Allocreadium neotenicum Peters, 1957, 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

publication ID 10.5281/zenodo.213869

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Allocreadium neotenicum Peters, 1957


Allocreadium neotenicum Peters, 1957 549 F 3979 - 54 E 2-4 EFC-B 579-640042 B 4 F 24 B

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, SD 47649802 Ings Pond, Westmorland, 03/ 11 / 2011, SD 442984 View Materials , Coll: G. N. Foster; Ings, Westmorland, SD44249838, 21/ 10 / 2010, Coll: G. N. Foster; a shallow marsh near Jordan Lane, Westmorland, SD635901 View Materials , 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 View FIGURES 2 – 5 ). 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 View FIGURES 2 – 5 ). 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 View FIGURES 2 – 5 ). 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 View FIGURES 2 – 5 ), not seen in adults.


Natural History Museum, London