Ocurrence of male morphotypes of Macrobrachium amazonicum (Caridea, Palaemonidae) in a population with an entirely freshwater life cycle

Abstract

This study records, for the first time, the occurrence of all four male morphotypes in a population of Macrobrachium amazonicum from a continental environment, with an entirely freshwater life cycle. The specimens studied came from the Tietê River, state of São Paulo, Brazil, and were collected in a lotic environment downstream from Ibitinga Dam. This population was compared with other continental populations, including a population from the dam itself, collected in a previous study. Four samples of 30 minutes were taken monthly, using a trap, from January to April 2011. Each male specimen was measured with respect to seven body dimensions as follows: carapace length (CL), right cheliped length (RCL), dactyl length (DCL), propodus length (PPL), carpus length (CRL), merus length (ML) and ischium length (IL). The relative growth was analyzed based on the change in growth patterns of certain body parts in relation to the independent variable CL. The four male morphotypes proposed for the species were found using morphological and morphometric analyses. Different biological characteristics were found between the populations studied. The male population of the lake of Ibitinga and from Pantanal presented mean sizes and number of morphotypes lower than the population studied here. These differences seem to be closely related to ecological characteristics of the environments inhabited by these populations. Our results supported the hypothesis that coastal and continental populations of M. amazonicum belong to the same species.Keywords: freshwater prawn, allometry, Tietê River, Amazon River Prawn, morphotype characterization. Ocorrência de morfotipos em machos de Macrobrachium amazonicum(Caridea, Palaemonidae) em uma população com ciclo de vida completamente dulcícola ResumoEste estudo registra, pela primeira vez, a ocorrência dos quatro morfotipos de Macrobrachium amazonicum em uma população continental com ciclo de vida totalmente dulcícola. Os camarões são provenientes do Rio Tietê, estado de São Paulo, Brasil, e foram coletados em um ambiente lótico abaixo da Barragem de Ibitinga. Essa população foi comparada com outras populações provenientes de ambientes continentais, incluindo a de um estudo anterior na represa da barragem de Ibitinga. Quatro amostras de 30 minutos foram realizadas mensalmente, utilizando armadilhas, de janeiro a abril de 2011. Cada indivíduo macho foi mensurado em relação a sete dimensões corporais, sendo elas: comprimento da carapaça (CL), comprimento total do quelípodo direito (RCL), comprimento do dáctilo (DCL), comprimento do própodo (PPL), comprimento do carpo (CRL), comprimento do mero (ML) e comprimento do ísquio (IL). O crescimento relativo foi analisado de acordo com as mudanças nas taxas de crescimento de determinadas partes do corpo em relação à variável independente CL. Os quatro morfotipos descritos para a espécie foram encontrados, utilizando análises morfológicas e morfométricas. Diferentes características biológicas foram encontradas entre a população estudada e as demais...

Growth and reproductive biology of the amphidromous shrimp Palaemon pandaliformis (Decapoda: Caridea) in a Neotropical river from northeastern Brazil

“…These studies concluded that species from inland waters have larger eggs and lower fecundity (and probably a higher RO) than marine species. Therefore, the hypothesis that Palaemonidae are undergoing a process of adaptation and colonization of freshwater environments ("freshwaterization"), as proposed by ODinetz-collart & Rabelo (1996) and Ashelby et al (2012), and registered by Pantaleão et al (2014), is supported when we compare the reproductive characteristics of marine species with those of P. pandaliformis.…”

Male morphotypes of the freshwater prawn Macrobrachium brasiliense (Decapoda: Caridea: Palaemonidae)

“…These morphotypes differed mainly in body size and in the morphology of the major chelipeds. They also differed with respect to the allometric growth pattern of the segments of the major chelipeds, as observed in other species of Macrobrachium (Kuris et al, ; Moraes‐Riodades & Valenti, ; Pantaleão et al, ; Wortham & Maurik, ).…”

“…Among the morphotype characteristics, the spine sets of the chelipeds may be quite variable, as seen in M. amazonicum (Moraes‐Riodades & Valenti, ; Pantaleão et al, ). According to Moraes‐Riodades and Valenti (), the spines are one of the structures used by males during agonistic encounters, to ensure their reproductive success, or during disputes for shelter and food.…”

“…After obtaining the results of the statistical analyses, we searched for macroscopic morphological characters to differentiate the male morphotypes. We investigated the ornamentation and angulation of the spines of the major cheliped, since these characters were important in M. amazonicum (Moraes‐Riodades & Valenti, ; Pantaleão, Hirose, & Costa, ) and M. rosenbergii (Kuris et al, ). The chelipeds of 10 individuals were analyzed per group, and 10 spines per cheliped segment of the largest second cheliped were measured.…”

Length/weight relationship and condition factor of Macrobrachium jelskii (Miers, 1877) and M. brasiliense (Heller, 1862) (Decapoda, Palaemonidae) in two locations in the state of São Paulo

“…The different increase in weight between sexes is related to the larger body size and larger chelipeds in males (Boschi, 1974;Pantaleão et al, 2014), as well as the gonadal development in adults over an extended period, and the slower growth rate when compared to females, as explained for M. jelskii. Additionally, females of M. brasiliense develop gonads only one period of the year, which reduces their weight and results in a negative allometric growth (Taddei, 2006).…”