Elucidating the molecular mechanisms that created ancient complex traits like insect wings is difficult. Fortunately, some complex traits have arisen recently. For example, hermaphroditic reproduction evolved independently many times during recent nematode evolution. Although C. elegans hermaphrodites require fog-2, which encodes an F box protein that regulates the translation of tra-2 mRNAs, the related species C. briggsae lacks fog-2. We identified a critical regulator of hermaphrodite development in C. briggsae, named she-1. Analysis of double mutants indicates that she-1 acts upstream of tra-2 in C. briggsae, just as fog-2 does in C. elegans. Molecular cloning shows that she-1 encodes a novel F box protein that was created by a recent gene duplication. Whereas FOG-2 acts through GLD-1 in C. elegans, SHE-1 does not bind GLD-1 in C. briggsae. Thus, both species recruited F box genes produced by recent duplication events into the sex-determination pathway to control hermaphrodite development, but these genes have distinct activities. This result implies that some gene families are more likely to give rise to novel regulatory genes than other families. Finally, we note that null mutations of she-1 are temperature sensitive, so C. briggsae might once have been a facultative hermaphrodite.
Background: Species of Hirudo are used extensively for medicinal purposes, but are currently listed as endangered due to population declines from economic utilization and environmental pollution. In total, five species of Hirudo are currently described throughout Eurasia, with Turkey being one of the major exporters of medicinal leech, primarily H. verbana. Results: To define the distribution of Hirudo spp. within Turkey, we collected 18 individuals from six populations throughout the country. Morphological characters were scored after dorsal and ventral dissections, and Maximum Likelihood (ML) and Bayesian Inference (BI) analyses resolved phylogenetic relationships using mitochondrial cytochrome c oxidase subunit I (COI), 12S ribosomal RNA (rRNA), and nuclear 18S rRNA gene fragments. Our results identify a new species of medicinal leech, Hirudo sulukii n. sp, in Kara Lake of Adiyaman, Sülüklü Lake of Gaziantep and Segirkan wetland of Batman in Turkey. Phylogenetic divergence (e.g., 10-14 % at COI), its relatively small size, unique dorsal and ventral pigmentation patterns, and internal anatomy (e.g., small and pointed atrium, medium-sized epididymis, relatively long tubular and arc formed vagina) distinguish H. sulukii n. sp. from previously described Hirudo sp. Conclusions: By ML and BI analyses, H. sulukii n. sp. forms a basal evolutionary branch of Eurasian medicinal leeches. Phylogeographic interpretations of the genus identify a European Hirudo "explosion" during the upper Miocene followed by geological events (e.g., Zanclean flood, mountain building) that likely contributed to range restrictions and regional speciation of extant members of the clade.
Myzobdella lugubris is a commensal leech on crustaceans and a parasite to fishes, surviving predominantly in brackish waters throughout North America. Specimens in this study were collected within the tidal zone of the Delaware River basin (New Jersey and Pennsylvania). To compare regional M. lugubris specimens, defined characters were scored after dorsal and ventral dissections, and phylogenetic relationships were resolved using cytochrome c oxidase subunit 1 (CO1), 12S ribosomal RNA (rDNA) and 18S rDNA gene fragments. Variance between regional populations was low, suggesting recent dispersal events and/or strong evolutionary constraints. The reproductive biology of M. lugubris was explored by quantitative analysis of secreted cocoons. Specimens produced 32.67 ± 4.50 cocoons with fertilization ratios of 88.1% and hatching times of 48 ± 7 days at 17°C under laboratory conditions. At 22°C, 46 ± 28 cocoons were produced with fertilization ratios of 70.27% and hatching times of 28 ± 5 days. Surprisingly, each cocoon supported only one embryo, which is unusual among oligochaetes.
Disentangling the contemporary and historical factors underlying the spatial distributions of species is a central goal of biogeography. For species with broad distributions but little capacity to actively disperse, disconnected geographical distributions highlight the potential influence of passive, long-distance dispersal (LDD) on their evolutionary histories. However, dispersal alone cannot completely account for the biogeography of any species, and other factors—e.g. habitat suitability, life history—must also be considered. North American ice worms ( Mesenchytraeus solifugus ) are ice-obligate annelids that inhabit coastal glaciers from Oregon to Alaska. Previous studies identified a complex biogeographic history for ice worms, with evidence for genetic isolation, unexpectedly close relationships among geographically disjunct lineages, and contemporary migration across large (e.g. greater than 1500 km) areas of unsuitable habitat. In this study, we analysed genome-scale sequence data for individuals from most of the known ice worm range. We found clear support for divergence between populations along the Pacific Coast and the inland flanks of the Coast Mountains (mean F ST = 0.60), likely precipitated by episodic ice sheet expansion and contraction during the Pleistocene. We also found support for LDD of ice worms from Alaska to Vancouver Island, perhaps mediated by migrating birds. Our results highlight the power of genomic data for disentangling complex biogeographic patterns, including the presence of LDD.
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