Aspartic proteinase in Dugesia tigrina (Girard) planaria

A proteolytic activity was identified in Dugesia tigrina planaria using the chromogenic substrate Phe-Ala-Ala-Phe (4-NO2)-Phe-Val-Leu-O4MP. The activity of the enzyme increased four times during the regeneration and presented a maximum at 120 hr being higher in tail than head regenerating segments. The protease that displays this activity was purified from worms by a single step on pepstatin-agarose followed by gel-filtration high performance liquid chromatography. The purification resulted in a 34-fold increase in specific activity and the final yield was 10%. The active D. tigrina hydrolase appears to be a dimeric protein composed of identical subunits with 34 kDa associated by disulphide bridges similar to vertebrate cathepsin D. By SDS-PAGE several bands were detected but upon gel filtration HPLC one proteolytically active component, termed Asp-68, was detected and isolated. The maximal activity was observed in a range between pH 3.5-5.0 and the enzyme became inactivated at a pH value above 7.2. The purified enzyme was not inhibited by inhibitors from serine (aprotinin, TPCK, PMSF and TLCK), metallo (EDTA) and cysteine proteinase (E-64) classes. In contrast, inhibitors such as pepstatin, EPNP, and 4-beta-PMA efficiently inhibited the activity of the 68-kDa protease.     

Phylogenetic relationships of the genus Dugesia (Platyhelminthes, Tricladida, Paludicola)

A phylogenetic analysis was performed on the genera and subgenera within the freshwater triclad family Dugesiidae, based on 19 terminal taxa and 17 morphological characters. The phylogenetic tree proposed has length of 27 steps and consistency index of 0.66. This phylogenetic hypothesis implies that the current genus Dugesia is paraphyletic and that its subgenera Girardia, Schmidiea and Dugesia S.S. should be elevated to the rank of genus. The genera Cura, Spathula and Neppia are presumed monophyletic by default because the database was unable to provide autapomorphies for any of these genera. The genera Dugesia S.S. and Neppia share sistergroup relationship. Several characters are discussed which were previously considered to be of phylogenetic importance but were not included in the present analysis. It is emphasized that sensory organs form potentially useful set of phylogenetic characters for the Dugesiidae.     

The freshwater planarian Dugesia sicula Lepori from Sardinia (Platyhelminthes,Tricladida)

Fissiparous strains of freshwater triclads of the Dugesia gonocephala group were collected from 12 localities in Sardinia all situated not more than 5 kilometers from the coast. Some environmental factors and the sexual status of the specimens were noted at the time of collection. During the laboratory rearing 30% of individuals of each strain became sexual (ex-fissiparous individuals). All the examined strains showed common karyological and morphological characteristics suggestive of the species Dugesia sicula Lepori. The chromosome complement, which was a constant 27+2–3 B chromosomes, was classified as aneutriploid, due to its clearly documented characteristics. The fissiparous populations of D. sicula appear to have a high degree of tolerance to variations in environmental factors, especially temperature. Within the D. gonocephala group this species has the broadest distribution in the Mediterranean region.     

Repeated DNA elements in planarians of the Dugesia gonocephala group (Platyhelminthes,Tricladida)

The results of the isolation of repetitive DNA elements in the genome of Dugesia etrusca, a species of the Dugesia gonocephala group, are reported. These sequences, about 1.4 kb long, represent only a part of longer interspersed genomic units (De1 family) and appear to be limited to the genome of some planarians of this group, as indicated by a Southern blot analysis performed in different species and populations. The genomic relationships among different species and populations of the D. gonocephala group are discussed in relation to the results obtained in the present work. This revised version was published online in July 2006 with corrections to the Cover Date.     

Bursa,bursa canal,and female antrum of Dugesia tigrina (Plathelminthes,Tricladida)

Summary The bursa of Dugesia tigrina is located between pharynx and penis and is suspended in a network of muscle fibers. Two cell types are present in the bursa: small outer cells which likely represent replacement cells and tall inner cells. During copulation seminal material, consisting of secretion products, fibrillar and tubular material, and small clusters of spermatozoa, is injected through the bursa canal into the bursa. During the 48 h post-copulatory period the seminal material is absorbed by the inner cells. Phagocytosis of the seminal material is facilitated by broad apical cytoplasm and modified distal cell membranes. Phagocytosed spermatozoa are enclosed in vaculoes and morphologic breakdown occurs as early as 4 h after copulation. Fibrillar and tubular material is phagocytosed directly into the apical, organelle-free cytoplasm without vacuole formation.The bursa canal is ciliated and the distal cell ends are studded with ultrarhabdites. These are also present in the epithelial cells of the female antrum. Antrum epithelial cells furthermore display apical organelle-free cell areas. Numerous glands penetrate through the antrum wall.     

Notes on the biology of the freshwater planarian Dugesia bengalensis (Platyhelminthes Turbellaria Tricladida)

Dugesia bengalensis was described by Kawakatsu (Kawakatsu et al., 1983) from specimens collected in West Bengal. We have been studying populations from many different localities in Santiniketan and adjoining areas of West Bengal and can provide additional biological information.The species is hermaphroditic, and its breeding season was found to occur usually between October and March when the winter temperature falls below 25 °C. Outside of the breeding season, D. bengalensis is capable of asexual reproduction by binary fission (Mahapatra et al., 1987).Development of the reproductive organs appeared to be from neoblasts and other mesenchymal cells and, therefore, to be like that typical of other triclads with the exception that some of the neoblasts used for the reproductive tissue appeared to be derived from the intestinal region (Ghosh, 1988; cf. Teshirogi, 1986).During copulation, the partners were oriented in the same direction and not in a head-to-tail position as has been reported (Hyman, 1945) for some planarians.The oval, stalked cocoons were laid in marshy places, and during the period of summer (usually from April to June) they lay dormant in the sandy soil until the onset of the monsoon rains. Then, typically three or four months after they were laid, the cocoons hatched to yield three or four young, a remarkably low number for freshwater triclads (cf Ball & Reynoldson, 1981).     

A new and aberrant species of Dugesia (Platyhelminthes,Tricladida, Dugesiidae) from Madagascar

In this paper we report a new species of Dugesia of the family Dugesiidae from Madagascar, representing the fourth species of freshwater planarian known from this global biodiversity hotspot. In some respects the new species is aberrant, when compared with its congeners, being characterized by a head with smoothly rounded auricles, a peculiar course of the oviducts, including the presence of a common posterior extension, and by the asymmetrical openings of the vasa deferentia at about halfway along the seminal vesicle. Further, it is characterized by a ventral course of the ejaculatory duct with a terminal opening, very long spermiducal vesicles and unstalked cocoons. Its diploid chromosome complement with 18 chromosomes represents an uncommon feature among fissiparous species of Dugesia.     

On the taxonomic status of a Dugesia species from Buenos Aires (Platyhelminthes: Turbellaria: Tricladida)

The taxonomic and distributional statuses of the freshwater planarians of South America are imperfectly understood, and a comprehensive review is sorely needed. The species known from the vicinity of Buenos Aires, Argentina, was first described by Böhmig (1902) under the name Planaria dubia Borelli, 1895. Subsequent authors (Kenk, 1930, 1974; Cazzaniga & Curino, 1987) have cast doubt on this assignation. Some have assigned it to Dugesia anceps Kenk; Hyman (1959) was inclined to regard the Buenos Aires planarian as a geographical variant of Dugesia sanchezi Hyman. A comparison of D. sanchezi from the mountainous region of central Chile with specimens from Buenos Aires confirms that the Argentinian material is a distinct species.The differences between the two species are subtle. The Argentinian specimens are distinctive in their possession of infranucleate epithelia of the atria, penis, and bursal canal, as well as in their penial structure. In both species, the epithelia of the atria and bursal canal are glandular. Those of D. sanchezi are nucleate and their secretions are cyanophilous. In the Argentinian specimens, these same epithelia are infranucleate; but while the secretion of the bursal canal is indeed cyanophilous, that of the atrium is erythrophilous. The presence, in these same specimens, of cyanophilous glands opening into the penial vesicles, and of erythrophilous glands whose secretions contribute to a viscous plug in the ejaculatory duct, suggests a difference in the physiology of copulation.It is apparent that the Argentinian specimens are distinct from D. sanchezi Hyman, and probably they represent a new species, one to be described in detail elsewhere. In any case, Hyman's (1959) suggestion that D. sanchezi occurs near Buenos Aires is mistaken; so also is Cazzaniga's & Curino's (1987) identification of specimens from Buenos Aires as D. anceps.     

A histochemical study of the reproductive structures in the flatworm Dugesia leporii (Platyhelminthes, Tricladida)

Abstract. The functional morphology and the topographic distribution of tissues in the reproductive system of specimens of Dugesia leporii , an endemic Sardinian free-living planarian, are investigated. Data are provided on the nature of epithelial and glandular secretions, spermatophores, and cocoons by histochemistry, light microscopy, and scanning electron microscopy. All secreting epithelial cells produce strongly acidic sulfated glycoproteins. Glandular cells secrete strongly acidic sulfated glycoproteins or keratohyalin-like material in the penis bulb, and prekeratin-like material in atrial glands. Secretions of the bursa copulatrix may be involved in the activation of sperm while material produced by the bursa canal and oviducts probably serves to propel spermatophores or sperm and eggs. Mucous secretion of the seminal vesicle may serve to dilute and activate sperm before copulation. The viscous secrete of the ejaculatory duct and vasa deferentia may play a protective role to maintain sperm viability. Materials produced by the penis papilla and atrium probably lubricate the epithelial surface. The bilayered wall of spermatophore made of keratohyalin-like material and strongly acidic sulfated glycoproteins is produced by two gland types of the penis bulb. The bilayered shell of cocoon made of prekeratin-like and keratohyalin-like materials is secreted by both atrial glands and vitelline cells. The cocoon stalk is made of keratohyalin-like material produced by cement glands. Shell glands, producing GAG, are not involved in cocoon formation, but they may be implicated in the dilution and activation of seminal material to favor sperm movement toward the oviducts.     

Colonization and extinction of land planarians (Platyhelminthes,Tricladida) in a Brazilian Atlantic Forest regrowth remnant

Long-term assessments of species assemblages are valuable tools for detecting species ecological preferences and their dispersal tracks, as well as for assessing the possible effects of alien species on native communities. Here we report a 50-year-long study on population dynamics of the four species of land flatworms (Platyhelminthes, Tricladida, Terricola) that have colonized or become extinct in a 70-year-old Atlantic Forest regrowth remnant through the period 1955–2006. On the one hand, the two initially most abundant species, which are native to the study site, Notogynaphallia ernesti and Geoplana multicolor have declined over decades and at present do not exist in the forest remnant. The extinction of these species is most likely related with their preference for open vegetation areas, which presently do not exist in the forest remnant. On the other hand, the neotropical Geoplaninae 1 and the exotic Endeavouria septemlineata were detected in the forest only very recently. The long-term study allowed us to conclude that Geoplaninae 1 was introduced into the study area, although it is only known from the study site. Endeavouria septemlineata, an active predator of the exotic giant African snail, is originally known from Hawaii. This land flatworm species was observed repeatedly in Brazilian anthropogenic areas, and this is the first report of the species in relatively well preserved native forest, which may be evidence of an ongoing adaptive process. Monitoring of its geographic spread and its ecological role would be a good practice for preventing potential damaging effects, since it also feeds on native mollusk fauna, as we observed in lab conditions. Júlio Pedroni: Granted by CNPQ–Brazil.     

The genus Dugesia in Australia, with its phylogenetic analysis and historical biogeography (Platyhelminthes, Tricladida, Dugesiidae)

The new species Dugesia notogaea Sluys & Kawakatsu, sp. n. is described from Queensland, Australia, representing the first record of the genus Dugesia for that continent. A phylogenetic analysis of the 68 species of Dugesia resulted in the discovery of a new apomorphy for the genus, and a cladogram showing two major phyletic groups. The distributional range of one group has a western accent, whereas that of the other group has an eastern emphasis; the ranges of these two groups overlap in Africa and the Mediterranean region. We attempt to determine the ancestral area for both the Dugesiidae and Dugesia. A scenario for the historical biogeography of the genus Dugesia is discussed. In this scenario it is presumed that the geological history of the Australasian region enabled Dugesia's from southeast Asia to colonize northern Australia. © 1998 The Norwegian Academy of Science and Letters     

The freshwater planarian Dugesia sicula Lepori, 1948 (Platyhelminthes, Tricladida) in Tunisia: ecology, karyology, and morphology

A study was carried out on freshwater planarians of the genus Dugesia from three localities in northern Tunisia: Joumine, Chiba, and Lebna. The three populations are fissiparous under field conditions and do not possess reproductive organs, except for some cases of hyperplastic ovaries in the Joumine population. After five months of breeding under laboratory conditions, with water temparature between 18 and 25?°C and under short photoperiod, 8.33 to 26% of specimens from the Joumine stream became sexualized, together with considerable increase of body length and width. For the other two populations the sexualization rate was very small. Extended period of darkness apparently played a positive role in this sexualization. The phenomenon of sexualization is discussed in the context of reproductive strategies. Histological and karyological studies of the sexualized animals allowed identification of these usually fissiparous planarians as representatives of Dugesia sicula Lepori, 1948. The species is here reported for the first time from Tunisia. The populations are restricted to permanent water basins resulting from the construction of dams in large rivers.     

A comparative study of the population biology of the American immigrant triclad Dugesia tigrina (Girard) in two British lakes

The population biology of the American immigrant triclad Dugesia tigrina was investigated in two British eutrophic lakes: Colemere, England, harbours an asexually reproducing population and Llyn Coron, North Wales, a population that reproduces both sexually and asexually. Monthly samples of triclads were taken from the undersides of stones in both lakes, and from ceramic tiles and plastic trays in Colemere and Llyn Coron, respectively, over two years. In both populations, body size-structure decreased slightly over winter, with an absence of very large and very small animals. Individual growth occurred in spring, and over summer the proportion of large and small individuals declined and increased, respectively. During September to November, size-structure was fairly stable. Increases in the size structure of the populations were associated with higher temperatures and an increased food supply; stability in size structure during the autumnal post-reproductive period, when temperatures were favourable for growth, to the occurrence of intraspecific competition for food; and decreases in size structure to lower temperatures during the winter. In both populations the density of triclads increased in summer to a peak in autumn, thereafter declining to a nadir in spring. The numerical peak in autumn was due to recruitment from reproduction, and the subsequent decline to deaths following the occurrence of intraspecific competition for food in late autumn, some invertebrate predation and winter mortality. Asexual reproduction (fission) started in June and finished during August in both populations. Laboratory experiments indicated that the occurrence and rate of fission is influenced by temperature and the amount of available food. The critical temperature for the initiation and cessation of fission lay between 14 and 16 °C in laboratory studies, and in the field fissioning started as temperatures approached 15 °C. In Llyn Coron, cocoon deposition commenced in June, peaked in July with only a very few produced in August. Triclads collected from the field outside these months could not be induced to lay cocoons in the laboratory. Laboratory experiments showed that cocoons were deposited at temperatures of 17.5, 20, and 25 °C, but not at 12.5 °C. Thus, in the field, cocoon production started when temperatures approached 15 °C in June, but had ceased whilst temperatures were still in excess of 15 °C in late August. Termination of cocoon dsposition is associated with the disappearance of large triclads in excess of 20 mm², below which animals are not sexually mature; disappearance of large animals was due to fissioning, death after sexual reproduction, and probably shrinkage due to severe intraspecific competition for food. Laboratory experiments indicated that the Colemere population had, potentially, greater fission production than the Llyn Coron population. Despite this, the numerical size of the Colemere and Llyn Coron populations increased seven-fold and eleven-fold, respectively, over the reproductive period. Whether or not this difference in reproductive potential between the populations will continue is speculative; the introduction of D. tigrina to Llyn Coron is relatively recent and the population may still be expanding to reach the carrying capacity of the habitat. Its high reproductive output must have helped its successful invasion of the lake.     

Karyology and karyotype analysis of diploid freshwater planarian populations of the Dugesia gonocephala group (Platyhelminthes,Tricladida) found in Sardinia

Karyology and karyotype analysis were carried out on freshwater planarian populations of the Dugesia gonocephala group. The strains studied were all diploid with chromosomic number 2n = 16; n = 8. They came from 12 sites mainly localized on the west of the island of Sardinia. Three karyotypes indicated with the letters A, B and C were found in which eight homomorphic pairs of chromosomes were easily identified. In karyotype A all chromosomes are metacentric. Ten populations of the twelve examined showed this karyotype which appears to be the most common. In karyotype B the seventh pair of chromosomes is submetacentric. This karyotype is quite common having been previously found in another eight Sardinian localities. Karyotype C differs from the others in having submetacentric third and seventh pairs of the chromosome complement. It was found in only one locality. The differences observed between these three karyotypes could be interpreted either as sign of differentiation at species level, or as an intraspecific variation due to chromosome mutations (pericentric inversions). This revised version was published online in July 2006 with corrections to the Cover Date.