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Despite the commercial potential of mussel populations along the Patagonian coast of Argentina, studies on mussel farming and fisheries to the south of parallel 42° S are clearly insufficient thus far. In this study, variations in mussel settlement (between sites and across depths) were monitored for 12 months at two contrasting sites in San Jorge Gulf, Argentina. The effect of depth on spat density was evaluated through monthly samples taken from artificial collectors at three depths (3, 7 and 11 m). The temporal settlement pattern was consistent at both sites, with the maximum spatfall recorded in early March (late summer), coinciding with the peak of sea water temperature. Settlement also correlated with Chl a and particulate organic carbon peak values, typically manifesting 2–3 months later and followed the initial decline in mussel condition during late spring and early summer. Significant differences between localities were detected in settlement abundance. The optimal temporal gap for mussel settlement was observed in mid / late summer, suggesting that this is the optimal time to deploy spat collectors in the field. Settlement was uniform between depths, thereby implying that the specific depth of collector placement did not appear to emerge as a key factor of settlement success. • Two mussel potential spawning events occurred, in early summer (January-February) and autumn (May). • Maximum mussel settlement occurred in mid-late summer and is the optimal time to deploy spat collectors. • Settlement was uniform among depths. [ABSTRACT FROM AUTHOR]

The Triassic Agua de la Zorra Formation crops out in the Paramillos de Uspallata area (NW of Mendoza) and represents a deltaic-lacustrine system with volcanic activity as well as episodic incursions of peperitic basalts. The succession is characterized by distal lacustrine facies at base and top, with proximal shallow facies in the middle section. The paleontological record includes invertebrates (spinicaudatans, insects), vertebrates (mainly fishs), tetrapod tracks and invertebrates traces, and plant remains (mainly referred to Umkomasiales). Kerogen in the distal facies is mostly terrigenous, with scarce amorphous and palynomorphs (disacates and microalgae). It shows a variable percentage of the total organic carbon content (between 0.2 and 4.6) with hydrogen and oxygen indices indicating a type III kerogen. In the shallow facies, kerogen is practically absent and the trace fossils reflect sporadic subaerial exposure. The palynological evidence indicates an oligotrophic lake and the low productivity recorded was likely caused by dilution of the lake water by strong fluvial influence in an overfilled lake basin type. The organic geochemistry data also suggests an overfilled lake basin and the inorganic geochemistry data support the development of anoxic conditions at the bottom of the paleolake. The spinicaudata valves occur in densely packed beds that could have been driven by changes in the water physicochemical parameters as a result of volcanic activity in the area. The volcanic activity in the area is a good explanation for variability in the biota diversity. However, the continuous record of plant remains through out the section seems to indicates that the paleoenvironmental conditions in the surrounding terrestrial areas were stables. • The palynological evidence indicates a lake with low productivity. • The organic geochemistry data is consistent with the parameters of an overfilled lake basin. • The spinicaudata beds registered could be driven by changes in the physicochemical parameters caused by volcanic activity. • The trace fossils recorded seem to reflect a sporadic subaerial exposure of the sediments. • The volcanic activity in the area is a good explanation for variability in the biota diversity. [ABSTRACT FROM AUTHOR]

The worldwide spread of diseases is considered a major threat to biodiversity and a possible driver of the decline of pollinator populations, particularly when novel species or strains of parasites emerge. Previous studies have suggested that populations of introduced European honeybee (Apis mellifera) and bumblebee species (Bombus terrestris and Bombus ruderatus) in Argentina share the neogregarine parasite Apicystis bombi with the native bumblebee (Bombus dahlbomii). In this study we investigated whether A. bombi is acting as an emergent parasite in the non-native populations. Specifically, we asked whether A. bombi, recently identified in Argentina, was introduced by European, non-native bees. Using ITS1 and ITS2 to assess the parasite's intraspecific genetic variation in bees from Argentina and Europe, we found a largely unstructured parasite population, with only 15% of the genetic variation being explained by geographic location. The most abundant haplotype in Argentina (found in all 9 specimens of non-native species) was identical to the most abundant haplotype in Europe (found in 6 out of 8 specimens). Similarly, there was no evidence of structuring by host species, with this factor explaining only 17% of the genetic variation. Interestingly, parasites in native Bombus ephippiatus from Mexico were genetically distant from the Argentine and European samples, suggesting that sufficient variability does exist in the ITS region to identify continent-level genetic structure in the parasite. Thus, the data suggest that A. bombi from Argentina and Europe share a common, relatively recent origin. Although our data did not provide information on the direction of transfer, the absence of genetic structure across space and host species suggests that A. bombi may be acting as an emergent infectious disease across bee taxa and continents.