Seasonal variations of the energy metabolism of two sympatric species of Hyalella (Crustacea, Amphipoda, Dogielinotidae) in the southern Brazilian highlands

Aquatic organisms exist in a constantly fluctuating habitat, with changes in photoperiod, temperature, pH, dissolved organic content, dissolved oxygen and food supply. Organisms must alter past of their physiological and biochemical processes to cope with these changes. We compared the effect of seasonal variations in factors related to energy metabolism of two species of sympatric amphipods, Hyalella pleoacuta and Hyalella castroi. The animals were collected monthly from April 2004 through March 2006. Contents of glycogen, proteins, lipids, triglycerides and the levels of lipoperoxidation were determined in males and females throughout the year by using spectrophotometric methods. Observations revealed significant seasonal differences in biochemical composition, as well as differences among sexes and species. Environmental conditions (e.g., trophic conditions) and reproduction are supposed to be the main processes influencing the seasonal patterns of variation in biochemical composition. Both species of Hyalella show ecological and behavioral differences, especially by resources such as food, space and seasonal variations of energy metabolism, which might facilitate their coexistence in the same habitat.     

Seasonal variations in the biochemical composition and lipoperoxidation of Hyalella curvispina (Crustacea, Amphipoda)

We assessed the effect of seasonal variations on the biochemical composition and lipoperoxidation of an amphipod crustacean, Hyalella curvispina, which inhabits the coastal plain of the state of Rio Grande do Sul, and correlated this with information on the biology of the species. The animals were collected monthly from September 2003 to August 2005, in Gentil Lagoon, Tramandaí, Rio Grande do Sul, Brazil. Glycogen levels, total proteins, total lipids, triglycerides, and lipoperoxidation were measured for each sex separately. The results suggest that these animals have seasonal storage and degradation of the energy substrates investigated. During summer, glycogen, total lipids, and triglycerides were stored, and were utilized especially during autumn and winter. Proteins were utilized differently in males and females. Females stored proteins especially in spring and used them in summer; whereas males stored proteins especially in spring and used them in winter. The levels of lipoperoxidation during the year differed between females and males. These variations may be related to biotic factors (e.g., reproduction period and others) and to abiotic factors (e.g., water temperature, salinity and others).     

Three new species of Hyalella from Chile (Crustacea: Amphipoda: Hyalellidae)

Hyalella is the only epigean freshwater amphipod present in Chile . H. chiloensis, H. costera and H. kochi are here described and illustrated. H. kochi is distributed in highland areas of the Andes in northern Chile; it is characterized by a short ramus on uropod 3 and a hammer-shaped gnathopod 1. H. costera and H. chiloensis are present in lowland areas, the latter restricted to the southern part of the country. These two species have a long ramus on uropod 3, but they differ in the shape and length of the palp on maxilla 1, the setation of peraeopods 3, 4, and telson. The presence in Chile of H. fossamancinii Cavalieri, 1959 is also reported here.     

A new species of Hyalella (Crustacea,Amphipoda, Dogielinotidae) from the Atlantic Forest of Misiones,Argentina

The freshwater genus Hyalella Smith, 1874 has a distribution restricted to the Western Hemisphere with most species being found in South America. In this report we describe a new species of Hyalella from the Atlantic Forest of the Misiones province, Argentina.     

Carbofuran-induced alterations in biochemical composition, lipoperoxidation, and Na+/K+ATPase activity of Hyalella pleoacuta and Hyalella curvispina in bioassays

The present study investigated the effects of carbofuran on the energy metabolism (levels of glycogen, total proteins, total lipids, triglycerides, and lipoperoxidation), Na+/K+ATPase activity, and reproductive parameters (formation of couples, ovigerous females, and mean number of eggs) in the freshwater amphipods Hyalella pleoacuta and Hyalella curvispina. These crustaceans live in limnetic environments of the plateau (H. pleoacuta) and coastal plain (H. curvispina) of the state of Rio Grande do Sul in southern Brazil. The animals were collected in the winter of 2006 in the Vale das Trutas (28 degrees 47'00'S-49 degrees 50'53'W) in the Municipality of S?o José dos Ausentes, and in Gentil Lagoon (29 degrees 56'30'S, 50 degrees 07'50'W) in the Municipality of Tramandaí. In the laboratory, the amphipods were kept submerged in aquariums under controlled conditions of photoperiod (12 h light: 12 h dark), temperature (23 degrees C+/-1), and constant oxygenation. Animals were exposed to carbofuran at a dose of 5 or 50 microg/L for a period of 7 days. At the end of this period, the animals were immediately frozen for determination of the biochemical parameters, lipoperoxidation levels (TBARS), and enzyme Na+/K+ATPase activity. During each day of culture, several reproductive parameters were observed. Statistical analysis (ANOVA) revealed that carbofuran induces significant decreases in glycogen, proteins, lipids, triglycerides, and Na+/K+ATPase, as well as a significant increase in lipoperoxidation levels. Studies of all the biochemical parameters seem to be quite promising, in order to assess and predict the effects of toxicants on non-target organisms. The results also suggest that the reproductive parameters (formation of couples, ovigerous females and mean number of eggs) may provide sensitive criteria for assessing ecotoxicological effects. Furthermore, H. pleoacuta and H. curvispina are suitable organisms for use in toxicity tests, and we suggest that they are sensitive species that could be used in monitoring studies.     

Redescription of the freshwater amphipod Hyalella faxoni from Costa Rica (Crustacea: Amphipoda: Hyalellidae)

Hyalella faxoni Stebbing, 1903 from Costa Rica is redescribed. The species was previously in the synonymy of Hyalella azteca (Saussure, 1858). The morphological differences between these two species are discussed.     

Life history and allozyme diversification in regional ecomorphs of the Hyalella azteca (Crustacea: Amphipoda) species complex

In North America, several species in the freshwater amphipod genus Hyalella occur as one of two alternative phenotypic types, or 'ecomorphs', each possessing life history traits that allow success in alternative habitats that differ in predation regime. This study documents life history diversification, reproductive isolation and allozyme differentiation of Hyalella ecomorphs in Oklahoma, and compares these results to previously reported patterns of phenotypic and systematic diversification in Michigan. As in Michigan, two ecomorphs are common in Oklahoma, with an early maturing, small sized ecomorph found in habitats containing Lepomis sunfish, which prey on Hyalella , and a late reproducing, large sized ecomorph found in fishless habitats and in very shallow margins of large reservoirs. Allozyme analysis and laboratory interbreeding trials demonstrated that ecomorphs in Oklahoma are reproductively isolated species. Phenotypically, these species are very similar to species of the same ecomorph in Michigan. Large ecomorph species in the two regions differ substantially in allozyme allele composition in a pattern consistent with reproductive isolation, yet these species did not differ in a comparison of phenotype. The small ecomorph in Oklahoma is similar in phenotype to two of three small ecomorph species in Michigan. Overall, this study supports the hypothesis that Hyalella diversification in North America is characterized by the evolution of similar phenotypic solutions to comparable ecological challenges.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 84 , 161–175.     

Two new species of Hyalella from Lake Titicaca,and redescriptions of four others in the genus (Crustacea: Amphipoda)

The amphipod genus Hyalella has its highest diversity in the Andean Lake Titicaca. This genus is the only epigean amphipod present in South America. Eleven endemic and one non-endemic species are known from Lake Titicaca. An additional endemic species, Hyalella nefrens n. sp. and one non-endemic species Hyalella tiwanaku n. sp. are described here. Hyalella cuprea(Faxon, 1876), Hyalella latimanus (Faxon, 1876), Hyalella montforti Chevreux, 1907, and Hyalella neveulemairei Chevreux, 1904 are redescribed. The high diversity of Hyalella in the lake is not well understood, and it has been compared with the spectacular diversity of Lake Baikal.     

Strahlenbiologische Untersuchungen an Gammariden (Crustacea,Amphipoda)

Zusammenfassung 1. Der Einfluß einmaliger Röntgenbestrahlungen auf die Überlebenszeiten der euryhalinen AmphipodenGammarus duebeni Lilljeborg,Gammarus salinus Spooner undGammarus zaddachi Sexton wurde bei einer konstanten Temperatur von 15⁰ C und einem Salzgehalt von 10 untersucht.2. Bestrahlungen mit Dosen von 625 und 1250 R führen beiG. duebeni zum vorzeitigen Tod von nur einigen Versuchstieren, Bestrahlungen mit 2500 R und höheren Dosen zum vorzeitigen Tod aller Versuchstiere.3. BeiG. duebeni sind die strahlenempfindlicher als die , die Jungtiere strahlenempfindlicher als adulte Individuen.4.G. salinus undG. zaddachi sind strahlenempfindlicher alsG. duebeni.5. Die LD₅₀-Kurven lassen drei Bereiche erkennen. Bei mittleren Dosen ändert sich die Zeitspanne, in der 50% der Versuchstiere sterben, nur wenig oder gar nicht mit der Dosis. Bei hohen und niedrigen Dosen ist die Überlebenszeit dosisabhängig.6. Die Strahlenempfindlichkeit vonG. duebeni war im ersten Quartal des Jahres 1967, in dem die Temperaturen über den langfristigen Monatsmitteln lagen, geringer als bei Flohkrebsen, die zu einem späteren Zeitpunkt gefangen wurden oder aus Laboratoriumszuchten stammten.7. Die Häutungsvorgänge, deren Beeinflussung nur beiG. duebeni untersucht wurde, werden durch Bestrahlungen mit 1250 R oder geringeren Dosen nicht beeinflußt.8. Nach einer Bestrahlung mit 20 000 R sind 2 Tage nach der Bestrahlung nur wenige oder gar keine Häutungen möglich. Nach Bestrahlungen mit 10 000 und 5000 R erfolgen die Häutungen verspätet.9. Als Folge von Bestrahlungen mit letalen Dosen nimmt die Zahl der Häutungen um den 30. Tag nach der Bestrahlung ab.10. Die Häutungsvorgänge waren bei Tieren, die im ersten Quartal 1967 gefangen und bestrahlt wurden, weniger beeinflußbar als bei Tieren, die aus Laboratoriumszuchten stammten oder zu einem späteren Zeitpunkt gefangen wurden.11. Nach Bestrahlungen mit letalen Dosen treten zwei kritische Phasen auf. Ein Teil der mit mittleren und der größte Teil der mit hohen Dosen bestrahlten Tiere stirbt bereits in der ersten kritischen Phase. Die zweite kritische Phase wird von allen mit niedrigen Dosen bestrahlten Tieren erreicht. Tiere, die sich in der ersten kritischen Phase häuten, haben eine geringe Lebenserwartung.12. Die Überlebenszeit des einzelnen Individuums hängt außer von der Bestrahlungsdosis von dem Zeitpunkt ab, zu dem es sich innerhalb der Versuchszeit häutet.

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Radiobiological investigations on gammarids (Crustacea, Amphipoda)

Effects of single exposures of X-radiation on survival were studied inGammarus duebeni, G. salinus andG. zaddachi under constant conditions of temperature (15⁰ C) and salinity (10 ). Effects on moulting were investigated inG. duebeni. The amphipods were irradiated with doses between 625 and 20,000 R.G. salinus andG. zaddachi are equally radioresistant (LD_50/30 : 1,700 R) but less resistant thanG. duebeni (LD_50/30(males) : 3,900 R; LD_{50/30(females)} : 3,500 R). At high doses, half of the test individuals die within a few days; at medium doses survival time is dose-independent; at lower doses survival time again increases with decreasing doses up to dose-ranges (below 1,250 R forG. duebeni, 1,000 R forG. salinus andG. zaddachi), at which only a few individuals die before their natural death. Subadult gammarids are less resistant;G. duebeni of 4 to 7 mm body length have a LD_50/30 of 2,200 R. Death distribution after medium doses indicates that at least two mechanisms are involved in acute mortality. A first mortality maximum occurs shortly after irradiation; subsequently, mortality decreases for a few days, and is followed by another maximum. At lower doses no individual dies during the first critical period. Shortening of survival time at higher doses results from survival of fewer individuals to the second critical period. Few or no moults occur inG. duebeni irradiated with 20,000 R following the second day after irradiation and after the 30th day in those individuals irradiated with 2,500 to 10,000 R; moulting is delayed after exposure to 5,000 to 10,000 R. Individuals ofG. duebeni taken from the field during the mild winter 1966/67 were more resistant to radiation, and moulting was less affected, than in laboratory-reared amphipods, or in those collected in the field during other seasons. Besides on irradiation dose, survival time of an individual depends on the time of its moulting in the course of an experiment.

     

Australian Iphimediidae (Crustacea: Amphipoda)

Australian species of the iphimediid amphipod genus Iphimedia are revised. Based on new material from inshore and continental shelf habitats six new species are described: Iphimedia beesleyae; I. filmersankeyi; I. kateae; I. lisae; I. neuweileri and I. oetkeri. Four established species are redescribed: I. ambigua Haswell, 1879; I. discreta Stebbing, 1910; I. edgari (Moore, 1981) and I. warraina (Thomas and Barnard, 1991). A key to Australian species of Iphimedia is provided. Full article published online at http://www.senckenberg.de/odes/06-09.htm     

Trophic Ecology of Hyalella sp. (Crustacea: Amphipoda) in a High Andes Headwater River with Travertine Deposits

We studied the diet of 50 individuals of Hyalella sp. collected in the karstic headwaters of a high‐altitude Andean river (3817 m a.s.l. Peru) in four different habitats: macrophytes, bryophytes, leaf litter, and layers of travertine. The gut content analysis showed a dominance of fine particulate organic matter (FPOM) in most habitats – layers of travertine (69.5%), Myriophylum (58.5%) and bryophytes (56.8%) – except for individuals collected in leaf litter where coarse particulate organic matter (CPOM) represented 68% of gut content, which indicates a high trophic flexibility of Hyalella sp. Likewise, in an experiment with feeding chambers in situ during three days, twenty individuals of Hyalella sp. presented a higher consumption of leaf litter of native species (Polylepis sp.) (0.025 mg/day) than those of an introduced species (Eucalyptus globulus) (0.008 mg/day). (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Digestive anatomy of Halella azteca (Crustacea,Amphipoda)

The digestive tract of the freshwater amphipod Hyalella azteca is a straight but differentiated tube consisting of foregut, midgut, and hindgut divisions. The foregut is subdivided into a tubular esophagus, a cardiac stomach, and a pyloric stomach. The cuticular lining of the cardiac stomach is elaborated into a set of food-crushing plates and ossicles, the gastric mill, while the pyloric cuticle forms a complex straining and pressing mechanism. Nine caeca arise from the midgut, seven anteriorly and two posteriorly. Four of the anterior caeca, the hepatopancreatic caeca, are believed to be the primary sites of digestion and absorption. The remaining caeca may be absorptive, secretory, or both. The much-folded hindgut wall is capable of great distention by extrinsic muscle action for water intake to aid in flushing fecal material out of the anus; such action also may stimulate antiperistalsis by intrinsic rectal muscles.     

Comparative analysis of the circulatory system in Amphipoda (Malacostraca, Crustacea)

We present data on the haemolymph vascular system (HVS) in four representatives of the major amphipod lineages Gammaridea, Hyperiidea and Caprellidea based on corrosion casting and three‐dimensional reconstructions of histological semi‐thin sections. In all these species the HVS comprises a dorsal pulsatile heart, which is continued in the body axis by the anterior and posterior aortae. The heart is equipped with three pairs of incurrent ostia. The number of cardiac arteries that lead off the heart varies among species: in the studied Gammaridea four pairs occur, in Hyperia galba only the three posterior pairs of cardiac arteries occur, while in Caprella mutica cardiac arteries are absent. In all the studied species the posterior aorta leads as a simple tube into the pleon attached to the dorsal diaphragm. The anterior aorta runs from its origin in the anterior part of the second thoracic segment into the cephalothorax. Both pairs of antennae have an arterial supply off the anterior aorta. An overview of previously studied species including our present findings shows the amphipod HVS to be relatively uniform and the gammarid form is discussed as being closest to the ground pattern of Amphipoda.     

Caprellids (Crustacea: Amphipoda) from India

The caprellid fauna of India is investigated. A total of 538 samples (including algae, seagrasses, sponges, hydroids, ascidians, bryozoans, encrusted dead corals, coral rubble, fine and coarse sediments) were collected from 39 stations along the coast of India, covering a wide diversity of habitats from intertidal to 12 m water depth. A new species (Jigurru longimanus n.sp.) is described, and figures of the 11 valid species reported so far from India are given together with a key for their identification. No caprellids were found in sediments from the northeast (16–20oN) coast of India while they were abundant in the southeast and west coast. Decreases in salinity due to river discharges associated with lower values of oxygen, higher water temperatures and lower nutrient inputs along the east coast could explain these differences in caprellid composition between the two coastlines. Significantly, lower abundance of caprellids in India, as in other tropical ecosystems, is probably related to the lack of species belonging to the genus Caprella, which reach very high abundances in temperate waters.     

Karyotypes of the Echinogammarus berilloni-group (Crustacea,Amphipoda) from Spain

The chromosome number and karyological features of Iberian populations of seven species of the Echinogammarus berilloni-group (Crustacea, Amphipoda) have been studied. For comparison, Gammarus gauthieri, belonging to the G. pulex-group was also studied. Four species of the berilloni-group share the same number n=27. Other numbers found were n=25, n=26 and n=28. The chromosomes of these species have a centromeric region surrounded by large heterochromatic blocks at late prophase. There-after, the centromere splits precociously. C. gauthieri has n=26, the same number found in the pulex-group. This species has larger chromosomes than the former but it does not show these karyological peculiarities.Cytological observations confirm both the close relationship among species of the berilloni-group and the differentiation with respect to the pulex-group. On the other hand, the existence of different numbers confirms other results that reject the older idea that speciation within Gammaridea occurred with minor changes in karyotypic characters.     

New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca

Two new species of hyalellid amphipods, Hyalella crawfordi and H. gauthieri, are described from Lake Titicaca; H. echinus (Faxon, 1876) is redescribed. The H. echinus group of species is newly proposed for these three species, and a group diagnosis is provided. A key to the three species in the group is provided Full article published online at http://www.senckenberg.de/odes/06-10.htm.     

Life cycle ofCorophium insidiosum (Crustacea,Amphipoda) in laboratory culture

The life cycle ofCorophium insidiosum (Crawford) was investigated for the first time in laboratory cultures. This amphipod is mainly a suspension feeder, but it can also switch to deposit feeding. It was cultivated in standing, unaerated finger bowls, feeding on detritus, living or dried algal matter, rotifers (Brachionus plicatilis), or large-sized phytoplankton (e. g. the flagellateScrippsiella faeroense). A mixture of these items gave best results and hence was used for long-term cultivation. Preliminary results are presented on ingestion rate (suspension feeding), digestion rate, starvation resistance, and elemental and biochemical composition. In the life cycle ofC. insidiosum, several factors were found to play an important role: temperature, individual age, sex, and in contrast to other amphipod species thus far studied also the age of the mother animal at the time of breeding. Increasing temperature reduces the total life span, the age and size at the time of attaining sexual maturity, and the duration of marsupial development. It increases growth and moulting rate. At increasing individual age, the growth rate, and in males also the moulting rate, decrease, while the number of offspring per brood and surprisingly also the duration of its marsupial development increase. Females generally have a longer life span than males, and they show a higher number of moults, higher moulting frequency and growth rate, and a larger maximum body size. Body length and age at the time of reaching sexual maturity are smaller in males than in females. Furthermore the age of the mother animal at the time of breeding proved to be of particular importance: Individuals from early broods have an apparently longer life span than those originating from late broods, and they have more moults, mostly a higher growth rate, higher number of broods, higher total number of offspring, and, surprisingly, also a longer period of incubating their broods. These major factors have differing combined effects.     

Experimental studies on the life cycle ofJassa falcata (Crustacea,Amphipoda)

Jassa falcata (Leach), an unselective suspension feeder, was cultivated in standing, unaerated finger bowls, feeding on a mixture ofBrachionus plicatilis, Scrippsiella faeroense, Ulva spec., and natural detritus. This amphipod can also be maintained with diets composed of dead or live material of both plant and animal origin, but an addition of living zooplankton is necessary for longterm cultivation. Starvation resistance is higher in females than in males, and it is increased by lower temperatures. The life span ofJ. falcata increases with decreasing temperature, and it is generally higher in females (maximum: 252 days at 10°C) than in males. In laboratory culture, a bimodal mortality pattern is typical with high juvenile death rates, low mortality during the reproductive phase, and again increasingly high death rates toward the end of the life cycle. Growth rate depends on temperature, sex, and individual age. The temperature dependence of growth is particularly high in males, and it is higher in adults than in juveniles. The total number of moults is lower in males (5 to 6) than in females (7 to 9). Sexual maturity is attained at moult IV to V. The average incubation time of eggs is about 9 to 16 days (highest value at 10°C). Three to 4 broods were observed, with largest numbers of offspring at 10°C.     

Global diversity of amphipods (Amphipoda; Crustacea) in freshwater

Amphipods are brooding peracaridan crustaceans whose young undergo direct development, with no independent larval dispersal stage. Most species are epibenthic, benthic, or subterranean. There are some 1,870 amphipod species and subspecies recognized from fresh or inland waters worldwide at the end of 2005. This accounts for 20% of the total known amphipod diversity. The actual diversity may still be several-fold. Amphipods are most abundant in cool and temperate environments; they are particularly diversified in subterranean environments and in running waters (fragmented habitats), and in temperate ancient lakes, but are notably rare in the tropics. Of the described freshwater taxa 70% are Palearctic, 13% Nearctic, 7% Neotropical, 6% Australasian and 3% Afrotropical. Approximately 45% of the taxa are subterranean; subterranean diversity is highest in the karst landscapes of Central and Southern Europe (e.g., Niphargidae), North America (Crangonyctidae), and Australia (Paramelitidae). The majority of Palearctic epigean amphipods are in the superfamily Gammaroidea, whereas talitroid amphipods (Hyalella) account for all Neotropic and much of the Nearctic epigean fauna. Major concentrations of endemic species diversity occur in Southern Europe, Lake Baikal, the Ponto-Caspian basin, Southern Australia (including Tasmania), and the south-eastern USA. Endemic family diversity is similarly centered in the Western Palearctic and Lake Baikal. Freshwater amphipods are greatly polyphyletic, continental invasions have taken place repeatedly in different time frames and regions of the world. In the recent decades, human mediated invasions of Ponto-Caspian amphipods have had great impacts on European fluvial ecosystems. Guest editors: E. V. Balian, C. Lévêque, H. Segers and K. Martens Freshwater Animal Diversity Assessment