Boyko B. Georgiev

Cestode parasitism in invasive and native brine shrimps (Artemia spp.) as a possible factor promoting the rapid invasion of A. franciscana in the Mediterranean region.

Artemia franciscana is an invasive crustacean expanding its range in hypersaline wetlands in the Mediterranean region and replacing native Artemia parthenogenetica and Artemia salina. Native brine shrimps are known as intermediate hosts of cestodes; infected individuals exhibit changes in their behaviour and appearance, thus facilitating the parasite transmission to the avian hosts by predation. To assess whether invasive brine shrimps participate in the cestode life cycles to the same extent as the native species, we examined the natural infections in seven populations of Artemia spp. along the southern coast of Spain and Portugal: three populations of each A. franciscana and A. parthenogenetica and one population of A. salina. Ten cestode species were found in A. parthenogenetica, while only six were recorded in each of A. salina and A. franciscana. The overall infection was consistently higher in native than in invasive populations. For a particular cestode species, the prevalence or abundance was significantly higher in a native population for 54 pairwise comparisons and only higher for an invasive population for 4 pairwise comparisons. These results suggest that cestodes may influence competitive interactions between native and invasive brine shrimps, thus partly explaining the invasive success of A. franciscana.

Red and transparent brine shrimps ( Artemia parthenogenetica ): a comparative study of their cestode infections

Although the red colour of brine shrimps has previously been supposed to be associated with cestode parasitism, no evidence has been provided that red and transparent brine shrimps differ in their role for cestode circulation. We compared the cestode infections in 100 red and 100 transparent Artemia parthenogenetica collected from the Odiel salt pans in Spain. Seven cestode species were recorded in red, and only four of them were recorded in transparent brine shrimps. The red brine shrimps were more infected with cysticercoids than transparent individuals (prevalence, 87 vs 21%; mean intensity, 1.56 vs 1.00; mean abundance, 1.35 vs 0.21). Three cestode species (Flamingolepis liguloides, Anomotaenia tringae and Confluaria podicipina) had significantly higher prevalence and mean abundance in red brine shrimps. These results suggest that red brine shrimps have a more important role for the circulation of avian cestodes than transparent individuals of the same population.

Avian cestodes affect the behaviour of their intermediate host Artemia parthenogenetica: An experimental study

The brine shrimp Artemia parthenogenetica (Crustacea, Branchiopoda) is intermediate host for several cestode species whose final hosts are waterbirds. Previous field studies have shown that brine shrimps infected with cestodes have a bright red colour and are spatially segregated in the water column. However, the ethological mechanisms explaining such field observations are unknown. Changes in appearance and behaviour induced by trophically transmitted parasites have been shown to increase the risk of predation by the final host. In this experimental study, we compared the behaviour of uninfected Artemia and those infected by avian cestodes. We found that parasitised individuals behave differently from unparasitised ones in several ways. In contrast to uninfected individuals, infected brine shrimps were photophilous and showed increased surface-swimming behaviour. These observations suggest that the modified behaviour (in addition to the bright red colour of the majority of the infected individuals) results in infected brine shrimps becoming more vulnerable to avian final hosts, which facilitates parasite transmission. We discuss our results in terms of the adaptive nature of behavioural changes and their potential implications for the hypersaline ecosystem.

Paranoplocephala aquatica n. sp. (Cestoda, Anoplocephalidae) from Arvicola terrestris and Ondatra zibethica (Rodentia), with redescriptions and comments on related species

Paranoplocephala aquatica n. sp. is described from Arvicola terrestris and Ondatra zibethica (Rodentia, Cricetidae) in Bulgaria. The new species is characterised by a band-like strobila, a uterus forming a fine reticulate structure in the early stages of development, numerous testes (approximately 92) situated mainly aporally to the ovary in both the median and the aporal lateral fields, few testes positioned anterior to the ovary and genital ducts, the prominent asymmetrical situation of the female organs, the length of the vagina c. 0.65–0.68 of the length of the cirrus-sac, and the external seminal vesicle covered by a cellular sleeve. The new species is distinguished from P. ondatrae, P. macrocephala, P. dasymidis and P. sciuri. The specimens from O. zibethica reported as P. ondatrae by Tenora & Murai (1980) and as Aprostatandrya macrocephala by Spasskii et al. (1951) are believed to belong to P. aquatica. The type-series of P. ondatrae and P. macrocephala are redescribed and figured; metric data and an illustration of the holotype of P. sciuri are presented. The genus Paranoplocephala sensu Tenora et al. (1986) is regarded as a heterogeneous group because of the two patterns of uterine development in the species studied. Taxonomic criteria used for distinguishing the genera Andrya and Paranoplocephala, and some criteria applicable at the species level, are discussed.

Ultrastructure of spermiogenesis and mature spermatozoon of Skrjabinoporus merops (Cyclophyllidea, Metadilepididae)

The ultrastructure of the mature spermatozoon and the spermiogenesis of a cestode belonging to the family Metadilepididae is described for the first time. The mature spermatozoon of Skrjabinoporus merops is characterized by twisted peripheral microtubules, the presence of a single crested body, periaxonemal sheath and electron-dense rods, and the absence of intracytoplasmic walls and inclusions (glycogen or proteinaceous granules); no peripheral microtubules where nucleus contacts the external plasma membrane. Four morphologically distinct regions of the mature spermatozoon are differentiated. The proximal part (Region I) contains a single crested body, periaxonemal sheath is absent in some (proximal) sections and is present in others situated closer to the nucleus. The central Region II is nucleated, and is followed by Region III that contains a periaxonemal sheath. The distal pole, Region IV, is characterized by disintegration of the axoneme. Spermiogenesis follows the type III pattern (Bâ and Marchand 1995) although in S. merops a slight flagellar rotation is observed. The differentiation zone is characterized by the absence of striated roots and intercentriolar body; two centrioles are present, one of which gives rise to a free flagellum. The latter rotates and undergoes proximodistal fusion with the cytoplasmic protrusion of the differentiation zone. Spermiological characters of S. merops are similar to those of the families Taeniidae and Catenotaeniidae. The mature spermatozoon differs from those of the Dilepididae (where the metadilepidid species have previously been classified) by the lack of glycogen.

Post-embryonic development and ultrastructural characteristics of the polycephalic larva of Taenia parva Baer, 1926 (Cyclophyllidea, Taeniidae)

Post-embryonic development and fully-formed polycephalic larvae of Taenia parva Baer, 1926 were examined by light (LM) and transmission electron microscopy (TEM). Three developmental stages were recognised: (1) an early stage of exogenous budding at the surface of the central vesicle; (2) a stage of polycephalic cyst development accompanied by segmentation of the growing larval strobile and an obvious decrease in the size of the central vesicle; (3) fully-formed larval strobile and invaginated scoleces. In fully-developed encysted polycephalic larvae, there are usually 14–24 segmented larval strobilae, each terminating with an invaginated scolex; larval strobilae arise from a common central vesicle and remain attached posterior to it during the entire development. The number of segments varies between 109 and 120 per larval strobila. The polycephalic larvae examined closely resemble the strobilocercus type of taeniid larvae. The structure of developing and fully-formed larvae was examined by TEM. The tegument, scolex, subtegumental musculature of the strobilar segments, protonephridial system, calcareous corpuscles and medullary parenchyma of larvae exhibit general similarity with the same structures in adults at both LM and TEM levels. The morphogenesis of the larva of T. parva is compared with that of the polycephalic larvae of other Taenia spp. (T. krepkogorski, T. twitchelli and T. endothoracica) and with other asexually-multiplying cestode larvae (mesocestoidids, hymenolepidids and dilepidids).

Cestodes of small mammals: Taxonomy and life cycles

Cestodes are diverse, ubiquitous parasites of vertebrates. They are frequent parasites of small mammals. It is not possible to provide a concise description of their taxonomy and life cycles without omitting many of the complexities, controversies and fascinating novelties of such a diverse group. Therefore, this chapter is introductory and not exhaustive. Its aim is to introduce the reader to the biology of cestodes and to present the basic components of their diversity in rodents, insectivores, lagomorphs and chiropterans as well as the major patterns of cestode life cycles, in which these mammalian groups participate. The appearance of cestodes in their contemporary vertebrate host range comes as a result of multiple independent evolutionary invasions, host shifts and coevolutionary history with their hosts. Appearing well before the origin of mammals, cestodes have not failed to follow their vertebrate hosts wherever they have gone. Not least, whether as intermediate or definitive hosts, small mammals have provided significant opportunities for cestodes to diverge in space and time. Likewise, cestodes have played an integral role in the evolutionary ecology of small mammals.

Records of cysticercoids of Fimbriarioides tadornae Maksimova, 1976 and Branchiopodataenia gvozdevi (Maksimova, 1988) (Cyclophyllidea, Hymenolepididae) from brine shrimps at the Mediterranean coasts of Spain and France, with a key to cestodes from Artemia spp. from the Western Mediterranean

Cysticercoids of two cestode species isolated from brine shrimps from the Mediterranean coasts of Spain and France are described. Fimbriarioides tadornae Maksimova, 1976 (adults known as parasites of Tadorna tadorna) was recorded from Artemia parthenogenetica and A. franciscana from Spain (Bras del Port and River Ebro Delta, respectively), and from A. franciscana from Aigues-Mortes, France (new geographical record). Branchiopodataenia gvozdevi (Maksimova, 1988) (adults known as parasites of Larus genei) was recorded from A. parthenogenetica (Bras del Port, Spain), A. salina (San Pedro del Pinatar, Spain) and A. franciscana (River Ebro Delta, Spain); this is the first record of the species in Europe. An illustrated key to cysticercoids of 12 cestode species from Artemia spp. from the Western Mediterranean is proposed.

Gastrointestinal Helminths of Cuvier's Beaked Whales, Ziphius cavirostris, From the Western Mediterranean

We examined the gastrointestinal helminth fauna of 2 Cuviers beaked whales, Ziphius cavirostris, stranded on the Spanish Mediterranean coast. Information regarding intestinal parasites of this species is provided for the first time. Six helminth taxa were identified. Thirty type II larvae of the nematode Anisakis sp. were found in the stomach and the intestine of both hosts; 2 type I larvae of Anisakis sp. were found in the intestine of 1 host. One juvenile of the acanthocephalan Bolbosoma vasculosum was found in the intestine; the metacestode Scolex pleuronectis was found mainly in the terminal colon and the anal crypts of both hosts; adult cestodes of Tetrabothrius sp., which may represent a new species, were collected from the duodenum of 1 host. Composition of the intestinal parasitic community is similar to that of other oceanic cetaceans, which mostly include species of Bolbosoma and tetrabothriids (Cestoda).

The erection of Leporidotaenia n. g. (Cestoda: Anoplocephalidae) for Anoplocephaloides spp. parasitising Leporidae (Lagomorpha)

Leporidotaenia n. g. is proposed for four cestode species parasitising Leporidae (Lagomorpha) which were previously considered as members of the genus Anoplocephaloides. The new genus is differentiated from Anoplocephaloides by the presence of a spinose covering on the tegument, the protrusible genital atrium, the massive cirrus-sac with highly developed musculature, the presence of a retractor muscle associated with the cirrus-sac, the posterior position of vaginal pore relative to the male orifice, the cirrus armed with long spines and its occurrence only in hosts of the family Leporidae (Lagomorpha). The genus includes: L. romerolagi (type-species), L. floresbarroetae, L. pseudowimerosa and L. wimerosa. the species (excluding L. floresbarroetae) are redescribed and figured and a differential key is presented. An attempt is made to explain the range of Leporidotaenia spp. in Central America and the western Palaearctic on the basis of the palaeozoogeography of rabbits and hares.