Ascocotyle (Phagicola) longa Ransom, 1920

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 : 1750-1752

Ascocotyle (Phagicola) longa Ransom, 1920

(®gure 7)

Metacercaria

Morphology. (Morphology based on 26 specimens from Mugil cephalus Linnaeus and M. curema Valenciennes in Cuvier and Valenciennes.) Cyst widely oval, thin-walled, 154±286 long and 131±207 wide. Body pyriform, 323±554 long and 115±202 wide, covered with scale-like tegumental spines. Remnants of eye-spots posterior to pharynx. Region between pharynx and ventral sucker containing oval cells with granular contents (? gland cells). Preoral lobe moderately developed; oral sucker 36±54 long and 36±54 wide, with well-developed posterior appendage, often sinuous, only rarely reaching to pharynx. Oral sucker surrounded by one row of 16 massive circumoral spines (n 519), 9±15 long and 3±4 wide. Prepharynx 40±102 long; pharynx strongly muscular, 30±45 long and 23±34 wide; oesophagus relatively short. Intestinal caeca narrow and long, surrounding ventral sucker and primordium of ovary, curved medially at level of anterior branch of excretory bladder, ®lled with spherical corpuscles. Ventral sucker spherical, well-developed, postequatorial, 23±40 long and 23±37 wide. Sucker width ratio 1 5 0.71±0.90. Testes symmetrical, near posterior extremity, 27±50 long and 27±55 wide. Seminal vesicle two-chambered, postacetabular. Genital sac anterosinistral to acetabulum, containing bipartite gonotyl composed of two pad-like lobes (®gure 7C). Primordium of ovary postacetabular, 18 long and 40 wide. Excretory bladder X-shaped, with short and wide arms, ®lled with numerous, dark granules. Flame cell formula most probably (posterior ducts not observed completely) 2 [(21 2)1 (21 2)] 516. First ¯ame cells posterolateral to oral sucker; second at pharyngeal level; third at level of caecal bifurcation; fourth anterolateral to acetabulum; ®fth and sixth posterolateral to ventral sucker; seventh lateral to anterolateral to testes and eighth posteromedial to testes.

Second intermediate hosts. Gobiesox X uviatilis Briggs and Miller ( Cyprinodontidae ); Dormitator latifrons (Richardson) (Eleotridae) ; Mugil cephalus , M. curema (Mugilidae) .

Site of infection. Heart, musculature of gill branches, body musculature, rarely intestinal wall, liver, gonads, mesenteries.

Distribution. Jalisco (El JabalõÂ, Marismas de Chalacatepec, RõÂo Cuitzmala, Salinas de Careyes, San NicolaÂs).

References from Mexico. Scholz (1999); present study.

Specimens deposited. BMNH 2000.6.1.9, CHCM-352, CNHE 3928, IPCAS D-445, USNPC 88537, 90192, 90193.

Adult

Morphology. Scholz (1999) redescribed the species on the basis of examination of the type specimens and reference material from diOEerent hosts and geographical regions.

De W nitive host. Ardea herodias .

Site of infection. Intestine.

Distribution. YucataÂn (CelestuÂn).

References from Mexico. Present study.

Specimens deposited. CNHE 3926, IPCAS D-295.

Comments. Metacercariae are frequent parasites of brackish-water ®sh, above all grey mullets ( Hutton and Sogandares-Bernal, 1959, 1960; Manfredi and Oneto, 1997). In Mexico, they have been found only in ®sh from its western (Paci®c) coast ( Scholz, 1999; present study).

Adults of A. (P.) longa found in a number of birds, mainly herons, and mammals (see Scholz, 1999 for review) are reported from Mexico for the ®rst time. Scholz (1999) synonymized A. (P.) arnaldoi Travassos, 1929 , A. (P.) byrdi ( Robinson, 1956) and A. (P.) longicollis (Kuntz and Chandler, 1956) with A. (P.) longa that is the most widely distributed species of Ascocotyle reported from North and South America, Europe, North Africa and Asia (Middle East) (see Scholz, 1999 for references).

Chie et al. (1992) reported human infections caused by a species of Phagicola (5 Ascocotyle ( Phagicola )), supposed to be A. (P.) longa by Manfredi and Oneto (1997). The latter authors discussed the capacity of this trematode to infect humans because of heavy infections of mullets with its metacercariae encysted in the muscles.