Lineage-level divergence of copepod glycerol transporters and the emergence of isoform-specific trafficking regulation

Transmembrane conductance of small uncharged solutes such as glycerol typically occurs through 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 apparent gene redundancy. Here, we show that Glp evolution in Crustacea is highly divergent, ranging from single copy genes in species of pedunculate barnacles, tadpole shrimps, isopods, amphipods and decapods to up to 10 copies in diplostracan water fleas although with monophyletic origins in each lineage. By contrast the evolution of Glps in Copepoda appears to be polyphyletic, with surprisingly high rates of gene duplication occurring in a genera- and species-specific 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. In the case of 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 protein kinase C (PKC)- or protein kinase A (PKA)-regulation of intracellular membrane trafficking. The combined data sets 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.

First record of swimming speed of the Pacific sleeper shark Somniosus pacificus using a baited camera array

The Pacific sleeper shark Somniosus pacificus is one of the largest predators in deep Suruga Bay, Japan. A single individual of the sleeper shark (female, ~300 cm in total length) was observed with two baited camera systems deployed simultaneously on the deep seafloor in the bay. The first arrival was recorded 43 min after the deployment of camera #1 on 21 July 2016 at a depth of 609 m. The shark had several remarkable features, including the snout tangled in a broken fishing line, two torn anteriormost left-gill septums, and a parasitic copepod attached to each eye. The same individual appeared at camera #2, which was deployed at a depth of 603 m, ~37 min after it disappeared from camera #1 view. Finally, the same shark returned to camera #1 ~31 min after leaving camera #2. The distance between the two cameras was 436 m, and the average groundspeed and waterspeed of the shark were 0.21 and 0.25 m s−1, respectively, which were comparable with those of the Greenland shark Somniosus microcephalus (0.22–0.34 m s−1) exhibiting the slowest comparative swimming speed among fish species adjusted for size. The ambient water temperature of the Pacific sleeper shark was 5.3 °C, which is considerably higher than that of the Greenland shark (~2 °C). Such a low swimming speed might be explained by the ‘visual interactions hypothesis’, but it is not a consequence of the negative effects of cold water on their locomotor organs.

Gauchergasilus euripedesi (Copepoda, Ergasilidae) parasitizing different species of fish from two environments in southern Brazil

The parasitic copepod Gauchergasilus euripedesi (Montú, 1980) Montú & Boxshall, 2002 was described from plankton samples and specimens found in four fish species from the estuarine area of Patos Lagoon, state of Rio Grande do Sul (RS), Brazil. Later, one different fish species was reported parasitized with G. euripedesi in the same locality. Species of Astyanax Baird & Girard, 1854 (Astyanax henseli Melo & Buckup, 2006 and Astyanax lacustris (Lütken, 1875)) and Psalidodon Eigenmann, 1911 (Psalidodon eigenmanniorum (Cope, 1894) and Psalidodon aff. fasciatus (Cuvier, 1819)) were collected in two environments (Pintada Island, municipality of Porto Alegre and Itapeva Lagoon, municipality of Terra de Areia, RS) to investigate their parasites. The copepods found in the gill arches were counted, processed, mounted in permanent slides, and photographed using light microscopy, or processed for observation in scanning electron microscopy. Specimens of P. eigenmanniorum from Pintada Island, A. lacustris and P. aff. fasciatus from Itapeva Lagoon, were parasitized by G. euripedesi, with prevalences of 29.03% (A. lacustris), 10.34% (P. eigenmanniorum), and 9.68% (P. aff. fasciatus). Measurements obtained for specimens of G. euripedesi were similar to those found in the literature, except for egg sacs which were larger in the specimens examined in the present study. In addition to being the first report of G. euripedesi parasitizing species of fish (A. lacustris, P. eigenmanniorum, and P. aff. fasciatus), the results presented here also extend the known geographic distribution of the copepod species.