The effect of octopaminergic compounds on the behaviour and transmission of Gyrodactylus

Background: The high transmission potential of species belonging to the monogenean parasite genus Gyrodactylus, coupled with their high fecundity, allows them to rapidly colonise new hosts and to increase in number. One gyrodactylid, Gyrodactylus salaris Malmberg, 1957, has been responsible for devastation of Altantic salmon (Salmo salar L.) populations in a number of Norwegian rivers. Current methods of eradicating G. salaris from river systems centre around the use of non-specific biocides, such as rotenone and aluminium sulphate. Although transmission routes in gyrodactylids have been studied extensively, the behaviour of individual parasites has received little attention. Specimens of Gyrodactylus gasterostei Gläser, 1974 and G. arcuatus Bychowsky, 1933, were collected from the skin of their host, the three-spined stickleback (Gasterosteus aculeatus L.), and permitted to attach to the substrate. The movements of individual parasites were recorded and analysed. Results: The behaviour patterns of the two species were similar and parasites were more active in red light and darkness than in white light. Four octopaminergic compounds were tested and all four inhibited the movements of parasites. Treatment ultimately led to death at low concentrations (0.2 μM), although prolonged exposure was necessary in some instances. Conclusions: Octopaminergic compounds may affect the parasite's ability to locate and remain on its host and these or related compounds might provide alternative or supplementary treatments for the control of G. salaris infections. With more research there is potential for use of octopaminergic compounds, which have minimal effects on the host or its environment, as parasite-specific treatments against G. salaris infections

Patterns of Diversity in Soft-Bodied Meiofauna: Dispersal Ability and Body Size Matter

Background: Biogeographical and macroecological principles are derived from patterns of distribution in large organisms, whereas microscopic ones have often been considered uninteresting, because of their supposed wide distribution. Here, after reporting the results of an intensive faunistic survey of marine microscopic animals (meiofauna) in Northern Sardinia, we test for the effect of body size, dispersal ability, and habitat features on the patterns of distribution of several groups.Methodology/Principal Findings: As a dataset we use the results of a workshop held at La Maddalena (Sardinia, Italy) in September 2010, aimed at studying selected taxa of soft-bodied meiofauna (Acoela, Annelida, Gastrotricha, Nemertodermatida, Platyhelminthes and Rotifera), in conjunction with data on the same taxa obtained during a previous workshop hosted at Tjärnö (Western Sweden) in September 2007. Using linear mixed effects models and model averaging while accounting for sampling bias and potential pseudoreplication, we found evidence that: (1) meiofaunal groups with more restricted distribution are the ones with low dispersal potential; (2) meiofaunal groups with higher probability of finding new species for science are the ones with low dispersal potential; (3) the proportion of the global species pool of each meiofaunal group present in each area at the regional scale is negatively related to body size, and positively related to their occurrence in the endobenthic habitat.Conclusion/Significance: Our macroecological analysis of meiofauna, in the framework of the ubiquity hypothesis for microscopic organisms, indicates that not only body size but mostly dispersal ability and also occurrence in the endobenthic habitat are important correlates of diversity for these understudied animals, with different importance at different spatial scales. Furthermore, since the Western Mediterranean is one of the best-studied areas in the world, the large number of undescribed species (37%) highlights that the census of marine meiofauna is still very far from being complete

First evidence of unpigmented rhabdomeric photoreceptors in a Microstomum species (Plathelminthes, Macrostomorpha, Microstomidae) and ultrastructure of photoreceptor-like ciliary aggregations

Microstomum spiculifer possesses a pair of intracerebral photoreceptors each consisting of a single rhabdomeric sensory cell and two cup or mantle cells. The mantle cells are devoid of pigment. In addition, four so-called ciliary aggregations, presumed to have a light-sensing function, are present. Each ciliary aggregation represents a specialized cell with an internal cavity filled with axonemes of modified cilia. Rhabdomeric photoreceptors consisting of one to three sensory cells and a single pigmented or unpigmented mantle cell are widespread within taxa of the Plathelminthes Rhabditophora. On the contrary, the existence of two mantle cells forming the eye cup is only known for M. spiculifer and a few other species of the Macrostomida. Therefore, at least two hypotheses are possible: (1) two cup cells are a basic characteristic of the Rhabditophora and a reduction from two to one cup cell has occurred secondarily or (2) the stem species of the Rhabditophora possessed rhabdomeric eyes with one cup cell, and two mantle cells have evolved within the Macrostomorpha. The existence of ciliary aggregates has been documented for several taxa of the Plathelminthes Rhabditophora. From their distribution it can not be concluded whether these differentiations are either a basic feature of the Rhabditophora or have evolved several times convergently

Ciliopharyngiella intermedia (Plathelminthes, Neoophora) - enigmatic as ever? Ultrastructural features and phylogenetic implications

Ultrastructural features of the epidermis, gonads and photoreceptors are presented. The following features of Ciliopharyngiella intermedia are considered to represent autapomorphies of this species or of the taxon Ciliophatyngiella: the special design of egg shell-forming granules in vitellocytes, the pattern of marginal granules in germocytes,. an intercentriolar body with strong striated supporting beams, cilia with a pair of rootlets in young spermatids, as well as intracerebral photoreceptors with both ciliary and rhabdomeric light-sensing organelles arising from the same cell. Based on present information it is hypothesized, that Ciliophatyngiella represents the sister taxon of the Eulecithophora (= Prolecithophora + Rhabdocoela)

Spermatozoa of Psammomacrostomum turbanelloides (Plathelminthes, Macrostomida) - submicroscopic anatomy and phylogenetic implications

The general submicroscopic anatomy of the thread-like spermatozoa in Psammomacrostomum turbanelloides corresponds to the basic pattern of male gametes in Macrostomida: the cells, which lack cilia, have longitudinal cortical microtubules subdivided into two sets, one thread-shaped nucleus, numerous mitochondria and dense bodies of a special type. Some features, however, such as two double rows of contralateral microtubules with a few microtubules set apart from the others, membranous lacunae, "dense-cored microtubules", the existence of tubuliform. organelles and two dense ledges do not fit this basic pattern. Several of these differentiations are hypothesized to be autapomorphic characteristics of P. turbanelloides whereas the two dense ledges, which are also known from the taxon Bradynectes and which are considered to correspond to the two bristles known from Macrostomum- and Promacrostomum-species, may corroborate the hypothesis of the existence of a monophyletic group including Bradynectes, Psammomacrostomum, Promacrostomum and Macrostomum

Spermiogenesis and submicroscopic features of spermatozoa in Typhloplana viridata (Plathelminthes, Rhabdocoela, Typhloplaninae)

Some aspects of spermiogenesis and the submicroscopic anatomy of male gametes in Typhloplana viridata are described. In general, spermiogenesis of T viridata follows conventional steps typical of the cytogenesis of male gametes in representatives of Plathelminthes Trepaxonemata. Spermatozoa bear two free cilia or flagella of the 2x9+"1" microtubular pattern. The filiform sperm body is characterized by the existence of dense granules linearly arranged, a single longitudinal string of mitochondria, numerous dense bodies and dense glycogen deposits. Two features are of special interest: a compartmentalization of the nucleus in meandering lamellae and a gutter-shaped structure. While most traits of mature gametes in T. viridata corroborate the hypothesis of the existence of a monophylum Rhabdocoela or of a subordinated monophylum within the Rhabdocoela encompassing distinct taxa of the "Typhloplanoida" and "Dalyellioida" (including all species of the Temnocephalida), the existence of nuclear lamellae seems to be more restricted and the gutter-shaped element may be an autapomorphic characteristic of the taxon Typhloplana (or of a monophylum that includes several genera of the Typhloplaninae) or of the species T viridata

Photoreceptors in species of the Macrostomida (Plathelminthes): ultrastructural findings and phylogenetic implications

The submicroscopic anatomy of intracerebral and pericerebral photoreceptors in six species of the Macrostomida is described. Cylindromacrostomum notandum, Paramyozonaria simplex and Macrostomum hystricinum marinum possess two rhabdomeric intracerebral photoreceptors each consisting of two pigmented cup cells and three (C. notandum and P. simplex) or two sensory cells (M. hystricinum marinum). In C. notandum and P. sinlplex two of the sensory cells are equal in size, while the third one is much smaller. This organisation is hypothesised as an autapomorphy of the Dolichomacrostomidae. Photoreceptors with two mantle cells are also known for Microstomum spiculifer. Since only one cup cell exists in representatives of nearly all other that ranked taxa of the Rhabditophora, it is concluded that the characteristic "two cup cells in rhabdomeric photoreceptors" has evolved in the stem lineage of the taxon Macrostomida or Macrostomorpha, respectively. In Myozona purpurea and Psammomacrostomum turbanelloides rhabdomeric intracerebral photoreceptors of a special type were encountered. These light-sensing organs consist of numerous cells forming an ellipsoid. The surface membranes of these cells are elongated to form filiform extensions which are tightly intertwined with each other. Pericerebral ciliary aggregations consisting of cells with an internal cavity into which axonemata of modified cilia project were observed in all species mentioned above and in Bradynectes sterreri as well. Such putative light-perceiving organs are widespread within taxa of the Plathelminthes Rhabditophora and have been hypothesised either as homologous characteristics or as analogous ones. With increasing examples being described it becomes likely that pericerebral ciliary aggregations are an apomorphic ground pattern characteristic of the Rhabditophora