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29
Boletim do Instituto de Pesca, São Paulo, 27 (1): 27 - 32, 2001
STAGES OF EMBRYONIC DEVELOPMENT OF THE “MATRINXÔ, Brycon cephalus
(PISCES, CHARACIDAE)
[Estágios do desenvolvimento embrionário de matrinxã, Brycon cephalus (Pisces, Characidae)]
Elizabeth ROMAGOSA1,3, Massuka Yamane NARAHARA1, Nelsy FENERICH-VERANI2
1 Pesquisador Científico do Centro de Pesquisa em Reprodução e Larvicultura, Instituto de Pesca, São Paulo
2 PhD Professor do Departamento de Hidrobiologia, Universidade Federal de São Carlos, São Paulo
3 Enderço/Adress: Av. Francisco Matarazzo, 455, Perdizes, São Paulo, Brasil, CEP: 05031-900
e-mail: romagosa@sti.com.br
ABSTRACT
The “Matrinxã” is an indigenous species from the Amazon Basin (Brazil). The development of oocytes is
of the synchronic type, i.e., a large number of ovules is released at the same time. The egg development is
characterized by a short embryonic differentiation and a larval period (26 ± 2.0 ºC). Metamorphosis ends
practically 36 hours after fertilization and individuals reach fingerling stage with a structure similar to that
of the adult, 48 hours after fertilization. The larvae hatch approximately 10-11 hours after fertilization,
displaying slightly pigmented body, well evidenced eyes, traces of a digestive system, and first swimming
movements. At the end of the first day of life, intense cannibalism is observed. Malformation of embryos is
also observed in some individuals.
Key words: embryonic development, Brycon cephalus, matrinxã, fish
RESUMO
O matrinxã é uma espécie de peixe, cuja ocorrência natural está restrita à Bacia Amazônica (Brasil). O
desenvolvimento dos ovócitos é do tipo sincrônico, isto é, inúmeros ovúlos, pequenos, são liberados em
conjunto. O desenvolvimento do ovo caracteriza-se por uma diferenciação embrionária rápida e período
larval curto, à temperatura de 26,0 ± 2,0 ºC. A metamorfose termina praticamente 36 horas após a fertilização,
e a fase de alevino, com estruturas semelhantes às do exemplar adulto foi alcançada 48 horas após a
fertilização. As larvas eclodiram aproximadamente 10-11 horas após fertilização, apresentavam o corpo
levemente pigmentado, olhos bem evidentes, esboço do trato digestivo e primeiros movimentos natatórios.
No final do 1º dia de vida observou-se intenso canibalismo. Também, foram registrados embriões mal-
formados.
Palavras-chave: desenvolvimento embrionário, matrinxã, Brycon cephalus, peixe
Introduction
Matrinxã is a native species from the Amazon
Basin, in Brazil. It is a teleost fish of the Brycon
genus and the Characidae family. The fish farmer
have been easily developing the fattening of this spe-
cies making the results available to everyone who
shows interest in the subject. These results make
the matrinxã culture increasingly popular in the
State of São Paulo (SCORVO FILHO; MARTIN;
AYROZA, 1998).
It is a very popular species in sport fishing. It
fights hard when hooked, which makes its fishery
attractive for the anglers and brings more and more
fans to this activity (ROMAGOSA, 1998). Biological
aspects of this species bred in captivity have been
studied by ROMAGOSA (1998) and the induced repro-
duction of it has been studied by many research In-
stitutions (MENDONÇA and MELO, 1994).
This paper presents preliminary observations on
the egg development stages, free embryo and larva
of Brycon cephalus, obtained in laboratory through
hormonal induction.
Material and Methods
The study was conducted at Centro de Pesquisa
em Aqüicultura do Vale do Ribeira (CEPAR)/ Instituto
de Pesca, located in the city of Pariquera-Açu, São
Paulo, Brazil (24º 43’ S and 47º 53’ W) during the
period of November 1995 to February 1996.
The breeders of Brycon cephalus utilized were
kept in 200 m2 ponds at a density of 1 fish/m2. Se-
lected breeders, twenty (20) females and ten (10)
Artigo Científico: Recebido em 16/06/00 - Aprovado em 19/03/01
30
ROMAGOSA, NARAHARA, FENERICH-VERANI
B. Inst. Pesca, São Paulo, 27 (1): 27 - 32, 2001
Figure 1. Egg of Brycon cephalus, 40 minutes after
fertilization. It is possible to observe the presence of cortical
alveolus (3,8 X)
males were submitted to inducted of the reproduc-
tion through hypophysation (BERNARDINO et al., 1993).
Soon after fertilization and hydration, the eggs were
transferred to 200 L. fiberglass conic incubators, with
constant water renewal in a flow rate of 8.0L/sec.
and temperature of 26.0 ± 2.0ºC. Six and eight hours
after the second hormonal application an abdominal
massage was performed in the female specimens, in
order to facilitate the eggs extrusion. Afterwards, the
eggs were collected in graduated plastic recipients,
in order to be weighed; the semen was softly mixed,
and so performing the dry fertilization (VON IHERING
and AZEVEDO, 1936). Right after fertilization, samples
were taken from the incubator every hour, in order to
observe the different stages of egg development un-
til the larvae hatched. The samples were collected in
Petri dishes, where they were examined under ste-
reoscopic microscope CARL ZEISS, equipped with
a micrometer in the eyepiece and micro-photografic
camera. Initially, the eggs were measured, and fi-
nally, alterations which occurred since the first cell
division until the larvae hatched were described.
Results and Discussion
The stages of embryonic development of
“matrinxã” are similar to other species of Brycon
(LOPES; SENHORINI; SOARES, 1995). The eggs are
spherical, translucent, demersal, surrounded by a ge-
latinous layer, non-adhesive, and have a large perivi-
telline space, and a diameter around 1,010 mm. The
eggs kept an olive green color until embryo was
formed . Similar observation was reported for the
same specie by LOPES; SENHORINI; SOARES (1995).
The observation of the sequence of events that
occurred in the development process of Brycon
cephalus the egg allowed the characterization of three
stages:
1) embryonic stage (cleavage, embryo , free em-
bryo);
2) larval stage (larvae);
3) juvenile stage (alevine).
Embryonic stage
In the cleavage stage it was possible to observe
the presence of organized cortical alveolis in the
peripherical cytoplasm 40 minutes after fertilization
(Figure 1). The cortical alveolis are usually disposed
in two layers, with fine and homogeneous granular
structure. The fusion and breaking of the cortical
alveolis probably happen during the fertilization. The
same was reported by HART (1980). The content is
released in the space created between the chorion
and the plasmatic membrane (perivitelline space). The
process of chorion hardening of the matrinxã egg is
very quick, taking approximately 5 to 7 minutes after
the insemination. One hour and a half after the fer-
tilization, divisions resulting in 2, 4, 8, 16 blastomeres
occurred up to the morula stage (Figure 2a). The eggs
were involved by a small perivitelline space and by a
clear and relative dense chorion. In this same stage,
after intense cellproliferation, the blastodisc expanded
over the yolk, and this process of cellular migration
formed a germ ring that involved the yolk. It was
possible to observe the process of gastrulation, with
differentiation of the embrionary tissues, after four
hours and thirty minutes.
In the embryo stage, the chorion was still rigid
and thick. After five hours and thirty minutes the so-
matic segmentation and the beginning of the tail and
the head differentiation were observed (Figure 2b).
After 7 hours, the optical vesicles could be visual-
ized. Afterwards, the first heart beatings and the cir-
culation were visible. The embryo had approximately
20 somites (Figure 2c). The chorion suffered a pro-
gressive softening. The hatching occurs 10 to 11 hours
after the fertilization, when it was possible to observe
the free embryo emerging by the head or the tail re-
gion. The just-hatched free embryo presented slightly
pigmented body and eyes very evident. The delinea-
tion of the digestive system could be seen (Figure 3).
In this stage, the animals presented intense horizon-
tal and vertical swimming movements.
Larval stage
Twenty-three hours, after fertilization, the larvae
had denticles and presented continuous movement
of the lower jaw (Figures 2 and 4). According to
LASKER (1962), the lower jaw is not functional until
the complete reabsorption of the yolk sac. In this stage
31
B. Inst. Pesca, São Paulo, 27 (1): 27 - 32, 2001
Stages of embryonic development of the Brycon cephalus
Figure 2. Egg of Brycon cephalus: 2a- in the cleavage
(1 hour half after the fertilization) (3,8 X); 2b and 2c- initial
formations of head and tail (3,0 X; 3,8 X)
the shrinkage of yolk sac is observed. The fins are
almost developed. Thirty-six hours after fertilization,
the exogenous nutrition (cannibalism) starts. There
are just traces of the yolk sac.
The occurrence of cannibalism in teleost fish dur-
ing the larval and juvenile stages was revised by HECHT
and PIENAAR (1991). In this study, an intense canni-
balism was also observed at the end of the first day
of life, among sibling larvae, as described by LOPES;
SENHORINI; SOARES (1995) and SATO et al. (1997) for
Brycon lundii.
The process of larval growth of “matrinxã”
is extremely fast, when compared to other species of
freshwater South American teleost fishes. The
“matrinxã” embrionary differentiation is quick, with
a short larval stage, and the metamorphosis practi-
cally ends 36 hours after fertilization (Figure 4). These
results are similar to those mentioned by LOPES;
SENHORINI; SOARES (1995), who state that “matrinxã”
presents a shorter development, when compared to
that of other species, representing an advantage in
the production of larvae process.
Juvenile stage
The alevine presents similar structures to those
of adult specimen 48 hours after the fertilization, with
a completely pigmented body, silvery scales and well-
formed caudal and pectoral fins. In larvae of other
species, like Colossoma macropomum and
Prochilodus margravii the complete reabsorption of
the yolk occurs only 72 hours after (JOHNSTON and
VIEIRA, 1996). It is important to observe the presence
of two spots, one crimson-colored in the operculum
region, and a black one near the caudal region. These
spots are characteristic of the species. In this study it
was observed that the larvae of “matrinxã” started
feeding at the end of the first day. TANIGUCHI (1981)
verified in Cynoscion nebulosus that larger larvae
feed specially an copepods and rotifers. In the first
two days of life, the larvae of “matrinxã” presented
chromatophores of dendritic shape in the cephalic
region, spreading all over the body after the sec-
ond day. The same kind of chromatophores was
observed by NAKATANI; BAUMGARTNER; BAUMGARTNER
(1997), studying the larvae of Plagioscion
squamosissimus.
Figure 3. Larva of Brycon cephalus, where it has been
possible to observe the very protusive mouth with the
presence of denticles, since the first day of life. In the
beginning the pigmentation is more concentrated in the
region of the head (4,9 X)
32
ROMAGOSA, NARAHARA, FENERICH-VERANI
B. Inst. Pesca, São Paulo, 27 (1): 27 - 32, 2001
Figure 4. Sequence of abnormal larval and embryonic
development of Brycon cephalus: 4a- (3,8 X); 4b- (3,8 X);
4c- (4,0 X); 4d- (4,0 X)
Occurrences of abnormalities in embryos and lar-
vae of “matrinxã” were verified only in those
provenient from spawning of females in the initial
regression stage (ROMAGOSA, 1998). Some very ap-
parent alterations have also been observed from the
blastula until the organogenesis (when the organs and
body systems take a definitive form). The alterations
in the embryo are the enlarged yolk sac and spinal
cord with curvatures. Most of the larvae were born
keeping these defects or abnormalities (Figure 5).
However, detailed studies characterizing each mal-
formation and the influence of the environment must
be developed in order to better understand its pos-
sible causes.
Ackowledgements
We are grateful to CEPTA/IBAMA, Pirassununga, São
Paulo, for providing the fish utilized in this study.
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