Megalophallus deblocki Kostadinova, Vaucher & Gibson, 2006

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 : 268

Megalophallus deblocki Kostadinova, Vaucher & Gibson, 2006

( Fig. 11 )

Hosts: Rostrhamus sociabilis (Vieillot) , snail kite (Accipitidae); Buteogallus meridionalis (Latham) , savanna hawk (Accipitidae).

Site of infection: intestine.

Voucher specimens: R. sociabilis MLP 6720, B. meridionalis MLP 6721.

Distribution and hosts: The adult forms of M. deblocki were described by Kostadinova et al. (2006) parasitizing R. sociabilis from Paraguay, and its metacercariae were found encysted in the digestive gland of the naturally infected crab, Dilocarcinus dentatus Randall ( Decapoda : Trichodactylidae ) from Venezuela ( Díaz et al. 2012).

Measurements: Based on 7 specimens. Body pyriform, 420–561 (478) long by 270–319 (298) wide. Forebody 256–314 (277) long, 56%–61% (58%) of body length. Tegument covered with minute spines. Oral sucker round, subterminal, 41–44 (43) long by 39–53 (46) wide. Ventral sucker round, post-equatorial, 29–55 (46) long by 29–48 (41) wide. Suckers width ratio 1:1–1.3 (1.2). Prepharynx 13–15 (14) long; pharynx oval, 39–43 (41) long by 21–29 (25) wide; esophagus 81–121 (99) long; ceca short, reach to level of ventral sucker, 107–150 (130) long. Testes symmetrical, located in last third of body; right 44–71 (58) long by 39–76 (58) wide; left 39–69 (54) long by 53– 107 (80) wide. Seminal vesicle 102–120 (110) long. Phallus ovoid, muscular, sinistral, located lateral to ventral sucker, 83–88 (85) long by 71–98 (87) wide, ornamented with 21–24 (23) stout spines. Ovary dextral, located at level of ventral sucker 29–38 (34) long by 53–71 (62) wide. Vitellarium in 2 lateral groups of 9–10 follicles, in testicular and post-testicular regions. Eggs numerous, 10–16 (12) long by 8–9 (8.2) wide.

Remarks: The specimens found in R. sociabilis and B. meridionalis from Argentina are in agreement with those originally described in Paraguay by Kostadinova et al. (2006), and those obtained experimentally in Venezuela ( Díaz et al. 2012). The life cycle of this microphallid species has been partially elucidated by Díaz et al. (2012), the metacercariae were found in crabs, and the adult forms were experimentally obtained from chickens and rats.

Rostrhamus sociabilis has a highly specialized diet, composed almost entirely of apple snails ( Pomacea spp.), but may take other preys including crabs, turtles and rodents ( Thiollay 1994). In Argentina, Di Giacomo (2005) mentioned that it feeds on crabs, in addition to aquatic snails in the Reserva Bagual, Formosa Province. The most part of snail kites examined had remains of Pomacea sp. in the stomach, but the only specimen parasitized with M. deblocki had the stomach empty. This suggests that when there is limited availability of snails in the environment, these birds can eat crabs infected with metacercariae. On the other hand, B meridionalis feeds on small mammals, birds, snakes, lizards, frogs, toads, eels, crabs, and large insects ( Thiollay 1994). This wide spectrum of food items can explain the low intensity of infection (1) of this microphallid in the savanna hawk. In Formosa Province, it mainly feeds on small vertebrates and large insects ( Di Giacomo 2005), but the finding of M. deblocki suggests that it also eats crabs.

The finding of M. deblocki parasitizing B. meridionalis 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.