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     

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.     

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.     

Morphometry of the eyes in regenerant of genus Dugesia (Platyhelminthes, Turbellaria, Dugesiidae).

The photodocumentation technique was used weekly to observe until the end of the regenerative process of eyes in three species of Dugesia. Morphometric data based on the measurement of 96 samples of the species: Dugesia tigrina, D. schubarti, and D. anderlani were analyzed. A comparative analysis was made through graphic representation of statistical parameters of the following morphometric characters: the length of the transversal and longitudinal axes of the macula alba, pigment spot, and ocular opening. An interesting feature appeared in D. schubarti: the average of ocular opening during the regenerative process is bigger than in the original samples.     

Molecular barcoding and phylogeography of sexual and asexual freshwater planarians of the genus Dugesia in the Western Mediterranean (Platyhelminthes, Tricladida, Dugesiidae)

Planarians of the genus Dugesia have a worldwide distribution with high species diversity in the Mediterranean area. In this area, populations with a triploid karyotype that reproduce by fissiparity are exceptionally frequent, outnumbering the sexual populations. This situation poses interesting questions, such as the age of these asexual lineages, whether they all belong to the same species or whether the triploidization event is recurrent, and what factors (climatic, geographical, historical...) explain the prevalence of these asexual forms. However, asexual populations cannot be assigned to a species due to the lack of copulatory apparatus – the main structure used in species identification. In this study, we have developed a DNA barcoding method, based on COI and ITS-1 sequences, which allows the assignment of the fissiparous forms to sexual species. At the same time, phylogenetic analysis from species of the western Mediterranean have unveiled the presence of species with highly differentiated populations alongside species with a wide distribution and almost no genetic variation. The roles of habitat instability, dispersal capacity and human activities are briefly discussed.     

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.     

Origin and Evolution of Paralogous rRNA Gene Clusters Within the Flatworm Family Dugesiidae (Platyhelminthes, Tricladida)

Analysis of the 18S rDNA sequences of five species of the family Dugesiidae (phylum Platyhelminthes, suborder Tricladida, infraorder Paludicola) and eight species belonging to families Dendrocoelidae and Planaridae and to the infraorder Maricola showed that members of the family Dugesiidae have two types of 18S rDNA genes, while the rest of the species have only one. The duplication event also affected the ITS-1, 5.8S, ITS-2 region and probably the 28S gene. The mean divergence value between the type I and the type II sequences is 9% and type II 18S rDNA genes are evolving 2.3 times more rapidly than type I. The evolutionary rates of type I and type II genes were calibrated from biogeographical data, and an approximate date for the duplication event of 80–120 million years ago was calculated. The type II gene was shown, by RT-PCR, to be transcribed in adult individuals of Schmidtea polychroa, though at very low levels. This result, together with the fact that most of the functionally important positions for small-subunit rRNA in prokaryotes have been conserved, indicates that the type II gene is probably functional. Received: 24 March 1998 / Accepted: 17 March 1999     

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.     

A new species of the genus Girardia (Tricladida: Dugesiidae) from China

The genus Girardia(Tricladida: Dugesiidae) was recorded in China for the first time. A new freshwater turbellarian species, G. sinensis Chen & Wang, sp. nov., is described, which was collected from Xinghu Lake, Zhaoqing, Guangdong Province, China. Observation and analysis of the new species was conducted on morphology, habits, reproduction, histochemistry and molecular phylogenetics. In addition, the results indicated that morphological differences of ACh E+ nerve structure can be used as a distinguishable character for species identification of Dugesiidae.     

The taxonomic status of Dugesia biblica from Israel and Turkey (Platyhelminthes,Tricladida, Dugesiidae)

The taxonomic status of Dugesia biblica (Platyhelminthes, Tricladida, Dugesiidae) from Israel and Turkey is problematic due to its morphological similarity with Dugesia sicula since these nominal species present overlapping characters. In this study we analyzed histological preparations of specimens of these two nominal species and also compared mitochondrial COI gene sequences from Israeli populations to the already known haplotype composition of Dugesia sicula. We concluded that these animals belong to the same species and therefore we consider Dugesia biblica to be a junior synonym of Dugesia sicula. This implies that the distribution range of Dugesia sicula is even wider than previously thought, and that the species is present all around the Mediterranean Basin and on many of its islands.     

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).     

Colonization of rivers and canals in Great Britain by Dugesia tigrina(Girard) (Platyhelminthes: Tricladida)

SUMMARY. 1. Prior to 1975 Dugesia tigrina , an Americati immigrant triclad, was known from only a few flowing water sites in Great Britain. Since then it has been found in a large number of lowland rivers and canals in England and Wales, and in 1985 it was reported from the lower reaches of the River Tweed in Scotland.
2. This note gives the recorded distribution of D. tigrina up to the end of 1985 (115 10 km squares now occupied) and summarizes the environmental conditions at a subset of twenty-five sites where D. tigrina occurs.
3. Information on the native triclads at sites recently colonized by D. tigrina is used as a basis for speculating on the rivers most vulnerable to the future spread of this species.
4. Possible methods of dispersal of D. tigrina and the features which make it a successful colonist are discussed.     

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.     

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.