Acanthocephalus lutzi (Hamann, 1891) is proposed to be transferred to the genus Pseudoacanthocephalus Petrochenko, 1956 based on the type material from Rhinella marina (L.) from Brazil and recently collected material from R. arenarum (Hensel) from Argentina. Pseudoacanthocephalus is characterised by the following features: a cylindrical trunk without spines, a cylindrical proboscis, testes in tandem, a compact cluster of cement glands, a nearly terminal male genital pore, a ventral and sub-terminal female genital pore, and egg without polar prolongations, containing a holoechinate acanthor. Pseudoacanthocephalus lutzi comb. n. has a proboscis armature of 14-18 longitudinal rows of 5-8 hooks each, with all roots formed by a posteriorly directed longitudinal spatulate sheet having a central rib, and an inconspicuous sheet directed anteriorly; a variable number (4, 5 or 6) of cement glands; a cerebral ganglion located near the base of the proboscis receptacle; digitiform to claviform lemnisci, as long as, or slightly shorter or slightly longer than the proboscis receptacle; a sigmoid-shaped posterior end in males; an egg with a conspicuous fibrillar coat; and one of the larval hooks more robust and different in shape than the others. Additionally, the type material of Acanthocephalus saopaulensis Smales, 2007 from Rhinella icterica (Spix) from Brazil and a paratype of A. caspanensis Fernández et Ibarra Vidal, 1992 from R. spinulosa (Wiegmann) from Chile were studied. Acanthocephalus saopaulensis is considered conspecific with P. lutzi and A. caspanensis is transferred to Pseudoacanthocephalus because it possesses all the characters of the genus mentioned above. The use of characters such as egg morphology and host ecology for distinguishing Acanthocephalus from Pseudoacanthocephalus is also discussed.
Helminths often occupy defined niches in the gut of their definitive hosts. In the dioecious acanthocephalans, adult males and females usually have similar gut distributions, but sexual site segregation has been reported in at least some species. We studied the intestinal distribution of the acanthocephalan Echinorhynchus borealis von Linstow, 1901 (syn. of E. cinctulus Porta, 1905) in its definitive host, burbot (Lota lota Linnaeus). Over 80% of female worms were found in the pyloric caeca, whereas the majority of males were in the anterior two-thirds of the intestine. This difference was relatively consistent between individual fish hosts. Worms from different parts of the gut did not differ in length, so site segregation was not obviously related to worm growth or age. We found proportionally more males in the caeca when a larger fraction of the females were found there, suggesting mating opportunities influence gut distribution. However, this result relied on a single parasite infrapopulation and is thus tentative. We discuss how mating strategies and/or sexual differences in life history might explain why males and females occupy different parts of the burbot gut., Arto Tuomainen, E. Tellervo Valtonen, Daniel P. Benesh., and Obsahuje bibliografii
The acanthocephalan Echinorhynchus bothniensis Zdzitowiecki and Valtonen, 1987 differs from most other species in the genus Echinorhynchus Zoega in Müller, 1776 by infecting mysids (order Mysida) instead of amphipods (order Amphipoda) as intermediate hosts. Here we report on the occurrence of E. bothniensis in mysids (Mysis segerstralei Audzijonytė et Väinölä) and in its fish definitive hosts in a high Arctic lake. Out of 15 907 sampled mysids, 4.8% were infected with a mean intensity of 1.05 worms (range 1-5), although there was notable variation between samples taken in different years and sites. Larger mysids appear more likely to be infected. Of five fish species sampled, charr,Salvelinus alpinus (Linnaeus), and a benthic-feeding whitefish morph, Coregonus lavaretus (Linnaeus), were the most heavily infected (mean abundances of 80 and 15, respectively). The adult parasite population in fish exhibited a female-biased sex ratio (1.78 : 1). Although E. bothniensis is rather unique in infecting mysids, many aspects of its natural history mirror that of other acanthocephalan species., Raija-Liisa Aura, Daniel P. Benesh, Risto Palomäki, E. Tellervo Valtonen., and Obsahuje bibliografii
The acanthocephalan Echinorhynchus salmonis Müller, 1784 is a common parasite of salmonid fish, but it has rarely been reported from an intermediate host. Samples of benthic amphipods, Monoporeia affinis (Lindström), were taken from multiple, deep sites (usually below 70 m) in the Gulf of Bothnia over the course of more than a decade and examined for acanthocephalans. Overall, only 0.44% of 23 296 amphipods were infected, all with just a single worm. This prevalence is consistent with several previous reports of acanthocephalans in deep-water, benthic amphipods, but it appears low compared to that often reported for acanthocephalan species infecting littoral amphipods. Parasite occurrence did not exhibit a clear regional pattern (i.e. northern vs southern sites) nor did it have any relationship with site depth. At sites sampled over multiple years, parasite abundance was consistently low (mostly < 0.01), though two spikes in abundance (over 0.06) were also observed, indicating that infection can be substantially higher at particular times or in particular places. The median density of E. salmonis in samples containing the parasite was estimated as 8.4 cystacanths per m2., Daniel P. Benesh, Raija-Liisa Aura, Ann-Britt Andersin, E. Tellervo Valtonen., and Obsahuje bibliografii