Introduction

The prawns of the genus Macrobrachium (Crustacea: Decapoda: Caridea: Palaemonidae) are a diverse group of freshwater and estuarine organisms, with 283 valid species (De Grave and Fransen 2011). These species are distributed worldwide in tropical and subtropical regions (Murphy and Austin 2005), and they play an important role in the environmental dynamics of rivers, freshwater, and coastal water bodies (García-Guerrero et al. 2013). They have, as well, economic importance: around the world, several species of Macrobrachium are subject to fisheries, and only two species are widely and intensively cultured: the giant freshwater prawn M. rosenbergii and the oriental river prawn M. niponense (FAO 2022).

In America, there are approximately 55 species of the genus Macrobrachium (Pileggi et al. 2014), but only five species (M. carcinus, M. acanthurus, M. tenellum, M. americanum, and M. amazonicum) are widely captured and have economic importance for local communities of fishermen (Loran-Núñez 2017; Agüero-Fernández et al. 2022). However, natural populations of these Macrobrachium species are declining along the continent due to several factors: artisanal fisheries that are not regulated; the numbers of extractions are not officially reported and prevents to have proper capture management; contamination with municipal and industrial water discharges and constructions of dams that affect the migration of the organisms (García-Guerrero et al. 2013; Loran-Núñez 2017; Kutty and Valenti 2010). The culture of these species has been suggested for several years now, as an alternative to fisheries, help to decrease the pressure on wild populations, provide local fishermen with economic resources, and benefit the communities settled on the banks of the rivers by providing them with protein-rich food (Agüero-Fernández et al. 2022).

According to Kutty and Valenti (2010) and Moraes-Valenti and Valenti (2010), the status of the culture development for the American species ranges from “researching” to “pilot culture projects.” Particularly, the Cinnamon River shrimp (Macrobrachium acanthurus) has several characteristics that make it a suitable species for aquaculture, like resistance to changes in environmental conditions, reproduction all year round, high fecundity, low aggressivity or cannibalism, and disease resistance (Kutty and Valenti 2010).

During the decades of the 1970s and 1980s, there was an impulse for culturing this species in several countries of America (mainly in the United States, Mexico, and Brazil), and this is reflected in the available literature, as nearly half of the references are before 2010. However, no significant progress has been done in the 14 years, even though this species represents the third most studied species in Latin America, just after M. carcinus and M. amazonicum (Chong-Carrillo et al. 2015, 2018). The foregoing highlights the interest that the species has for the scientific community in the region, not only as an organism of biological interest, but also to lay the foundations for the development of cultivation technology, which seem to be an option for the conservation of this species in the face of the alarming loss of natural populations and the natural water systems. For these reasons, the aim of this review is to present the actual knowledge regarding the environmental and biological conditions of M. acanthurus that might help to develop its culture. The information is presented in several parts, which include the species description, environmental conditions, reproduction, larvae and juvenile stages, culture experience, and diseases.

Species description

Macrobrachium acanthurus (Wiegmann, 1836) is distributed in rivers, lagoons, and estuarine zones throughout the American continent (Albertoni et al. 2002) along the Atlantic coast, from North Carolina, United States until Rio Grande do Sul, Brazil (Bowles et al 2000).

On the other hand, Carrillo (1968) and Bowles et al. (2000) reported specific morphological characteristics of the species: the rostrum of M. acanthurus is sharp and almost flat, with 8–11 teeth in the dorsal margin and 4–6 in the ventral margin. There is sexual dimorphism: adult males reach a total length of 166 mm, while females a maximum of 110 mm (Fig. 1). Males present a small filiform structure near the base of the second pair of pleopods and another globular structure called gonopore in the fifth pair of the pereiopods. In females, the gonopore is in the base of the third pair of pereiopods. However, the most relevant morphological characteristic in males is the elongated carpus and the palm of the propodus, which gives a very long second pair of pereiopods and are nearly equal in length to the body. Recently, Rios et al. (2021) reported the occurrence of three morphotypes of males found in the Jequitinhonha River in Brazil. The authors found sexually mature males with different morphology and size of the second pair of pereiopods, and they classified them in the morphotypes M3 or dominant M2 or subdominant, and M1 or subordinate, which resembles the morphology of females.

Fig. 1
figure 1

External morphology of the freshwater prawn Macrobrachium acanthurus: a close-up the rostrum of a male, showing nine teeth in the dorsal margin of the rostrum and six in the ventral margin; b comparative sizes of adults male and female; c an ovigerous female, and d male showing the size of the second pair of pereiopods

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Regarding color, living animals are from translucid to yellow-brownish with red spots. In males, the tips of the second pair of pereiopods become darker when reaching sexual maturity, which happens as well with the three vertical purple-red bands that are found in the carapace (Bowles et al. 2000).

Interestingly, M. acanthurus is usually related to M. tenellum as a sibling species. M. tenellum is distributed on the other slope of America, the Pacific coast (from Baja California, Mexico to Peru). Morphologically and from the ecological point of view, both species are very alike, but recent information based on analysis of sequences of the 16 s, COI, and 18 s genes showed that both species are valid taxa, probably separated by a mechanism of sympatric speciation (Pileggi et al. 2014).

Temperature and salinity conditions

Among the environmental conditions, salinity and temperature have been extensively studied in the different life stages of M. acanthurus.

This species is reported to be an amphidromous species (Bauer 2013), a life history pattern in which the adults live in freshwater and migrate to estuarine areas for breeding, the larvae are fully developed in brackish water, and then juveniles return to freshwater. So, it is well known that they are adapted to changes in salinity and, indeed, are efficient osmoregulators (Cuenca et al. 2021). Regarding juvenile, the respiratory cost was the lowest at a salinity of 10‰, indicating that is the isosmotic point (Gasca-Leyva et al. 1991). Choudhury (1970) reported the rearing of larvae at different salinities, 0, 5, 10, 15, 20, 25, and 33‰, finding the maximum survival rate at 15 and 20‰. Freshwater and 33‰ caused high mortalities after 5 days of rearing. According to Ismael and Moreira (1997), the different stages of zoea larvae can develop in different salinities, but they do not survive in freshwater for more than 6 days. The same authors found that larvae have higher survival rates and lower values of oxygen consumption in salinities between 14 and 21‰. Also, Signoret and Brailovsky (1997) showed that juveniles have an isosmotic point between 8 and 10‰ and observed 100% mortality when the organisms were maintained above 24‰. The embryonic development was not affected by salinities from 10 to 17‰, but high mortalities were observed at a level of 20‰ (Fukuda et al. 2017).

Regarding temperature, juveniles showed higher locomotion and food ingestion when maintained at a range of 25–30 °C, compared with those maintained between 15 and 20 °C (Bernardi 1990). Díaz et al. (2002) reported that preferendum temperature is 29.5 °C in which growth and reproduction are maximized. The same authors state that the temperature limits were 15 °C for the lower and 38 °C for the higher.

Finally, Elmor et al. (1981) found that oxygen consumption was higher in the smaller organisms, and in juveniles, there is an increasing consumption just after molting.

According to all this information (Table 1), the temperature range for all the stages of development is between 28 and 30 °C. Regarding salinity, juveniles and adults develop well in freshwater. For the larvae, a range between 15 and 18‰ allows normal development. So far, no other water parameter has been studied in deep, but observations in our laboratory show that all stages are very susceptible to nitrogen compounds, such as ammonium and nitrites.

Table 1 Reported temperature and salinity ranges for rearing several stages of Macrobrachium acanthurus
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Reproduction

Reproductive traits

Information regarding the reproduction of M. acanthurus is mostly available on wild populations in several locations along the Gulf of Mexico and the Atlantic Ocean, with most of the reports focused on female fecundity. Several authors (Roman-Contreras and Campos-Lince 1993; Bertini et al. 2014; Bertini and Baeza 2014; Cruz-Sánchez et al. 2018) reported that this species reproduces all year round with higher peaks during the warmer and rainy months, regardless of their distribution at the south or north hemisphere. According to Albertoni et al. (2002), females were found in higher proportion in areas closer to the ocean, than in the inner zones of the Imboassica lagoon (Brazil), indicating that females travel to marine areas to spawn. However, Bertini et al. (2014) reported that females in the Riberia de Iguape River (Brazil) release the larvae as far as 150 km from the coast and allow the currents to bring them down to the coast. The wide distribution of this species probably causes different geographical variations of reproductive traits (Mejía-Ortíz et al. 2001).

Little information is available regarding the size of sexual maturity in males, but in the Jequitinhonha River (Brazil), they reach an average carapace length of 11.85 mm (Ríos et al. 2021). In contrast, the size at sexual maturity for females is available in several localities along the Atlantic coast (Table 2). The smallest size was registered by Tamburus et al. (2012) of 6.07 mm of carapace length in São Sebastião, São Paulo (Brazil). Females collected in the Ribeira de Iguape River (Brazil) attained sexual maturity at smaller body sizes during the hotter season of the year (Bertini and Baeza 2014).

Table 2 Size and fecundity of M. acanthurus females in several locations along the coast of Atlantic Ocean
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Under captive conditions, sexual maturity was attained in an average of 173 days, a period which included the whole larval stage (Dugan et al. 1975). Willis et al. (1976) reported that postlarvae became sexually mature at the age of two and a half months. Juveniles reached sexual maturity after 80 days at a mean weight of 1.3 g (Valera-Granados et al. 2021). This information indicates that M. acanthurus can reach maturity at a small size when reared under controlled conditions, an aspect that affects the growth and potentially the culture of the species.

Female fecundity (the number of eggs produced per female during a determined period) increased as the weight and longitude do. The female fecundity in several locations is shown in Table 2. The registered number of eggs is as low as 15 (Müller et al. 1992) and may be as high as 17,769 (Valenti et al. 1989).

Regarding the fertility (number of hatched larvae as Zoea I per female), the information available is less than those reported for fecundity. Valenti (1984) reported between 390 and 6543 larvae/female in São Paulo, Brazil. Females collected from Ribeira de Iguape River, Brazil, showed an average of 3981 larvae for each female with a great variation (from 545 to 12,465) (Bertini and Baeza 2014). The same authors estimated an average egg loss of 24% for each spawning.

Nutrition of broodstock

In crustaceans, the egg production requires that nutrients be transferred from the female hepatopancreas to the ovaries and then deposited in oocytes (Subramoniam 2011). In general, nutritional prawn reproduction effects have been assessed mainly in females. However, males may also contribute to the limited success of certain native species in captive breeding activities (Da Costa et al. 2020). The quantity and quality of the nutrients will determine the survival and normal development of embryos and early larvae (Harrison 1990).

Regarding nutrition in reproductive females of M. acanthurus, Gastelú et al. (2011) reported that feeding females with a diet with a 16% lipid content improved the molting and ovarian maturation. A similar trend was observed when females were fed with 15 and 17.5% lipid inclusion (as cod liver and krill oils) and improved the fecundity and the content of lipids in the eggs (Hernández-Abad et al. 2018). It seems that lipids are an important nutrient for females during sexual maturation and egg production and should have an important effect on embryonic development, as embryos tended to use lipids as the main source of energy (Anger et al. 2002). On the other hand, the inclusion of dietary prebiotics such as fructooligosaccharides (FOS) and mannanoligosaccharides (MOS) plays a role in the sexual maturation of adults, as individuals fed on the prebiotics showed a higher percentage of males and egg-bearing females (Valera-Granados 2021).

Food management regarding adult M. acanthurus maturation includes fresh food (fish and squid muscle) to influence diets on the sperm survival of this specimen. According to Da Costa et al. (2020), the 100% fresh diet provided the best sperm survival performance with significant results in relation to a natural environment diet.

Techniques for sexual maturation and reproduction

Few attempts have been done to induce the sexual maturation of M. acanthurus, as is usually done with the penaeids shrimps. Cunha and Oshiro (2010) reported that unilateral eyestalk of females improved the time of ovary development and decreased the time between spawns. However, females subjected to eyestalk ablation showed a reduction of reproductive performance when compared with intact females and do not recommend this procedure, as it produces physiological stress (Rodrigues et al. 2021). Accordingly, histochemical analyses of the ovaries revealed that unilateral ablation did not significantly influence the accumulation of nutrients in the ovaries. Although eyestalk hormones regulate carbohydrate, nitrogen, and lipid metabolism in crustaceans, the growth of M. acanthurus oocytes seemed not to be impaired by the removal of a single eyestalk (Rodrigues et al. 2022). This technique was likely not enough to disrupt vitellogenesis in this species.

For males, Da Costa et al. (2016) reported that optimal stimulation for spermatophore extraction was 6.0 V, considering the survival of the organisms and sperm. The conservation of spermatophores by means of cryopreservation was better in 10% glycerol, with a freezing rate of 2 °C/min and cold storage of 5 °C during a maximum period of 3 days (Da Costa et al. 2017).

Embryonic and larval development

Embryonic development

Some aspects of the embryonic development were reported by Rauh et al. (2007) in which, females of M. acanthurus maintained under laboratory conditions showed an average incubation period of 16 days. The authors divided embryonic development into 16 stages, one per day, based on the morphological changes of the embryos. Cunha and Oshiro (2010) reported an incubation period of 18 days, varying from 13 to 32 days depending on water temperature. Anger et al. (2002) showed that during embryonic development, fractions of carbon and hydrogen decreased at a higher degree than nitrogen. This trend indicates that during development, the embryos use lipids as energy sources, rather than proteins.

Larval development

Like other species of diadromous Macrobrachium, M. acanthurus presents an extended larval development (Mejía-Ortíz et al. 2016) that requires brackish water to complete its larval stage. Larvae hatch as Zoea I, which presents a lecithotrophic behavior during the first days of development (Anger 2013). The first description of larval development was made by Choudhury (1970), a process that occurs in ten stages that were described based on morphology criteria. According to the author, molting of the first to fifth stages resulted in a new larval stage; but starting from the sixth molting, it does not necessarily result in s a new stage, and the development of larvae becomes irregular. On the other hand, Dobkin (1971) reported that larvae were reared at three different salinities (35, 23.5, and 12 ‰). The author did not find any differences between the survivals of larvae reared at the three different salinities. The larvae reached the post-larvae stage after 43 to 56 days and 18 to 23 molts. This work contributes, as well, with a more accurate description of the first to fourth larval stages. Rocha et al. (2018) revised the development of the feeding appendages and foregut of the larval stages. They found that Zoea I stage does not have the mouthparts developed, which indicates the lecithothropic behavior during the first days of larval development.

Larval rearing

Larval rearing is still problematic and represents the bottleneck for the culture of this species (Kutty and Valenti 2010). Temperature and salinity conditions are relatively well studied (Table 1), but little information is available regarding techniques of larval rearing. One of the best reports regarding these aspects is the one of Dugan et al. (1975), in which the authors showed the use of different systems of rearing: unfiltered closed system, closed system with periodic water exchange, and a variety of recirculation systems. Authors reported that best results were obtained when conical tanks with filtration were used during the first stages (I–V) and after that (stages VI–X), larvae were transferred to 1000-l tanks without filtration and subsequently to others, when the organic material started to decay.

According to observations made in our laboratory (unpublished data), all the larval stages are very susceptible even to low levels of nitrogen compounds such as ammonium (concentrations higher than 0.01 mg/ml) and nitrites (concentrations higher than 0.05 mg/ml). Considering these aspects, larval rearing requires the development of effective recirculation systems that help to maintain excellent water conditions.

Roegge et al. (1977) reported the infestation of larvae with the ciliated Zoothamnium sp., and they tried ten different chemicals and found that treatment with formalin at a concentration of 50 ppm for 24 h reduced the infestation and did not affect the larvae. Also, they reported that water filtration might help to reduce the possibility of the appearance of protozoa.

Feeding protocols and nutrient requirements of larvae

One of the critical points in Cinnamon River shrimp farming is the feeding strategy, which must be adequate for the nutritional needs of the larvae (Harrison 1990). Traditionally, the rearing of M. acanthurus larvae has followed the protocols developed for the Malayan prawn M. rosenbergii, and the use of live feed and particularly the use of Artemia nauplii for each larval stage are still mandatory, at least during the first stages of development. The first works of larval rearing reported that feeding Artemia nauplii improved the survival and development of the larvae (Choudhury 1970, 1971; Dobkin 1971; Dobkin et al. 1974). Dugan et al. (1975) showed that the acceptability of nauplii was 98%, while copepods, groundfish, and ground beef heart were 95%.

Regarding the nutrient requirements, Hernández et al. (2015) reported the use of microcapsules with different concentrations of DL-methionine to enrich the Artemia nauplii, and a concentration of 40 mg/ml showed a higher survival rate of the larvae. Also, they reported that larvae fed on nauplii enriched with 40 mg/ml of vitamin C (as 2-phospho-L trisodium ascorbic acid) reached the post-larvae stage at day 33 and a survival rate of 20%. On the other hand, the enrichment of Artemia nauplii with 10 mg/ml of vitamin A (as retinyl palmitate) significantly improved the survival rate to 40%, compared with the 18.3% of larvae fed with Artemia nauplii without vitamin A (Castillo 2021). Rodrigues et al. (2018) concluded that Artemia + inert diet (chicken egg, squid flesh, fish flesh among other ingredients) were the most effective diets for larval development and survival, increasing by 281 and 199 times, respectively, the chances of survival compared to the inert diet alone.

This information indicates that the sole use of Artemia nauplii might be not enough to fulfill the nutrient requirements of larvae and the necessity of optimization of nutrient concentrations in the nauplii for successful rearing. According to Frías et al. (2022), larvae do not consume microdiets during the first five stages of larval development, but we have observed that after stage six, they are able to consume feed particles of about 500 μ (unpublished data). Thus, the use of microdiets during the late stages of larvae development might help to improve the survival rates and reduce the reliance on Artemia nauplii, and they could provide useful information regarding nutrient requirements in these stages. Besides, several microdiets are commercially available for the different larval stages of penaeids shrimps, and their use might be helpful to read the M. acanthurus larvae.

Juveniles

Rearing conditions and growth performance

Dugan et al. (1975) reported for the first time the rearing of 110 juveniles of M. acanthurus in a 1000-l tank without filtration. Organisms were fed on a trout diet and after 133 days; they reached a mean length and weight of 65.5 mm and 6.4 g, respectively. The authors reported, as well, a heterogenous growth among the individuals. Willis et al. (1976) used four different stocking densities: 215, 430, 645, and 860 individuals/m2 for 2 months and despite the initial densities, the growth and survival rates were heterogenous and erratic. Villafuerte et al. (2016) reported weight gains between 14 and 30% after feeding juveniles diets with different levels of protein for 80 days. In this trial, the authors used casein as the main protein source. Weight gains in juveniles fed a diet based on fish and krill meals were between 257 and 335% in 60 days (Varela-Granados et al. 2021). Similar values of growth performance were reported by Frías et al. (2023a) in juveniles fed diets with different levels of protein, lipids, and carbohydrates for 60 days, as well. This information indicates that using adequate feeds, juveniles can grow at levels like those reported for penaeid shrimps.

Nutrient requirements

Juveniles of M. acanthurus have been reported as omnivores (Rocha-Ramírez et al. 2007), as detritus, different insects, and macroalgae were found in the digestive tract of wild individuals (Albertoni et al. 2003). This information has led to thinking that low-protein diets might be used under culture conditions (Kutty and Valenti 2010). However, Villafuerte et al. (2016) reported that protein requirement was determined to be 37.8% by using the broken-line model with weight gain data as variable, which is similar to values reported for commercial species of crustaceans (NRC 2011). Besides, Frías-Gómez et al. (2023a) reported that juveniles were fed several diets with different levels of protein, lipids, and carbohydrates and determined that a diet that included 35% protein, 15–20% lipid, and a maximum of 20% carbohydrate was optimal for growth performance. Levels higher than 20% of carbohydrates caused oxidative stress. Also, Frías-Gómez et al. (2023b) observed that a low level of protein in the diet downregulated the expression of the gene of the fatty acid synthetase (FAS), an enzyme that oversees de novo synthesis of the long-chain fatty acid palmitate, the main form of lipid storage. This information indicates that proteins and lipids represent the main substrates of energy for this species, and high inclusion of carbohydrates is not recommended for juveniles. The knowledge of protein and lipid requirements is a step forward that will allow the formulation of practical diets and the use of alternative meals and oils such as plant-origin or renders that are cheaper than fish meal and oil.

Culture aspects

A few attempts of culture have been tried, and all of them have been done at the experimental level: Dugan et al. (1975) used 49 individuals/m2 which were reared in 1000-l tanks without filtration and fed with rainbow trout feed for 133 days. The authors found 88% of survival, but growth was heterogenous due to overcrowding, water quality, or feeding problems. Willis et al. (1976) reported that prawns were held in 300-l tanks connected with filters and fed a diet with marine protein for two months; however, the growth performance and survival rate were very erratic. A polyculture model was performed with the curitamã-pacu (Prochilodus argenteus) and M. acanthurus at different stocking densities and found that more than five prawns per m2 affected the growth performance of the fish (Almeida et al. 2015). Soares et al. (2019) reported that polyculture of the curitamã-pacu and M. acanthurus and fed a supplemental diet with different inclusions of cassava leaf meal. The authors found that biomass production was higher in the polyculture than those monocultured, but in general, the presence of prawns affected the growth of the fish.

Hagood and Willis (1976) made the only report regarding the economic aspects of rearing larvae until juveniles. The average production of a thousand was US$13.42 considering labor, water, electricity, and food. This was four times higher than the cost of producing juveniles of M. rosebergii.

The information about rearing juveniles of M. acanthurus for culture proposes is still very limited and requires studies on different types of culture such as extensive, recirculation, bio-floc, or even polyculture with different species of fish.

Diseases

Although it has been reported that M. acanthurus is resistant to diseases (Kutty and Valenti 2010), the available reports describe only the incidence of epibionts in wild adults and juveniles. Epibiosis of the barnacle Amphibalanus improvisus in eight adults was reported in the Mansaú Laggon, Brazil (Rocha and dos Santos 2010). On the other hand, 90 juveniles collected in the Jamapa River, Veracruz, Mexico, presented protozoan epibionts such as Epistylis sp., Acineta sp., and Lagenophrys sp., species that are indicators of environments with high quantities of organic matter which were observed in several appendages. Also, the authors found an unidentified ciliated in the gills and the gregarine Nematopsis in the intestine (Domínguez-Machín et al. 2011). Without a doubt, more surveys are necessary along the Atlantic coast to find out if bacterial or viral diseases are present in wild populations that potentially affect individuals under captive conditions.

Research perspectives and conclusions

As mentioned before, there are several human-related factors that are contributing to the continuous disappearance of M. acanthurus along the Atlantic coast of America. In addition, global climate change now represents a major threat to this species and all other Macrobrachium species; thus, their conservation seems to rely on the development of aquaculture supplementation.

As has been described previously, the research regarding M. acanthurus had an impulse during the decades of 1970s and 1980s. Most of the information from these years is related to population ecology and the effects of temperature and salinity on growth and survival. However, several gaps in the knowledge of the biology of this species might have influenced the fact that culture does not surpass the experimental status. So, the next basic steps in research are recommended to improve culture during the different stages of development of M. acanthurus:

As mentioned before, the process of larval rearing has been not completely successful, and the reported survival rates barely reach 40%, so research on feeding protocols, use of live preys, and nutrient requirements might help to improve the survival rates. The sole use of Artemia nauplii as live feed during the larval development seems not to be enough, especially after the larval stage 6, and the supplementation of microdiets might be useful to allow normal development, decrease cannibalism among the individuals, and generally improve the survival rates. Also, the assessment of the nutrient requirements for the larvae stage, particularly those of fatty acids and micronutrients such as vitamins. The use of pre- and probiotics during larval rearing periods might help to improve the resistance of organisms to changes in environmental conditions and diseases.

Also, larval rearing might benefit from the use of new technologies, such as flow-through water or recirculation systems that help to maintain the water quality until it reaches the postlarvae stage.

Regarding the reproductive stage, the optimization of diets for females during sexual maturation and egg production should be deeply studied as much of the quality of eggs depends on female nutrition. Particularly, the requirements of nutrients such as polyunsaturated fatty acids, fat-soluble vitamins, and carotenoids should be determined. The same nutrients might be useful to improve the sperm quality of males, which is an aspect that has been poorly studied in general for crustaceans. The presence of different morphotypes in males has been reported in several species of Macrobrachium; abiotic and social factors seem to influence the apparition of the different morphotypes. Such factors should be carefully studied in M. acanthurus to reduce the presence of males which resembles females.

On the other hand, the use of different rearing systems such as extensive, recirculation, bio-floc, or even polyculture should be assessed to determine the best grow-out conditions for juveniles, as the production of this species depends on an economical and feasible system. The selection of individuals with high growth performance should be an important part of culturing this species, particularly of males as often they have shown slow growth.

Finally (and not only for M. acanthurus, but for all other American Macrobrachium species), the collaborative research between different academic institutions which are working with these species should draw near and intensify. Governmental entities should be invited to participate and help with resources that allow research.