Tadpole Shrimps – A General Review of the Little Known Crustaceans of Ephemeral Waterbodies

In time of global climate changes, astatic inland water reservoirs that contribute to water retention and alleviation of adverse effects of periodic river floods, are getting more and more important. Small, periodically drying off water reservoirs are also rich hubs of biodiversity. Animals especially connected to such ecosystems are primitive but unique crustaceans called tadpole shrimps (order Notostraca). Those animals seem to have universal significance – both ecological and economic. Though their primitive morphology and small size, they can radically affect the nature of their habitats, sometimes even helping us fight with noxious pests. Unfortunately, due to progressing global warming, intensification in agriculture, and urbanisation, habitats of notostracans are disappearing rapidly. Simultaneously, because of their rare occurences and taxonomic difficulties, tadpole shrimps have been insufficiently studied. However, protection of these crustaceans is inseparably connected with conservation of once numerous, periodically drying reservoirs as tadpole shrimps are referred as keystone species of such habitats. Thus, the aim of this review article is to sum up and disseminate current state of knowledge about Notostraca by a general overview of available international literature. This might help to engage more scientists into research and conservation of these little known, yet interesting crustaceans and their unique habitats.

The living fossil concept: reply to Turner

Despite the iconic roles of coelacanths, cycads, tadpole shrimps, and tuataras as taxa that demonstrate a pattern of morphological stability over geological time, their status as living fossils is contested. We responded to these controversies with a recommendation to rethink the function of the living fossil concept (Lidgard and Love in Bioscience 68:760–770, 2018). Concepts in science do useful work beyond categorizing particular items and we argued that the diverse and sometimes conflicting criteria associated with categorizing items as living fossils represent a complex problem space associated with answering a range of questions related to prolonged evolutionary stasis. Turner (Biol Philos 34:23, 2019) defends the living concept against a variety of recent skeptics, but his criticism of our approach relies on a misreading of our main argument. This misreading is instructive because it brings into view the value of three central themes for rethinking the living fossil concept—the function of concepts in biology outside of categorization, the methodological importance of distinguishing parts and wholes in conceptualizing evolutionary phenomena, and articulating diverse explanatory goals associated with these phenomena.

Lineage-level Divergence of Copepod Glycerol Transporters and the Emergence of Isoform-specific Trafficking Regulation

Transmembrane conductance of glycerol is typically facilitated by aquaglyceroporins (Glps), which are commonly encoded by multiple genes in metazoan organisms. To date, however, little is known concerning the evolution of Glps in Crustacea or what forces might underly such gene redundancy. Here we show that Glp evolution in Crustacea is highly divergent, ranging from single copy genes in species of tadpole shrimps, isopods, amphipods and decapods to up to 10 copies in diplostracan water fleas although with monophyletic origins in each lineage. By contrast Glp evolution in Copepoda appears to be polyphyletic, with high rates of gene duplication occurring in a genera- and species-specifc manner. Based upon functional experiments on the Glps from a parasitic copepod (Lepeophtheirus salmonis), we show that such lineage-level gene duplication and splice variation is coupled with a high rate of neofunctionalization. For L. salmonis, splice variation of a given gene resulted in tissue- or sex-specific expression of the channels, with each variant evolving unique sites for PKC or PKA regulation of intracellular membrane trafficking. The data thus reveal that mutations favouring a high fidelity control of intracellular trafficking regulation can be a selection force for the evolution and retention of multiple Glps in copepods.