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

Abstract

Some decapod species have intraspecific morphological variations that result in distinct adult morphotypes that influence the population structure, social dominance, and reproduction of the population. Here we investigated whether this differentiation into morphotypes occurs in adult males of Macrobrachium brasiliense, through the analysis of relative growth and morphology. Specimens were collected in the region of Uberlândia, Minas Gerais state, southeastern Brazil. Seven dimensions of each male were measured: carapace length (CL), ischium length, merus length, carpus length, propodus length, dactylus length, and major cheliped length. Principal component analysis, clustering, and discriminant analyses were used to identify possible morphotypes. The analysis of relative growth was employed to estimate the growth patterns of body structures (dependent variables) in relation to the CL (independent variable). Two morphotypes were identified: Mirim, which has less developed chelipeds (23.31 ± 3.08 mm) with fewer spines, and Açu, which has larger chelipeds (41.39 ± 8.14 mm) with many well‐developed spines, especially in the merus. Most morphometric relationships differed significantly (p < .01) between the two morphotypes. The chelipeds were useful characters for the identification of the morphotypes of M. brasiliense, corroborating previous descriptions of the genus. We provide a detailed description of the main macroscopic characteristics that differed between morphotypes, which will enable their identification in future studies. Our results contribute to the knowledge of the population biology of M. brasiliense and should be considered in future investigations, since the presence of these male morphotypes probably influences the reproductive biology and population ecology of the species.

Integrated morphometric and molecular analyses indicate three male morphotypes in the freshwater prawn Macrobrachium olfersii (Decapoda, Palaemonidae) along the Brazilian neotropical region

“…For many decapods, the smallest cheliped is used for food capture and grooming, while the biggest plays an important role in agonistic, social and reproductive behaviour (Mariappan et al, 2000). As the biggest second pereiopod, the major cheliped length (P2L) and its propodus length (P2PL) were the variables with greater contributions in the PCA analysis in the present study, these dimensions separated the three morphotypes, corroborating the findings of previous studies (Moraes‐Riodades & Valenti, 2004; Nogueira et al, 2020; Pantaleão et al, 2014) with Macrobrachium male morphotypes.…”

“…The presence of male morphotypes was observed in approximately 24 world species of Macrobrachium (see the revision of Karplus & Barki, 2019), including some representatives from the neotropical regions independently of the life cycle pattern, that is abbreviated larval development (ALD) or extended larval development (ELD) (for details and definitions see Anger, 2013; Pereira & Garcia, 1995). To cite, Macrobrachium brasiliense that has ALD pattern (Nogueira et al, 2020), and M. rosenbergii , M. amazonicum and M. acanthurus that have ELD pattern (Kuris et al, 1987; Moraes‐Riodades & Valenti, 2004; Pantaleão et al, 2014; Rios et al, 2021).…”

“…All the morphological analyses were performed at LBSC/FFCLRP/USP under stereomicroscope ZEISS® (SV Stemi 6) and/or Leica® (MD 1000). Following previous results from literature (Kuris et al, 1987; Moraes‐Riodades & Valenti, 2004; Nogueira et al, 2020; Pantaleão et al, 2014; Rios et al, 2021), we selected some dimensions of the biggest second pereiopod that were frequently effective to differentiate Macrobrachium male morphotypes. The following measures were obtained using a digital caliper for each specimen (male and female): TL = total length (from the beginning of the rostrum to the posterior portion of the telson); CL = carapace length (from the posterior edge of the orbit to the posterior edge of the carapace); PlW = width of the pleura of the second abdominal segment; P2L = length of the biggest second pereiopod (cheliped); P2PL = length of the propodus (chela) of the biggest second pereiopod (Figure 2).…”

“…In decapod crustaceans, morphometric studies have been widely used to discriminate populations (Chace & Bruce, 1993; Jayachandran & Joseph, 1988; Karplus et al, 2000; Konan et al, 2008) or intrapopulation groups (Mossolin & Bueno, 2003; Nobrega et al, 2014; Nogueira et al, 2020; Pantaleão et al, 2014; Zimmermann et al, 2012). Considering that the available studies on morphotypes of Macrobrachium were developed only with a focus on the local population of each studied species and its males, we found that M. olfersii like a promising model to check the presence of possible morphotypes in both sexes.…”

Filling gaps in the biology of the endemic and threatened freshwater shrimp Macrobrachium candango (Caridea: Palaemonidae) through basic morphometric and reproductive approaches

“…The lack of a laterality pattern seems to be a common feature in Macrobrachium species that have heterochely, this was also observed in Macrobrachium olfersii (Wiegmann, 1836) by Mossolin and Bueno (2003), and in Macrobrachium brasiliense (Heller, 1862) by Nogueira et al (2020), where the males and females analyzed did not have a constant between which propodus (left or right) would be the most developed. Therefore, it has been suggested that this characteristic (i.e., laterality) may not be genetically predetermined (Mossolin and Bueno, 2003).…”