Factors influencing densities and distributions of Pontoporeia hoyi in Lake Ontario

The physical and chemical characteristics of the sediment-water interface greatly influence distributions of the bottom-feeding amphipod Pontoporeia hoyi which is a major component of the Great Lakes aquatic food-webs. Sediment-water interface samples from the Great Lakes indicate that Pontoporeia densities are positively correlated with sediment concentrations of organic carbon, particularly in the upper depth range of the species. Pontoporeia is not found in anoxic sediments. Growth rates and production of Pontoporeia are influenced by the quality of food supplies and there appears to be a seasonal response to the down-flux of plankton detritus. Comparisons of numerations and distribution patterns also revealed an apparent positive relationship between Pontoporeia and sediment-associated bacteria. Interlake comparisons of population densities provide no clear evidence of any large scale impact by contaminated sediment on this species. Depending upon the extent to which organic carbon (OC) is assimilated in the water column, bottom sediments may store and buffer the quantity of OC available to Pontoporeia. Thus, if the annual down-flux of OC remains generally constant, populations of Pontoporeia should also remain constant unless influenced by changes in predation intensity.Numerations of Pontoporeia revealed that populations of this amphipod are much larger in Lake Michigan than in Lake Ontario. We suggest that much of this difference can be accounted for by different forms of predator-prey interaction near the base of the benthic food-web. Commercial fisheries data tend to support this idea. We also speculate that differences in the concentration of dissolved silica may figure prominantly among factors that affect Pontoporeia population densities.Under proposed new taxonomy (Bousfield, 1989), Pontoporeia hoyi is now classified as Diporeia hoyi. However, for convenience, we have retained the commonly used genus Pontoporeia throughout this text.     

Visual pigment,dark adaptation and rhodopsin renewal in the eye of Pontoporeia affinis (Crustacea,Amphipoda)

The benthic amphipod Pontoporeia affinis lives in the Baltic sea and in northern European lakes in an environment where very little light is available for vision. The eyes, consisting of 40–50 ommatidia, are correspondingly modified. Microspectrophotometric recordings on isolated eyes show the presence of at least two kinds of screening pigments in the ommatidia with maxima at 540–580 nm and 460–500 nm. Difference spectra obtained from the rhabdoms after exposure to red and blue light, respectively, give evidence of a single rhodopsin with its maximum at 548 nm and a 500-nm metarhodopsin. In ERG recordings sensitivity in the dark-adapted state, after saturating exposures to blue and to red light, stabilizes at levels determined by the rhodopsin concentration. No change is observed during 10–14 h after the beginning of dark adaptation. However, using animals pre-exposed with a strong red light and then kept in darkness, it is found that after a delay of 20–40 h sensitivity of the dark-adapted eye begins to increase and finally, after 5–6 days reaches a level corresponding to 100% rhodopsin. Thus, a slow renewal of rhodopsin appears to occur in darkness, where a photoisomerization of metarhodopsin is excluded.Abbreviations ERG electroretinogram - IR infrared - MSP microspectrophotometry     

Life history of Corophium curvispinum G. O. Sars (Crustacea,Amphipoda) living on macrophytes in Lake Balaton

Samples of the amphipod Corophium curvispinum were collected from Myriophyllum spicatum twice a month during the vegetation period. The animals were sexed, their length measured and the eggs of females were counted. Length frequency histograms served to follow the life history of C. curvispinum.Reproduction lasts from May to October. The animals born in May–June reproduce in the same year while the summer-autumn generation reproduces the following year. The life span is about 1 year. The highest fecundity was found in June, the lowest in October.     

Life history, aspects of reproductive biology and production of Corophium orientale (Crustacea: Amphipoda) in Monolimni lagoon (Evros Delta, North Aegean Sea)

Monthly samples of Corophium orientale were collected during February 1998–February 1999 in both parts of Monolimni lagoon (0.3 < Sal. < 6 psu, 2 < Temp. < 28.5 °C). Corophium orientaleshowed a semiannual life cycle. In the southern part, breeding occurred from early spring to mid autumn having three peaks, in early spring, early summer and early autumn, and three cohorts were produced, a spring cohort, a summer cohort and an overwintering one. In the shallower innermost northern part of Monolimni lagoon, breeding peaked in mid-spring and, also, in early autumn, and two discrete cohorts, a spring and an overwintering one, were produced. A lack of large individuals, attributed to a temporary size – selective predation by migrating shorebirds, was observed during summer. That lack possibly contributed to the hiatus in reproduction. Photoperiod seemed to be a more important cue than temperature in the initiation of the reproductive cycle, while extremely low salinities (<1 psu) did not deter breeding. Females attained maturity at a smaller size in late spring and, especially, in summer than in early spring at lower temperatures. Brood size was a function of females body size. Females, matured during summer at high temperatures, showed the lowest brood size, body length ratio. Mean brood size was small (12–13 early embryos) and embryo loss during development high (54%), possibly due to a negative effect of low salinities. A 1:1 sex ratio existed in the small body length classes, but females preponderated in the large ones. The spring cohort in the southern part, which developed at moderate temperatures, showed the highest growth rate (40 m day^–1). Secondary production of C. orientalecalculated by Hyness method gave a mean annual density of 4562.5 and 9327.6 ind. m^–2, a mean annual crop (B) of 1.03 and 2.67 g DW m^–2, an annual production (P) of 6.91 and 22.54 g DW m^–2 and a P/B ratio of 6.7 and 8.4 in the northern and southern part of the lagoon, respectively.     

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.     

Aquatic amphipods (Crustacea: Amphipoda: Crangonyctidae) in three pieces of Baltic amber

Three amber pieces containing crangonyctid aquatic amphipods are examined. One of the specimens appears to have the urosome unsegmented, and uropods 3 shortened, resembling extant Synurella sp. In another amber piece there are eight specimens of Palaeogammarus sp. which look as if they had been dry prior to becoming embedded in the resin.     

Life history characteristics and distribution of Bythotrephes longimanus Leydig (Crustacea,Onychopoda) in the Biesbosch reservoirs

The diel and horizontal distributions of Bythotrephes longimanus Leydig, Leptodora kindti (Focke) and Anomopoda (cladocerans), as well as several life history parameters of each developmental stage of B. longimanus were studied in the non-stratified Biesbosch reservoirs. Anomopoda avoided the surface layer during the day only in the pelagic zone. In the surface layer near the shore, however, they were very abundant. Because densities in the pelagic zone during the day were very low, and high during the night, the population undoubtedly moved from the littoral zone or from the sediments to the pelagic. Accumulation of zooplankton at the littoral site is either the result of random dispersal or wind-induced movements. Bythotrephes' diel distribution pattern is possibly related to that of their prey, the anomopods. Leptodora mostly exhibited a normal diel vertical migration with a small amplitude. Wind most likely influenced the horizontal distribution of the zooplankton. Bythotrephes body length increased with higher temperatures, whereas spine length was constant throughout the year. Bythotrephes can already be fertile in the first developmental stage, indicating that a rapid adaptation to a favourable environment is possible. The number of parthenogenetically produced eggs per ovigerous female was higher at the start of the growing season and constant throughout the rest of the year. Relatively few resting eggs and males were found in autumn.     

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.     

Patterns of genetic diversity in Great Lakes bloaters (Coregonus hoyi) with a view to future reintroduction in Lake Ontario

The originally diverse ciscoe fish fauna of the Laurentian Great Lakes has suffered many extinctions and local extirpations. Bloaters (Coregonus hoyi) are presumed extirpated from Lake Ontario and the reintroduction of this deepwater fish is under consideration. Given the demographic fluctuations of this species in the other Great Lakes and its recent intralacustrine origin, we sought to identify a genetically diverse and similar source of C. hoyi via an analysis of genetic diversity and population structure using 10 microsatellite loci. Despite well-documented demographic declines, we found no genetic evidence of bottlenecks in 12 C. hoyi samples from the four potential donor lakes (Huron, Michigan, Superior and Nipigon). By contrast, evidence of bottlenecks in historical samples of C. artedi from Lake Ontario suggested that standard genetic methods frequently used to identify population bottlenecks can only detect very severe and long-lasting demographic declines in naturally large populations. Patterns of genetic differentiation and assignment tests indicated that C. hoyi from Lake Huron and Lake Michigan, which are not differentiated, are genetically most similar to Lake Ontario ciscoes. The small available sample of deepwater ciscoes recently caught in Lake Ontario did not allow determining if these represent a small undetected C. hoyi population or a recent invasion of the deep section by C. artedi. On the basis of genetic criteria, we conclude that C. hoyi from any location within Lake Huron or Lake Michigan would be judicious sources of breeders for reintroducing C. hoyi in Lake Ontario.     

A new marine interstitial ingolfiellid (Crustacea,Amphipoda, Ingolfiellidea) from Tenerife and Hierro

Ingolfiella canariensis n. sp., from coarse sand and gravel in the mediolittoral zone of Tenerife and Hierro, Canary Islands, is described. The new species shares supposedly apomorphous characters with species from comparable habitats from the Andaman Islands, Bermuda and Curaçao (Netherlands Antilles). The female of Ingolfiella similis Rondé-Broekhuizen & Stock, 1987, from Fuerteventura is also described.     

Life cycle and production of Skwala parallela (Frison) (Plecoptera: Perlodidae) in a Colorado montane stream

The life cycle and production of Skwala parallela, a perlodid stonefly, was investigated in a third-order Colorado montane stream. The species exhibited a univoltine life cycle with a distinct cohort. Small nymphs appeared in May. Rapid growth was exhibited throughout summer and autumn. During winter, growth slowed somewhat but was continuous until April. Maximum density of 34 nymphs/m² occurred in July. Based upon the instantaneous growth method, annual production was 395.3 mg/m² or 3.95 kg/ha dry weight with a P/B ratio of 4.4     

Echiuropus bekmanae n.sp. (Crustacea, Amphipoda, Carinogammaridae) from Lake Baikal, retrieved by a new deep-water sampling device

Lake Baikal is well known for its exceptional diversity of gammarid amphipods, with 95% of endemics from its 270 described species representing about 20% of the world freshwater fauna. Echiuropus (Asprogammarus) bekmanae n.sp. was collected by an `autonomous trap system', a sampling device thoroughly described here. Although not necrophagous itself, this new species was found in two baited trap samples (at 750 and more than 1600 m) from 1995 and 1996. This rather small (13 mm) deep water species is the eighth species of the subgenus Asprogammarus, of the Baikal endemic genus Echiuropus. Diagnoses of the subgenus and the closer species are given.     

Life history and production of filter-feeding insects on stone dikes in the lower Mississippi River

Population and production dynamics of two filter-feeding macroinvertebrates, the caddisfly Hydropsyche orris and the midge Rheotanytarsus sp., were examined in the lower Mississippi River Miles 510–515. Samples were collected from September to November 1987, May to December 1988, and March to May 1989 from stone dikes that protrude into the river. Developmental synchrony was high among individuals in both populations, and seasonal changes in the relative abundance of instars indicated bivoltine and trivoltine life cycles for H. orris and Rheotanytarsus sp., respectively. The size frequency method was used to estimate production (P) and biomass (B) of each cohort in each population. P/B ratios for spring and fall cohorts of H. orris equaled 4.5 and 3.7. Spring, summer, and fall cohorts of Rheotanytarsus sp. had P/B ratios of 4.0, 4.7, and 4.1, respectively. Annual production, estimated as the sum of cohort production values, of the H. orris and Rheotanytarsus sp. population equaled 10.1 and 0.359 g m^–2 (dry weight). Annual P/B ratios equaled 10.8 and 16.1 for the H. orris and Rheotanytarsus sp. populations, closely matching values expected for bivoltine and trivoltine populations, respectively. Annual production of H. orris is in the low end of the range of published estimates for other lotic hydropsychid populations inhabiting coarse substratum in warm, lowland rivers of medium size or small, trophically enriched streams. Annual production of Rheotanytarsus sp. is the first such estimate based on a simultaneous assessment of life cycle and production. Given the lack of naturally occurring gravel and cobble substrate in the lower Mississippi River, stone dikes are an especially important habitat for H. orris and Rheotanytarsus sp.     

Life history adaptation of Tanymastix stagnalis (Crustacea,Branchiopoda) to habitat characteristics

Life histories of two populations of Tanymastix stagnalisfrom sites in central Italy, differing in climate and altitude above sea level, were compared to obtain information on the tolerance limits of this species.Temperature was the main factor affecting the biology of Tanymastix stagnalis. Significant differences in growth patterns occurred at different sites. A colder climate induced delayed hatching, slower differentiation and maturation, but a longer life span in the mountain population (Forca Canapine) than in the plain (Fosso dei Mergani).Both populations exhibited an initial fluctuating sex ratio, which later became female biased, a pattern which could be the consequence of adaptation to the unstable nature of the biotopes studied.     

The North-American amphipods, Melita nitida Smith, 1873 and Incisocalliope aestuarius (Watling and Maurer, 1973) (Crustacea: Amphipoda: Gammaridea), introduced to the Western Scheldt estuary (The Netherlands)

The American amphipod species Melita nitida andIncisocalliope aestuarius have been found in the WesternScheldt estuary (the Netherlands). This is the first record of these species inthe north-east Atlantic. Shipping is the most likely vector of introduction.Thedistribution of both species is investigated and compared with the distributionand the microhabitat of co-occurring amphipod species. Melitanitida is known from both the east and west coast of North Americaand I. aestuarius originates from the east coast of NorthAmerica. Until now neither has been reported from other parts of the world. Inthe Netherlands both species are restricted to the mesohaline part of theWestern Scheldt. Melita nitida occurs predominantly underPacific oysters at the underside of boulders, mainly sublittorally.Incisocalliope aestuarius is associated to hydrozoans.Bothmicrohabitats are hardly utilized by other amphipod species. Therefore, thetheory that the existence of many empty niches in north-western Europeanbrackish waters make this environment particularly susceptible to invasions ofalien species is corroborated. The application of hard substrates in a regionoriginally predominated by soft bottoms moreover facilitates the introductionofexotic species. The species community on hard substrates in the mesohaline partof the Western Scheldt contains a high proportion of introduced species:approximately one third of the macrofauna species is of allochthonous origin.     

Life history and production of Caenis luctuosa (Burmeister) (Ephemeroptera, Caenidae) in two nearby reaches along a small stream

Population dynamics and production of C. luctuosa were compared in two reaches of the Agüera stream (northern Spain). This species showed univoltine winter life history in both sites. However, the start of the recruitment period, and the cohort production interval differed in 1 month between reaches. Secondary production of C. luctuosa ranged from 76 mg m^–2 year^–1 (upper site) to 93 mg m^–2 year^–1 (lower site). Although annual production seemed to be mainly influenced by the biomass found at each site, changes in life history may have also been important. The need to have accurate information about life history of the analysed species at the study sites when assessing secondary production is highlighted.     

Feeding tests with caddis larvae (Insecta: Trichoptera) and amphipods (Crustacea: Amphipoda) on Platanus orientalis (Platanaceae) and other leaf litter

In the southern parts of the Mediterranean region, as in the island of Crete, there are few species of riparian trees and shrubs among the dominant Platanus orientalis. Feeding tests have shown that leaves of Platanus are not eaten by aquatic shredders of continental and Cretean origin. The large quantities of organic matter are therefore not used as a source of food and energy by the stream communities. In addition, the high winter flow shortly after leaf fall, and the short courses of rivers result in loss of most of the leaf litter to the sea. The River Continuum Concept does therefore not apply to this region. Field observations have shown that amphipods and limnephilid larvae are shifting from shredding to scraping habits if no leaf litter except Platanus was available.     

Amphipoda (Crustacea) in the Littoral Zone of Lake Balaton (Hungary). Qualitative and Quantitative Studies

Species composition, size distribution, egg number and biomass of different amphipod species on littoral submerged aquatic vegetation (Myriophyllum, spicatum and Potamogeton perfoliatus stands) and on the stony shores of Lake Balaton at Tihany were estimated in August 1983 and 1985. Three species occurred in the material: Corophium curvispinum, Dikerogammarus haemobaphes and Dikerogammarus villosus. The bulk was formed by C. curvispinum. The mean number of eggs per female of the three investigated species showed differences at the different sampling stations and ranged between the following values: C. curvispinum from 3.3 to 8.8, D. haemobaphes from 16.4 to 22.8 and D. villosus from 8.0 to 17.5. The total biomass of amphipods was 1.8 and 3.5 mg dry weight/g fresh weight of macrophytes in 1983 and 1985 respectively, and 4.7 mg animal per dm² stone surface in the stony littoral zone in 1983.     

Next-generation sequencing,phylogenetic signal and comparative mitogenomic analyses in Metacrangonyctidae (Amphipoda: Crustacea)

Background

Comparative mitochondrial genomic analyses are rare among crustaceans below the family or genus level. The obliged subterranean crustacean amphipods of the family Metacrangonyctidae, found from the Hispaniola (Antilles) to the Middle East, including the Canary Islands and the peri-Mediterranean region, have an evolutionary history and peculiar biogeography that can respond to Tethyan vicariance. Indeed, recent phylogenetic analysis using all protein-coding mitochondrial sequences and one nuclear ribosomal gene have lent support to this hypothesis (Bauzà-Ribot et al. 2012).

Results

We present the analyses of mitochondrial genome sequences of 21 metacrangonyctids in the genera Metacrangonyx and Longipodacrangonyx, covering the entire geographical range of the family. Most mitogenomes were attained by next-generation sequencing techniques using long-PCR fragments sequenced by Roche FLX/454 or GS Junior pyro-sequencing, obtaining a coverage depth per nucleotide of up to 281×. All mitogenomes were AT-rich and included the usual 37 genes of the metazoan mitochondrial genome, but showed a unique derived gene order not matched in any other amphipod mitogenome. We compare and discuss features such as strand bias, phylogenetic informativeness, non-synonymous/synonymous substitution rates and other mitogenomic characteristics, including ribosomal and transfer RNAs annotation and structure.

Conclusions

Next-generation sequencing of pooled long-PCR amplicons can help to rapidly generate mitogenomic information of a high number of related species to be used in phylogenetic and genomic evolutionary studies. The mitogenomes of the Metacrangonyctidae have the usual characteristics of the metazoan mitogenomes (circular molecules of 15,000-16,000 bp, coding for 13 protein genes, 22 tRNAs and two ribosomal genes) and show a conserved gene order with several rearrangements with respect to the presumed Pancrustacean ground pattern. Strand nucleotide bias appears to be reversed with respect to the condition displayed in the majority of crustacean mitogenomes since metacrangonyctids show a GC-skew at the (+) and (-) strands; this feature has been reported also in the few mitogenomes of Isopoda (Peracarida) known thus far. The features of the rRNAs, tRNAs and sequence motifs of the control region of the Metacrangonyctidae are similar to those of the few crustaceans studied at present.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-566) contains supplementary material, which is available to authorized users.