Specifics of the morphological identification of the pathogen of passaluariasis of rabbits

Passalurus ambiguus (Nematoda, Oxyuroidae) is one of the most common parasites of digestive tract of domestic and wild rabbits and rodents. Passalurus spp. are cosmopolitan, and the mature nematodes are localized in the appendages and large intestine of animals. The passaluariasis infections remain quite relevant in modern rabbit breeding, because the disease is highly contagious, with the possibility of unlimited spread inducing significant economic losses. The aim of the study was to determine the identifying morphological species characteristics of P. ambiguus nematodes, which were isolated from the colon of domestic rabbits (Oryctolagus cuniculus domesticus). The identifying characters of Passalurus include morphological features, namely the presence of a spherical bulb in the esophagus, and the presence of three teeth in the oral capsule. Males of P. ambiguus have a characteristic structure of the tail end, namely the presence of papillary protrusions and a massive narrowed part with a spicule handle, and five papillae around the cloaca. Twenty-eight metric indicators are proposed that characterize the size of the body, oral capsule, esophagus in different parts of it, the tail end, spicules, the location of the cloaca. Two different morphotypes of mature females of P. ambiguus were revealed – short-tailed and long-tailed, which were larger by 19 indicators (by 3.2–43.6%). The morphotypes of P. ambiguus females are characterized; the length of the tail, body length and width in different areas, depth of the oral capsule, esophageal size and its structural elements, the location of the vulva and nerve ring, the width of the caudal process. At the same time, the parameters of esophageal bulb length and caudal process in short-tailed females were higher (by 13.9% and 11.9%, respectively) than in the long-tailed females. A total of 25 morphometric parameters were proposed for the identification of P. ambiguus females. The obtained data indicate the feasibility of further research on the causes of occurrence of such morphotypes in P. ambiguus females and the need to take into account the existence of such forms of females for their differential diagnosis taking into account their proposed morphometric parameters.

The first species of Embioptera (Insecta) from the archipelago of Fernando de Noronha (Pernambuco: Brazil)

Pararhagadochir is a South American genus of Archembiidae that can be identified by its anterior margin of submentum strongly concave, caudal process of the 10th left hemitergite forked, with internal tip seemingly a hook and the external tip a flat lobe, both tips always shorter than the width of 10th left hemitergite. Six species are recorded in Brazil, being distributed in all regions. In this work, Pararhagadochir noronhensis sp. nov. is described from the archipelago of Fernando de Noronha, Brazil.

Description of a new species in the genus Bythotrephes Leydig, 1860 (Crustacea: Cladocera: Onychopoda), supplements to selected species, and concluding remarks on the genus

A new species of the genus Bythotrephes is described based on material collected in the mountain lakes of Tyva Republic (Southern Siberia, Russia). The representatives of the new species are especially close to those of B. longimanus having long tl I, straight caudal process, and only two pairs of claws on postabdomen and caudal process, respectively. At the same time, the new species is, on average, smaller with shorter caudal process and fairly long apical setae of second endopodital segment of the thoracic limbs of first pair (tl I). Supplemental data on morphology, taxonomy, and geographic distribution of other species of the genus, e.g., B. arcticus, B. cederströmii, B. brevimanus, and B. lilljeborgi, are presented. For B. cederströmii, in particular, females of first generation hatched from resting eggs are described for the first time. Classification of the genus is discussed and an updated key for species and a hybrid form is presented. The highest species richness of the genus, observed within the Scandinavian Peninsula and in the north of European Russia, may indicate the central region of primary speciation which generally coincides with the region of the last Quaternary maximum glaciation. The isolated occurrence of three species, B. longimanus, B. transcaucasicus, and B. centralasiaticus sp. nov. on the southern border of the genus’ range, in pre-Alpine and mountain lakes of Europe, Transcaucasia, and Southern Siberia (Tyva) and isolated localities of B. arcticus in Northern Kazakhstan, could also be due to the effect of glaciation(s). Regarding the origin of the genus Bythotrephes, it is hypothesized that it occurred in pre-Pleistocene time in the ancient Ponto-Caspian basin, experiencing large-scale transgressions, where the intensive radiation of ancestral Onychopoda probably took place.

Caecidotea camaxtli (Isopoda: Asellidae) a new species from the Tlaxcala valley, Mexico

A new freshwater isopod, Caecidotea camaxtli sp. nov. (Isopoda, Asellidae) is described from Mexico. The new species can be distinguished from all other species of Caecidotea by the presence of cuticular scales on the caudal process, as well as a short and simple cannula in the apex of the endopodite of pleopod II. [Zoobank URL: urn:lsid:zoobank.org:act:082CF870-ABC3-4E25-B5F2-8CA59359C2B0]

Further revision of the genus Bythotrephes Leydig (Crustacea: Cladocera: Onychopoda): redescription of B. brevimanus Lilljeborg, reevaluation of B. cederströmii Schödler, and description of a new species of the genus

Two species of the genus Bythotrephes Leydig, B. brevimanus Lilljeborg and B. cederstrӧmii Schӧdler, are analysed. The former of them is redescribed on the basis of type material and other materials from Northern Europe while the latter one is reevaluated, in comparison with the previous recent investigation which was based on limited material being not enough for the adequate species assessment. The species under consideration were investigated with the application of detailed morphological analysis, including intra- and interpopulation variability and the original scheme of morphometric measurements. The lectotype and paralectotypes of B. brevimanus were selected. Both species are characterized by considerable morphological variability which was especially prominent in taxonomically important features, such as structure and armament of thoracic limbs of first pair (tl I), caudal process, and claws of postabdomen and caudal process. It was concluded that the taxonomic identification of such variable units like B. brevimanus, B. cederstrӧmii and hybrid forms close to the latter species should be based only on comparison of sets of specimens of particular populations; the usage of single specimens can lead to incorrect results. Pedogenesis, in B. brevimanus and in family Cercopagididae in general, was recorded and described for the first time.A new species, B. lilljeborgi, is described based on material from Southern Sweden and Norway. It differs from the closely related species B. longimanus and B. brevimanus in number and size of claws of postabdomen and caudal process.The ranges of the above considered species overlap, especially prominently in North-Western Europe where all three species under consideration co-occur. B. brevimanus dominates in the Circumbaltic region and eastward through Central European Russia and the Ural Mountain region, possibly to the Yenisei River which requires further confirmation. B. cederstrӧmii is distributed further to the east, being recorded in Central Yakutia (Eastern Siberia). Data on co-occurrence of Bythotrephes species are limited and not always adequate because identification of taxa was often confused. Based on the information contained in the present paper, in particular the reevaluation of B. cederstrӧmii taxonomy, it may be suggested that both interspecific hybrid forms and B. cederstrӧmii s. str. could have invaded North American inland waters.

Sakakibarana, a new genus of Gyponini (Hemiptera: Cicadellidae: Iassinae) from the Amazon Rainforest

A new genus of Gyponini, Sakakibarana gen. nov., is proposed and its type species S. amazonica sp. nov. is described and illustrated based on specimens from the Amazon Rainforest of Northern Brazil (states of Amazonas and Pará) and French Guiana. The new genus can be distinguished from other members of the Gyponini by the following morphological features: robust body, short crown, crown and face transition distinct and subfoliaceous, pronotum strongly declivous, male pygofer with caudal process, and aedeagus with dorsal apodemes with a pair of processes. A discussion comparing the new genus with the related genus Tenuacia DeLong, 1977 is provided.

On Retortamonas cheloni sp.nov., a parasitic Protozoon from the starred tortoise

Retortamonas cheloni sp.nov., from the large intestine of the starred tortoise, Testudo elegans Schoepff, 1792, is described. Body oval with a long caudal process; length of body 4·2–11·5μ, 7·9 average; breadth 3·0–6·5μ, average 4·4; length of caudal process 1·0–7·0μ, average 4·0. Nucleus round, situated at the extreme anterior end, with a thin ring of chromatin adjacent to the nuclear membrane and sometimes an endosome. Cytostome deep, extending one-third to one-half of the body-length and bordered by two siderophilic threads. Close to the nucleus are two blepharoplasts from which arise two unequal flagella and the two siderophilic threads. Periplast rigid.