Allocreadium neotenicum Peters, 1957

Bray, Rodney A., Foster, Garth N., Waeschenbach, Andrea & Littlewood, D Timothy J, 2012, The discovery of progenetic Allocreadium neotenicum Peters, 1957 (Digenea: Allocreadiidae) in water beetles (Coleoptera: Dytiscidae) in Great Britain, Zootaxa 3577, pp. 58-70 : 61-66

Allocreadium neotenicum Peters, 1957

urn:lsid:zoobank.org:act:549F3979-54E2-4EFC-B579-640042B4F24B

Synonyms: Pseudallocreadium neotenicum ( Peters, 1957) Yamaguti, 1971 ; Allocreadium sp. of Peters (1955); allocreadiid trematode of Jackson (1958).

Probable synonym: Allocreadium sp. of Crawford (1940).

Hosts: Hydroporus rufifrons (Müller) ( Coleoptera : Dytiscidae ); Agabus melanarius Aubé ( Coleoptera : Dytiscidae ); Agabus paludosus (Fabricius) ( Coleoptera : Dytiscidae ).

Site: Haemocoel.

Localities: H. rufifrons, Staveley, Westmorland , 21/10/2010, Coll: G. N. Foster, SD47649802 Ings Pond, Westmorland, 03/11/2011, SD442984, Coll: G. N. Foster; Ings, Westmorland, SD44249838, 21/10/2010, Coll: G. N. Foster; a shallow marsh near Jordan Lane, Westmorland, SD635901, 24/03/2012, Coll: G. N. Foster; A. melanarius, Hindleap Warren, Ashdown Forest , East Sussex, Oct. 1968, Coll: R.B. Angus; A. paludosus , near St Andrews, Fife, October 1956. Coll.: D.J. Jackson.

Vouchers: NHMUK 2012.9.28.1-11.

Description: Based mainly on 6 specimens from H. rufifrons , because specimens from A. melanarius are immature and the single specimen from A. paludosus is damaged. Measurements in Table 2. Body broadly oval, robust ( Fig. 2 ). Tegument unarmed. Eye-spots discrete, lateral to oesophagus. Oral sucker rounded, subterminal, no stylet seen. Ventral sucker transversely oval, larger than oral sucker, in anterior third of body. Prepharynx not seen. Pharynx oval. Oesophagus short. Intestinal bifurcation in posterior forebody or dorsal to ventral sucker. Caeca wide, reaching just into post-testicular zone or to level of posterior testis.

Testes 2, large oval, entire, but flattened on contiguous parts of margins, oblique in anterior hindbody. Cirrussac oval, in forebody and overlapping ventral sucker ( Fig. 3 ). Internal seminal vesicle broad, long with globular and tubular parts, coiled. Pars prostatica not distinct, but a few large glandular cells surround junction of seminal vesicle and ejaculatory duct. Ejaculatory duct long, thick-walled. Genital atrium distinct, surrounded by large gland cells. Genital pore median, bifurcal, surrounded by wide sphincter.

Ovary large, oval, entire, mostly dorsal to ventral sucker, may reach into hindbody. Seminal receptacle overlapping ovary and anterior testis, in dorsal plane. Laurer’s canal opens dorsally to left caecum at level of ovary ( Fig. 4 ). Mehlis’ gland not clearly distinguished. Uterus pretesticular, ventral and sinistro-lateral to ovary, partly dorsal to ventral sucker. Vitellarium follicular; follicles large, irregular, tightly packed, anterior extent at level of ventral sucker, reaching to posterior extremity, confluent in post-testicular region, overlaps testes slightly, dorsal and ventral. Metraterm approaches genital atrium from left, about half length of cirrus-sac, with glandular sheath. Eggs large, tanned, operculate, numerous; not found in specimens from Agabus melanarius .

Excretory pore terminal. Vesicle traced to anterior testis in immature specimens ( Fig. 5 ), not seen in adults.

Figures

FIGURES 2 – 5. Allocreadium neotenicum (Peters, 1957) 2, 3. ex Hydroporus rufifrons. 2. Ventral view, uterus in outline. 3. Terminal genitalia. Abbreviations: cs, cirrus-sac; ed, ejaculatory duct; ga, genital atrium; gp, genital pore; os, outline of oral sucker; mt, metraterm; pgc, prostatic gland cell; sv, seminal vesicle; vs, outline of ventral sucker. 4, 5. ex Agabus melanarius. 4. Proximal female genitalia. Abbreviations: at, outline of anterior testis; ca, caecum, Lc, opening of Laurer’s canal; ov, ovary; sr, seminal receptacle; vs, outline of ventral sucker. 5. Ventral view of immature specimen showing extent of excretory vesicle. Abbreviations: cs, outline of cirrus-sac; es, eyespot; ev, excretory vesicle; ov, ovary; ca, caecum; tt, testes. Scale bars: 2, 500 μm; 3, 100 μm, 4, 5, 200 μm.