Ecosystem Engineering by a Tropical Tadpole: Density-Dependent Effects on Habitat Structure and Larval Growth Rates

Copeia ◽  
1999 ◽  
Vol 1999 (2) ◽  
pp. 495 ◽  
Author(s):  
Alexander S. Flecker ◽  
Brian P. Feifarek ◽  
Brad W. Taylor
Keyword(s):  
Growth Rates ◽  
Habitat Structure ◽  
Larval Growth ◽  
Ecosystem Engineering ◽  
Density Dependent

The missing links: larval and post-larval development of the ascoglossan opisthobranch Elysia viridis

2000 ◽  
Vol 80 (6) ◽  
pp. 1087-1094 ◽  
Author(s):  
Cynthia D. Trowbridge
Keyword(s):  
Larval Development ◽  
Growth Rates ◽  
Shell Length ◽  
Larval Growth ◽  
Model Organism ◽  
Larval Life ◽  
Codium Fragile ◽  
Planktotrophic Larvae ◽  
Algal Diet ◽  
Better Than

The stenophagous ascoglossan (=sacoglossan) opisthobranch Elysia viridis has long been a model organism for the study of endosymbiosis or kleptoplasty as well as one of the few herbivores to consume the introduced green macroalga Codium fragile on European shores. Larval and post-larval dynamics of the ascoglossan were investigated. Planktotrophic larvae of E. viridis grew at 5–10 μm d−1 (shell length) at 15°C on a unicellular algal diet (the cryptophyte Rhodomonas baltica); larvae became competent one month post-hatching. Effective feeding and chloroplast acquisition typically started within 2–3 d of metamorphosis. Slugs grew about 8 mm in the first month of post-larval life. During this period, juveniles held in the light did not grow faster or survive better than conspecifics held in the dark; thus, functional kleptoplasty did not occur during first three weeks of benthic life. While larval growth rates and the nature of metamorphic cues are consistent with those of many other opisthobranch species with planktotrophic larvae, measures of post-larval growth—particularly as it pertains to kleptoplasty—is a new contribution to opisthobranch biology.

scholarly journals Variation in growth and instar number in field and laboratory Manduca sexta

2007 ◽  
Vol 274 (1612) ◽  
pp. 977-981 ◽  
Author(s):  
Joel G Kingsolver
Keyword(s):  
North Carolina ◽  
Body Size ◽  
Manduca Sexta ◽  
Growth Rates ◽  
Developmental Plasticity ◽  
Larval Growth ◽  
Physiological Control ◽  
Larval Instars ◽  
Laboratory Colony ◽  
Early Larval Development

The tobacco hornworm Manduca sexta has been an important model system for understanding physiological control of growth, development and metamorphosis of insects for more than half a century. Like all Manduca , M. sexta typically has five larval instars, with developmental commitment to metamorphosis occurring early in the 5th (final) instar. Here we show that M. sexta from a field population in North Carolina (USA) shows substantial intraspecific variation in the number of larval instars when feeding on a modified artificial diet. Individuals with six instars consistently exhibited slower growth rates during early larval development than individuals with five instars. The frequency of individuals with six instars decreased with increased rearing temperature. In contrast, M. sexta from a laboratory colony consistently had five instars, and had more rapid larval growth rates than M. sexta from the field. We identify a threshold body size at the start of the 5th instar that predicts whether an individual will have five (greater than 600 mg) or six instars (less than 600 mg). Variation in field populations in Manduca provides an important resource for understanding physiological control, developmental plasticity and evolution of growth rate, body size and instar number.

Do abiotic mechanisms determine interannual variability in length-at-age of juvenile Arcto-Norwegian cod?

2002 ◽  
Vol 59 (1) ◽  
pp. 57-65 ◽  
Author(s):  
Geir Ottersen ◽  
Kristin Helle ◽  
Bjarte Bogstad
Keyword(s):  
Growth Rates ◽  
Gadus Morhua ◽  
Barents Sea ◽  
Water Masses ◽  
Inverse Relation ◽  
Lower Growth ◽  
Density Dependent ◽  
The Barents Sea ◽  
The Mean ◽  
Dependent Growth

For the large Arcto-Norwegian stock of cod (Gadus morhua L.) in the Barents Sea, year-to-year variability in growth is well documented. Here three hypotheses for the observed inverse relation between abundance and the mean length-at-age of juveniles (ages 1–4) are suggested and evaluated. Based on comprehensive data, we conclude that year-to-year differences in length-at-age are mainly determined by density-independent mechanisms during the pelagic first half year of the fishes' life. Enhanced inflow from the southwest leads to an abundant cohort at the 0-group stage being distributed farther east into colder water masses, causing lower postsettlement growth rates. We can not reject density-dependent growth effects related to variability in food rations, but our data do not suggest this to be the main mechanism. Another hypothesis suggests that lower growth rates during periods of high abundance are a result of density-dependent mechanisms causing the geographic range of juveniles to extend eastwards into colder water masses. This is rejected mainly because year-to-year differences in mean length are established by age 2, which is too early for movements over large distances.

Production and Population Dynamics of the Crayfish Orconectes virilis in Three Michigan Lakes

1977 ◽  
Vol 34 (11) ◽  
pp. 2030-2040 ◽  
Author(s):  
Walter T. Momot ◽  
Howard Gowing
Keyword(s):  
Population Dynamics ◽  
Growth Rates ◽  
Age Groups ◽  
Mortality Rates ◽  
Reproductive Age ◽  
Annual Production ◽  
Effective Density ◽  
Orconectes Virilis ◽  
Brood Stock ◽  
Density Dependent

Fluctuations in mortality rather than in growth rates produced most of the year-to-year differences in biomass accumulation of three different populations of the crayfish Orconectes virilis. Yearly biomass changes resulted from density-dependent control of mortality and fecundity during certain portions of the life cycle. Density-dependent changes in mortality rates controlled population size for adults in all lakes and for young-of-the-year in two of the three study lakes. Growth rates were much less responsive to fluctuating densities. Disparity between the number of ovarian and attached eggs increased as density of age I+ crayfish increased. This provided a strong density regulator on fecundity. Differences occurred in the number of recruits produced by a brood stock that survive to the end of the first growing season in the various lakes. Yet the number of females surviving to reproductive age 2 yr later was strongly regulated. Strong population regulation produced two female recruits of breeding age for every two–six parental breeding females. The high biomass and production levels of crayfish discovered in West Lost Lake in 1962–63 also occurred in the other area lakes. Higher but variable levels of recruitment resulted in larger standing crops and production in West Lost lake. This resulted from less effective density controls on the mortality rates of younger age-groups in that lake. Despite great variation in biomass of from 46 to 213 kg/ha and annual production from 60 to 142 kg/ha, the annual turnover ratio of the biomass was found to vary only between 0.94 and 1.53. Key words: crayfish, Orconectes virilis, population dynamics, annual production, Michigan lakes

Positive solutions of certain elliptic systems with density-dependent diffusions

1995 ◽  
Vol 125 (5) ◽  
pp. 1031-1050 ◽  
Author(s):  
Inkyung Ahn ◽  
Lige Li
Keyword(s):  
Positive Solutions ◽  
Growth Rates ◽  
Smooth Boundary ◽  
Elliptic Systems ◽  
Biological Interactions ◽  
Bounded Region ◽  
Density Dependent ◽  
Existence Of Positive Solutions ◽  
Image Position ◽  
Increasing Functions

Results are obtained on the existence of positive solutions to the following elliptic system:in a bounded region Ω in Rn with a smooth boundary, where the diffusion terms φ ψ are non-negative functions and the system could be degenerate, β γ are strictly increasing functions, k,σ ≧ 0 are constants. We assume also that the growth rates f, g satisfy certain monotonicities. Applications to biological interactions with density-dependent diffusions are given.

GROWTH AND DEVELOPMENT OF LARVAE OF THE GRANARY WEEVIL, SITOPHILUS GRANARIUS (COLEOPTERA: CURCULIONIDAE), ON NATURAL AND MERIDIC DIETS

1973 ◽  
Vol 105 (2) ◽  
pp. 249-256 ◽  
Author(s):  
J. E. Baker ◽  
J. M. Mabie
Keyword(s):  
Wheat Flour ◽  
Growth Rates ◽  
Adult Stage ◽  
Larval Growth ◽  
Pupal Stage ◽  
Sitophilus Granarius ◽  
Granary Weevil ◽  
Whole Wheat Flour ◽  
Whole Wheat ◽  
Meridic Diet

AbstractA procedure is described for obtaining free eggs and first-stage larvae of Sitophilus granarius (L.) and rearing the larvae to the adult stage on whole wheat, corn, and rice flours and on diet 2, a casein–starch-based meridic diet.Larval growth rates of males and females reared at 29 °C and 65% R.H. on whole wheat flour were comparable although males attained a higher maximum mean weight. Days to 50% adult emergence (eclosion) were 25.5 and 26.5 for females and males, respectively.Larval growth rates on whole wheat flour were comparable with those on whole corn flour but were better than the rates obtained on whole rice flour; however, growth on diet 2 was improved compared with that on whole wheat flour. The mean weights of 14-day-old larvae were 2.51 ±.40 mg and 1.25 ±.16 mg for those reared on diet 2 and wheat flour, respectively. Similarly, survival to the adult stage was slightly greater (79%) on diet 2 than on wheat (70%). On diet 1, a casein–glucose-based meridic diet, no larvae developed to the pupal stage.

scholarly journals Evaluation of the Shepherd and Cushing (1980) model of density-dependent survival: a case study using striped bass (Morone saxatilis) larvae in the Potomac River, Maryland, USA

2003 ◽  
Vol 60 (6) ◽  
pp. 1275-1287 ◽  
Author(s):  
Edward S Rutherford ◽  
Kenneth A Rose ◽  
James H Cowan
Keyword(s):  
Regression Model ◽  
Striped Bass ◽  
Carrying Capacity ◽  
Field Data ◽  
Larval Growth ◽  
Fish Population ◽  
Potomac River ◽  
Average Growth ◽  
Density Dependent ◽  
Dependent Growth

Abstract Quantifying the degree of density-dependence in stock–recruit relationships is critical to understanding fish population dynamics. The Shepherd and Cushing (1980) model couples a simple model of density-dependent larval growth with a constant rate of mortality to predict numbers surviving to recruitment. The model has not been evaluated using field data, nor have its predictions been compared with those from other models. Here, the S&C model, an individual-based model (IBM), and a regression model are applied to 8 years of field data for striped bass larvae in the Potomac River, Maryland, USA, to predict larval carrying capacity (K) and percentage of recruitment lost as a consequence of density-dependent growth. The IBM and the regression model were corroborated by comparing their predictions of average growth rates of larvae and relative recruitment strengths to observed values for the 8 years of field data. Although the IBM and the regression model differed in their predictions of several important intermediate variables, both models predicted higher values of K and lower values of density-dependent growth than did the S&C model. Over the 8 years, the IBM and the regression model predicted an average of 0.3 and 1.8% recruitment lost as a result of density-dependent growth, respectively. In contrast, the S&C model predicted much higher recruitment lost (average of 27%). Slight differences in the assumed rate of mortality used in the S&C model resulted in values of carrying capacity similar to those predicted by the IBM and the regression model. Difficulties in estimating parameters of the S&C model from field data are discussed.

Competitive interactions and distributional dynamics in two Malagasy frogs

2005 ◽  
Vol 21 (5) ◽  
pp. 569-576 ◽  
Author(s):  
Richard M. Lehtinen
Keyword(s):  
Growth Rates ◽  
Field Data ◽  
Community Dynamics ◽  
Interspecific Interactions ◽  
Larval Growth ◽  
Competitive Interactions ◽  
Frog Species ◽  
Distributional Dynamics ◽  
Population And Community Dynamics ◽  
Forest Plants

Ecological theory predicts that interspecific interactions can affect population and community dynamics. Two experiments were conducted on Mantidactylus bicalcaratus and M. punctatus, two sympatric frog species from Madagascar that live and breed in rain-forest plants (Pandanus spp.), to test for interspecific competition. The first experiment examined larval growth rates and survivorship with and without conspecifics. While survivorship did not differ among treatments, mean growth rates for M. bicalcaratus were significantly reduced in the presence of M. punctatus larvae. The second experiment manipulated the presence and density of adults in Pandanus plants. Emigration from and immigration to experimental plants tended to be higher and lower, respectively, for M. bicalcaratus in the presence of M. punctatus, but these differences were not significant. These results demonstrate asymmetric competition (at least as larvae) and indicate that M. punctatus is the superior competitor. Field data showed that M. bicalcaratus was found significantly more frequently in the absence of M. punctatus. Also, M. bicalcaratus populations were significantly more likely to go locally extinct in the presence of M. punctatus. These data suggest that asymmetric competitive interactions are important influences on the dynamics of these populations.

The effects of spatial habitat structure on the evolution of density-dependent growth and reproduction in freshwater snails

Hydrobiologia ◽  
2005 ◽  
Vol 533 (1-3) ◽  
pp. 229-241 ◽  
Author(s):  
Masakado Kawata ◽  
Hiroshi Sawada ◽  
Jun Yokoyama ◽  
Lázaro M. Echenique-Díaz ◽  
Yasuyuki Ishibashi
Keyword(s):  
Habitat Structure ◽  
Freshwater Snails ◽  
Density Dependent ◽  
Dependent Growth ◽  
Spatial Habitat ◽  
Growth And Reproduction
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