Project description:BackgroundTubifex tubifex is a widespread annelid characterized by considerable variability in its taxonomic characteristics and by a mixed reproductive strategy, with both parthenogenesis and biparental reproduction. In a molecular phylogenetic analysis, we detected substantial genetic variability among sympatric Tubifex spp. from the Lambro River (Milano, Italy), which we suggested comprise several cryptic species. To gain insights into the evolutionary events that generated this differentiation, we performed a cytogenetic analysis in parallel with a molecular assay. Approximately 80 cocoons of T. tubifex and T. blanchardi were collected and dissected. For each cocoon, we sequenced a fragment of the 16S rRNA from half of the sibling embryos and karyotyped the other half. To generate a robust phylogeny enabling the reconstruction of the evolutionary processes shaping the diversity of these sympatric lineages, we complemented our original 16S rRNA gene sequences with additional COI sequences.ResultsThe chromosome number distribution was consistent with the presence of at least six sympatric euploid chromosome complements (one diploid, one triploid, three tetraploids and one hexaploid), as confirmed by a FISH assay performed with an homologous 18S rDNA probe. All the worms with 2n = 50 chromosomes belonged to an already identified sibling species of T. tubifex, T. blanchardi. The six euploid sets were coherently arranged in the phylogeny, with each lineage grouping specimens with the same chromosome complement.ConclusionsThese results are compatible with the hypothesis that multiple polyploidization events, possibly enhanced by parthenogenesis, may have driven the evolution of the T. tubifex species complex.
Project description:The study goal was to examine the effects of sand and mud on the propagation of Myxobolus cerebralis, the whirling disease agent, in four mitochondrial 16S ribosomal DNA lineages (I, III, V, VI) of its oligochaete host, Tubifex tubifex (Tt). In all the lineage groups held continuously in either substrate (non-shifted) or transferred from sand to mud (shifted), substrate influenced parasite proliferation only in lineage III. Sporogenesis and release of triactinomyxon spores (TAMs) were more prevalent in lineage III Tt in mud compared to sand. Low-infection prevalence and lack of parasite development in lineage I is associated with the greater number of resistant worms and were not affected by substrate type. Substrate did not impact Tt from lineages V and VI that failed to develop any parasite stages in either substrate even after shifting from sand to mud. The relationship between the microbial community in the substrate and parasite proliferation in lineage III was described but not analyzed due to small sample size. Substrate-associated bacteria were hypothesized as essential dietary source for the oligochaete host feeding selectively on fine (mud)-microflora. Progeny was produced by all lineage groups shifted to mud with disparate survival profiles in lineage V and VI and high mortalities in lineage III. Our study demonstrates that substrate type can alter parasite proliferation in lineage III. Conversely, parasite development and infectivity were not altered in lineage V and VI that are refractory to the parasite nor among the more resistant phenotypes (I), regardless of substrate type.
Project description:Dufulin is a highly effective antiviral pesticide used in plants. In this study, a seven-day experiment was conducted to evaluate the effects of Dufulin at five different concentrations (1 × 10-4, 1 × 10-3, 1 × 10-2, 0.1, and 1 mg/L) on Tubifex. LC-MS-based metabolome analysis detected a total of 5356 features in positive and 9110 features in negative, of which 41 showed significant changes and were identified as differential metabolites. Four metabolic pathways were selected for further study. Detailed analysis revealed that Dufulin exposure affected the urea cycle of Tubifex, probably via argininosuccinate lyase (ASL) inhibition. It also affected the fatty acid metabolism, leading to changes in the concentration of free fatty acids in Tubifex. Furthermore, the changes in metabolites after exposure to Dufulin at 1 × 10-2 mg/L were different from those at the other concentrations.
Project description:The super-phylum Lophotrochozoa contains the plurality of extant animal phyla and exhibits a corresponding diversity of adult body plans. Moreover, in contrast to Ecdysozoa and Deuterostomia, most lophotrochozoans exhibit a conserved pattern of stereotyped early divisions called spiral cleavage. In particular, bilateral mesoderm in most lophotrochozoan species arises from the progeny of micromere 4d, which is assumed to be homologous with a similar cell in the embryo of the ancestral lophotrochozoan, more than 650 million years ago. Thus, distinguishing the conserved and diversified features of cell fates in the 4d lineage among modern spiralians is required to understand how lophotrochozoan diversity has evolved by changes in developmental processes. Here we analyze cell fates for the early progeny of the bilateral daughters (M teloblasts) of micromere 4d in the leech Helobdella sp. Austin, a clitellate annelid. We show that the first six progeny of the M teloblasts (em1-em6) contribute five different sets of progeny to non-segmental mesoderm, mainly in the head and in the lining of the digestive tract. The latter feature, associated with cells em1 and em2 in Helobdella, is seen with the M teloblast lineage in a second clitellate species, the sludgeworm Tubifex tubifex and, on the basis of previously published work, in the initial progeny of the M teloblast homologs in molluscan species, suggesting that it may be an ancestral feature of lophotrochozoan development.