Phocitremoides ovale Martin, 1950

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 : 1762-1764

* Phocitremoides ovale Martin, 1950

(®gure 11)

Metacercaria

Morphology. (Morphology based on 16 live metacercariae from Fundulus grandissimus .) Cyst almost spherical, thin-walled, 138±165 long and 128±163 wide. Excysted metacercaria elongate, 301±383 long and 138±163 wide, covered with conspicuous scale-like tegumental spines, pectinate in anterior third of body and decreasing in size posteriorly. Eye-spot remnants scattered between pharynx and acetabulum, sometimes present even in postacetabular region. Numerous cells with granular content lateral to oesophagus and intestinal caeca. Oral sucker spherical to widely oval, 48±58 long and 48±68 wide. Prepharynx very short; pharynx strongly muscular, 25±32 long and 24±30 wide; oesophagus longer than prepharynx. Intestinal caeca long and wide, reaching to anterior arms of excretory bladder, ®lled with discoidal corpuscles; intestinal wall in posterior part with granular content (®gure 11G). Ventral sucker spherical, slightly postequatorial, embedded in parenchyma, 46±50 long and 48 ±52 wide. Sucker ratio 1 5 0.81±1.00. Testis single, large, near posterior extremity. Ventrogenital sac formed, thick-walled, anterior to ventral sucker. Ovary anterodextral to testis. Excretory bladder V-shaped, with short arms, reaching to anterior half of testis, containing numerous dark granules. Flame cell pattern not determined but cells apparently in pairs, with ®rst pair posterolateral to oral sucker and one pair posterolateral to acetabulum.

Second intermediate hosts. Floridichthys polyommus , Fundulus grandissimus , F. persimilis (Cyprinodontidae) .

Site of infection. Scales (internal side).

Distribution. YucataÂn (CheleÂm Lagoon).

References from Mexico. Present study.

Specimens deposited. None.

Adult

Morphology. (Morphology based on eight hot formalin-®xed specimens from chicks infected with metacercariae from scales of Fundulus grandissimus , 4 days post infection; measurements of seven ¯attened specimens in parentheses.) Body small, pyriform, 320±370 (390±580) long and 170±250 (192±230) wide, covered with scalelike tegumental spines. Pectinate spines with four to six teeth covering ventral surface except for periacetabular zone, decreasing in size and less dense posteriorly. Dorsal side covered with spines up to anterior margin of testis. Remnants of eye-spots scattered throughout body between pharynx and posterior extremity. Oral sucker widely oval, 45±50 (52±70) long and 47±52 (49±75) wide. Sucker surrounded by numerous elongate cells with granular contents; four small gland cells present near base of oral sucker (®gure 11C). Prepharynx 12±22 (7±60) long; pharynx strongly muscular, 17±22 (22±30) long and 17±22 (17±27) wide; oesophagus longer than prepharynx. Intestinal caeca thick-walled, narrow and long, reaching posteriorly to excretory bladder. Ventral sucker spherical, slightly postequatorial, 39±40 (44±59) long and 40±47 (42±52) wide, recessed in parenchyma, with small opening situated slightly dextral to median line of body, separated from mouth of ventrogenital sac. Tegument at level of posterior margin of ventral sucker covered with semilunar circle of narrow, simple spines arranged in two to three irregular rows. Sucker ratio 1 5 0.81±0.95 (1 5 0.64±0.84). Testis single, 47±63 (80±105) long and 52 ±72 (90±92) wide, in posterior third of body. Seminal vesicle postero- to laterodorsal to ventral sucker, voluminous, bipartite, with feebly separated chambers often overlapping one another. Ventrogenital sac well-developed, thick-walled, opening by slit-like mouth, anterosinistral to ventral sucker; gonotyl absent. Ovary just anterior to testis, slightly shifted dextral to median line of body, 32±42 (36±50) long and 45±65 (52±80) wide. Seminal receptacle spherical, anterolateral to testis (32±42 long and 32±42 wide). Vitelline follicles small, laterodorsal to ovary and testis, anteriorly reaching to posterior margin of acetabulum, posteriorly not overlapping testis. Uterus tubular; uterine loops ®lling most space between caecal bifurcation and posterior extremity. Eggs operculate, 25.0 Ô 1.5 (range 23±28; n 536) (20±28) long and 15.1 Ô 1.3 (range 14±17.5) (10±16) wide. Excretory bladder V-shaped with short arms, not reaching to pretesticular level, containing numerous dark granules.

De W nitive hosts. Chick, duck (experimental).

Site of infection. Intestine.

Distribution. Not known.

References from Mexico. Present study.

Specimens deposited. BMNH 2000.6.1.11, CHCM-351, CNHE 3936, IPCAS D-395, USNPC 90196.

Comments. Metacercariae were found exclusively in scales of three species of cyprinodontid ®sh that represent new second intermediate hosts. The parasite was infrequent in Floridichthys polyommus but very common in both species of Fundulus . The morphology of the metacercariae corresponds to that of metacercariae of Phocitremoides ovale found in experimentally infected Atherinopsis californiensis Girard and Fundulus parvipinnis ( Martin, 1950b) .

Adults from experimental hosts were almost identical in their morphology and measurements, including the egg size, to those described by Martin (1950b) as Phocitremoides ovale . There was only a slight diOEerence in the shape of the body that was reported to be oval to pyriform by Martin (1950b: ®gure 1) whereas the trematodes from Mexico were elongate and pyriform, thus not corresponding to the speci®c name `ovale ’. However, this diOEerence may be related to diOEerent ®xation of worms.

Martin (1950b: ®gure 1) illustrated the mouth of the ventral sucker to be common with that of the ventrogenital sac. In fact, both openings are distinctly separated one from another as observed both in living and ®xed metacercariae and adults (®gure 11D, G).

Natural de®nitive hosts of P. ovale are not known and adults were obtained only from experimentally infected hosts ( Martin, 1950b; Yoshino, 1972) in California. Oculopleurolophocercous cercariae of P. ovale were found in Cerithidea californica (Prosobranchia) . The present data expand the range of distribution of P. ovale to the Atlantic coast of Mexico, from which it is reported for the ®rst time.