fig. I D , G ) .
Holotype male: 2.0 mm long and 4 0 wide at mid-body, including c a r e n e 22 long; c e p h a l i c vesicle 3 0 long by 22 wide; nerve ring, excretory pore and deirids situated at 95, 1 4 0 and 145 from a p e x , respectively; o e s o p h a g u s 2 7 0 long. Ratio o f position o f e x c r e t o r y p o r e o n o e s o p h a g u s length, 8 2 %.
Strongly asymmetrical caudal bursa with left lateral l o b e m o r e d e v e l o p e d and pattern o f type 1-3-1 (rays 2 and 6 separating first from c o m m o n trunk o f rays 2 to 6) (Fig. I K ) . Rays 2 and 3 totally separated up to their b a s e . Rays 4 and 5 thick, strongly divergent at distal third. Spindly rays 6. Rays 8 arising from proximal third o f dorsal ray at varying levels (Fig. I I , K ) . Dorsal ray divided at mid length into t w o b r a n c h e s , e a c h branch giving rise to 2 small b r a n c h e s , rays 9 ( e x t e r n a l b r a n c h e s ) b e i n g thicker and slightly longer than rays 10 (internal b r a n c h e s ) .
Filiform, alate spicules, 4 9 0 long, with sharp extremi
ties (Fig. 1J, K ) ) . Ratio o f spicule length o n b o d y length: 24 %. Genital c o n e with linguiform papilla zero and 2 rounded papillae 7 (Fig. 1 J ) . Gubernaculum absent.
Main m e a s u r e m e n t s (average and range o f ten para- type m a l e s ) : b o d y 1.9 (1.6-2.1) m m long; e x c r e t o r y p o r e 175 ( 1 4 0 - 2 1 0 ) from a p e x ; o e s o p h a g u s 2 2 9 ( 2 0 0 - 2 8 5 ) long; ratio o f position o f e x c r e t o r y pore o n o e s o phagus length, 7 6 . 4 % (61.5-95) %; spicules 4 6 5 ( 3 7 0 - 5 3 0 ) long, ratio o f spicule length o n b o d y length 24.5 (17.6-27.9) %.
Allotype female: 2.0 mm long and 1 0 0 wide at mid- b o d y , including c a r e n e 2 5 long. C e p h a l i c v e s i c l e 4 0 long b y 2 5 wide; nerve ring, e x c r e t o r y pore and deirids situated at 110, 150 and 150 from a p e x , res
pectively; o e s o p h a g u s 2 4 0 long (Fig. 1A). Ratio o f position o f e x c r e t o r y p o r e o n o e s o p h a g u s length, 62.5 %.
30 Mémoire Parasite, 2002, 9, 29-35
NEW HEUGMONELLIDAE (NEMATODA) FROM MADAGASCAR
Fig.l- Heligmonitia wrightae n. sp. A, female, anterior extremity, right lateral view; B, female, head, apical view; C-H, cuticular ridges, transverse sections, C-F, female, C, at the beginning of the intestine, D, at mid-body, E, at 900 from caudal extremity, F, at 100 from vulvar opening; G, H, male, G, at mid-body, H, in front of caudal bursa; I, male, arising of rays 8, dorsal view; J , male, genital cone, right lateral view; K, other male, caudal bursa, ventral view; L, female, posterior extremity, right lateral view. Transverse sections orientated as figure 1, D.
Abbreviations : V, ventral side; L, left side.
D U R E T T E - D E S S E T M . C . , L E T H O N E N J . T . & H A U K I S A L M I V .
M o n o d e l p h y : vulva at 9 0 from c a u d a l e x t r e m i t y . Vagina vera 3 0 long. O v e j e c t o r 178 long with vesti
b u l e 7 0 , sphincter 3 8 long b y 2 0 wide and infundi- bulum 7 0 long (Fig. 1L). Uterus 3 8 0 long with 5 eggs, 50 long b y 3 0 w i d e at 2 blastomere stage near vulva.
Ratio o f uterus length o n b o d y length: 19 %. Tail 35 long with r o u n d e d extremity (Fig. 1L).
Main m e a s u r e m e n t s (average and range o f ten para- type females): b o d y 2.2 ( 1 . 8 - 2 . 4 ) m m long; excretory p o r e 168 ( 1 5 0 - 1 8 0 ) from a p e x ; o e s o p h a g u s 2 4 2 ( 2 0 0 - 2 7 0 ) long; ratio o f position o f excretory p o r e o n o e s o p h a g u s length, 6 9 . 3 % (61.2- 7 7 . 3 ) %; vulva at 104 ( 8 0 - 1 3 0 ) from caudal extremity; vestibule 8 4 ( 6 5 - 9 0 ) long;
sphincter 2 8 ( 2 0 - 3 0 ) long by 31 ( 2 5 - 4 0 ) wide; infun- dibulum observed only in three specimens, 97 ( 9 0 - 1 0 0 ) long; uterus 4 4 0 ( 3 5 0 - 5 5 0 ) long with 5 ( 3 - 7 ) eggs 62 ( 5 0 - 7 0 ) long by 3 3 ( 3 0 - 4 0 ) wide; tail 3 8 ( 3 5 - 4 0 ) long;
ratio o f uterus length o n b o d y length: 20 (16.2-27.8) %.
DIAGNOSIS
T h e s e s p e c i m e n s b e l o n g to the genus Heligmonina Baylis, 1 9 2 8 ( H e l i g m o s o m o i d e a , Heligmonellidae, Nip- postrongylinae), redefined b y Durette-Desset ( 1 9 7 1 ) . This genus, mainly characterised b y o n e left hyper- trophied ridge in b o t h s e x e s , o c c u r s in the Muridae from Africa and Madagascar. Sixteen species w e r e des
cribed, 14 from Africa o f w h i c h 12 are parasites o f Murinae, o n e b o t h from Murinae and Cricetomyinae, o n e o f Cricetomyinae and two s p e c i e s from Mada
gascar parasites o f N e s o m y i n a e .
In the g e n u s Heligmonina, the pattern o f the caudal bursa is variable ( 1 - 3 - 1 , 1-4, 2 - 2 - 1 . . . ) and can b e dif
ferent for e a c h l o b e . Five s p e c i e s o f Heligmonina, including the s p e c i m e n s described a b o v e have the pat
tern o f type 1-3-1 for e a c h l o b e . It c o n c e r n s with H. betsiloensis Quentin & Durette-Desset, 1974, a para
site o f Brachyuromys betsiloensis from Madagascar and two parasites from Africa: H. chabaudi (Desset, 1 9 6 4 ) , a parasite o f Mastomys natalensis and Lemniscomys striatus from the Central African Republic, H. possom- pesi (Durette-Desset, 1 9 6 6 ) a parasite o f Mus (Leggada)
minutoides from the Central African R e p u b l i c and H. praomyos Baylis, 1 9 2 8 , a parasite o f Praomys tul- bergi from Niger. T h e s p e c i m e n s described a b o v e are differentiated from these s p e c i e s b y strongly divergent extremities o f rays 4 and 5.
A m o n g the s p e c i e s with k n o w n synlophe, three spe
cies are related to the Malagasy s p e c i m e n s : H. mala- comys Sakka & Durette-Desset, 1 9 8 8 , a parasite o f Malacomys longipes from the Central African Republic, H. albignaci Quentin & Durette-Desset, 1 9 7 4 , a para
site o f Brachiuromys betsiloensis from Madagascar and H. betsiloensis. H. malacomys and H. albignaci p o s sess ventral comaretes, H. albignaci and H. betsiloensis p o s s e s s a c a r e n e at mid-body. Therefore, the axis o f
orientation o f the cuticular ridges at mi-body is sub- frontal in H. betsiloensis, inclined at 7 0 ° o n sagittal axis in H. albignaci, 4 5 ° ( m a l e ) , 5 0 ° (female) in H. mala
comys versus 6 0 ° in the Malagasy s p e c i m e n s . T h e s p e c i m e n s from Madagascar are also differen
tiated from all the other s p e c i e s , e x c e p t H. malaco- mysi b y the ratio o f the length o f the spicules o n the length o f the body. This ratio varies b e t w e e n 9.5 % and 17 % within the species o f Heligmonina. It is 25 % in H. malacomys and 17.6-27.9 % in the s p e c i m e n s from Madagascar.
T h e n e w s p e c i e s is n a m e d Heligmonina wrightae n.
sp. after Patricia Wright and in appreciation o f her a c h i e v e m e n t s in lemur and biodiversity conservation and research in Madagascar.
NESOMYSTRONGYLUS FISSICAUDA N. GEN., N. SP.
S t u d i e d m a t e r i a l : h o l o t y p e m a l e , a l l o t y p e f e m a l e MNHN 196 M Q b , 3 male, 7 female paratypes, MNHN
196 M Q c , coparasites o f Heligmonina wrightae n. sp.
Host: Nesomys audeberti (Jentink, 1 8 7 9 ) (Muridae) male.
Site: small intestine ( S I 1- SI 4 ) .
Geographical origin: V e v e m b e , Madagascar, D e c e m b e r 1995, coll. J . Jernvall.
O t h e r material: 1 m a l e , 1 anterior part o f f e m a l e MNHN 1 9 0 MQ, parasites o f the s t o m a c h o f Nesomys rufus in R a n o m a f a n a National Park, 10 N o v e m b e r 1998, coll: J . T . Lehtonen.
DESCRIPTION
Very small n e m a t o d e s with b o d y u n c o i l e d o r coiled only in its anterior pan. Excretory pore situated at mid
w a y b e t w e e n nerve ring and e n d o f o e s o p h a g u s . Dei- rids situated at s a m e level as e x c r e t o r y p o r e , setiform with rectangular basis (Fig. 2 K ) .
Head: Cephalic vesicle present, strongly striated and sligthly longer o n dorsal side. In apical view, r o u n d e d oral opening surrounded by two amphids, four externo labial papillae and four cephalic papillae. O e s o p h a g e a l dorsal gland well d e v e l o p e d (Fig. 2A').
Synlophe: (studied in o n e male and o n e female para- type). In b o t h s e x e s , b o d y bearing ridges regularly interrupted and set out in alternate series (Fig. 2 B , C).
Ridges appearing b e h i n d c e p h a l i c vesicle and disap
pearing in front o f caudal bursa in m a l e and vulvar o p e n i n g in female. In transverse sections, strut o f e a c h ridge ending in small tip apparently e x t e n d i n g outside cuticle. Number o f ridges: at oesophago-intestinal junc
tion, 2 0 (10 dorsal, 10 ventral) in b o t h s e x e s , at mid- body, 21 ( 1 0 dorsal, 11 ventral) in males (Fig. 2 G ) and 25 ( 1 2 dorsal, 13 ventral) in female (Fig. 2 F ) . Ridges disappearing about 5 0 a b o v e caudal bursa in male and at level o f infundibulum in female. Ridges o f similar
32 Mémoire Parasite, 2002, 9, 29-35
Fig. 2. — Nesomystrongylus fissicauda n. gen., n. sp. A-E, female, A, anterior extremity, right lateral view, A', head, apical view; B, C, beginning of cuticular ridges, respectively left lateral and ventral view, D, caudal extremity with spine, left lateral view, E, posterior extre
mity, left lateral view; F-G, cuticular ridges, transverse sections at mid-body. F, female, G, male; H-J, caudal bursa of male, H, right lobe, ventral view, I, left lobe, latero dorsal view, J , left lobe, ventral view; K, female, detail of the deirids and the excretory pore, ventral view;
L, male, caudal bursa, ventral view; M, male, detail of the dorsal ray and rays 8, dorsal view; N, male, tips of the spicules, ventral view.
Transverse sections orientated as figure 2, F.
Abbreviations: V, ventral side; L. left side.
NEW HELIGMONELUDAE (NEMATODA) FROM MADAGASCAR
DURETTE-DESSET M.C., LETHONEN J.T & HAUKISALMI V.
size, sligthly smaller in front o f left lateral field, orien
tated from right to l e f t , according to a sub-frontal axis.
Holotype male: 2.0 mm long and 4 0 wide at mid-body;
cephalic vesicle 5 3 long b y 25 wide; nerve ring, e x c r e tory pore and deirids situated at 163, 2 3 0 a n d 235 from a p e x , respectively; o e s o p h a g u s 3 2 0 long.
Caudal bursa symmetrical, o f very particular pattern:
very short rays 2 separated from c o m m o n trunk belon
ging t o rays 2 t o 8, arising at s a m e level a s dorsal ray o n c o m m o n trunk (Fig. 2H-J). Rays 3 strongly deve
loped; length o f rays decreasing from rays 3 to rays 8.
D o r s a l r a y d e e p l y d i v i d e d a l m o s t u p t o its b a s e (Fig. 2L, M ) . E a c h b r a n c h divided at its distal part into t w o b r a n c h e s , e a c h o n e giving rise to 2 small twigs, rays 9 ( e x t e r n a l ) a n d rays 1 0 (internal) (Fig. 2 M ) . Filiform, alate spicules, 3 0 0 long, e a c h ending in sharp tip (Fig. 2N). Genital c o n e discrete, 25 long and 15 wide with t w o small r o u n d papillae 7. Papilla zero n o t observed. Gubernaculum 12 long and 10 wide (Fig. 2L).
Main m e a s u r e m e n t s (average a n d range o f t h e three paratypes): body: 2.02 (2.0 - 2 . 0 5 ) mm long and 42 ( 4 0 - 4 5 ) wide; c e p h a l i c vesicle: 5 0 ( 4 8 - 5 2 ) long b y 2 0 ( 2 0 - 2 0 ) w i d e ; n e r v e ring, e x c r e t o r y p o r e a n d deirids situated at 1 4 8 ( 1 3 0 - 1 5 0 ) , 2 1 5 ( 1 7 5 - 2 4 0 ) , 2 2 5 ( 1 8 5 - 2 5 0 ) from a p e x , respectively; o e s o p h a g u s 3 0 0 ( 2 6 0 - 3 2 0 ) long; spicules 2 9 7 ( 2 8 0 - 3 1 0 ) long.
Allotype female: 2.65 m m long a n d 5 0 wide at mid- body. Cephalic vesicle 5 0 long b y 2 8 wide; nerve ring, excretory pore and deirids situated at 155, 2 5 0 a n d 245 from apex, respectively; oesophagus 3 6 0 long (Fig. 2A).
M o n o d e l p h y : vulva at 162 from c a u d a l extremity.
Vagina vera 3 0 long. O v e j e c t o r 140 long with vesti
b u l e 4 0 , sphincter 2 0 long b y 22 wide a n d infundi- bulum 8 0 long (Fig. 2 E ) . Uterus 3 6 0 long with 6 eggs, 55 long b y 3 0 wide at 2 b l a s t o m e r e stage near vulva;
ratio o f uterus length o n b o d y length: 13. 4 %. Tail 50 long with caudal spine 12 long (Fig. 2 D ) .
Main m e a s u r e m e n t s (average a n d range o f the s e v e n paratypes): b o d y 2. 6 5 (2.6-2.75) m m long a n d 47 ( 4 0 - 5 0 ) wide; c e p h a l i c vesicle 5 0 ( 4 8 - 5 5 ) long b y 2 4 . 5 ( 2 2 - 2 8 ) w i d e ; n e r v e ring, e x c r e t o r y p o r e a n d deirids situated at 162 ( 1 5 0 - 1 9 5 ) , 2 4 3 (232-266) a n d 241 ( 2 2 0 - 2 6 0 ) from a p e x , respectively; o e s o p h a g u s 3 4 2 ( 3 1 5 - 3 6 0 ) ; vulva at 144 ( 1 1 2 - 1 6 2 ) from caudal extremity;
vagina vera 2 8 ( 2 0 - 3 0 ) long; vestibule 4 2 ( 4 0 - 4 5 ) long;
sphincter 2 4 ( 2 0 - 2 8 ) long b y 26 ( 2 0 - 3 0 ) wide; uterus:
3 9 3 ( 2 6 0 - 4 2 0 ) long with 6 ( 4 - 7 ) eggs 5 3 ( 4 6 - 6 0 ) long by 2 8 ( 2 2 - 3 0 ) wide; tail 5 0 ( 4 2 - 6 0 ) long; caudal spine 11. 5 ( 1 0 - 1 2 ) long; ratio o f uterus length o n b o d y length: 14. 8 ( 1 0 . 0 - 1 6 . 5 ) % .
DIAGNOSIS
The Malagasy specimens belong to the sub-order Helig- m o s o m o i d e a b y the features o f the synlophe which is not symmetrical in relation to the sagittal axis (Durette-
Desset & Chabaud, 1993). Amongst t h e six families o f the sub-order, the p r e s e n c e o f discontinous, alternate ridges likens them most to the Brevistriatinae (Helig- monellidae). T h e y are closely related to the genus Fis- sicauda Durette-Desset & Krishnasamy, 1976, b y the absence o f the carene, by the ridges being discontinuous o n all sides o f the b o d y a n d b y the deeply divided dorsal ray. However, in comparison to Fissicauda, they possess very particular features: different staicture o f the ridges; caudal bursa with rays 2 to 6 faned out and not o f type 2-2-1; rays 2 very tiny a n d rays 3 strongly deve
loped with length decreasing from rays 3 to rays 8; rays 8 arising from c o m m o n trunk o f rays 2 to 6; female tail with a spine. In all the other g e n e r a o f the Heligmo- nellidae, the female tail is without a spine.
T h e n e w genus is n a m e d Nesomystrongylus after the host a n d the n e w s p e c i e s is n a m e d fissicauda accor
ding to the division o f the branches o f the caudal bursa.
Definition o f Nesomystrongylus n. gen.: Heligmonel- lidae, Brevistriatinae with s y n l o p h e without c a r e n e ; ridges interrupted regularly all along body; in trans
verse section, e a c h ridge ending in a small tip e x t e n ding outside cuticle; ridges orientated from right to left according to a sub-frontal axis; ridges o f similar size.
Caudal bursa with rays 2 to 6 faned o u t ; rays 2 ari
sing at s a m e level as dorsal ray o n c o m m o n trunk; rays 8 arising o n c o m m o n trunk o f rays 2 to 6; dorsal ray deeply divided; female tail with spine.
Parasites from Malagasy N e s o m y i n a e (Muridae).
T y p e a n d sole s p e c i e s : Nesomystrongylus fissicauda n.
gen., n. sp.
ACKNOWLEDGEMENTS
W
e are grateful to the Association Nationale p o u r la G e s t i o n d e s A i r e s P r o t e g e e s (ANGAP) for permission to w o r k within Ranomafana National Park a n d to Madagascar Institut pour la Conservation d e s E n v i r o n n e m e n t s T r o p i c a u x (MICET) for logistic support. S a m p l e s from V e v e m b e w e r e generously donated by J u k k a Jernvall and Patricia Wright. J e a n - C l a u d e Rakotoniaina, Haingotiana Ramia- rinjanahary a n d Francois Z a k a m a n a n a a r e t h a n k e d for help in t h e field work. T h e w o r k is financially supported b y t h e Finnish Cultural Foundation (JTL).
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Reçu le 23 mai 2001 Accepté le 19 juin 2001
