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The amphipods of the genus Hyalella have many endemic species throughout South America, and these may have poorly studied associated species as epibionts. The aim of the present study was to review the literature on the presence of the protozoon Lagenophrys lenticulata (Kellicott, 1885) on species of Hyalella and contrast the results with the geographical distribution of the reported hosts. The literature records the presence of L. lenticulata on populations of H. azteca from Canada, Mexico and the United States of America, and on populations of H. curvispina from Uruguay. The literature also reports that H. curvispina is widespread throughout southern South America, including Argentina and Chile, and that it would be possible to find the presence of epibionts on other populations of H. curvispina. The corresponding biogeographical and evolutionary topics are discussed. [ABSTRACT FROM AUTHOR]

The Hyalella species diversity in the high-altitude water bodies of the Andean Altiplano is addressed using mitochondrial cox1 sequences and implementing different molecular species delimitation criteria. We have recorded the presence of five major genetic lineages in the Altiplano, of which one seems to be exclusive to Lake Titicaca and nearby areas, whereas the rest occur also in other regions of South America. Eleven out of 36 South American entities diagnosed by molecular delimitation criteria in our study are likely endemic to the Titicaca and neighbouring water bodies. We have detected a remarkable disagreement between morphology and genetic data in the Titicacan Hyalella, with occurrence of several cases of the same morpho-species corresponding to several Molecular Operational Taxonomic Units (MOTUs), some even distantly related, and other instances where a particular MOTU is shared by a morphologically heterogeneous array of species, including species with body smooth and others with body heavily armoured. Species diversification and incongruence between morphological and molecular boundaries within this species assemblage may be associated to the sharp changes in hydrological conditions experienced by the water bodies of the Altiplano in the past, which included dramatic fluctuations in water level and salinity of Lake Titicaca. Such environmental shifts could have triggered rapid morphological changes and ecological differentiation within the Hyalella assemblage, followed by phenotypic convergence among the diverse lineages. Factors such as phenotypic plasticity, incomplete lineage sorting or admixture between divergent lineages might lie also at the root of the morphological-genetic incongruence described herein. [ABSTRACT FROM AUTHOR]

The article presents a study that examined the crustaceans in freshwater bodies in the Katalapi Park, a private protected area in Chile. The crustaceans examined by the researchers include the cladoceran branchiopods Simocephalus and Chydorus sphaericus, the amphipod Hyalella chiloensis and the cyclopoid copepod Eucyclops serrulatus. Information on the impact of human intervention on the preservation of endangered species is also offered.

The northern Chilean (18-27°S) inland waters have been poorly studied, because of difficulties in accessing the area, and the aquatic fauna is sculpted by the high conductivity. The few studies that are available are based on fragmented information on shallow mountain ponds associated with saline deposits ("salares"), and shallow ponds and the Loa river. The aim of the present study is provide a review of the malacostracan ecology of northern Chilean inland waters. The information of shallow mountain ponds and lagoons reveals the presence of the amphipods Hyalella fossamanchini and H. kochi. They are only found at low salinity levels (<3 g/1), although a different situation was observed for Loa river, which has low abundance populations of the northern Chilean river prawn Cryphiops caementarius and the amphipods H. fossamanchini and H. kochi. However the first species is scarce due excessive fisheries activities and habitat fragmentation, whereas there are no studies about amphipods populations. Nevertheless in Loa river these species can be an important prey for introduced salmonids (Oncorhynchus mykiss and Salmo trutta). Similar patterns were observed for other comparable ecosystems in the Andes mountains of Argentina and Peru. [ABSTRACT FROM AUTHOR]

Distributional patterns in Chile of species of the freshwater amphipod genus Hyalella were analysed. The results show that H. fossamanchini and H. kochi can be found in Andean mountain inland waters between 18-27°S, H. costera in coastal inland waters between 24-40°S, H. chiloensis and H. patagonica in inland waters between 39-51°S, and finally H. simplex and H. franciscae in inland waters south of 44°S. The literature is mainly based on studies recording species in northern and southern Patagonia and the Atacama desert. Few studies on the presence of Hyalella have been carried out in central Chilean and northern and central Patagonian inland waters. [ABSTRACT FROM AUTHOR]

Two new freshwater species of amphipods from Brazil are described here. Hyalella xakriaba n. sp. occurs in the hydrographic basin of the São Francisco River, in a biome characterized by a semiarid climate, in the state of Minas Gerais. This new species constitutes the northernmost record of the genus in Brazil. Hyalella kaingang n. sp. occurs in the hydrographic basin of the Mampituba River, located in Rio Grande do Sul, the southernmost state in Brazil. Currently 14 species of Hyalella are known in Brazil, cave species among them. Some morphological characters and their respective states are analyzed, and constitute an important new tool for species identifications. In particular, we describe the cuticular structures, defined as denticles, on the distal inner margin of the carpus of gnathopods 1 and 2. These structures may have a polygonal pattern or appear as comb scales, and may be arranged in one or more rows. [ABSTRACT FROM AUTHOR]

We compared the effect of different diets biochemical composition, levels of lipid peroxidation, survival rate, and reproductive aspects of Hyalella pleoacuta and H. curvispina. These crustaceans live in limnetic environments of the plateau and coastal plain, respectively, in southern Brazil. In the laboratory, the animals were kept in aquariums under controlled conditions and fed ad libitum, for 30 days with different diets. Macrophyte only (MO) mimicked a caloric restriction in both species and sexes, because they showed depletion of glycogen and proteins, this fact was reinforced by the decrease in the levels of lipoperoxidation. These responses were probably a result of the low caloric input. In the animals that received macrophyte plus commercial food (MCF) these responses were reversed when the energy reserves were maintained and the levels of lipoperoxidation were higher than those of animal that received MO. Animals fed on MCF showed more activity, higher numbers of couples, ovigerous females and eggs for females, however, the rate of survival was similar in both diets. The caloric requirements of both species were probable supplied with MCF, which provided more carbohydrates, proteins and lipids, and this diet provided valuable information concerning adequate maintenance of the animals for toxicology experiments, and principally increases the knowledge about the physiology of this genus. [ABSTRACT FROM AUTHOR]

We compared the effect of different diets in the biochemical composition, levels of lipoperoxidation and survival rates of males and females of Hyalella bonariensis. These crustaceans live in limnetic environments and different kinds of food habits are present in the genus Hyalella. Adult animals were collected in the spring (September) in a stream near to Salto city, Buenos Aires. In the laboratory, the animals were kept submerged in aquariums, separated by sex, under controlled conditions and survive rates were observed. They were fed ad libitum for 45 days with four different diets, and after this period the animals were used for biochemical determinations. Statistical analysis revealed significant differences in the responses to glycogen, proteins, lipids, triglycerides and lipoperoxidation levels in both sexes of these amphipods taken from the natural environment. Animals that received macrophytes associated a ration with high content of proteins (43%) during 45 days presented the major survival rates (males= 86.6% and females= 96.6%). These responses can be revealed that this specie primarily feeding macrophytes associated with deposit feeder, and that this diet is more generalized. This study showed the importance of the proteins in diet of this amphipod, were the females increased the reserves of proteins and triglycerides with different diets probably for reproductive events and male increased the reserves of glycogen and triglycerides for reproductive events and growth. [ABSTRACT FROM AUTHOR]

The benthic crustaceans in Chilean rivers and streams are characterized by their marked endemism and low species number. Ecological studies have indicated that some species may be used as indicators of water quality, considering the involvement of river basins in human agricultural, industrial, and urban activities. The aim of the present study was to study the abundance of benthic crustaceans in a small stream located inside Temuco town, and to determine correlations of their various abundances with pH, temperature, and dissolved oxygen. The species discussed here are Aegla rostrata, Hyalella araucana, and Parastacus pugnax. We report an inverse correlation between dissolved oxygen and A. rostrata abundance, as well as of temperature with H. araucana abundance, whereas P. pugnax showed no significant correlations. The ecological results are discussed. [ABSTRACT FROM AUTHOR]

Hyalella curvispina Shoemaker, 1942 has a broad distribution across freshwater habitats of southern South America, where it can reach very high densities. This species plays an important role in food webs, linking a main portion of primary production with higher order consumers. In this work we provide the first data on the metabolic rate of H. curvispina and determine how it is affected by environmental temperature and individual body weight. Additionally, we present a predictive equation that allows the estimation of standard metabolic rate from temperature and body weight. The mean standard metabolic rate of juveniles of both sexes and adult males of H. curvispina was measured for a wide range of body weights (0.07 to 2.90 mg dry weight) at four temperatures (11.5, 18, 24, and 30°C), covering the thermal range of its natural habitat. Metabolic rate showed an allometric scaling with body weight. Scaling exponents were significantly less than 1, having a mean value of 0.66 ± 0.032. There was an interaction between body weight and temperature, thus scaling exponents varied with temperature, from 0.51 at 24°C to 0.78 at 30°C. An increase in temperature over the range 11.5-24°C produced a raise in metabolic rate irrespective of body weight; between 24 and 30°C, however, response to temperature varied with body weight. The metabolic rate of H. curvispina is similar to that in the two other species of Hyalella for which published data are available. Scaling of metabolic rate with body weight is similar to commonly reported results for other species, as well as to what is expected from theoretical considerations. The predictive equation presented in this work provides a means to estimate the standard metabolic rate of H. curvispina in further studies from temperature and body weight data. [ABSTRACT FROM AUTHOR]

The article focuses on the new record of Hyalella azteca Saussure, 1858, an abundant amphipod in aquatic communities of invertebrates from the Lerma-Chapala Basin, Mexican Pacific Coast. According to the authors, records of H. azteca in Mexico are scarce and the studies of the principal lakes of the Lerma-Chapala basin have focused mainly on the ichthyofauna, aquatic invertebrates other than amphipods and water quality.

The water bodies studied herein are located in the Huerquehue National Park, a mountain zone with Nothofagus alpina, N. pumilio, N. dombeyi, and Araucaria araucana forests, at 700-1500 m a. s. l. There are numerous oligotrophic lakes, with characteristics similar to the deep Araucanian lakes. Many of these small lakes are difficult to reach, because the only routes leading there are long mountain paths. The sites studied in the present paper are five lakes: the first is located at the basis of the mountains (700 m a.s.l.) and is fed by a river that reaches it from series of three other lakes higher in the mountains (1300 m a.s.l.), which are connected by small streams. These four lakes are inhabited by fish populations. The fifth site is a small, shallow, and fishless pond located at one of the highest sites in the park (1400 m a.s.l). Samples were collected for analysis of chlorophyll concentrations and for littoral, aquatic crustaceans. All sites are oligotrophic, and show low crustacean species richness. In the four lakes with fishes, the crustacean littoral fauna was composed of Hyalella araucana (Amphipoda) only. In the fifth lake, the crustaceans collected were H. araucana, copepods (Boeckella gracilis and Mesocyclops longisetus), and large cladocerans (Scapholeberis spinifera and Simocephalus serrulatus). A direct relationship between species richness and both chlorophyll a and humic acid concentrations was found at all sites studied. These results would agree with literature descriptions that indicate the role of ultraviolet radiation and trophic status as conditioning factors for aquatic communities in Patagonian fresh waters. [ABSTRACT FROM AUTHOR]

Presents information on a study which examined the growth, development and reproduction of the amphipod Hyalella azteca obtained from culture and maintained under optimal conditions in laboratory experiments. Description of the amphipod; Background to the study; Materials and methods; Results.