Posthodiplostomum macrocotyle Dubois, 1937

Drago, Fabiana B., Lunaschi, Lía I. & Draghi, Regina, 2014, Digenean fauna in raptors from northeastern Argentina, with the description of a new species of Strigea (Digenea: Strigeidae), Zootaxa 3785 (2), pp. 258-270 : 266-267

Posthodiplostomum macrocotyle Dubois, 1937

( Figs. 8–9 )

Host: Busarellus nigricollis (Latham) , black–collared hawk ( Accipitridae ).

Site of infection: small intestine.

Voucher specimens: MLP 6716, 6717.

Distribution and hosts: This species was described by Dubois (1937, 1970) based on material from Rynchops niger L. ( Laridae ) in Brazil. Later, Dubois & Macko (1972) reported it parasitizing ardeid birds from Cuba [ Ardea alba (L.), Butorides virescens maculata (Boddaert) , Egretta caerulea (L.), Egretta tricolor ruficollis Gosse , and Nycticorax nycticorax hoactli (Gmelin)]. Recently, Brandão et al. (2013) found specimens of P. macrocotyle parasitizing Spheniscus magellanicus (Forster) (Spheniscidae) from Brazil.

Measurements: Based on 5 specimens. Body distinctly bipartite, 435–1114 (814) long. Forebody 299–677 (521) long by 217–459 (316) wide. Hindbody 133–474 (319) long by 208–328 (266) wide. Ratio of forebody length to hindbody length 1:0.4–0.7 (0.8) Oral sucker round, subterminal, 29–45 (39) long by 26–45 (37) wide. Ventral sucker subspherical, located in second half of forebody, 40–48 (43) long by 44–52 (48) wide. Suckers width ratio 1:1.2. Pharynx oval, immediately posterior to oral sucker, 35–48 (41) long by 29–38 (33) wide. Pseudosuckers absent. Holdfast organ subspherical, 121–174 (154) long by 83–169 (124) wide. Testes tandem, continuous; anterior testis asymmetrical, oval to subtriangular, just posterior to junction of fore– and hindbody, 76– 111 (93) long by 155–217 (182) wide; posterior testis symmetrical, horseshoe shaped, 107–198 (163) long by 228– 275 (251) wide. Genital cone 67–107 (80) long by 93–193 (131) wide. Ovary elliptical, posterior to junction of fore– and hindbody, dextral, 43–72 (58) long by 117–169 (138) wide. Vitellarium in fore– and hindbody; vitelline follicles extending from midway between intestinal bifurcation and ventral sucker to posterior testis. Eggs 81–90 (85) long by 52–57 (55) wide.

Remarks: The specimens obtained from B. nigricollis possess morphological and morphometric characters similar to those described by Dubois (1937, 1970) and Dubois & Macko (1972). The specimens described by Brandão et al. (2013) from S. magellanicus agree well morphologically with our specimens, but differ by being larger (1192–1.529 vs. 435–1114), by having larger oral sucker (57–72 x 59 –75 vs. 29– 45 x 26–45), ventral sucker (84–102 x 69 –98 vs. 40–48 x 44 –52), pharynx (54–65 x 33 –47 vs. 35– 48 x 29–38) and holdfast organ (215–224 x 174–226 vs. 121–174 x 83 –169). However, these authors consider that the differences in size are related to the high morphometric variability of this diplostomid and its presence in an unusual host.

The life cycle of P. macrocotyle has not been elucidated yet, but its metacercariae have been reported in freshwater fishes (see Brandão et al. 2013). This diplostomid has scarce specificity, because it parasitizes phylogenetically unrelated ichthyophagous birds. Then, the presence of this parasite is associated with the diet of the black–collared hawk, which is mainly ichthyophagous ( Thiollay 1994).

The finding of P. macrocotyle parasitizing B. nigricollis represents a new host record and the first record of this species in Argentina.

Figures

FIGURES 4 – 11. Digeneans from raptors. 4. Strigea proteolytica n. sp. from Buteogallus urubitinga, scale bar = 250 µm. 5. Strigea falconis brasiliana Szidat, 1929 from Caracara plancus, scale bar = 250 µm. 6. Neodiplostomum travassosi Dubois, 1937 from Buteogallus meridionalis, scale bar = 200 µm. 7. Tylodelphys brevis Drago & Lunaschi, 2008 from Busarellus nigricollis, scale bar = 100 µm. 8. Posthodiplostomum macrocotyle Dubois, 1937 from B. nigricollis, scale bar 200 µm. 9. Enlarged view of copulatory bursa of P. macrocotyle, scale bar 50 µm. 10. Spaniometra variolaris (Fuhrmann, 1904) from R. sociabilis, scale bar 500 µm. 11. Megalophallus deblocki Kostadinova, Vaucher & Gibson, 2006 from R. sociabilis, scale bar 100 µm. Abbreviations: B, body wall; Gc, genital cone; P, prepuce.