Ascocotyle (Leighia) nunezae

Scholz, T., Aguirre-Macedo, M. L. & Salgado-Maldonado, G., 2001, Trematodes of the family Heterophyidae (Digenea) in Mexico: a review of species and new host and geographical records, Journal of Natural History 35 (12), pp. 1733-1772 : 1746-1750

Ascocotyle (Leighia) nunezae

Scholz, Vargas-VaÂzquez, Vidal-MartõÂnez and Aguirre-Macedo, 1997

Metacercaria

Morphology. Scholz et al. (1995: 184; ®gure 8A±GÐas Ascocotyle (Phagicola) sp. 3) and Scholz et al. (1997b: 143; ®gures 9±15) provided detailed descriptions of metacercariae. The most typical characters enabling diOEerentiation of A. (L.) nunezae from congeners are as follows: body elongate to conical, tapering anteriorly, entirely spined; preoral lobe feebly developed; posterior appendage conical, not reaching to pharynx; circumoral spines forming one complete row of 25±26 and seven to nine accessory spines on dorsal side; intestinal caeca long, reaching to ovarian primordium, slightly curved medially around ventral sucker.

Second intermediate hosts. Cichlasoma aureum , C. helleri , C. meeki (Brind) , C. octofasciatum , C. pasionis Rivas , C. pearsei , C. robertsoni Regan , C. salvini , C. synspilum , C. urophthalmus , Petenia splendida (Cichlidae) .

Site of infection. Gills.

Distribution. Campeche (El Viento, La Pera, Palizada, Rancho II, Santa Gertrudis, Zoh Laguna); Chiapas (LacanjaÂ); Quintana Roo (Box Toro, CabanÄas, La UnioÂn, Laguna Paiyegua, Los Cuates, Ramonal, Raudales, RõÂo Hondo); Tabasco (Las Ilusiones, Puyacatengo, Yucateco, YumkaÂ); YucataÂn (Chaamac, Chek-haÂ, Dzonot Cervera, Noc-choncunchey, Petentuche).

References from Mexico. Scholz et al. (1995 Ðas Ascocotyle (Phagicola) sp. 3); Scholz et al. (1997a, 1997b); Scholz and Vargas-VaÂzquez (1998); Vidal-MartõÂnez et al. (2000); present study.

Specimens deposited. CNHE 3729, 3731, IPCAS D-349.

Adult

Morphology. Adults from naturally and experimentally infected de®nitive hosts from Mexico were described and illustrated by Scholz et al. (1997b: 141, 143; ®gures 1±8).

De W nitive hosts. Casmerodius albus (natural); chicks (experimental).

Site of infection. Intestine.

Distribution. YucataÂn (CelestuÂn).

References from Mexico. Scholz et al. (1997b).

Specimens deposited. CNHE 2849 (holotype) ; BMNH 1996.10 .7.5; CHCM 185; IPCAS D-348 ; USNPC 86819 (paratypes).

Comments. Numerous recent ®ndings of metacercariae from cichlid ®sh do not correspond with the fact that adults have been found only once in naturally infected hosts. In Ardea herodias from the type locality examined by the present authors, A. (L.) nunezae was not found, similarly during a large-scale survey of the parasites of the little blue heron ( Egretta caerulea ) and great egret ( Casmerodius albus ) carried out in Florida by SepuÂlveda et al. (1996, 1999).

As pointed out by Scholz et al. (1997b), A. (L.) nunezae possesses features that place it in the intermediate position among Ascocotyle subgenera. Scholz et al. (1997b) placed this species to the nominotypical subgenus Ascocotyle following Yamaguti’s (1971) concept of the subgenera of Ascocotyle . However, the authors overlooked that members of the subgenus Ascocotyle have the uterus con®ned mainly to the postacetabular area whereas those of Leighia in its original concept by Sogandares-Bernal and Lumsden (1963) possess uterine loops reaching anteriorly to the pharyngeal level. Therefore, A. nunezae is transferred to the subgenus Leighia .

* Ascocotyle (Phagicola) ampullacea Miller and Harkema, 1962 (®gure 6)

Metacercaria

Morphology. (Morphology based on one specimen from Gambusia yucatana Regan , two from Poecilia sphenops , one from Poecilia sp. and two from Belonesox belizanus .) Cyst large, almost spherical, 342±365 long and 335±365 wide, with thick (13±20), mechanically resistant and elastic outer wall, and thin, transparent internal wall. Body ¯ask-shaped, tapering anteriorly, 490±670 long and 230±279 wide, covered with small tegumental spines becoming smaller posteriorly. Preoral lobe indistinct; oral sucker spherical, subterminal, 45 ±47 long and 42±51 wide, with short, conical posterior appendage, not reaching to pharynx. Oral sucker armed with 44±54 circumoral spines forming two complete rows each of 22±27 spines each. Spination patterns 221 22 (n 52); 251 23 (n 51); 251 25 (n 52); 271 27 (n 51). Anterior spines 10±12 long and 2 wide; posterior spines 9±11 long and 2 wide. Prepharynx 35±120 long; pharynx oval, 42±47 long and 32±42 wide; oesophagus relatively short. Intestinal caeca long and narrow, surrounding ventral sucker, terminating anterior to excretory bladder, containing numerous spherical bodies. Ventral sucker spherical, slightly postequatorial, 58±62 long and 62±77 wide. Sucker ratio 1 5 1.48±1.83. Testes symmetrical, near posterior extremity, 35±50 long and 47±60 wide. Ventrogenital sac anterosinistral to ventral sucker, containing gonotyl with 12±14 refractile bodies. Primordium of ovary postacetabular. Flame cell pattern not determined but probabl y 16 ¯ame cells present, arranged in four pairs. First pair situated between mouth and pharynx, second pair at acetabular level, third between acetabulum and excretory bladder and fourth pair at level of excretory bladder. Excretory bladder X-shaped, with prominent anterior arms and reduced posterior ones, ®lled with spherical droplets.

Second intermediate hosts. Belonesox belizanus , Gambusia yucatana , Poecilia sphenops , Poecilia sp. (Poeciliidae) .

Site of infection. Muscles ( G. yucatana ), intestinal wall ( P. sphenops ), mesenteries ( Poecilia sp. ), gonads ( B. belizanus ).

Distribution. Tabasco (El Yucateco); YucataÂn (Chaamac, Mitza).

References from Mexico. Present study.

Specimens deposited. CNHE 3923, IPCAS D-400.

Comments. Despite slight diOEerences in the size of the prepharynx and oesophagus, and the site of infection, all metacercariae found in poeciliids from Tabasco and YucataÂn are considered to be conspeci®c because of similar size and shape of cysts and their walls, a ¯ask-shaped body, an indistinct preoral lobe, a conical posterior appendage not reaching to the pharynx, armament of the oral sucker, long and narrow intestinal caeca, and the presence of more than 10 refractile bodies within the gonotyl.

In all these features, the metacercariae ®t best into the diagnosis of the species A. (P.) ampullacea as described by Miller and Harkema (1962) from Procyon lotor (Linnaeus) from North Carolina and as observed in its paratypes (USNPC 59584). It should be mentioned that refractile bodies within the gonotyl of adults of A. (P.) ampullacea were incorrectly described as spines by Miller and Harkema (1962). The only diOEerence was in slightly higher number of circumoral spines in some metacercariae (22±27 spines but mostly 22 ±25 spines) than in adults (20±24). However, this may be due to intraspeci®c variation in the number of spines.

Stein (1968) ®rst reported metacercariae of this trematode from the the intestinal mesenteries and body musculature of the poeciliid ®sh Gambusia a nis from Florida but the author did not provide any description or illustrations. Adults obtained from chicks fed with infected organs possessed 22 1 22 circumoral spines ( Stein, 1968). The present ®ndings represent a new geographical record of this fairly rare trematode known only from the USA and Mexico.

Ascocotyle (Phagicola) diminuta Stunkard and Haviland, 1924 (®gure 1E)

Metacercaria

Morphology. Descriptions were provided by Scholz et al. (1995: 180 ±181; ®gures 5, 7B) and Scholz et al. (1997a: 172 ±173; ®gures 2A±E, 5A±D, F, 7E). Metacercariae can be distinguished from those of congeneric species by the elongate shape of cyst, the presence of 18 massive circumoral spines arranged in one complete row of 16 spines and two smaller additional spines on the dorsal side, narrow and long intestinal caeca reaching posterior to the ventral sucker, and a simple gonotyl lacking refractile bodies.

Second intermediate hosts. Belonesox belizanus , Poecilia latipunctat a, P. mexicana , P. petenensis , P. sphenops , P. velifera (Poeciliidae) ; Cyprinodon artifrons Hubbs (reported as C. variegatus by Sogandares-Bernal and Lumsden, 1963), Fundulus grandissimus , F. persimilis , Floridichthys polyommus Hubbs (reported as F. carpio Hubbs by Scholz et al., 1997a) ( Cyprinodontidae ).

Site of infection. Gills.

Distribution. Quintana Roo (Box Toro, Cenote Azul, Ramonal); Veracruz (Los TuxtlasÐBalzapote); YucataÂn (Chaamac, Chek-haÂ, CheleÂm, Chen-haÂ, DzibilchaltuÂn, Noc-choncunchey, Progreso, Sahkaba).

References from Mexico. Sogandares-Berna l and Lumsden (1963 Ðas Ascocotyle angrense ); Scholz et al. (1995, 1997a); Scholz and Vargas-VaÂzquez (1998); present study.

Specimens deposited. CHCM-358, IPCAS D-343.

Adult

Morphology. Scholz et al. (1997a: 173; ®gures 5E, G±I, 7F, G) described adults from naturally and experimentally infected hosts.

De W nitive hosts. Ardea herodias , Casmerodius albus (natural), chicks (experimental).

Site of infection. Intestine.

Distribution. YucataÂn (CelestuÂn).

References from Mexico. Scholz et al. (1997a); present study.

Specimens deposited. CNHE 3924, IPCAS D-342, USNPC 88538, 90191.

Comments. Metacercariae from the gill ®laments of poeciliid ®shes ( Belonesox belizanus , Cyprinodon variegatus (5 C. artifrons ) and Mollienisia sphenops (5 Poecilia sphenops )) from Progreso, YucataÂn, identi®ed by Sogandares-Bernal and Lumsden (1963) as Ascocotyle angrense , were undoubtedly conspeci®c with A. (P.) diminuta because they possessed 161 2 circumoral spines (instead of 181 2 in A. (P.) angrense Ðsee Ostrowski de NuÂnÄez, 1993 and Scholz et al., 1997a).

In Mexico and the USA, only poeciliid and cyprinodontid ®sh serve as second intermediate hosts of A. (P.) diminuta (see Stunkard and Uzmann, 1955; Sogandares - Bernal and Bridgman, 1960; Stein, 1968; Scholz et al., 1997a). In Argentina, Ostrowski de NuÂnÄez (1993) found ®sh of the families Cichlidae and Jenynsidae to be suitable second intermediate hosts.

SepuÂlveda et al. (1999) found A. (P.) diminuta to be one of the most frequent parasites of the great egret ( Casmerodius albus ) from Florida, with prevalence of infection being 33% (n 570) and mean intensity 64 specimens (range 1±3580). Besides ®sh-eating birds, mammals such as raccoon, rats, mice and hamsters have been reported as de®nitive hosts of this trematode reported from a large area between northeastern USA (Connecticut, MD) and Argentina ( Stunkard and Haviland, 1924; Stunkard and Uzmann, 1955; Ostrowski de NuÂnÄez, 1993).

The life cycle of this trematode was ®rst elucidated by Ostrowski de NuÂnÄez (1993) who found the hydrobiid snails Littoridina castellanosae Gaillard and L. parchappi d’Orbigny to serve as the ®rst and cyprinodontid ®sh as the second intermediate hosts in Argentina. Scholz et al. (1997a) successfully infected ®sh with cercariae of A. (P.) diminuta released from the hydrobiid snail Pyrgophoru s coronatus (PfeiOEer) in YucataÂn.