RESUMO

Allometric growth is a common feature during fish larval development. It has been proposed as a growth strategy to prioritize the development of body segments related to primordial functions like feeding and swimming to increase the probability of survival during this critical period. In the present study we evaluated the allometric growth patterns of body segments associated to swimming and feeding during the larval stages of Pacific red snapper Lutjanus peru. The larvae were kept under intensive culture conditions and sampled every day from hatching until day 33 after hatching. Each larva was classified according to its developmental stage into yolk-sac larva, preflexion larva, flexion larva or postflexion larva, measured and the allometric growth coefficient of different body segments was evaluated using the potential model. Based on the results we can infer the presence of different ontogenetic priorities during the first developmental stages associated with vital functions like swimming during the yolk-sac stage [total length (TL) interval = 2.27-3.005 mm] and feeding during the preflexion stage (TL interval = 3.007-5.60 mm) by promoting the accelerated growth of tail (post anal) and head, respectively. In the flexion stage (TL interval = 5.61-7.62 mm) a change in growth coefficients of most body segments compared to the previous stage was detected, suggesting a shift in growth priorities. Finally, in the postflexion stage (TL interval = 7.60-15.48 mm) a clear tendency to isometry in most body segments was observed, suggesting that growth priorities have been fulfilled and the larvae will initiate with the transformation into a juvenile. These results provide a framework of the larval growth of L. peru in culture conditions which can be useful for comparative studies with other species or in aquaculture to evaluate the changes in larval growth due to new conditions or feeding protocols.

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RESUMO

Effective conservation and management necessitate an understanding of the ecological mechanisms that shape species life histories in order to predict how variability in natural and anthropogenic impacts will alter growth rates, recruitment, and survival. Among these mechanisms, the interaction between parturition timing and prey availability frequently influences offspring success, particularly when postnatal care is absent. Here, we assess how parturition timing and nursery conditions, including prey abundance and environmental conditions, influence the growth and potential survival of blacktip sharks (Carcharhinus limbatus) in western Gulf of Mexico (GOM) estuaries over their first year. Catch data from long-term gillnet monitoring allowed for clear delineation of cohorts based on size frequency distribution plots, and showed that late parturition cohorts born in estuaries with fewer prey resources exhibited more rapid growth than early parturition cohorts that experienced more abundant prey. Compensatory behaviors that promoted accelerated growth led to reduced second year residency, likely due to reduced survival resultant from greater risk taking and potentially due to reduced site fidelity attributed to larger body size. Water temperatures influenced blacktip growth rates through physiological increases in metabolism and potential premigratory foraging cues associated with cooling temperatures. Gradual warming of the GOM (0.03°C year-1) was also correlated with earlier parturition across the study period (1982-2017), similar to other migratory species. Considering current trends in climate and associated phenological shifts in many animals, testing hypotheses assessing compensatory growth-risk trade-offs is important moving forward to predict changes in life histories and associated recruitment in concert with current and future conservation actions, like wildlife management.

RESUMO

The first record of the amphioxus Branchiostoma californiense on seagrass patches of Halodule wrightii in the Gulf of California is reported. Sixty individuals (19 males, 18 females, and 23 undifferentiated) were collected in May 2017 at Bahía Balandra, Gulf of California, from subtidal seagrass patches at a depth of 0.5 m at low tide. The length and weight ranged from 15.88-28.44 mm and from 0.01-0.11 g for females and 11.7-27.9 mm and 0.01-0.09 g for males, respectively. The minimum size of sexually mature individuals was 11.70 mm for males and 15.88 mm for females; 62% of the specimens were sexually mature. Analysis of the total length-weight relationship suggested an allometric growth pattern among females, males and undifferentiated individuals, whereas an analysis of the entire sample suggested an isometric growth pattern. Typical and additional morphological characters were used to identify the amphioxi. High morphological variability between individuals was found, suggesting the presence of several morphotypes. Branchiostoma californiense had been previously reported as exclusively associated with bare sandy areas, but our study shows that this species can also be found in seagrass patches, using them as breeding and feeding grounds. Thus, seagrass patches are evidenced as suitable habitats for amphioxus.

RESUMO

The objective of the present study was to estimate and compare allometric coefficients of the major chemical components of meat quail raised in different thermal environments, based on protein weight of feather free body (FFB) and feathers. In total, 300 meat quail, males and females, were distributed in a completely randomized design with 2 treatments (climatized environment, 26°C, and non-climatized environment, 29°C) and 6 replicates of 25 birds each. On the first day, 36 birds were selected to form the reference group and from this day on, 2 quail were weekly sampled from each cage. All selected birds were fasted for 24 h, weighed, slaughtered, plucked, and reweighed. The FFB and feathers were ground separately to obtain homogeneous samples, which were freeze-dried to determine the water content, and thereafter, ground again in a micromill before analyzing for protein, lipid, and ash using AOAC procedures. The adjustment of the allometric equations was made using crude protein (CP) weight as the independent variable and water, lipid, and ash weight as the dependent variables. The data of each dependent variable were transformed into natural logarithm (ln), regressed according to lnCP, and subjected to a parallelism test. In the FFB, water showed early development and lipid and ash showed late development in relation to the CP weight. In feathers, water and ash weight showed early development in relation to the feathers protein weight, whereas lipids showed late development. The environments of 26°C and 29°C did not affect the allometric coefficients that described the growth between the chemical components in the body and in the feathers, except for lipids in male FFB, that showed higher allometric coefficient at 29°C than 26°C. Describing the allometric relationships between the major chemical components of meat quail body is an important step in supporting future research comprised modeling of body growth and nutrition for meat quail.

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RESUMO

Abstract Length and weight relationships and descriptive statistics are reported for six shrimp species caught off the Madeira archipelago between 1983 and 2014 using bottom and floating traps from depths ranging from 50 to 1,300 m. The parameter b ranged between 2.36 for Plesionika ensis and 2.97 for Plesionika williamsi. All species showed a pattern of negative allometric growth. To the authors' knowledge all weight-length relationships presented herein are recorded for the first time from the Madeira area, and in the cases of Ligur ensiferus and Plesionika ensis are the first references worldwide.

Resumo As relações peso-comprimento e a estatística descritiva foram estimadas para seis espécies de camarões, capturados ao largo do arquipélago da Madeira, entre 1983 e 2014, usando armadilhas de fundo e alvoradas entre os 50 e 1.300 metros de profundidade. O parâmetro b variou entre 2,36 para Plesionika ensis e 2,97 para Plesionika williamsi. Todas as espécies evidenciaram um padrão de crescimento alométrico negativo. De acordo com o conhecimento dos autores, todas as relações peso-comprimento são aqui apresentadas pela primeira vez para a área da Madeira e no caso de Ligur ensiferus e Plesionika ensis são a primeira referência mundial.

Assuntos

RESUMO

Length and weight relationships and descriptive statistics are reported for six shrimp species caught off the Madeira archipelago between 1983 and 2014 using bottom and floating traps from depths ranging from 50 to 1,300 m. The parameter b ranged between 2.36 for Plesionika ensis and 2.97 for Plesionika williamsi. All species showed a pattern of negative allometric growth. To the authors knowledge all weight-length relationships presented herein are recorded for the first time from the Madeira area, and in the cases of Ligur ensiferus and Plesionika ensis are the first references worldwide.(AU)

As relações peso-comprimento e a estatística descritiva foram estimadas para seis espécies de camarões, capturados ao largo do arquipélago da Madeira, entre 1983 e 2014, usando armadilhas de fundo e alvoradas entre os 50 e 1.300 metros de profundidade. O parâmetro b variou entre 2,36 para Plesionika ensis e 2,97 para Plesionika williamsi. Todas as espécies evidenciaram um padrão de crescimento alométrico negativo. De acordo com o conhecimento dos autores, todas as relações peso-comprimento são aqui apresentadas pela primeira vez para a área da Madeira e no caso de Ligur ensiferus e Plesionika ensis são a primeira referência mundial.(AU)

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RESUMO

Spiny lobsters have a protracted pelagic, oceanic larval phase. The final larval stage metamorphoses into a non-feeding postlarva (puerulus) that actively swims towards the coast to settle in shallow habitats and does not resume feeding until after the molt into the first-stage juvenile. Therefore, the body dimensions and nutritional condition of both settled pueruli and first juveniles are likely to vary over time, potentially playing a crucial role in the recruitment to the benthic population. We compared carapace length (CL), height (CH), and width (CW); total length (TL), and body weight (W) between pueruli and first juveniles of the Caribbean spiny lobster, Panulirus argus, as well as morphometric relationships between both developmental stages. Except for CL, all other dimensions were larger in first juveniles, but more markedly CH and W. The slopes of the CH vs CL, CW vs CL, and W vs CL regressions differed significantly between stages, and all log-transformed relationships showed isometry in both stages, except for the CH vs CL relationship, which showed positive allometry. These results reflect a morphological change from the flatter, more streamlined body of the puerulus, to the heavier, more cylindrical body of the juvenile. We also analyzed seasonal variations in CL, W, the W/CL index (a morphometric condition index), and a modified W/CL index (i.e. after controlling for a significant effect of CL) of both stages using individuals monthly collected over 12 consecutive seasons (Autumn 2010-Summer 2013). In both stages, all three variables exhibited significant seasonal variation. For pueruli, the modified W/CL index differed from average in only two seasons, winter 2011 (higher) and summer 2013 (lower), but showed great within-season variation (larger coefficients of variation, CV), potentially reflecting variability in nutritional condition of larvae prior to metamorphosis and in the distances swum by individual pueruli to the settlement habitats. For first juveniles, the modified W/CL index was higher than average in winter and spring 2011, and lower in autumn 2011 and winter 2012, but showed less within season variation (smaller CVs), suggesting a combination of carry-over effects of puerulus condition and effects of local conditions (e.g., food availability and predation risk). These findings warrant further investigation into factors potentially decoupling settlement from recruitment processes.

RESUMO

We present two cases of study of ontogenetic allometry in outlines of bivalves using longitudinal data, a rarity among fossils, based on the preserved post-larval record of shells. The examples are two infaunal burrowing bivalves of the southern South America, Claibornicardia paleopatagonica (Archiheterodonta: Carditidae) (early Paleocene) and Crassatella kokeni (Archiheterodonta: Crassatellidae) (late Oligocene-late Miocene). Outline analyses were conducted using a geometric morphometric approach (Elliptic Fourier Analysis), obtaining successive outlines from shells' growth lines, which were used to reconstruct ontogenetic trajectories. In both taxa, ontogenetic changes are characterized by the presence of positive allometry in the extension of posterior end, resulting in elongated adult shells. This particular allometric growth is known in others infaunal burrowing bivalves (Claibornicardia alticostata and some Spissatella species) and the resulting adult morphology is present in representatives of several groups (e.g., Carditidae, Crassatellidae, Veneridae, Trigoniidae). Taxonomic, ecological and evolutionary implications of this allometric growth pattern are discussed.

RESUMO

Defining the appropriate scale is important when trying to understand distribution patterns in community studies. Fiddler crabs are among the most common organisms inhabiting estuarine environments, and despite having a wide latitudinal distribution, are limited by shifts in temperature, current and wind pattern. Thus, many co-occur at a local scale, where their distribution is influenced by variables such as mean sediment grain diameter, salinity and tidal level. Our goal was to test intra and interspecific segregation in two similar and commonly co-occurring fiddler crabs species (Leptuca leptodactyla and Leptuca uruguayensis) at a small scale (10 m²). Interspecific segregation was observed, with L. leptodactyla occurring mainly at the upper level in relation to the water line and L. uruguayensis, at the lower. However, this pattern was irrespective of sex and developmental stage, as no intraspecific segregation was seen. Possible impacts of tidal level, soil silt/clay content and competition on interspecific segregation are discussed. Although L. leptodactyla and L. uruguayensis overlap in their occurrence when intertidal zonation is disregarded, they segregate when tidal levels are individually sampled as habitats. This highlights the importance of small-scale studies to identify patterns unobserved at regional scales, even when no environmental gradient is readily apparent.

Definir a escala apropriada de um estudo é importante quando tentamos entender os padrões de distribuição em estudos de comunidade. Caranguejos chama-maré estão entre os organismos mais comuns que habitam os ambientes estuarinos, e apesar de possuírem uma ampla distribuição latitudinal, são limitados por alterações em temperatura, correntes e padrões dos ventos. Dessa forma, muitas espécies co-ocorrem em escala local, onde suas distribuições são influenciadas por variáveis como diâmetro do grão de sedimento, salinidade e nível de maré. Nosso objetivo foi testar a segregação intra- e interespecífica em duas espécies similares de caranguejos chama-maré, que comumente são encontradas em co-ocorrência (Leptuca leptodactyla e Leptuca uruguayensis), em uma pequena escala (10 m²). Foi observada segregação interespecífica, com L. leptodactyla ocorrendo primariamente no nível superior em relação à linha de maré, e L. uruguayensis no inferior. Entretanto, esse padrão foi independente de gênero e estágio de desenvolvimento, uma vez que segregações intraespecíficas não foram registradas. Possíveis influências do nível de maré, teor de silte/argila e competição na segregação interespecífica são discutidas. Apesar de L. leptodactyla e L. uruguayensis terem sobreposição em ocorrência quando a zonação do entremarés é desconsiderada, elas segregam quando os níveis de maré são individualmente amostrados. Esse resultado destaca a importância de estudos em pequena escala para identificar padrões não observados em escala regional, mesmo quando nenhum gradiente ambiental é inicialmente observado.

Assuntos

RESUMO

ABSTRACT Defining the appropriate scale is important when trying to understand distribution patterns in community studies. Fiddler crabs are among the most common organisms inhabiting estuarine environments, and despite having a wide latitudinal distribution, are limited by shifts in temperature, current and wind pattern. Thus, many co-occur at a local scale, where their distribution is influenced by variables such as mean sediment grain diameter, salinity and tidal level. Our goal was to test intra and interspecific segregation in two similar and commonly co-occurring fiddler crabs species (Leptuca leptodactyla and Leptuca uruguayensis) at a small scale (10 m²). Interspecific segregation was observed, with L. leptodactyla occurring mainly at the upper level in relation to the water line and L. uruguayensis, at the lower. However, this pattern was irrespective of sex and developmental stage, as no intraspecific segregation was seen. Possible impacts of tidal level, soil silt/clay content and competition on interspecific segregation are discussed. Although L. leptodactyla and L. uruguayensis overlap in their occurrence when intertidal zonation is disregarded, they segregate when tidal levels are individually sampled as habitats. This highlights the importance of small-scale studies to identify patterns unobserved at regional scales, even when no environmental gradient is readily apparent.

RESUMO Definir a escala apropriada de um estudo é importante quando tentamos entender os padrões de distribuição em estudos de comunidade. Caranguejos chama-maré estão entre os organismos mais comuns que habitam os ambientes estuarinos, e apesar de possuírem uma ampla distribuição latitudinal, são limitados por alterações em temperatura, correntes e padrões dos ventos. Dessa forma, muitas espécies co-ocorrem em escala local, onde suas distribuições são influenciadas por variáveis como diâmetro do grão de sedimento, salinidade e nível de maré. Nosso objetivo foi testar a segregação intra- e interespecífica em duas espécies similares de caranguejos chama-maré, que comumente são encontradas em co-ocorrência (Leptuca leptodactyla e Leptuca uruguayensis), em uma pequena escala (10 m²). Foi observada segregação interespecífica, com L. leptodactyla ocorrendo primariamente no nível superior em relação à linha de maré, e L. uruguayensis no inferior. Entretanto, esse padrão foi independente de gênero e estágio de desenvolvimento, uma vez que segregações intraespecíficas não foram registradas. Possíveis influências do nível de maré, teor de silte/argila e competição na segregação interespecífica são discutidas. Apesar de L. leptodactyla e L. uruguayensis terem sobreposição em ocorrência quando a zonação do entremarés é desconsiderada, elas segregam quando os níveis de maré são individualmente amostrados. Esse resultado destaca a importância de estudos em pequena escala para identificar padrões não observados em escala regional, mesmo quando nenhum gradiente ambiental é inicialmente observado.

RESUMO

Abstract Length and weight relationships and descriptive statistics are reported for six shrimp species caught off the Madeira archipelago between 1983 and 2014 using bottom and floating traps from depths ranging from 50 to 1,300 m. The parameter b ranged between 2.36 for Plesionika ensis and 2.97 for Plesionika williamsi. All species showed a pattern of negative allometric growth. To the authors knowledge all weight-length relationships presented herein are recorded for the first time from the Madeira area, and in the cases of Ligur ensiferus and Plesionika ensis are the first references worldwide.

Resumo As relações peso-comprimento e a estatística descritiva foram estimadas para seis espécies de camarões, capturados ao largo do arquipélago da Madeira, entre 1983 e 2014, usando armadilhas de fundo e alvoradas entre os 50 e 1.300 metros de profundidade. O parâmetro b variou entre 2,36 para Plesionika ensis e 2,97 para Plesionika williamsi. Todas as espécies evidenciaram um padrão de crescimento alométrico negativo. De acordo com o conhecimento dos autores, todas as relações peso-comprimento são aqui apresentadas pela primeira vez para a área da Madeira e no caso de Ligur ensiferus e Plesionika ensis são a primeira referência mundial.

RESUMO

Defining the appropriate scale is important when trying to understand distribution patterns in community studies. Fiddler crabs are among the most common organisms inhabiting estuarine environments, and despite having a wide latitudinal distribution, are limited by shifts in temperature, current and wind pattern. Thus, many co-occur at a local scale, where their distribution is influenced by variables such as mean sediment grain diameter, salinity and tidal level. Our goal was to test intra and interspecific segregation in two similar and commonly co-occurring fiddler crabs species (Leptuca leptodactyla and Leptuca uruguayensis) at a small scale (10 m²). Interspecific segregation was observed, with L. leptodactyla occurring mainly at the upper level in relation to the water line and L. uruguayensis, at the lower. However, this pattern was irrespective of sex and developmental stage, as no intraspecific segregation was seen. Possible impacts of tidal level, soil silt/clay content and competition on interspecific segregation are discussed. Although L. leptodactyla and L. uruguayensis overlap in their occurrence when intertidal zonation is disregarded, they segregate when tidal levels are individually sampled as habitats. This highlights the importance of small-scale studies to identify patterns unobserved at regional scales, even when no environmental gradient is readily apparent.(AU)

Definir a escala apropriada de um estudo é importante quando tentamos entender os padrões de distribuição em estudos de comunidade. Caranguejos chama-maré estão entre os organismos mais comuns que habitam os ambientes estuarinos, e apesar de possuírem uma ampla distribuição latitudinal, são limitados por alterações em temperatura, correntes e padrões dos ventos. Dessa forma, muitas espécies co-ocorrem em escala local, onde suas distribuições são influenciadas por variáveis como diâmetro do grão de sedimento, salinidade e nível de maré. Nosso objetivo foi testar a segregação intra- e interespecífica em duas espécies similares de caranguejos chama-maré, que comumente são encontradas em co-ocorrência (Leptuca leptodactyla e Leptuca uruguayensis), em uma pequena escala (10 m²). Foi observada segregação interespecífica, com L. leptodactyla ocorrendo primariamente no nível superior em relação à linha de maré, e L. uruguayensis no inferior. Entretanto, esse padrão foi independente de gênero e estágio de desenvolvimento, uma vez que segregações intraespecíficas não foram registradas. Possíveis influências do nível de maré, teor de silte/argila e competição na segregação interespecífica são discutidas. Apesar de L. leptodactyla e L. uruguayensis terem sobreposição em ocorrência quando a zonação do entremarés é desconsiderada, elas segregam quando os níveis de maré são individualmente amostrados. Esse resultado destaca a importância de estudos em pequena escala para identificar padrões não observados em escala regional, mesmo quando nenhum gradiente ambiental é inicialmente observado.(AU)

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RESUMO

Pseudanisakis argentinensis n. sp. is proposed to accommodate parasitic nematodes found in six skate species (Rajidae and Arhynchobatidae) examined from southern Southwest Atlantic waters. The new species differs from its congeners by the following combination of characters: a cupola on each lip, males with 8-12 pairs of precloacal genital papillae, a larger size for both males and females, a greater length-to-breadth ratio of the ventriculus and the presence of a small knob on the tip of the tail. Allometric growth was observed for several morphometric features; however, the slopes of the allometric relationships across host species exhibited non-significant differences and were considered as a strong evidence for conspecificity. Congruent results were obtained after the genetic characterization of the mitochondrial cytochrome c oxidase subunit 1 gene of worms obtained from different skate species, whose values of genetic divergence (1.3) lay within the range of intraspecific variation. Previous records of specimens referred to as Pseudanisakis tricupola in skates from South American waters are regarded as conspecific with P. argentinensis n. sp.

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RESUMO

This study describes the morphology, morphometry and meristic characters of larval and juvenile Tatia intermedia collected in the middle Tocantins River and some of its tributaries. Six larvae of T. intermedia were examined and they have a moderately elongate body, head slightly dorso-ventrally depressed with a convex snout, small and round eyes and a subterminal mouth. In five juvenile stages observed, the head and eye are relatively smaller than in the larval stage and the snout remains convex and mouth becomes terminal.

Assuntos

RESUMO

Abstract Length and weight relationships and descriptive statistics are reported for six shrimp species caught off the Madeira archipelago between 1983 and 2014 using bottom and floating traps from depths ranging from 50 to 1,300 m. The parameter b ranged between 2.36 for Plesionika ensis and 2.97 for Plesionika williamsi. All species showed a pattern of negative allometric growth. To the authors knowledge all weight-length relationships presented herein are recorded for the first time from the Madeira area, and in the cases of Ligur ensiferus and Plesionika ensis are the first references worldwide.

Resumo As relações peso-comprimento e a estatística descritiva foram estimadas para seis espécies de camarões, capturados ao largo do arquipélago da Madeira, entre 1983 e 2014, usando armadilhas de fundo e alvoradas entre os 50 e 1.300 metros de profundidade. O parâmetro b variou entre 2,36 para Plesionika ensis e 2,97 para Plesionika williamsi. Todas as espécies evidenciaram um padrão de crescimento alométrico negativo. De acordo com o conhecimento dos autores, todas as relações peso-comprimento são aqui apresentadas pela primeira vez para a área da Madeira e no caso de Ligur ensiferus e Plesionika ensis são a primeira referência mundial.

RESUMO

The implementation of elemental chlorine-free (ECF) bleaching methods has drastically reduced the aquatic toxicity of Kraft mill effluents during the last decade. However, the residual toxicity of Kraft mill effluents is still a potential concern for the environment, even when subjected to secondary wastewater treatment. The aim of this study is characterize potential sublethal effects of ECF Kraft mill effluents using Daphnia magna as model species. D. magna exposed towards increasing concentration of ECF Kraft mill effluent showed a significant, dose-dependent reduction in feeding. Conversely, post-feeding assay, life history, and allometric growth analyses showed stimulatory, rather than inhibitory effects in exposed animals at low concentrations, while high concentrations of ECF Kraft mill effluents reduced their reproductive output. These results suggest a hormetic effect in which moderate concentrations of the effluent had a stimulatory effect with higher concentrations causing inhibition in some variables.

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RESUMO

A weight-length relationship was established for Corydoras paleatus (Jenyns, 1842) (Siluriformes, Callichthyidae) (n=596) from samples taken in November-December 2009 and March-April 2010, in Pinguela Lagoon (29°46'57"S; 50°11'16"W), Rio Grande do Sul, Brazil. The species showed a polyphasic allometric growth pattern, each stanza described by an independent power equation controlled by a switch function: W = a1Lb1 ∙ (1 + eRsc ∙ (L-SCP))-1 + a2Lb2 ∙ [1 - (1 + eRsc ∙ (L-SCP))-1] ; where W is the expected weight for a specific length L, a1 and a2 are the proportionality coefficients for stanzas 1 and 2, b1 and b2 are the allometric coefficients for stanzas 1 and 2, Rsc is the stanza changing rate for the switch function and SCP is the stanza changing point for the switch function. The stanza changing point was estimated as 5.28 cm, corresponding with the length at first maturity for this species Lmat (5.29 cm). Our data suggest that a complex growth pattern can be in nature, and perhaps not often identified because trends are obscured by natural variability.(AU)

Foi estabelecida uma relação peso-comprimento para Corydoras paleatus (Jenyns, 1842) (Siluriformes, Callichthyidae) (n = 596) a partir de amostras obtidas em novembro-dezembro de 2009 e março-abril de 2010, na lagoa da Pinguela (29°46'57"S; 50°11'16"W), Rio Grande do Sul, Brasil. A espécie apresentou um padrão de crescimento alométrico polifásico, cada estágio descrito por uma equação de potência independente e controladas por uma função de interruptora: W = a1Lb1 ∙ (1 + eRsc ∙ (L-SCP))-1 + a2Lb2 ∙ [1 - (1 + eRsc ∙ (L-SCP))-1] ; onde W é o peso esperado para um comprimento L, a1 e a2 são os coeficientes de proporcionalidade para as fases 1 e 2, b1 e b2 são os coeficientes alométricos para as fases 1 e 2, Rsc é a taxa de mudança de fase e SCP é o ponto de mudança de fase. O ponto de mudança fase foi estimado em 5,28 cm, correspondendo com o comprimento de primeira maturação desta espécie (Lmat) (5,29 cm). Nossos dados sugerem que um padrão de crescimento complexo pode ser frequente na natureza, e que talvez muitas vezes não seja identificado porque as tendências são obscurecidas pela variabilidade natural.(AU)

Assuntos

RESUMO

A weight-length relationship was established for Corydoras paleatus (Jenyns, 1842) (Siluriformes, Callichthyidae) (n=596) from samples taken in November-December 2009 and March-April 2010, in Pinguela Lagoon (29°46'57"S; 50°11'16"W), Rio Grande do Sul, Brazil. The species showed a polyphasic allometric growth pattern, each stanza described by an independent power equation controlled by a switch function: W = a1Lb1 ∙ (1 + eRsc ∙ (L-SCP))-1 + a2Lb2 ∙ [1 - (1 + eRsc ∙ (L-SCP))-1] ; where W is the expected weight for a specific length L, a1 and a2 are the proportionality coefficients for stanzas 1 and 2, b1 and b2 are the allometric coefficients for stanzas 1 and 2, Rsc is the stanza changing rate for the switch function and SCP is the stanza changing point for the switch function. The stanza changing point was estimated as 5.28 cm, corresponding with the length at first maturity for this species Lmat (5.29 cm). Our data suggest that a complex growth pattern can be in nature, and perhaps not often identified because trends are obscured by natural variability.

Foi estabelecida uma relação peso-comprimento para Corydoras paleatus (Jenyns, 1842) (Siluriformes, Callichthyidae) (n = 596) a partir de amostras obtidas em novembro-dezembro de 2009 e março-abril de 2010, na lagoa da Pinguela (29°46'57"S; 50°11'16"W), Rio Grande do Sul, Brasil. A espécie apresentou um padrão de crescimento alométrico polifásico, cada estágio descrito por uma equação de potência independente e controladas por uma função de interruptora: W = a1Lb1 ∙ (1 + eRsc ∙ (L-SCP))-1 + a2Lb2 ∙ [1 - (1 + eRsc ∙ (L-SCP))-1] ; onde W é o peso esperado para um comprimento L, a1 e a2 são os coeficientes de proporcionalidade para as fases 1 e 2, b1 e b2 são os coeficientes alométricos para as fases 1 e 2, Rsc é a taxa de mudança de fase e SCP é o ponto de mudança de fase. O ponto de mudança fase foi estimado em 5,28 cm, correspondendo com o comprimento de primeira maturação desta espécie (Lmat) (5,29 cm). Nossos dados sugerem que um padrão de crescimento complexo pode ser frequente na natureza, e que talvez muitas vezes não seja identificado porque as tendências são obscurecidas pela variabilidade natural.

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ABSTRACT A weight-length relationship was established for Corydoras paleatus (Jenyns, 1842) (Siluriformes, Callichthyidae) (n=596) from samples taken in November-December 2009 and March-April 2010, in Pinguela Lagoon (29°46'57"S; 50°11'16"W), Rio Grande do Sul, Brazil. The species showed a polyphasic allometric growth pattern, each stanza described by an independent power equation controlled by a switch function: W = a1Lb1 (1 + eRsc (L-SCP))-1 + a2Lb2 [1 - (1 + eRsc (L-SCP))-1] ; where W is the expected weight for a specific length L, a1 and a2 are the proportionality coefficients for stanzas 1 and 2, b1 and b2 are the allometric coefficients for stanzas 1 and 2, Rsc is the stanza changing rate for the switch function and SCP is the stanza changing point for the switch function. The stanza changing point was estimated as 5.28 cm, corresponding with the length at first maturity for this species Lmat (5.29 cm). Our data suggest that a complex growth pattern can be in nature, and perhaps not often identified because trends are obscured by natural variability.

RESUMO Foi estabelecida uma relação peso-comprimento para Corydoras paleatus (Jenyns, 1842) (Siluriformes, Callichthyidae) (n = 596) a partir de amostras obtidas em novembro-dezembro de 2009 e março-abril de 2010, na lagoa da Pinguela (29°46'57"S; 50°11'16"W), Rio Grande do Sul, Brasil. A espécie apresentou um padrão de crescimento alométrico polifásico, cada estágio descrito por uma equação de potência independente e controladas por uma função de interruptora: W = a1Lb1 (1 + eRsc (L-SCP))-1 + a2Lb2 [1 - (1 + eRsc (L-SCP))-1] ; onde W é o peso esperado para um comprimento L, a1 e a2 são os coeficientes de proporcionalidade para as fases 1 e 2, b1 e b2 são os coeficientes alométricos para as fases 1 e 2, Rsc é a taxa de mudança de fase e SCP é o ponto de mudança de fase. O ponto de mudança fase foi estimado em 5,28 cm, correspondendo com o comprimento de primeira maturação desta espécie (Lmat) (5,29 cm). Nossos dados sugerem que um padrão de crescimento complexo pode ser frequente na natureza, e que talvez muitas vezes não seja identificado porque as tendências são obscurecidas pela variabilidade natural.

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This study described the initial development of Pseudoplatystoma reticulatum, as well as changes in growth patterns. Morphometric and meristic variables were analyzed during embryonic, larval and juvenile periods, even as allometric growth coefficients for larvae and juveniles. Eggs showed an average diameter of 1.79 mm and broad perivitelline space (23.41%). The total length (TL) of the larvae ranged from 3.05 to 25.72 mm, and the total number of myomeres ranged from 45 to 50 (preanal = 13-16 and postanal = 30-35). Initial pigmentation is poor, concentrated at the extremities of the yolk sac. In the flexion stage, the pigmentation intensifies and forms a longitudinal stripe extending from the snout to the operculum and two longitudinal stripes on the body, one dorsal and the other ventral, that unite at the caudal peduncle. At first, there is a differential growth of the head and tail, and then there is the growth of the body, which shows changes in the ontogenetic priorities of feeding, swimming, and breathing capacities. Our results are very important for ecology, systematics, and hatchering, especially in terms of ontogenetic variation in morphology, growth, feeding, behavior, and mortality of P. reticulatum.(AU)

Este estudo descreveu o desenvolvimento inicial de Pseudoplatystoma reticulatum, bem como as mudanças nos padrões de crescimento, testando a hipótese da ocorrência de crescimento diferencial durante a ontogenia inicial da espécie. Variáveis morfométricas e merísticas foram analisadas durante os períodos embrionário, larval e juvenil, assim como os coeficientes de crescimento alométrico para larvas e juvenis. Os ovos apresentaram diâmetro médio de 1,79 mm e espaço perivitelino amplo (23,41%). O comprimento total (CT) das larvas variou de 3,05 a 125,72 mm e o número total de miômeros de 45 a 50 (pré-anal=13-16 e pós-anal=30-35). A pigmentação inicial é escassa, concentrada nas extremidades do saco vitelino. A partir do estágio de flexão a pigmentação se intensifica, formando uma faixa longitudinal que se estende do focinho ao opérculo e duas no corpo, uma dorsal e outra ventral, que se unem no pedúnculo caudal. Inicialmente há um crescimento diferenciado da cabeça e da cauda, com posterior crescimento do tronco, que demonstra mudanças nas prioridades ontogenéticas para as capacidades de alimentação, natação e respiração. Nossos resultados são de grande importância para a ecologia, sistemática e larvicultura, especialmente em termos de variação ontogenética na morfologia, crescimento, alimentação, comportamento e mortalidade P. reticulatum.(AU)

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