Fishes and salinities in the St Lucia estuarine system—a review

The recorded salinity ranges of freshwater, estuarine and marine fish species in Lake St Lucia, a Ramsar and World Heritage Site, are documented. The freshwater group is most diverse and abundant under oligohaline conditions, although the Mozambique tilapia (Oreochromis mossambicus) was common under all salinity regimes. Estuary resident species also favoured oligohaline conditions but, in contrast to the freshwater taxa, were well represented in salinities up to 40 ‰. The marine group was most diverse and abundant within the salinity range 10–40 ‰, but a large number of species could also be found in salinities up to 70 ‰. Very few fish species were able to tolerate salinities between 70 ‰ and 110 ‰, with only O. mossambicus surviving for extended periods in salinities above 110 ‰. All the aquatic macrophytes and most of the zoobenthos within the lake appear to die out within the salinity range of 50–60 ‰, thus creating additional stress to those fish present under such conditions. The food resources least affected by extreme hypersalinity are the microphytobenthos and detritus food chains, with detritivorous fishes being dominant when the lake is in this state. Mass mortalities of fishes in Lake St Lucia have been recorded under both low (<5 ‰) and high salinity (>70 ‰) conditions. The fish kills are often triggered by exceptionally low or high water temperatures which affect the osmoregulatory abilities of these species. Hypersaline conditions and fish mortalities under the most recent closed estuary mouth conditions (2002–2005) are reviewed. If the surface area of St Lucia (35,000 ha) is compared to the total surface area of all South African estuaries (approximately 70,000 ha), then the possibility exists that the loss of the Lake St Lucia nursery area for estuary-associated marine fish species over the past few years may cause significant short-term declines in the future abundance of these taxa on both a local and regional scale.     

Salinity tolerance and osmotic regulation in the diamond killifish,Adinia xenica

Synopsis Salinity tolerances and plasma osmotic regulatory capacity were determined in individuals of Adinia xenica following laboratory acclimations. Survival of individuals was better than 90% of those entered into the acclimation sequence from an initial acclimation salinity of 17.0 ppt down to fresh-water, and up to 95.0 ppt. Survival of individuals transferred from 95.0 to 105.0 ppt was low. Adinia showed most consistent plasma osmotic regulation in the range of ambient salinities from 17.0 to 60.0 ppt, but responded well over the ambient salinity range from 0.5 ppt to 85.0 ppt. Plasma osmotic concentrations were higher at common ambient salinities, but in a generally similar overall pattern of response, compared with such euryhaline cyprinodontids as Cyprinodon variegatus and Fundulus kansae.     

A latitudinal gradient of seasonal temperature variation recorded in oyster shells from the coastal waters of France and The Netherlands

Cathodoluminescence (CL) microscopy of the foliated calcite shell hinge sections of live-collected oyster Crassostrea gigas collected at seven locations along a latitudinal gradient from the Netherlands in the North Sea to the Atlantic coast of France, revealed variations in luminescence that were attributable to seasonal variations in calcification of the hinge. Photomicrographs of hinge sections and luminescence profiles were analyzed to define a micro-sampling strategy that was adopted to drill the hinge samples to determine their isotopic composition. Reconstructed seasonal seawater temperatures determined from the stable oxygen isotope (δ¹⁸O) composition along growth profiles from 32 oyster shell hinges showed distinct seasonal isotopic cycles that were compared with in situ measured seawater temperatures and salinities at each location. Comparison of the amplitude of the (δ¹⁸O) signal and the annual maximum and minimum seawater temperatures demonstrated that C. gigas shells from several locations provided a reliable record of seasonal seawater temperature variation. The exception to this was oysters from the Netherlands and northern France where winter growth rates at low temperatures were slow so that insufficient shell was deposited to allow adequate spatial resolution of sampling and this resulted in time-averaging of the reconstructed seawater temperatures and an overestimation of winter seawater temperature. A potential variability in δ¹⁸O_w–salinity relationship at low salinities could also explain the high difference between measured and predicted seawater temperatures in Dutch areas. The finding that latitudinal differences in oyster hinge growth rates and/or changes in the δ¹⁸O_w–salinity relationship can result in bias of the seawater temperature deduced from the stable isotopic composition of the hinge should be taken into account when reconstructing latitudinal gradients in seawater temperature.     

Local adaptation at range edges: comparing elevation and latitudinal gradients

Local adaptation at range edges influences species’ distributions and how they respond to environmental change. However, the factors that affect adaptation, including gene flow and local selection pressures, are likely to vary across different types of range edge. We performed a reciprocal transplant experiment to investigate local adaptation in populations of Plantago lanceolata and P. major from central locations in their European range and from their latitudinal and elevation range edges (in northern Scandinavia and Swiss Alps, respectively). We also characterized patterns of genetic diversity and differentiation in populations using molecular markers. Range‐centre plants of P. major were adapted to conditions at the range centre, but performed similarly to range‐edge plants when grown at the range edges. There was no evidence for local adaptation when comparing central and edge populations of P. lanceolata. However, plants of both species from high elevation were locally adapted when compared with plants from high latitude, although the reverse was not true. This asymmetry was associated with greater genetic diversity and less genetic differentiation over the elevation gradient than over the latitudinal gradient. Our results suggest that adaptation in some range‐edge populations could increase their performance following climate change. However, responses are likely to differ along elevation and latitudinal gradients, with adaptation more likely at high‐elevation. Furthermore, based upon these results, we suggest that gene flow is unlikely to constrain adaptation in range‐edge populations of these species.     

Influences of Salinity on Growth and Survival of Juvenile Pinfish <Emphasis Type="Italic">Lagodon rhomboides</Emphasis> (Linnaeus)

We investigated the effect of salinity on growth, survival, and condition of pinfish Lagodon rhomboides juveniles (36–80 mm standard length) in two laboratory experiments in July 2003 and June/July 2004. Our results show that juvenile pinfish grown in laboratory conditions under a range of salinities experience rapid growth and high survival in typical estuarine-like salinities (15–30 ppt). We also found that relative weight as an index of condition corroborates the idea that pinfish are well adapted to survive and grow in a wide range of salinities. Such rapid growth and high survival in a dynamic environment may afford juvenile pinfish potential ecological advantages over other estuarine-dependent fish species that are relatively more constrained by changes in salinity regime. Because coastal development is wide-spread throughout Gulf of Mexico and Atlantic estuaries, insights concerning the impacts of human-induced changes to estuarine environments are essential for effective management practices.     

Disparity in elevational shifts of European trees in response to recent climate warming

Predicting climate‐driven changes in plant distribution is crucial for biodiversity conservation and management under recent climate change. Climate warming is expected to induce movement of species upslope and towards higher latitudes. However, the mechanisms and physiological processes behind the altitudinal and latitudinal distribution range of a tree species are complex and depend on each tree species features and vary over ontogenetic stages. We investigated the altitudinal distribution differences between juvenile and adult individuals of seven major European tree species along elevational transects covering a wide latitudinal range from southern Spain (37°N) to northern Sweden (67°N). By comparing juvenile and adult distributions (shifts on the optimum position and the range limits) we assessed the response of species to present climate conditions in relation to previous conditions that prevailed when adults were established. Mean temperature increased by 0.86 °C on average at our sites during the last decade compared with previous 30‐year period. Only one of the species studied, Abies alba, matched the expected predictions under the observed warming, with a maximum abundance of juveniles at higher altitudes than adults. Three species, Fagus sylvatica, Picea abies and Pinus sylvestris, showed an opposite pattern while for other three species, such as Quercus ilex, Acer pseudoplatanus and Q. petraea, we were no able to detect changes in distribution. These findings are in contrast with theoretical predictions and show that tree responses to climate change are complex and are obscured not only by other environmental factors but also by internal processes related to ontogeny and demography.     

Two parthenogenetic populations of <Emphasis Type="Italic">Chara canescens</Emphasis> differ in their capacity to acclimate to irradiance and salinity

The parthenogens of Chara canescens (Charophyceae) occupy broader geographical and ecological ranges than their sexual counterparts. Two possible hypotheses explain the ubiquity of parthenogens: the occurrence of one or several parthenogens with wide niches, or of many parthenogens that are restricted to narrow ecological niches. For the purposes of this study, C. canescens individuals from two neighbouring populations of the Baltic Sea (Bodstedter Bodden = BB; Salzhaff = SH), which differed significantly in water transparency and salinity, were investigated for significant differences in physiological capacity. Individuals of both habitats acclimated quickly to daily changes in irradiances in the field, but the photosynthetic efficiency of PS II showed a significant decrease with increasing daily irradiance in the habitat BB, which has lower levels of salinity and water transparency. In addition to the field study, individuals were reared under different levels of environmental factors in the laboratory: four irradiances (70–600 μmol m⁻² s⁻¹) and five salinity levels (0–24 psu). The individuals of both habitats grew almost equally well at intermediate salinity levels. Growth under the artificial light supply was highest at levels corresponding to the in situ conditions for each population. Total chlorophyll was highest at intermediate salinities (BB), or hardly changed with salinity (SH). The physiological capacity for individuals from SH clearly depends upon changing growth irradiance, whereas the capacity for individuals from BB was relatively independent of salinity and irradiance. These findings indicate that both parthenogenetic C. canescens populations are locally adapted to light. However, to test adaptive potential of the parthenogens, more than two populations should be tested in future.     

Host specificity of <Emphasis Type="Italic">Ischnodemus variegatus</Emphasis>, an herbivore of West Indian marsh grass (<Emphasis Type="Italic">Hymenachne amplexicaulis</Emphasis>)

West Indian marsh grass, Hymenachne amplexicaulis Rudge (Nees) (Poaceae), is an emergent wetland plant that is native to South and Central America as well as portions of the Caribbean, but is considered invasive in Florida USA. The neotropical bug, Ischnodemus variegatus (Signoret) (Hemiptera: Lygaeoidea: Blissidae) was observed feeding on H. amplexicaulis in Florida in 2000. To assess whether this insect could be considered as a specialist biological control agent or potential threat to native and cultivated grasses, the host specificity of I. variegatus was studied under laboratory and field conditions. Developmental host range was examined on 57 plant species across seven plant families. Complete development was obtained on H. amplexicaulis (23.4% survivorship), Paspalum repens (0.4%), Panicum anceps (2.2%) and Thalia geniculata (0.3%). Adults survived 1.6 times longer and laid 6.6 times more eggs on H. amplexicaulis than the other species. Oviposition on suboptimal host species was positively related to I. variegatus density under multiple choice conditions. Results from field experiments indicated that H. amplexicaulis had higher densities of I. variegatus than other species. Spill-over to suboptimal hosts occurred in an area where H. amplexicaulis was growing in poor conditions and there was a high density of I. variegatus. Thus, laboratory and field studies demonstrate that I. variegatus had higher performance on H. amplexicaulis compared to any other host, and that suboptimal hosts could be colonized temporarily. Handling Editor: John Scott. An erratum to this article can be found at     

Osmotic and ionic regulation in response to salinity variations and cold resistance in the Arctic under-ice amphipod <Emphasis Type="Italic">Apherusa glacialis</Emphasis>

Amphipods living at the underside of Arctic sea ice are exposed to varying salinities due to freezing and melting, and have to cope with the resulting osmotic stress. Extracellular osmotic and ionic regulation at different salinities, thermal hysteresis, and supercooling points (SCPs) were studied in the under-ice amphipod Apherusa glacialis. The species is euryhaline, capable to regulate hyperosmotically at salinities S _R < 30 g/kg, and osmoconforms at salinities S _R ≥ 30 g/kg. Hyperosmotic regulation is an adaptation to thrive in low-salinity meltwater below the ice. Conforming to the ambient salinity during freezing reduces the risk of internal ice formation. Thermal hysteresis was not observed in the haemolymph of A. glacialis. The SCP of the species was −7.8 ± 1.9°C. Several ions were specifically downregulated ([Mg²⁺], [SO₄ ²⁻]), or upregulated ([K⁺], [Ca²⁺]) in comparison to the medium. Strong downregulation of [Mg²⁺], is probably necessary to avoid an anaesthetic effect at low temperatures.     

Isolation of sex-specific AFLP markers in Spotted Halibut (<Emphasis Type="Italic">Verasper variegatus</Emphasis>)

Spotted Halibut (Verasper variegatus) is a commercially important marine fish species. In the present study, to isolate sex-specific markers in Spotted Halibut, we screened the genomes of Spotted Halibut by AFLP technique with 64 different primer combinations. Two primer combinations, MseI-CAG/EcoRI-ACC and MseI-CAT/EcoRI-AGG, produced a female-specific fragment in all females (n = 88) and in no males (n = 60, except 3 individuals), respectively. Both fragments were excised from the gel, cloned and characterized. The first fragment (named VevaF533) was 533 bp long, while the length of the second one (named VevaF218) was 218 bp. The two sequences showed no similarity to each other, and to the known sequences existing in the GenBank database using BLASTn. Cross-species amplification showed that the marker VevaF218 is a species-specific marker which is present in Spotted Halibut females but absent in Barfin Flounder (Verasper moseri). So this marker could be used for discriminating unambiguously between Spotted Halibut females and Barfin Flounder. Examination of the patterns of inheritance of VevaF218 in an interspecific hybrid family (V. variegatus ♂×V. moseri ♀) showed a female-specific pattern of inheritance from mother to daughter, implying that the marker VevaF218 is located on the female sex chromosome. This study provides a reliable AFLP-based genetic sexing of Spotted Halibut that could be useful for genetic mapping of the sex chromosomes and identification of sex-linked genes.     

Ecology of a saline stream: community responses to spatial gradients of environmental conditions

Spatial changes in structural and functional characteristics of fish and macroinvertebrate communities in eastern Kentucky were investigated in a drainage system chronically exposed to high levels of chloride salts from nearby oilfield operations. Salinity levels at biological monitoring stations ranged from 0.12–31.3‰. Lotic regions with salinities greater than 10‰ were dominated by larvae of the dipterans Ephydra and Culicoides. In regions with salinities less than 10‰ species richness increased more or less linearly with decreasing levels of chloride salts. Ephemeropterans appeared to be one of the major invertebrate groups least tolerant of elevated NaCl levels and were absent in regions with salinities greater than 2‰ Availability of food resources, such as periphyton and particulate organic matter, did not appear to be grossly altered in disturbed regions, and it is suggested that the observed distribution of macroinvertebrate fauna was largely in response to taxonomic differences in salt tolerance. Fish seemed to be more tolerant of highly saline conditions, and several species were observed in regions experiencing salinities as high as 15‰. Accordingly, assemblages of fish taxa along the salinity gradient may have been influenced by trophic factors, such as spatial limitations in availability of invertebrate prey.     

Effects of latitude and allopatry on body size variation in European water shrews

We studied the intra- and interspecific size variability of 271 water shrewsNeomys fodiens (Pennant, 1771) andN. anomalus Cabrera, 1907 from seven sample sites along a latitudinal transect from Bosnia and Herzegovina to Poland.Neomys anomalus was the only water shrew in three Dinaride karst fields, while it was sympatric with N.fodiens in remaining sites. The first principal component scores (PC1; 72.2% of variance explained), derived from principal components analysis of 13 cranial, mandibular and dental measurements, were used as the size factor. One-way ANOVA detected significant interpopulation variation in both species; intraspecific variation, however, was much more pronounced inN. anomalus. No latitudinal size pattern was found in N. fodiens (r = −0.42, p = 0.58), while mean PC1 scores correlated significantly and negatively with latitude inN. anomalus (r = −0.92, p = 0.004). Therefore, along a north to south transect,N. anomalus converged in size towards N. fodiens, which suggests that the former species occupies increasingly more aquatic habitats in the same direction. Individuals from allopatric populations ofN. anomalus from Slovenia and Bosnia and Herzegovina were, on average, larger than sympatric conspecific populations from the same latitudinal zone, which is consistent with the hypothesis of character displacement.     

Incubation temperature and phenotypic traits of Sceloporus undulatus: implications for the northern limits of distribution

Cold environmental temperature is detrimental to reproduction by oviparous squamate reptiles by prolonging incubation period, negatively affecting embryonic developmental processes, and by killing embryos in eggs directly. Because low soil temperature may prevent successful development of embryos in eggs in nests, the geographic distributions of oviparous species may be influenced by the thermal requirements of embryos. In the present study, we tested the hypothesis that low incubation temperature determines the northern distributional limit of the oviparous lizard Sceloporus undulatus. To compare the effects of incubation temperature on incubation length, egg and hatchling survival, and hatchling phenotypic traits, we incubated eggs of S. undulatus under temperature treatments that simulated the thermal environment that eggs would experience if located in nests within their geographic range at 37°N and north of the species’ present geographic range at latitudes of 44 and 42°N. After hatching, snout–vent length (SVL), mass, tail length, body condition (SVL relative to mass), locomotor performance, and growth rate were measured for each hatchling. Hatchlings were released at a field site to evaluate growth and survival under natural conditions. Incubation at temperatures simulating those of nests at 44°N prolonged incubation and resulted in hatchlings with shorter SVL relative to mass, shorter tails, shorter hind limb span, slower growth, and lower survival than hatchlings from eggs incubated at temperatures simulating those of nests at 37 and 42°N. We also evaluated the association between environmental temperature and the northern distribution of S. undulatus. We predicted that the northernmost distributional limit of S. undulatus would be associated with locations that provide the minimum heat sum (∼495 degree-days) required to complete embryonic development. Based on air and soil temperatures, the predicted northern latitudinal limit of S. undulatus would lie at ∼40.5–41.5°N. Our predicted value closely corresponds to the observed latitudinal limit in the eastern United States of ∼40°N. Our results suggest that soil temperatures at northern latitudes are not warm enough for a sufficient length of time to permit successful incubation of S. undulatus embryos. These results are consistent with the hypothesis that incubation temperature is an important factor limiting the geographic distributions of oviparous reptile species at high latitudes and elevations.     

Confirmation of natural hybrids between Gentiana straminea and G. siphonantha (Gentianaceae) based on molecular evidence

A few individuals with intermediate morphology always appeared in the sympatric distributions of Gentiana straminea and G. siphonantha. These intermediate individuals were hypothesized to be the hybrids of two species after a careful evaluation of their morphological characteristics. To test this hypothesis, sequence comparison of the internal transcribed spacer (ITS) regions of the nuclear ribosomal and trnS (GCU)-trnG (UCC) intergenic spacer region of the chloroplast DNA from Gentiana straminea, G. siphonantha and the putative hybrids was performed. The results suggest that most intermediate individuals were the natural hybrids between G. straminea and G. siphonantha. In addition, we examined the sequence variation among the individuals of both parent species and analyzed the possibility leading to the incongruent identification in some individuals based on morphologic and molecular evidences, respectively. The intraspecific diversification of DNA fragments within both parent species and their high variability in hybrid swarms probably resulted from chloroplast genome recombination and incomplete lineage sorting during the early stages of speciation origin of the parent species. __________ Translated from Acta Botanica Yunnanica, 2007, 29 (1): 91–97 [译自:云南植物研究]     

A halotolerant,thermotolerant, and facultative biosurfactant producer: Identification and molecular characterization of a bacterium and evolution of emulsifier stability of a lipopeptide biosurfactant

A halotolerant, thermotolerant, and facultative biosurfactant producing bacterium was identified as a strain of Bacillus mojavensis based on the phenotypic data, a phylogenetic analysis, and DNA-DNA relatedness with closely-related species. This strain grew at temperatures and salinities up to 55°C and 0 ∼ 10% (w/v) NaCl, respectively, and under anaerobic conditions. A batch fermentation showed that this strain secreted a lipopeptide biosurfactant that can reduce surface tension to 27 mN/m while growing on mineral medium. The emulsifying activity of the cell-free supernatant and stability of the formed emulsions were studied at various temperatures and salinities. The results showed that the ability to significantly reduce surface tension was not sufficient to form stable emulsions. The ability of this strain to grow and reduce surface tension under a wide range of salinities and temperatures gives it an advantage for many applications.     

Comparative Phylogeography of the Atlantic Forest Endemic Sloth (Bradypus torquatus) and the Widespread Three-toed Sloth (Bradypus variegatus) (Bradypodidae, Xenarthra)

The comparative phylogeographic study of the maned sloth (Bradypus torquatus) and the three-toed sloth (Bradypus variegatus) was performed using a segment of mitochondrial DNA (mtDNA) control region. We examined 19 B. torquatus from two regions and 47 B. variegatus from three distant regions of Atlantic forest. This first characterization of molecular diversity indicates a great diversity (B. torquatus: h = 0.901 ± 0.039 and π = 0.012 ± 0.007; B. variegatus: h = 0.699 ± 0.039 and π = 0.010 ± 0.006) and very divergent mitochondrial lineages within each sloth species. The different sampled regions carry distinct and non-overlapping sets of mtDNA haplotypes and are genetically divergent. This phylogeographic pattern may be characteristic of sloth species. In addition, we infer that two main phylogeographic groups exist in the Atlantic forest representing a north and south distinct divergence.     

GROWTH RESPONSES TO SALINITY VARIATION IN FOUR ARCTIC ICE DIATOMS1,2

During spring, extensive blooms of microalgae grow on the underside of arctic sea ice. The brownish, algal layer penetrates ca. 2 cm into the bottom surface of the ice and the algae are potentially exposed to very high salinities. Four diatom species, Melosira juergensii Ag., Porosira glacialis (Grun.) Jørg., Navicula transitans var. derasa (Grun.) Cleve, and Coscinodiscus lacustris Grun., isolated from, sea ice samples taken from the Beaufort and Chukchi seas near Barrow, Alaska, were grown at 11 salinities ranging from 5 to 70‰ at 5 C under constant illumination. All of the species grew at 5‰ except N. transitans whose lower growth limit was 15‰. Growth was high over a broad range of salinities, but none of the species grew at salinities above 60‰. These diatom species appear to be well suited to tolerate the salinities in the brine pockets near the bottom of annual arctic sea ice where they are found. High brine-cell salinity, however, may limit the upward, penetration of ice algae into the bottom of sea ice.     

Salinity affects growth but not thermal preference of adult mummichogs Fundulus heteroclitus

The effects of an ecologically relevant range of salinities (2, 12, 22, 32) on thermal preferences and growth of adult mummichogs Fundulus heteroclitus were determined for fish from a southern Chesapeake Bay population. Salinity did not affect the mean temperature selected by F. heteroclitus in a thermal gradient, which was identified as 26.6°C based on observations of 240 individuals. Salinity and temperature had significant and interacting effects on growth rates of F. heteroclitus measured over 12 weeks. Growth rates were highest overall and remained high over a broader range of temperatures at moderate salinities (12 and 22), while high growth rates were shifted toward lower temperatures for fish grown at a salinity of 2 and higher temperatures at a salinity of 32. Significant reductions in growth relative to the optimal conditions (28.6°C, salinity of 22) were observed at the coolest (19.6°C) and warmest (33.6°C) temperature tested at all salinities, as well as temperatures ≥ 26.6°C at a salinity of 2, ≥ 28.6°C at a salinity of 12 and ≤ 26.6°C at a salinity of 32. Growth rates provide a long-term, organismal measure of performance and results of this study indicate that performance may be reduced under conditions that the highly euryhaline F. heteroclitus can otherwise easily tolerate. The combination of reduced salinity and increased temperature that is predicted for temperate estuaries as a result of climate change may have negative effects on growth of this ecologically important species.     

Asymmetric changes of growth and reproductive investment herald altitudinal and latitudinal range shifts of two woody species

Ongoing changes in global climate are altering ecological conditions for many species. The consequences of such changes are typically most evident at the edge of the geographical distribution of a species, where range expansions or contractions may occur. Current demographical status at geographical range limits can help us to predict population trends and their implications for the future distribution of the species. Thus, understanding the comparability of demographical patterns occurring along both altitudinal and latitudinal gradients would be highly informative. In this study, we analyse the differences in the demography of two woody species through altitudinal gradients at their southernmost distribution limit and the consistency of demographical patterns at the treeline across a latitudinal gradient covering the complete distribution range. We focus on Pinus sylvestris and Juniperus communis, assessing their demographical structure (density, age and mortality rate), growth, reproduction investment and damage from herbivory on 53 populations covering the upper, central and lower altitudes as well as the treeline at central latitude and northernmost and southernmost latitudinal distribution limits. For both species, populations at the lowermost altitude presented older age structure, higher mortality, decreased growth and lower reproduction when compared to the upper limit, indicating higher fitness at the treeline. This trend at the treeline was generally maintained through the latitudinal gradient, but with a decreased growth at the northern edge for both species and lower reproduction for P. sylvestris. However, altitudinal and latitudinal transects are not directly comparable as factors other than climate, including herbivore pressure or human management, must be taken into account if we are to understand how to infer latitudinal processes from altitudinal data.     

Larval salinity tolerance of the South American salt-marsh crab, Neohelice (Chasmagnathus) granulata: physiological constraints to estuarine retention, export and reimmigration

The semiterrestrial crab Neohelice (=Chasmagnathus) granulata (Dana 1851) is a predominant species in brackish salt marshes, mangroves and estuaries. Its larvae are exported towards coastal marine waters. In order to estimate the limits of salinity tolerance constraining larval retention in estuarine habitats, we exposed in laboratory experiments freshly hatched zoeae to six different salinities (5–32‰). At 5‰, the larvae survived for a maximum of 2 weeks, reaching only exceptionally the second zoeal stage, while 38% survived to the megalopa stage at 10‰. Shortest development and negligible mortality occurred at all higher salt concentrations. These observations show that the larvae of N. granulata can tolerate a retention in the mesohaline reaches of estuaries, with a lower limit of ca. 10–15‰. Maximum survival at 25‰ suggests that polyhaline conditions rather than an export to oceanic waters are optimal for successful larval development of this species. In another experiment, we tested the capability of the last zoeal stage (IV) for reimmigration from coastal marine into brackish waters. Stepwise reductions of salinity during this stage allowed for moulting to the megalopa at 4–10‰. Although survival was at these conditions reduced and development delayed, these results suggest that already the zoea-IV stage is able to initiate the reimmigration into estuaries. After further salinity reduction, megalopae survived in this experiment for up to >3 weeks in freshwater, without moulting to juvenile crabs. In a similar experiment starting from the megalopa stage, successful metamorphosis occurred at 4–10‰, and juvenile growth continued in freshwater. Although these juvenile crabs showed significantly enhanced mortality and smaller carapace width compared to a seawater control, our results show that the late larval and early juvenile stages of N. granulata are well adapted for successful recruitment in brackish and even limnetic habitats.