Brazilian Journal of Animal and Environmental Research 605 ISSN: 2595-573X
Birth of Narcine brasiliensis (Chondrichthyes, Elasmobranchii) at the Santos City Aquarium in São Paulo, Brazil (2016-2018)*
Nascimento de Narcine brasiliensis (Chondrichthyes, Elasmobranchii) no Aquário de Santos em São Paulo, Brasil (2016-2018)*
DOI: 10.34188/bjaerv4n1-052
Recebimento dos originais: 20/11/2020 Aceitação para publicação: 20/12/2020
Alex Sandro Luiz dos Santos-Ribeiro Mestre em Aquicultura e Pesca pelo Instituto de Pesca/APTA/SAAESP Av. Bartolomeu de Gusmão, 192 - Ponta da Praia, Santos-SP, Brasil [email protected]
Alberto Ferreira de Amorim Doutor em Ciências Biológicas pela Universidade Estadual Paulista/Instituto de Biociências/Campus de Rio Claro Instituto de Pesca/APTA/SAAESP Av. Bartolomeu de Gusmão, 192 - Ponta da Praia, Santos-SP, Brasil [email protected]
ABSTRACT The Santos City Aquarium (AQS) maintains sharks and rays to develop environmental education, informing its visitors about their importance. A pregnant specimen of electric ray or shakes, Narcine brasiliensis, fished in Santos (São Paulo, Brazil) was donated to AQS. After about two months, 9 individuals were born, of which three were live births. In order to observe the development and well-being of the 3 specimens, monitoring was carried out for 24 months (Total Length-TL and Total Weight-TW). The females, called R1, R2 and R3, were kept in a 200-Liter enclosure, with a closed mechanical and biological filtration system and a daytime photo period of 12h/day and 12h/night. The water’s parameters were periodically checked (temperature, pH, NO2, NH3 and salinity). The initial growth phase and the well-being assessment were obtained through the weight/growth ratio and the condition factor. Through the condition factor analysis, it was observed that R1 and R2 had positive asymmetric growth in the first 4 months and maintained symmetrical growth until the end of the experiment. However, R3 displayed less development from the first months, probably due to a malformation of the mandible. Results demonstrate that the R1 and R2 specimens had similar growth and doubled in size in the first year of life. There was no significant difference between weight/length regressions, showing the similarity of growth between captive and free-living specimens (caught in fishing). It can be said that the good conditions of the AQS system probably contributed to the welfare of the specimens.
Key words: electric ray, shaking ray, management, growth, captivity.
* Part of the Master Science by Alex Sandro Luiz dos Santos-Ribeiro.
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RESUMO O Aquário Municipal de Santos (AQS) mantém tubarões e raias para desenvolver a educação ambiental, informando seus visitantes sobre sua importância. Um exemplar prenhe de raia-elétrica, Narcine brasiliensis, pescado em Santos (São Paulo, Brasil) foi doado para a AQS. Após cerca de dois meses, nasceram 9 indivíduos, dos quais três nasceram vivos. A fim de observar o desenvolvimento e o bem-estar dos três neonatos, foi realizado o monitoramento por 24 meses (Comprimento Total-CT e Peso Total-CT). As fêmeas, denominadas R1, R2 e R3, foram mantidas em recinto de 200 litros, com sistema fechado de filtração mecânica e biológica e fotoperíodo diurno de 12h/dia e 12h/noite. Periodicamente foram verificados os parâmetros da água (temperatura, pH, NO2, NH3 e salinidade). A fase inicial de crescimento e a avaliação do bem-estar foram obtidas por meio da relação peso/crescimento e do fator de condição. Por meio da análise do fator de condição, observou-se que R1 e R2 tiveram crescimento assimétrico positivo nos primeiros quatro meses e mantiveram crescimento simétrico até o final do experimento. Porém, R3 apresentou menor desenvolvimento desde os primeiros meses, provavelmente devido a uma malformação da mandíbula. Os resultados demonstram que os espécimes R1 e R2 tiveram crescimento semelhante e dobraram de tamanho no primeiro ano de vida. Não houve diferença significativa entre as regressões peso/comprimento, mostrando a similaridade de crescimento entre espécimes em cativeiro e em vida livre (capturados na pesca). Pode-se dizer que as boas condições do sistema AQS provavelmente contribuíram para o bem-estar dos espécimes.
Palavras-chave: raia-elétrico, raia-tre-treme, manejo, crescimento, cativeiro.
1 INTRODUCTION In the three Oceans, the Narcinidae family is represented by 29 species, and only three occur in Brazil. Narcine brasiliensis is present in the south-southeast; N. brancofti in the northeast; and N. sp. in the North (Last et al., 2016). In the south-southeast they are popularly known as shaking or electric ray (Gomes et al., 2010; Rolim et al., 2015). N. brasiliensis is found in muddy bottoms of coastal waters from southeastern Brazil to Argentina, present at up to 20 meters deep. Since they have no commercial value, when caught in seven-bearded shrimp trawling and pair fishing, they are discarded (Rolim et al., 2015). As for their conversational status, they are data deficient (DD) according to the Red List of the International Union for Conservation of Nature and Natural Resources – IUCN (2019). The maintenance of elasmobranchs in public aquariums is a reminiscent from the 19th century (Koob, 2004; Brunner, 2005). It can be considered a growing science, and there are no limits on the size or degree of complexity for keeping specimens in captivity, including manta rays and whale sharks (Coco and Schreiber, 2017; Matsumoto et al., 2017). Sharks and rays are important attractions in public aquariums, representing an interesting and invaluable educational tool, as well as their use in laboratories for research purposes (Gendron, 2004).
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The birth of elasmobranchs in artificial conditions of a controlled environment has already been reported by Rudloe (1989), Michaelson and Sternberg (1979) and Gonzalez (2004), with specimens of N. brasiliensis, Torpedo ocellata, Zapteryx brevirostris, Dasyatis americana. Growth analyses of elasmobranchs are widely used to generate data on the well-being of a given population of individuals. Studies of growth, reproduction and diet of N. brasiliensis, have been carried out by Rudloe (1989), Martins et al. (2009), Viana and Vooren (2009), Ferreira and Vooren (2012) and Rolim et al (2015). Similar works were carried out with N. entemedor by Villavicencio-Garayzar (2000) and with N. brancoftii by Moreno et al (2010), which demonstrate the need for more work on these species. Sawaya and Mendes (1951) studied Cholinesterase in specimens of N. brasiliensis at the Santos City Aquarium. Regarding captive maintenance, birth records of benthic rays were reported by some authors such as Michaelson and Sternberg (1979), who received pregnant electric ray specimens of Torpedo ocellata. However, some authors such as Uchida et al. (1990) and Gonzalez (2004) reported the reproduction and birth of Torpedo marmorata and the birth of specimens of Zapterix brevirostix in a captive system, respectively. Henningsen and Leaf (2010) also observed the birth of Dasyatis americana maintained for 13 years, at the Baltimore Aquarium, Atlanta, New York-USA. The aim of this study was to monitor the birth and growth of three individuals of N. brasiliensis over a 24-month period, at the Santos City Aquarium. This study also was intended to contribute to assessing the maintenance conditions (well-being) of the species in captivity, and to compare growth with free-living individuals.
2 MATERIAL AND METHODS The Santos City Aquarium (AQS) regularly receives donations of aquatic animals, from aquarists, residents and fishermen in the region. This activity is supported by Interministerial Instruction Norm No. 09 of June 13, 2012 (Brazil, 2012), which regulates the items and permitted quantities of captured specimen, by fishermen who: i) fish the animal and take it for consumption; ii) keep it in an aquarium or iii) donate it for ornamentation in a public aquarium. The Santos City Aquarium has an Authorization for Use and Management under No. 162.472 for this species. In February 2016, the AQS received a female of N. brasiliensis as a donation, captured with a beach trawl (10 mm beach trawler mesh) at Ponta da Praia, in Santos, São Paulo (Figure 1). The adult female was transported in a 50x50 cm Styrofoam box, with aeration. At the AQS, it was placed in a 200-L tank, with a mechanical glass wool filter and a biological bio-ball filter, with oxygen
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Brazilian Journal of Animal and Environmental Research 608 ISSN: 2595-573X entering through the tank surface. The enclosure substrate was composed of fine sand for filters (Ø4 mm) approximately 5 cm high.
Figure 1. Capture area of female N. brasiliensis, with beach-trawl, Ponta da Praia, Santos, SP, Brazil.
To confirm the pregnancy status, the specimen was submitted to an ultrasound examination at the University Monte Serrat-Unimonte. In transport, the 50x50 cm polystyrene box was used, with the aid of aeration. Upon examination, only the dorsal region of the animal was exposed outside the water. The transducer was positioned on the animal's dorsal region to locate the uterus. The N. brasiliensis adult, as well as the newborns were placed in separate tanks and their feeding was monitored. The feeding schedule was always in the morning when the animals were most active. Regarding the feeding of the newborns, different types of food were tested according to the size of the animal's mouth. The food items offered were: redworms (small dehydrated freshwater invertebrates), pieces of shrimp and fish, following the AQS’s guidelines. Food was offered using a pipette or tweezers. At the AQS, the water quality of the tanks was monitored weekly from March 2016 to March 2018. The values of pH, ammonia, nitrite, salinity and temperature were observed according to reference values proposed by Mohan and Aiken (2004). For the tests of pH, ammonia and nitrite, the ALCON TESTES KIT was used, for salinity a P-RHS-10ATC Salinity Refractometer (0- 100ppm) model was used, and the temperature was measured with a floating glass mercury thermometer. When any value outside the reference standard was observed, a Partial Water Change- PWC of 10 to 20% of the volume was performed. For the safe handling of specimens, rubber gloves were used to minimize the effects caused by electrical discharges.
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The relationship between total weight (TW) and total length (TL) was calculated using the least squares method after logarithmic transformation of the data through the equation, for the sexes separately: TW = a.TLb. Where: TW = total weight in grams; TL = total length in centimeters; a = intersects with the y-axis; b = regression coefficient. In the weight/length ratio, the constant a is related to the degree of fattening of individuals and the coefficient b with the type of growth (Araújo and Vicentini, 2001). For this purpose, b can take on different values ranging from 2-4 (Le Cren, 1951). The weight/length ratio was individually estimated for the neonates (R1, R2 and R3). The neonates' measurements were taken before feeding at 15-day intervals for 24 months. Biometrics was performed with the aid of a caliper and digital scale with precision from 1 g to 500 g; as the animals grew, an ichthyometer and digital scale was used with an accuracy of 40 g to 20 kg. The weight/length ratio was also carried out with 35 free-living individuals, caught in the seven- bearded shrimp trawl fishing in order to compare the relationships due to the different living and maintenance conditions. The free-living N. brasiliensis individuals used in this study belong to the zoological collection of Santa Cecília University (Unisanta), donated by commercial fishermen. Aiming at comparing the weight/length relations obtained, the F test of parallelism was performed between the regression lines, which allowed verification of the null hypothesis of homogeneity of the pending regressions (Valle and Rebelo, 2002). For the diagnosis of the regression, the normality and homogeneity were verified, along with the variances with the Shapiro- Wilks and F tests, respectively. The elaborations were carried out with the aid of Microsoft Excel 2007 and the free software, Past version 3.19. Two types of Condition Factors were carried out, which allows assessing the nutritional status or “well-being” of each individual in the population examined: 1) Fulton Condition Factor (1911): K = (TW/TL3) * 100, where : TW = total weight; TL = total length. In this case, the calculated K represents the ideal deviation of a fish, with isometric growth (Weatherley, 1972) and allows the comparison between different individuals, sexes and populations (Ricker, 1975); 2) Allometric Factor (Le Cren, 1951; Wootton et al., (1978): K = TW/TLb, where TW = total weight; TL = total length and b = allometry coefficient (regression).
3 RESULTS The streak specimen donated to AQS in January 2016 was identified as Narcine brasiliensis (Olfers, 1831), according to Figueiredo (1977), Gomes et al. (2010) and Last et al. (2016). At the time of capture, the individual was 38 cm long and weighed 736 g (Figure 2).
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Figure 2. Female specimen of Narcine brasiliensis at the Santos City Aquarium placed under observation, due to its distended dorsal region.
The ultrasound result, performed on February 23, 2016, showed the presence of four embryos in the left uterus, confirming the pregnancy state (Figure 3).
Figure 3. Observation of four Narcine brasiliensis embryos, in the left uterus, through ultrasound, confirming the state of pregnancy.
On March 3, 2016, (57 days after her capture), the female gave birth to nine newborns, three live females (Figure 4A), and six stillbirths, two females and four males (Figure 4B). The newborns were entitled R1, R2 and R3. All embryos showed complete development, suggesting that the captured female was in the final stage of the gestational period.
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Figure 4. Three female neonates (A) and six stillborn specimen ((B) two females and four males) of Narcine brasiliensis.
The averages of the water quality variables from February 2016 to March 2018 were: pH 8.4 (±0.08 SD); salinity 28 ppm (±0.37 SD) and temperature of 26˚C (±0.50 SD), for ammonia and nitrite, the values were below the sensitivity of the determination method. There were no significant changes in the analyzed parameters and at least 50% partial water change (PWC) was performed (Table 1).
Table 1. The water quality variables of the tank of the three newborns of Narcine brasiliensis, from February 2016 to March 2018.
Variable Mean±SD Max. Min. Salinity 28.16±0.37 29 28
Temperature 25.6±0.5 26 25
Ph 8.36±0.08 8.4 8.2 NH³ 0 0 0 NO² 0 0 0 Table 2 shows the weight, length, and sex data for the nine newborns.
Females had an average length of 8.1 cm with a standard deviation of 0.08. The average length of the males was 8.0 cm with a standard deviation of 0.28. The average weight of females was 6.6 g with a standard deviation of 0.92 and of males 7.3 g with a standard deviation of 0.55. The three live female specimens, R1, R2 and R3, had similar total lengths (TL) and weighed between 6.6 g and 8.1 g. Regarding appearance, the three neonates had patterns with distinct dorsal patches, making them easily identifiable, without the need for external marking.
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Table 2. Relationship of length (TL), weight (TW) and sex of the nine embryos on the date of birth (03/03/2016).
Shortly after birth, the three female newborn specimens R1, R2 and R3 intercalated, partial periods of swimming in water and buried still in the substrate, with the dorsal fins kept hidden in the substrate and only the eyes and spiracles exposed. Within the first days of birth, when specimens were manipulated to obtain biometrics and weighing, small electrical discharges were noted. The newborns were offered food the day after their birth. For the first thirty days, redworms were offered. From the second to the third month the specimens were fed with manjuba eggs (Anchoviella lepidentostole), which were offered with the aid of a pipette. Then for the third month, pieces (0.2 mm) of seven-bearded shrimp Xiphopenaeus kroyeri and merluza fish, Merluccius spp, were offered with the help of tweezers. Finally, from the fourth month to 24 months, the food was prepared with pieces of about 5 mm of fish and shrimp (Figure 5).
Figure 5. Neonate of Narcine brasiliensis, being fed with manjuba eggs, with the aid of tweezers.
The greatest growth in neonates occurred in the first 12 months, where the R1 and R2 specimens doubled in size (16 and 16.7 cm, respectively). In the following 12 months, this growth rate decreased (4 cm and 7 cm respectively). After 16 months it was observed that R1 and R2 had the same length (18 cm TL), and approximately the same weight (91 and 92 g TW). However, R3,
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Brazilian Journal of Animal and Environmental Research 613 ISSN: 2595-573X in the twelfth month, displayed a lower development than the others (12 cm TL), and also with a lower weight (26.5 g TW). In the nineteenth month, the R3 specimen died. At the end of 12 months, the relative average length and standard deviation were 12.56 cm and 2.60 for R1; 12.65 cm and 2.52 for R2 and 10.75 cm and 1.58 for R3. Regarding the average weight, R1 was 34.39 g, R2 was 32.64 g and R3 was 18.84 g. At the end of the second year of life, the average length of R1 and R2 was 18.62 cm and 19.07 cm, respectively, and the average weight was 106.01 g for R1 and 104.55 g for R2 (Figure 6).
Figure 6. Relationship between weight-TW/length-TL for R1, R2 and R3 (females), during the first and second year.
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The weight-TW/length-TL ratio for the three newborns (R1, R2 and R3) is shown in Figure 8. The regression model for each individual was: R1: TW = 0.0131 x TL3.0737 and (r² = 0.983); R2: TW = 0.0156 x TL2.8811 and (r² = 0.988); and R3: TW = 0.0187 x TL2.98993 (r² = 0.981), observed in Figure 7. The R1 and R2 specimens showed similar growth over the twenty-four months, however R2 died in the twenty-fifth month and R1 in the twenty-seventh month. The R3 specimen remained in the period of only up to 19 months and then died. The probable cause of death was related to the appearance of a mouth deformation that prevented its proper feeding.
Figure 7. Weight-TW/length-TL relationships of the three newborns (R1, R2 and R3) of Narcine brasiliensis, for 24 months.
200 180 160 R1 140 120 100 R2 80 60
Total Weight TW (g) TW Weight Total 40 20 R3 - 6 8 10 12 14 16 18 20 22 24 Total Length TL (cm)
Regarding the values of the regression coefficients (b) for the three individuals (R1, R2 and R3), they show that the growth was allometric, being positive for R1 and negative for R2 and R3 (Table 3). The determination coefficient (R2) greater than 98% showed adequacy of the adjustment of the applied model. In Figure 8, the linearized model (log-log) of the weight-TW/length-TL regressions of the three samples (R1, R2 and R3) is shown. Comparing the growth of the three newborns, there was no statistically significant difference (p> 0.05) between them.
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Figure 8. Log-log transformation of the weight-TW/length-TL ratio of the three newborns (R1, R2 and R3) of Narcine brasiliensis for 24 months.
The data for the three neonates (females) were also grouped to obtain a combined weight- TW/length-TL ratio (Figure 9). The relationship obtained was as follows: TW = 0.0134 x TL3.0461 and (r2 = 0.987).
Figure 9. Weight-TW/length-TL ratio of the three newborns (R1, R2 and R3) of Narcine brasiliensis grouped. 200 180 160 140 120 100 80 60
Total Weight WT (g) WT Weight Total 40 20 - 6 8 10 12 14 16 18 20 22 24 Total Length CT (cm)
The regression coefficient confirmed the type of allometric growth in relation to the species’ initial stages of life. The average lengths at 12 and 24 months of the individuals observed (R1, R2 and R3) were 15.37 cm, 15.62 cm and 11.10 cm (first year), and 18.41 cm and 18.83 cm (second year), respectively. A new association (grouped data) allowed an approximate corresponding weight of 55.20 g, 51.45 g and 20.48 g for the first year and 95.63 g and 102.43 g for the second year, respectively, to be estimated.
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Regarding the free-living specimens, the weight-TW/length-TL ratio was applied separately with 18 males and 17 females. The regression equations are as follows: males, TW = 0.01 x TL3.0257 and (r2 = 0.9571); and females TW = 0.0035 x TL3.3604 and (r2 = 0.9588), observed in Figure 10.
Figure 10. Weight-TW/length-TL ratio of male and female (separately) of free-living Narcine brasiliensis.
The values of the regression coefficient show positive allometric growth for both sexes, which were higher in females (3.36) than in males (3.03). Figure 11 shows the comparison between the linearized regressions (log-log) of males and females of free-living individuals. The comparison of relationships through the F test (parallelism), did not show any significant difference (p>0.05) indicating the absence of sexual dimorphism between the sexes. To compare neonates and free-living, only data from females were used.
Figure 11. Log/log transformation of the weight-TW/length-TL ratio of free-living males and females of Narcine brasiliensis.
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Considering that the weight-TW/length-TL ratio is important to improve knowledge about the first stages of development of the species. Therefore, data on captive individuals and data on free-living individuals were compared. The comparison showed that the allometric coefficient of juvenile females (captivity) is close to that of males and females (Figure 12), indicating a possible effect of reproduction on the type of growth. Somehow, the comparison of the regression lines was not significant.
Figure 12. Weight/length ratio of the grouped data of Narcine brasiliensis newborns, males and females. 1.400 R1 R2 R3 2.7832 TL = 0.0257.TW 1.200 R² = 0.9835 Femea vida livre 1.000 800 Macho vida livre 600 400 Beginning/reproductiv
(g) TW Weight Total e fase 200 2º - 1º - 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 Total Length TL (cm)
According to Fishbase (2019) the length the first reproductive activity of the species is 27 cm for males and 28.8 cm for females (Martins et al 2009), showing that the rays in captivity did not reach the length of first maturation. In Figures 13, 14 and 15, the values of the Fulton condition factor (K) and of the Relative Condition Factor are shown. It is possible to observe that in the first three months the R1 and R2 specimens had a positive isometric growth and in the following months the growth was asymmetrical until 24 months. Thus, in the first four months (March to June 2016) the specimens grew more in length than in volume, which demonstrates a characteristic of a fast-growing animal, doubling its size even within the first year.
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Figure 13. Fulton and Relative Condition Factor of the neonate, female, R1 of Narcine brasiliensis, in the 24 months.
Figure 14. Fulton and Relative Condition Factor of the newborn, female, R2 of Narcine brasiliensis, in the 24 months.
Figure 15. Fulton and Relative Condition Factor of the neonate, female, R3 of Narcine brasiliensis, in the 12 months.
4 DISCUSSION Monitoring the growth of elasmobranchs at birth or for long periods can help to better understand the evolutionary behavior of these organisms. Among the pioneering works with the reproduction of rays in an aquarium is that of Uchida et al. (1990), who reported the copulation and birth behavior of Aetobatus narinari. Since information about the behavioral biology of these animals is little known, these data can provide especially important information about the biology of these animals, as well as assist in the maintenance of species in the captivity (Mohan et al., 2004).
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Recent studies show that copulation behaviors, eating habits and reproductive strategies are poorly known, showing the need for further studies to fill the knowledge gap (Rudloe, 1989; Martins et al., 2009; Viana and Vooren, 2009; Ferreira and Vooren , 2012 and Rolim et al. 2015). In Brazil, the cultivation of elasmobranchs in captivity is quite rare. Badalssin et al., (2008), observed the copulation of Rhinoptera bonasus and 14 months later, the birth of an individual, who was maintained for 23 days with a balanced diet. However, Narcine brasiliensis, is not a species widely found in aquariums due to the difficulty of managing it and the low supply of individuals. However, Moreno et al. (2010) studied the reproduction of the electric ray, Narcine bancrofti, in the Colombian Caribbean. The authors Rudloe (1989), Bornatowski (2014) and Rolim et al. (2015) studied the eating and reproductive habits of N. brasiliensis. Sawaya and Mendes (1951), studied Cholinesterase in specimens of Narcine brasiliensis at the Santos City Aquarium. The specimen gave birth to nine newborns, and reports for this species are from 2 to 17 embryos (Michael, 2001). The same author has reported the occurrence of females in shallow areas of the beach during late summer. The female from the present study was also captured in the hot summer period in the Santos bay. Rolim et al. (2015) describe the presence of pregnant females in the landings of industrial fisheries during the summer and autumn in the state of São Paulo. Michael (2003) and Gomes et al. (2010), report the presence of 4 to 15 embryos per pregnancy in N. brasiliensis, while Gonzalez, observed the presence of 6 embryos for Z. brevirostris. For Narcine brasiliensis, no reports of ultrasound examination of pregnant females were found. Tomita et al. (2012), successfully performed ultrasound exams in a pregnant female of Manta alfredi at the Okinawa Aquarium, Japan, and was able to observe the presence of embryos. In this present study, the ultrasound examination was also shown to include embryos; in this case four embryos, in the left uterus. The R1 and R2 specimens reached a maximum total length of 20 and 23 cm respectively, knowing that the species reaches its sexual maturity starting from 28 cm for females and 23 cm for males (Michael, 2003), it can be suggested that probably this species, would be in its reproductive period at closer to four years of life. Information of this nature can assist in the proper management of this vulnerable species to different types of fishing. Finally, N. brasiliensis probably lived under good conditions since they presented a slight positive allometric growth, indicating that their length grew less proportionally to the other dimensions. Similar values were observed by Martins et al. (2009) and Rolim et al. (2015) for female neonatal specimens observed on landings.
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The specimens showed small electrical discharges from the first days of birth, as observed by Michaelson et al. (1979), in newborns of Torpedo ocellata. Cox et al (1946), reported electrical discharges while still inside the uterus of pregnant specimens of N. brasiliensis. The specimens were born with similar sizes to each other, with an average of 8 cm, but the consulted literature reports newborns from 11 to 12 cm, (Michael, 2001; Last et al., 2016). Even though the size was small compared to that mentioned in the literature, the survival of the specimens demonstrated that even though they were born underweight, they survived and developed normally. The weight-length relationship of grouped data from the three females R1, R2 and R3, showed a positive allometric growth close to that presented for free-living males. In the case of free- living females, the regression coefficient was 3.36, indicating a possible reproductive effect; however, the comparison between regression coefficients was not significant. Moreover, due to the low number of specimens examined in captivity, it was not possible to obtain better confirmation and it is recommended that observations be made including both sexes. Oliveira-Freitas et al. (2011) obtained values for specimens of N. brasiliensis analyzed in Santa Catarina, where the regression coefficient was 3.00 and r² = 0.989. From the combined analysis of data from captive specimens with free-living specimens, we deduce that the rays in captivity did not reach the age of first reproduction. This information can be considered quite important, as it shows the weight-length relationship for length classes that are not the target for fishers and are, therefore, difficult to observe in free-living specimens. Considering that the specimens developed similarly to the free-living specimens, we can consider the conditions of maintenance in the captive system of the AQS, satisfactory. According to Michaleson et al (1979) who observed the growth of Torpedo ocellata neonates born in captivity, the species doubled its size in four months. The specimens studied also doubled in length in the first year, suggesting an evolutionary strategy for a species that needs to grow rapidly in the first months for feeding and protection. The results for the two condition factors analyzed showed that R1 and R2 had similar behavior with maximum values corresponding to the same periods of the year; but were different from R3, which showed less fluctuations. In the case of R1 and R2, the highest values were observed in June 2016, April 2017 and March 2018. However, the average for the first year showed that the R3 had the lowest performance and in fact died at the beginning of the second year. R1 and R2 doubled in size within the interval of twelve months, the same was not observed for the second year when R1 and R2 grew 4 cm and 7 cm, respectively. With few reports for food items offered to newborns of N. brasiliensis, for this purpose, data from studies with stomach contents of this species by Bornatowski (2014) were used. Rudloe (1989)
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Brazilian Journal of Animal and Environmental Research 621 ISSN: 2595-573X reported having offered clamworms (Nereis nereis) and lugworms (Arenicola cristata) for adult specimens. Based on this information, redworms were offered due to their similarity with one of the items found (polychaetes). Success in the development of the newborn specimen was fundamental in the initial phase with the first food item offered and the concern regarding their maintenance. Dean and Motta (2004), who describe in detail the propulsion of the mandible of N. brasiliensis as a unique and extreme method, similar to terrestrial tetrapods, demonstrated the importance of this buccal apparatus in the species for the success of food capture. This fact leads one to believe that the specimen R3 affected its growth, causing it difficulty to capture the available food, as observed by the lowest values for TL and TW. Water quality values for elasmobranchs were used according to Michael (2001) and Mohan and Aiken (2004), where tropical benthic elasmobranchs are more adapted to captive environments, with parametric variation. According to Gendron (2004), for a successful management of elasmobranchs in captivity, acclimatization and introduction into the enclosure are directly linked to the animals' expectation of survival; so all water changes in the enclosure were performed slowly to cause the least amount of stress. The success of this experiment is likely related to the good water quality.
ACKNOWLEDGMENT I would like to thank Professors Alberto Amorim, Maria Letizia Petesse and Carlos Eduardo Malavasi Bruno, for their valuable contribution. To Mr. Sérgio Luiz and other employees and volunteers at the Santos City Aquarium, for their patience and support in carrying out this study. The team at the Veterinary Hospital of Unimonte University in Santos, for their help with ultrasound. To Professor Matheus Rotundo (MSc), for making copies of the Unisanta Zoo Collection available. To Mr. Marcos Libório, Secretary of the Environment, Santos-SEMAM, for his support. To Mr. Eder Santana and Mr. Marcio Paulo, DEPAVI-Department of Parks and Animal Life, for their understanding and continuous support. To my parents, my wife Ludmila and my little Analu and everyone who may have helped directly and indirectly to carry out this work. Fapesp for submitting this article (Process 2016 / 05259-0).
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