Life history characteristics and strategies of the American eel, Anguilla rostrata

1999 ◽  
Vol 56 (5) ◽  
pp. 795-802 ◽  
Author(s):  
Kenneth Oliveira
Keyword(s):  
Life History ◽  
Rhode Island ◽  
Life History Traits ◽  
Life History Strategies ◽  
Anguilla Rostrata ◽  
Female Size ◽  
Silver Eel ◽  
Male Size ◽  
American Eel ◽  
Female Age

Several life history hypotheses for the American eel, Anguilla rostrata, were examined using seaward-migrating silver-phase eels collected in the Annaquatucket River, Rhode Island, U.S.A. Female eels were significantly larger and older than males. Female eels also had a significantly higher mean growth rate. The addition of life history data from Annaquatucket River eels to published silver eel data from locations throughout the eels' range shows that female size at migration is positively correlated with latitude (r = 0.56, p = 0.05) but male size is not (r = 0.54, p = 0.17). Female age was not related to latitude (r = 0.57, p = 0.27) but male age showed a positive relationship (r = 0.87, p = 0.05). Growth rates for females and males were inversely related to latitude (r = -0.98, p = 0.02 and r = -0.95, p = 0.05, respectively). Differences between the latitudinal relationships and life history traits of the sexes may be due to differences in life history strategies.

Geographic effects on American eel (Anguilla rostrata) life history characteristics and strategies

2010 ◽  
Vol 67 (2) ◽  
pp. 326-346 ◽  
Author(s):  
B. M. Jessop
Keyword(s):  
Life History ◽  
Growth Rates ◽  
Atlantic Coast ◽  
Life History Strategies ◽  
Anguilla Rostrata ◽  
Annual Growth Rate ◽  
Degree Days ◽  
Silver Eel ◽  
American Eel ◽  
Spawning Site

Latitudinal variability in length and age at maturity and annual growth rate for the American eel ( Anguilla rostrata ) along the Atlantic coast of North America was examined with respect to life history strategies and theory. Maturing (silver phase) female lengths and ages increased with increasing latitude (and distance) from the Sargasso Sea spawning site, as did male ages but not lengths. Growth rates for females (and males) declined with increasing latitude south of 44°N latitude, approximately the entrance to the Cabot Strait, but were constant or increased within the Gulf of St. Lawrence and St. Lawrence River, depending on the analysis method. The growing season and the number of degree-days ≥ 10 °C declined with increasing latitude. Female growth rates adjusted for the number of degree-days were approximately constant south of 44°N but increased further north, suggesting countergradient variation in growth. The temperature–size rule (increase in body size at lower temperatures) evidently applies to American eel females, but not males. No current life history model provides a satisfactory explanatory mechanism for the temperature–size rule and for anguillid life history strategies. A genetic link is proposed between increasing age (length) at elver and silver eel stages with increasing distance from the spawning area.

Demographic life history traits of reproductive natterjack toads (Bufo calamita) vary between northern and southern latitudes

2006 ◽  
Vol 27 (3) ◽  
pp. 365-375 ◽  
Author(s):  
Delfi Sanuy ◽  
Christoph Leskovar ◽  
Neus Oromi ◽  
Ulrich Sinsch
Keyword(s):  
Life History ◽  
Life History Traits ◽  
Large Female ◽  
Breeding Period ◽  
Female Size ◽  
Data Set ◽  
Bufo Calamita ◽  
Trade Offs ◽  
Age Variation ◽  
The Cost

AbstractDemographic life history traits were investigated in three Bufo calamita populations in Germany (Rhineland-Palatinate: Urmitz, 50°N; 1998-2000) and Spain (Catalonia: Balaguer, Mas de Melons, 41°N; 2004). We used skeletochronology to estimate the age as number of lines of arrested growth in breeding adults collected during the spring breeding period (all localities) and during the summer breeding period (only Urmitz). A data set including the variables sex, age and size of 185 males and of 87 females was analyzed with respect to seven life history traits (age and size at maturity of the youngest first breeders, age variation in first breeders, longevity, potential reproductive lifespan, median lifespan, age-size relationship). Spring and summer cohorts at the German locality differed with respect to longevity and potential reproductive lifespan by one year in favour of the early breeders. The potential consequences on fitness and stability of cohorts are discussed. Latitudinal variation of life history traits was mainly limited to female natterjacks in which along a south-north gradient longevity and potential reproductive lifespan increased while size decreased. These results and a review of published information on natterjack demography suggest that lifetime number of offspring seem to be optimized by locally different trade-offs: large female size at the cost of longevity in southern populations and increased longevity at the cost of size in northern ones.

Sexual size dimorphism and life history traits in an island-mainland system: an overview of the lizard genus Microlophus

2021 ◽  
pp. 1-7
Author(s):  
Ken S. Toyama ◽  
Christopher K. Boccia
Keyword(s):  
Life History ◽  
South America ◽  
Life History Theory ◽  
Life History Traits ◽  
Sexual Size Dimorphism ◽  
Life History Strategies ◽  
Galápagos Islands ◽  
Size Dimorphism ◽  
Rensch's Rule ◽  
Comprehensive Compilation

Abstract Opposing life history strategies are a common result of the different ecological settings experienced by insular and continental species. Here we present a comprehensive compilation of data on sexual size dimorphism (SSD) and life history traits of Microlophus, a genus of lizards distributed in western South America and the Galápagos Islands, and test for differences between insular and continental species under life history theory expectations. Contrary to our predictions, we found no differences in SSD between localities or evidence that Microlophus follows Rensch’s rule. However, as expected, head dimensions and maturity sizes were significantly larger in insular species while continental species had larger clutches. Our results show that Microlophus exhibits some of the patterns expected from an island-mainland system, but unexplained patterns will only be resolved through future ecological, morphological and behavioural studies integrating both faunas.

Eels at the Edge: Science, Status, and Conservation Concerns

2009 ◽  
Keyword(s):  
Gonadosomatic Index ◽  
Reproductive Potential ◽  
Anguilla Rostrata ◽  
Spawning Ground ◽  
Silver Eel ◽  
Migration Distance ◽  
American Eel ◽  
Individual Fitness ◽  
Silver Eels ◽  
Somatic Tissues

<em>Abstract.—</em>The American eel <em>Anguilla rostrata </em>is declining in the St. Lawrence River watershed, where sex ratio is highly unbalanced in favor of females. Since the American eel is a panmictic species, this demographic dominance is implicated in reproductive potential of the species. The major objective of this study was to evaluate the reproductive strategies of five subpopulations of female eels. It was assumed that fecundity varies among subpopulations according to their migration distance because of the tradeoff between energy allocated to gonads and to somatic tissues. Thirty female silver eels were collected from each of five locations in the St. Lawrence watershed 2,850–4,300 km from the spawning area. Among subpopulations, mean length ranged from 67.9 to 104.3 cm, weight from 595 to 2,366 g, fecundity from 6.5 to 14.5 million oocytes, age from 20 to 23 years, gonadosomatic index from 2.9 to 4.1%, and somatic lipid content from 17.5 to 21.7%. Because of panmixia, no genetic influence on intersite variability is expected. Environmental differences in growth habitats and individual fitness might determine acquisition and allocation of resources, as well as subsequent variability in traits that would affect reproduction. In contrast to previous hypotheses, variations in such traits were attributed to eel size rather than migration distance. The number of oocytes per silver eel was positively correlated with length rather than negatively correlated with migration distance. In the St. Lawrence watershed, large eels are highly fecund regardless of their distance from the spawning ground.

scholarly journals Corticosterone, testosterone and life-history strategies of birds

2010 ◽  
Vol 277 (1697) ◽  
pp. 3203-3212 ◽  
Author(s):  
Michaela Hau ◽  
Robert E. Ricklefs ◽  
Martin Wikelski ◽  
Kelly A. Lee ◽  
Jeffrey D. Brawn
Keyword(s):  
Life History ◽  
Body Mass ◽  
Breeding Season ◽  
Life History Traits ◽  
Survival Rates ◽  
Life History Strategies ◽  
Adult Survival ◽  
Tropical Species ◽  
Published Data ◽  
Season Length

Steroid hormones have similar functions across vertebrates, but circulating concentrations can vary dramatically among species. We examined the hypothesis that variation in titres of corticosterone (Cort) and testosterone (T) is related to life-history traits of avian species. We predicted that Cort would reach higher levels under stress in species with higher annual adult survival rates since Cort is thought to promote physiological and behavioural responses that reduce risk to the individual. Conversely, we predicted that peak T during the breeding season would be higher in short-lived species with high mating effort as this hormone is known to promote male fecundity traits. We quantified circulating hormone concentrations and key life-history traits (annual adult survival rate, breeding season length, body mass) in males of free-living bird species during the breeding season at a temperate site (northern USA) and a tropical site (central Panama). We analysed our original data by themselves, and also combined with published data on passerine birds to enhance sample size. In both approaches, variation in baseline Cort (Cort0) among species was inversely related to breeding season length and body mass. Stress-induced corticosterone (MaxCort) also varied inversely with body mass and, as predicted, also varied positively with annual adult survival rates. Furthermore, species from drier and colder environments exhibited lower MaxCort than mesic and tropical species; T was lowest in species from tropical environments. These findings suggest that Cort0, MaxCort and T modulate key vertebrate life-history responses to the environment, with Cort0 supporting energetically demanding processes, MaxCort promoting survival and T being related to mating success.

scholarly journals Switch between Life History Strategies Due to Changes in Glycolytic Enzyme Gene Dosage inSaccharomyces cerevisiae

2010 ◽  
Vol 77 (2) ◽  
pp. 452-459 ◽  
Author(s):  
Shaoxiao Wang ◽  
Aymé Spor ◽  
Thibault Nidelet ◽  
Pierre Montalent ◽  
Christine Dillmann ◽  
...  
Keyword(s):  
Life History ◽  
Cell Size ◽  
Carrying Capacity ◽  
Life History Traits ◽  
Gene Dosage ◽  
Single Gene ◽  
Glycolytic Enzyme ◽  
Life History Strategies ◽  
Glucose Consumption Rate ◽  
Glycolytic Gene

ABSTRACTAdaptation is the process whereby a population or species becomes better fitted to its habitat through modifications of various life history traits which can be positively or negatively correlated. The molecular factors underlying these covariations remain to be elucidated. UsingSaccharomyces cerevisiaeas a model system, we have investigated the effects on life history traits of varying the dosage of genes involved in the transformation of resources into energy. Changing gene dosage for each of three glycolytic enzyme genes (hexokinase 2, phosphoglucose isomerase, and fructose-1,6-bisphosphate aldolase) resulted in variation in enzyme activities, glucose consumption rate, and life history traits (growth rate, carrying capacity, and cell size). However, the range of effects depended on which enzyme was expressed differently. Most interestingly, these changes revealed a genetic trade-off between carrying capacity and cell size, supporting the discovery of two extreme life history strategies already described in yeast populations: the “ants,” which have lower glycolytic gene dosage, take up glucose slowly, and have a small cell size but reach a high carrying capacity, and the “grasshoppers,” which have higher glycolytic gene dosage, consume glucose more rapidly, and allocate it to a larger cell size but reach a lower carrying capacity. These results demonstrate antagonist pleiotropy for glycolytic genes and show that altered dosage of a single gene drives a switch between two life history strategies in yeast.

scholarly journals Artificial selection on male size depletes genetic variance but not covariance of life history traits in the yellow dung fly

2019 ◽  
Author(s):  
WU Blanckenhorn ◽  
V Llaurens ◽  
C Reim ◽  
Y Teuschl ◽  
E Postma
Keyword(s):  
Genetic Variation ◽  
Life History ◽  
Body Size ◽  
Artificial Selection ◽  
Development Time ◽  
Life History Traits ◽  
Genetic Variance ◽  
Genetic Correlations ◽  
Male Size ◽  
First Clutch

SUMMARYThe evolutionary potential of organisms depends on the presence of sufficient genetic variation for traits subject to selection, as well as on the genetic covariances among them. While genetic variation ultimately derives from mutation, theory predicts the depletion of genetic (co)variation under consistent directional or stabilizing selection in natural populations. We estimated and compared additive genetic (co)variances for several standard life history traits, including some for which this has never been assessed, before and after 24 generations of artificial selection on male size in the yellow dung fly Scathophaga stercoraria (Diptera: Scathophagidae) using a series of standard half-sib breeding experiments. As predicted, genetic variances (VA), heritabilities (h2) and evolvabilities (IA) of body size, development time, first clutch size, and female age at first clutch were lower after selection. As independent selection lines were crossed prior to testing, we can rule out that this reduction is due to genetic drift. In contrast to the variances, and against expectation, the additive genetic correlations between the sexes for development time and body size remained strong and positive (rA = 0.8–0.9), while the genetic correlation between these traits within the sexes tended to strengthen (but not significantly so). Our study documents that the effect of selection on genetic variance is predictable, whereas that on genetic correlations is not.

scholarly journals Environmentally Modulated Repeat Evolution of Polymorphic Arctic Charr Life History Traits

2021 ◽  
Vol 9 ◽  
Author(s):  
Gabrielle Grenier ◽  
Aslak Smalås ◽  
Runar Kjær ◽  
Rune Knudsen
Keyword(s):  
Life History ◽  
Life History Traits ◽  
Growth Parameters ◽  
Salvelinus Alpinus ◽  
Arctic Charr ◽  
Local Environment ◽  
Life History Strategies ◽  
Age At Maturity ◽  
First Time ◽  
Sympatric Morphs

Sympatric Arctic charr, Salvelinus alpinus (L. 1758), morphs have flexible but repeated life history strategies tested across five Norwegian lakes. In several Scandinavian polymorphic Arctic charr populations differentiated by their diet and habitat use, a large littoral omnivorous (LO) morph commonly cooccurs with a smaller profundal spawning (PB/PZ) morph. A third, large piscivorous (PP) morph is also known to occur within a portion of Arctic charr populations in the profundal habitat along with the PB/PZ individuals. Life history traits, such as age at maturity, growth, and diet are known to differ among coexisting morphs. Notably, the PP morph was the longest morph with the oldest age at maturity while the PB/PZ morph showed the shortest lengths overall and youngest age with LO morph being intermediate in both traits. Growth parameters differed across all the morphs. When examining growth within morph groups, the LO morph was found to have different growth across all lakes, while similar reproductive investments and different energy acquisition patterns were seen within the PB/PZ and PP morphs. These results suggest repeat evolution in several life history strategies of reproductively isolated Arctic charr sympatric morphs, notably for the first time in the PP morph, while also highlighting the importance of the local environment in modulating life history traits.

scholarly journals Variation in Demography and Life-History Strategies Across the Range of a Declining Mountain Bird Species

2021 ◽  
Vol 9 ◽  
Author(s):  
Arnaud G. Barras ◽  
Sébastien Blache ◽  
Michael Schaub ◽  
Raphaël Arlettaz
Keyword(s):  
Life History ◽  
Environmental Change ◽  
Life History Traits ◽  
Local Population ◽  
Bird Species ◽  
Life History Strategies ◽  
Adult Survival ◽  
Northwestern Part ◽  
European Alps ◽  
Demographic Processes

Species- and population-specific responses to their environment may depend to a large extent on the spatial variation in life-history traits and in demographic processes of local population dynamics. Yet, those parameters and their variability remain largely unknown for many cold-adapted species, which are exposed to particularly rapid rates of environmental change. Here, we compared the demographic traits and dynamics for an emblematic bird species of European mountain ecosystems, the ring ouzel (Turdus torquatus). Using integrated population models fitted in a Bayesian framework, we estimated the survival probability, productivity and immigration of two populations from the Western European Alps, in France (over 11 years) and Switzerland (over 6 years). Juvenile apparent survival was lower and immigration rate higher in the Swiss compared to the French population, with the temporal variation in population growth rate driven by different demographic processes. Yet, when compared to populations in the northwestern part of the range, in Scotland, these two Alpine populations both showed a much lower productivity and higher adult survival, indicating a slower life-history strategy. Our results suggest that demographic characteristics can substantially vary across the discontinuous range of this passerine species, essentially due to contrasted, possibly locally evolved life-history strategies. This study therefore raises the question of whether flexibility in life-history traits is widespread among boreo-alpine species and if it might provide adaptive potential for coping with current environmental change.

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