Ascocotyle ( Leighia ) megalocephala Price, 1932

Ascocotyle ( Leighia) megalocephala Price, 1932 View in CoL

(®gure 5A±D)

Metacercaria

Morphology. Scholz et al. (1995: 179 ±180; ®gure 4) had described a metacercaria designated as Ascocotyle ( Ascocotyle) sp. 1 that was later identi®ed as A. ( L.) megalocephala by Scholz et al. (1997a). A description of six metacercariae from Poecilia mexicana is provided: cyst widely oval to almost spherical, 432±472 long and 288±368 wide, with thick outer wall, often brownish, and thinner internal wall. Metacercarial body ¯ask-shaped, slightly tapering towards anterior end, 376±700 long and 220±330 wide, densely covered with simple tegumental spines. Spines almost completely covering ventral side of body except for small area around subterminal excretory pore; dorsally, spines reaching only to level of excretory bladder. Remnants of eye-spot granules scattered at pharyngeal level. Preoral lobe feebly developed (®gure 5A) but in some living specimens may be protruded (®gure 5C, D). Oral sucker spherical, 67±97 long and 80±140 wide, with conical posterior appendage, usually not reaching to pharynx, sometimes curved. Oral sucker armed with 74±80 ®ne but well-visible circumoral spines arranged in two complete rows of 36±40 spines each; anterior spines 12±17 long and 3±4 wide; posterior spines 10±16 long and 3±4 wide. Spination pattern 361 38 ( n 51); 371 38 ( n 51); 381 39 ( n 51); 391 39 ( n 52); 401 40 ( n 51). Prepharynx 80±102 long; pharynx oval to almost pyriform, 40±72 long and 30 ±52 wide; oesophagus very short or indistinct. Intestinal caeca short and wide, often forming a sac, reaching only to anterior margin of ventral sucker. Ventral sucker spherical, postequatorial, 68 ±90 long and 62±80 wide. Sucker ratio 1 5 0.55±0.80. Testes symmetrical, at distance from posterior extremity, 37±80 long and 30±55 wide. Ventrogenital sac feebly developed, with simple, pad-like, transversely oval gonotyl. Primordium of ovary anteromedial to testes. Excretory bladder voluminous, X-shape d to sac-like, in encysted metacercariae occupying more than half of metacercarial body, ®lled with large droplets. Excretory pore subterminal, ventral.

Second intermediate hosts. Poecilia mexicana , P. velifera (Poeciliidae) .

Site of infection. Wall of stomach and intestine, mesenteries.

Distribution. Veracruz (Los TuxtlasÐarroyo Balzapote); YucataÂn (Mitza, Sahkaba).

References from Mexico. Scholz et al. (1995 Ðas Ascocotyle ( A.) sp. 1); Scholz et al. (1997a); present study.

Specimens deposited. CHCM-356a, CNHE 3925, IPCAS D-351, USNPC 90189.

Adult

Morphology. No substantial diOEerences were observed between the specimen found in Ardea herodias from CelestuÂn and that described by Scholz et al. (1997a: 176, 178; ®gure 7A, B, D) from the intestine of Casmerodius albus from the same locality. Therefore, only a brief description of newly collected specimen is provided here: body 800 long and 360 wide. Oral sucker 125 long and 197 wide. Sucker armed with simple spines forming two rows, with 38 spines in anterior complete row; posterior row with several spines apparently missing, most probably containing 38 spines as well. Anterior spines 25 long and 6 wide; posterior spines 21±22 long and 5±6 wide. Ventral sucker 56 long and 55 wide. Sucker ratio 1 5 0.34. Testes 107±115 long and 137±160 wide. Ovary 100 long and 140 wide. Seminal receptacle 87 long and 97 wide. Eggs 19±21 long and 9±11 wide.

De W nitive host. Ardea herodias , Casmerodius albus .

Site of infection. Intestine.

Distribution. YucataÂn (CelestuÂn).

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

Specimens deposited. CHCM-356, CNHE 3925, IPCAS D-446.

Comments. Two species of Poecilia from Mexico represent new ®sh hosts of A. ( L.) megalocephala . Stein (1968) reported the poeciliid Mollienisia latipinna (5 Poecilia latipinna ) as its natural intermediate host in Florida but he did not provide descriptions or ®gures of the metacercariae.

Ascocotyle ( L.) megalocephala View in CoL was described by Price (1932) from Butorides sp. from Puerto Rico. Up to date, adults have been found only in Puerto Rico ( type locality) and Mexico ( Price, 1932; Scholz et al., 1997a). The heron Ardea herodias View in CoL is a new de®nitive host of this trematode that seems to be a rare parasite of herons.