Aleksander Bielecki

Germ-line cysts are formed during oogenesis in Erpobdella octoculata (Annelida, Clitellata, Erpobdellidae)

Abstract Erpobdella octoculata (Clitellata, Hirudinea, Erpobdellidae) has paired ovarian sacs, each containing several rod-shaped structures termed ovarian bodies. Oogenesis takes place within the ovarian bodies. We show that in the apical part of the bodies the germ-line cells form syncytial cysts of cells interconnected by stable intercellular bridges. Germ-line cyst architecture is broadly similar to that of other clitellate annelids; that is, each germ cell has only one intercellular bridge connecting it to the anuclear cytoplasmic mass, the cytophore. Unlike germ-line cysts described in other leech species, the cytophore in cysts of E. octoculata is poorly developed, taking the form of thin cytoplasmic strands. Oogenesis in E. octoculata is meroistic because the germ cells forming the cysts (cystocytes) have diverse fates, i.e., nurse cells and oocytes appear. One large ramified cell (apical cell) occurs within the apical part of the ovarian body. We compare the ultrastructure of the apical cell found in E. octoculata with that of apical cells described recently in some hirudiniform leeches. The germ-line cysts as well as the oocytes are enveloped by somatic follicular cells. As in other leeches, the follicular cells surrounding the growing oocytes have cytoplasm perforated by intracellular canals. In view of the many similarities between E. octoculata ovarian bodies and the ovary cords described in glossiphoniids and especially in hirudiniform leeches, we suggest that the ovarian bodies found in E. octoculata are in fact modified ovary cords.

Diversity of features of the female reproductive system and other morphological characters in leeches (Citellata, Hirudinida) in phylogenetic conception

An epistemological–evolutionary conception of leeches (Hirudinida) based on features of the female reproductive system in combination with other morphological characters is presented in the spirit of the cladistic school of taxonomy. Characters relating to the structure of the ovary and the course of oogenesis in leeches were interpreted in this manner, for the first time. Each study was conducted on type species of higher taxonomic groups of true leeches. Results of analyses using features of the reproductive system only as well as in combination with other morphological characters show Piscicolidae and Glossiphoniidae as sister clades making Rhynchobdellida a monophyletic group. Also, Hirudiniformes and Erpobdelliformes appeared to be sister clades within Arhynchobdellida. The relationship between the outgroup specimens and leeches remained unresolved, because both Acanthobdella peledina and branchiobdellidans appeared to be in an equivocal relationship to hirudinidans. Characters concerning the structure of the female reproductive system and course of oogenesis thus appeared to be useful, although conservative, for reconstruction of leech phylogeny, and they well reflect phylogenetic relationships of Hirudinida at the family level.

Coexistence of Placobdella costata (Fr. Müller, 1846) (Hirudinida: Glossiphoniidae) and mud turtle Emys orbicularis

Emys orbicularis is receding from Europe, mainly due to anthropogenic habitat changes. Its parasite, Placobdella costata, is widely distributed within both the former and the present distribution range of the host. Though closely associated with the mud turtle, it may have other hosts (birds, amphibians, reptiles). Its reproductive period coincides with that of its host’s migration to the breeding grounds, thus facilitating dispersal of the parasite. Based on literature data we have analyzed the geographic spread of P. costata and mud turtle to observe the possible overlap of their habitats. Observations on the population of mud turtle and the associated leech species (P. costata) were carried out in eastern Poland — Podlasie Lowland. The studies were conducted in spring and summer in 1986–1993. The leeches were collected from the turtles caught in the water and on land. Observations showed that most leeches were found on turtles inhabiting the lake or moving to a breeding area. The greatest intensity of invasion was observed in June and July and that most leeches were observed in female E. orbicularis characterized by greater length of the carapace and weight, compared with males and juvenile individuals.

Morphology and ultrastructure of the midgut in Piscicola geometra (Annelida, Hirudinea)

This paper presents information on the organization of the midgut and its epithelium ultrastructure in juvenile and adult specimens of Piscicola geometra (Annelida, Hirudinea), a species which is a widespread ectoparasite found on the body and gills and in the mouth of many types of fish. The analysis of juvenile nonfeeding specimens helped in the explanation of all alterations in the midgut epithelium which are connected with digestion. The endodermal portion (midgut) of the digestive system is composed of four regions: the esophagus, the crop, the posterior crop caecum, and the intestine. Their epithelia are formed by flat, cuboidal, or columnar digestive cells; however, single small cells which do not contact the midgut lumen were also observed. The ultrastructure of all of the regions of the midgut are described and discussed with a special emphasis on their functions in the digestion of blood. In P. geometra, the part of the midgut that is devoid of microvilli is responsible for the accumulation of blood, while the epithelium of the remaining part of the midgut, which has a distinct regionalization in the distribution of organelles, plays a role in its absorption and secretion. Glycogen granules in the intestinal epithelium indicate its role in the accumulation of sugar. The comparison of the ultrastructure of midgut epithelium in juvenile and adult specimens suggests that electron-dense granules observed in the apical cytoplasm of digestive cells take part in enzyme accumulation. Numerous microorganisms were observed in the mycetome, which is composed of two large oval diverticles that connect with the esophagus via thin ducts. Similar microorganisms also occurred in the cytoplasm of the epithelium in the esophagus, the crop, the intestine, and in their lumen. Microorganisms were observed both in fed adult and unfed juvenile specimens of P. geometra, which strongly suggests that vertical transmission occurs from parent to offspring.

The invasion of the leech Piscicola respirans (Hirudinea: Piscicolidae) on the fins of European grayling Thymallus thymallus

This study presents the parasitical relationships between the leech Piscicola respirans and European grayling Thymallus thymallus. It determines leech invasion intensity and extensity as well as describes the preferences of fin selection by the parasite as a place to attach and feed. It also shows the significance of fin selection by the leech in the initial phase of life cycle. Finally, the study defines P. respirans as a predominantly fin-parasite of fishes. Most probably the host-searching mechanism is based on positive phototaxis.

Piscicola siddalli n. sp., a Leech Species from the United Kingdom (Clitellata: Hirudinida: Piscicolidae)

Abstract A new species of fish leech from England, Piscicola siddalli n. sp. (Piscicolidae), was collected in 2006 on stones and on grayling (Thymmallus thymmallus L.) in the River Ure, North Yorkshire, Great Britain. The leech is 4(12) annulate; gonopores are separated by four annuli. The male gonopore is much larger than the female gonopore. Seminal receptacle consists of a round aperture, located at a distance of 3 annuli behind the female gonopore. Copulatory area on the clitellum is in the form of a circle. Vector tissue has the form of a circular plate, below the oviduct opening.

New information on the geographical distribution of Piscicola brylinskae Bielecki, 2001 (Hirudinea: Piscicolidae) in Poland and remarks on its systematic position

For the first time, Piscicola brylinskae was described from Lake Vechten in the village of Bunnik, near Utrecht — The Netherlands. Until now, P. brylinskae has been found in Poland in Lake Maróz and in the Łyna River near Olsztyn (the northern part of Warmian-Masurian voivodeship). Thanks to proper conservation the coloration of P. brylinskae was described for the first time. Applying 32 indexes resulted that P. brylinskae clustered to Caspiobdella fadejewi. Analysis based on 113 non-metric characteristics has shown that P. brylinskae is most similar to Piscicola margaritae. Though, P. brylinskae do not form with P. margaritae dichotomic branching nor with any other species from this cluster, it could confirm that it is an individual species of the Piscicola genus.

Atlantic sturgeon, Acipenser oxyrinchus Mitchill, infected by the parasitic leech, Caspiobdella fadejewi (Epshtein) (Hirudinea; Piscicolidae), in the Drwêca River

Atlantic sturgeon, Acipenser oxyrinchus Mitchill, infected by the parasitic leech, Caspiobdella fadejewi (Epshtein) (Hirudinea; Piscicolidae), in the Drwęca River This study presents the parasitic relationship between the leech, Caspiobdella fadejewi, and the juvenile Atlantic sturgeon, Acipenser oxyrinchus. The aim was to determine leech invasion intensity and extensity and describe parasite feeding location preferences on the ventral side of the snout and gill cavities. The prevalence of C. fadejewi occurrence was 37.3%, at an intensity of one to eight leeches. It was confirmed that the intensity of leech occurrence was positively correlated with sturgeon total length (r=0.545, P<0.05, N=15). The host-searching mechanism is most probably based on positive phototaxis. This is the first record of C. fadajewi from A. oxyrinchus. The leech was first observed during routine examinations of sturgeon collected in June 2008. The leeches were usually attached to the inside lower portion of opercula near the isthmus. Zarażenie jesiotra Acipenser oxyrinchus Mitchill pasożytniczą pijawką Caspiobdella fadejewi (Epstein) (Hirudinea; Piscicolidae) w Drwęcy Słodkowodne gatunki pijawek pasożytujące na rybach (Piscicolidae) jako monofiletyczna rodzina, z nielicznymi wyjątkami, zamieszkują wody kontynentalne Holarktyki. W pracy scharakteryzowano występowanie pasożytniczej pijawki Caspiobdella fadejewi u juwenalnych jesiotrów Acipenser oxyrinchus Mitchill. Określono ekstensywność oraz intensywność zarażenia jesiotrów wpuszczonych do Drwęcy. Ekstensywność występowania C. fadejewi wynosiła 37,3%, a intensywność od 1 do 8 pijawek. Stwierdzono, że intensywność występowania pijawek była dodatnio skorelowana z długością całkowitą jesiotrów (r=0,545, P<0,05, N=15). Pijawki najczęściej były zlokalizowane na płetwach parzystych lub rostrum, rzadziej na bokach ciała, płetwach odbytowej lub ogonowej. Prawdopodobnie odszukiwanie żywiciela związane jest z pozytywną fototaksją. Pijawki wykorzystują w odszukiwaniu żywiciela jego cień, który powoduje spadek natężenia światła odbierany przez plamki oczopodobne znajdujące się na przyssawce tylnej.

Environmental factors associated with biodiversity and the occurrence of rare, threatened, thermophilous species of aquatic beetles in the anthropogenic ponds of the Masurian Lake District

This paper presents the results of an analysis of species richness (expressed as number of species), biodiversity (the H′ index) and synecological structure of communities of aquatic beetles living in clay and gravel pits. It evaluates the analyzed habitats in terms of the influence of water physical and chemical parameters on the characteristics of beetle assemblages. The assessment of beetle communities was performed from the point of view of ecology and nature conservation. The analyzed physical and chemical parameters of water as well as the presence of certain species, mainly rheophiles, indicate very weak eutrophication of the ponds. The parameters which most significantly distinguish gravel pits from clay pits are specific conductivity, HCO3−, SO42− and Cl–. The PCA analysis, however, suggests that the abundance and species richness as well as the biodiversity of beetles living in the analyzed ponds were most closely correlated with temperature and with NH4-N, total N and the BOD5 of water. The analyzed ponds proved to be very attractive habitats populated by numerous species, including rare, threatened (listed in the Polish Red Book of Species) and termophilous ones, or organisms valuable to Polish wildlife for other reasons. They include two species rare in Poland—Hydrochus ignicollis and Ochthebius hungaricus, one species fully protected in Poland—Hydrophilus aterrimus (VU), as well as Haliplus fulvicollis (VU) and Gyrinus caspius (EN). The findings are important for the preservation of biodiversity, both locally and on a scale surpassing the region, a conclusion which highlights the value of anthropogenic ponds such as clay pits and gravel pits, in the ecological landscape and implies that they deserve an adequate protection in order to sustain their function.

Environmental factors determining the distribution pattern of leeches (Clitellata: Hirudinida) in large river systems: A case study of the Oder River system

Abstract The largest rivers in Europe are under strong human pressure, resulting in habitat changes and consequently in structural changes in the quantitative and qualitative composition of fauna assemblages. The aim of this study was to identify the taxonomic structure of leech assemblages and the main environmental factors influencing their distribution pattern on a 306 km stretch of the Oder River encompassing different habitat types. Representatives of 28 leech taxa were recorded in 527 samples of bottom macrofauna. The most abundant and most frequently recorded species was the eurytopic Erpobdella octoculata, occurring in all examined habitat types. Although a significant influence of habitat type on the species composition of leech assemblages was noted, a significant positive correlation with habitat type was found only in the case of Piscicola pojmanskae and P. geometra. Our results show that abundance of food resources was the most important factor influencing the distribution of leeches.