Spawning and early development of the endemic and threatened Yellow
Catfish Horabagrus brachysoma (Günther, 1864) (Teleostei: Bagridae)
L. Bindu 1 & K.G. Padmakumar 2
1,2 Kerala Agricultural University, Regional
Agricultural Research Station, Kumarakom, Kerala 686566, India
1 Present address: M.S.M. College,
Kayamkulam, Alappuzha District, Kerala 690502, India
1 bindukylm@gmail.com (corresponding author), 2 kgpadman@gmail.com
Abstract: The present study documents the
embryonic and post embryonic development of the endemic and threatened bagrid
catfish Horabagrus brachysoma under captive conditions. Ovaprim® induced fishes spawned after a
latency period of 11.61±1.53 hr with 95.57±3.101 % fertilization and 68.6±30.96
% hatching rates. The fertilized
eggs were non-adhesive and spherical with an average diameter of 1.61±0.05
mm. Hatching occurred in 24.9±1.75
hr after fertilization, producing larvae with a mean size of 3.94±0.112
mm. Mouth and barbels were
prominent in two day old larvae. Yolk absorption was completed and the
larvae attained a size of 5.9±0.307 mm by four daypost hatch. The larvae accepted
exogenous particulate feed from the fifth day onwards. The characteristic black humeral ocellus
appeared in one week old larvae. The larvae achieved
58–65 mm in 85 days.
Keywords:Embryonic development, incubation period, larvae,
Yellow Catfish
doi: http://dx.doi.org/10.11609/JoTT.o3365.5368-74 | ZooBank: urn:lsid:zoobank.org:pub:0CDBEBCF-844D-4E55-BA72-B74003768200
Editor: Rajeev Raghavan, St. Albert’s
College, Kochi, India. Date
of publication: 26 January 2014 (online & print)
Manuscript details: Ms #
o3365 | Received 26 September 2012 | Final received 05 November 2013 | Finally
accepted 19 November 2013
Citation: Bindu, L. & K.G. Padmakumar (2014). Spawning and early development of
the endemic and threatened Yellow Catfish Horabagrus brachysoma(Günther, 1864) (Teleostei: Bagridae). Journal of Threatened Taxa 5(17): 5368–5374; http://dx.doi.org/10.11609/JoTT.o3365.5368-74
Copyright: © Bindu & Padmakumar 2014. Creative
Commons Attribution 3.0 Unported License. JoTT allows unrestricted use
of this article in any medium, reproduction and distribution by providing
adequate credit to the authors and the source of publication.
Funding: Indian Council of Agricultural
Research (ICAR), New Delhi Project- ICAR-NATP-Germplasm Inventory, Evaluation
and
Gene Banking of Freshwater
Fishes (F.No.27 (28)/98/NATP/MM-III-18).
Competing Interest: The
authors declare no competing interests.
Acknowledgements: The authors are
indebted to the ICAR for financial assistance and to the Kerala Agricultural
University (KAU), India for the facilities provided during the study. We place
our sincere thanks to Dr. A. Gopalakrishnan and Dr. V.S. Basheer, NBFGR,
Regional centre, Kochi for their cooperation and assistance during the
investigation period.
For figures, images, tables -- click here
The
Golden or the Yellow Catfish Horabagrus brachysoma (Günther, 1864), is an endemic species of the Western Ghats
river systems in India (Dahanukar et al. 2011). The species is listed as
‘Vulnerable’ in the IUCN Red List of Threatened Species due to declining
populations as a result of overfishing and habitat loss (Raghavan
& Ali 2011). It enjoys a very
high consumer preference in the local market as an edible fish, and high value
in the international aquarium pet trade (Ali et al. 2007). Their utilization in the ornamental fish
trade is however dependent on its capture from the wild. Although the fish could be domesticated
and was observed to attain maturity in pond conditions (Padmakumar et al.
2011), there are no reports on its natural breeding in confined waters. Artificial breeding of this species was
successfully carried out in the year 2000, by the Regional Agricultural
Research Station (RARS), Kumarakom, Kerala under a network project in
collaboration with the National Bureau of Fish Genetic Resources (NBFGR),
Lucknow, India (Padmakumar et al. 2004). The RARS is engaged in a program for
mass production of seeds of H. brachysoma with the goal of promoting
larval rearing and aquaculture (Bindu 2006; Padmakumar et al. 2011) and
the seeds produced as part of the Indian Council of Agricultural Research
(ICAR) Mega Seed Project were utilized for stocking the Sasthamcotta Lake by
the Kerala State Fisheries Department (Padmakumar et al. 2011). Previous research on H. brachysomafocused on its biology (Sreeraj et al. 2006; Padmakumar et al. 2010;
Bindu et al. 2012), fishery (Sreeraj et al. 2007), breeding (Padmakumar et al. 2011), population genetics (Muneer et al. 2009, 2012) and aquaculture
(Sahoo et al. 2010; Giri et al. 2011). However, there is only limited information on the embryonic development
of this species under captive conditions (Padmakumar et al. 2004).
Factors
like reproductive strategies, fecundity, ease of larviculture, economic
acceptance and profitability are essential to determine the viability of a
species for aquaculture (Wittenrich et al. 2007). Studies on early development of fish
species are useful to improve the understanding of larval development and
aquaculture practices. The present paper documents the embryonic and post embryonic development of H. brachysoma subjected
to induced spawning.
Methods
Horabagrus
brachysoma were collected from the riverine stretches of
Vembanad Lake (09031’–09041’N & 76021’–76026’E),
India and stocked in earthen ponds (250m2) at RARS, for induced
breeding experiments. Adult fishes
of size 13–27 cm (19.26±3.33 cm) collected and farm-reared during
2003–2004 were utilized for the present study. Studies on the reproductive biology of
the species revealed that the major spawning season in the wild is during the
monsoon from June to July (Bindu et al. 2012) and is therefore categorized as a
seasonal strategist spawner (Winemiller 1989). Based on this information,
breeding trials were taken up during the monsoon months
(June–September). Male and
female fishes were selected based on their secondary sexual characters
which were prominent during the breeding season (Padmakumar et al.
2011). Selected fishes were weighed
and subjected to induced ovulation, intraperitonially, just below the pectoral
fin, by using Ovaprim® (contains 20g SGnRHa and 10mg Domperidone in
1ml) at the rate of 1ml kg-1 body weight. For studying the development, seven sets
of experiments were carried out during 2004–2005. Since males were
smaller than females in most cases, each breeding set
comprised two males and one female, maintaining a sex ratio of 2:1. Injected fishes were kept in 1000 litre
flat bottom Fibre Reinforced Plastics (FRP) tanks holding filtered freshwater
up to a height of 20–30 cm. Spawning and fertilization occurred in this tank. Polyvinyl
chloride (PVC) pipe was provided in each tank as hide outs.
The
released eggs were collected and spread in glass tanks (123x49x47 cm)
containing filtered freshwater (up to 10–15 cm) with gentle aeration, for
hatching. Temperature, dissolved oxygen (DO) and pH of the water were monitored
using a digital water quality analyzer (Eutech, Singapore). The spawning and hatching tanks were
provided with well-aerated water (DO 5.0–5.6 mg l-1, pH
6.5–7.8 and temperature 24–26 0C). Spawning fecundity (total eggs per
spawning) was calculated by multiplying the eggs in one subsample with the
total. Fertilization and hatching
rates were calculated according to Lagler (1982). The diameter of the mature egg was
determined to the nearest 0.01mm by averaging the measurements of at least 50
eggs. Random samples of 10–15
eggs were collected and observed periodically at 15 minuteintervals, under a trinocular microscope (CETI, Belgium) at 10X
magnification. All the embryonic
and larval development stages were documented using Magnus Imaging System
supported by PixelView software, with the aid of a microscope, connected to a
computer. For this purpose, eggs
were collected at the time of fertilization and the time was denoted as
0:0h. At each stage of development,
dead eggs were removed from the spawning tank by siphoning from the bottom.
In the
present study, early developmental stages of H. brachysoma were grouped
into embryonic (from fertilized egg stage to the time when heart pulsation in
the embryo became apparent), yolk-sac larvae period (from hatching to when the
yolk of the larvae was absorbed), post yolk-sac larvae period (from complete
absorption of yolk to the juvenile stage) and juvenile period (Liang et al.
2003). The embryonic and post embryonic stages were recorded as hours post
fertilization (HPF) and days post hatching (DPH) respectively. After hatching, hatchlings were kept in
1000l FRP tanks. From four DPH they
were fed with boiled egg yolk. Larval size up to five DPH was measured by
taking the mean total length of 15 individuals on each day. One week oldlarvae were shifted to manured cement tanks (5x3x1.2 m) and hapa net (5x4x1 m)
with 50% shade. The experiment (in
duplicate) was conducted for 85 days, at the end of which the final length and
weight of the juveniles were recorded. During this period, the larvae were fed twice a day with powdered
commercial pellets Higashi Fresh (Higashimaru Limited, Chennai; crude protein
20%), containing fish meal as the major ingredient, at
10% of the tank biomass.
Results and
Discussion
Spawning,
embryonic development, hatching and larval development of H. brachysomaresemble other catfishes with slight variations in latency period, incubation
time, egg size and larval size (Thakur 1980; Arockiaraj et al. 2003; Rahman et
al. 2004; Islam 2005; Aneesh et al. 2013). Results of the selected breeding trials are provided in Table 1. Horabagrus
brachysoma was observed to be a broadcast spawner and the eggs were
scattered on the bottom of the spawning tank. Spawning occurred 11.61±1.53 hr, after
hormonal administration, at mean water temperature of 24.64 ±0.75 0C.
Spawning fecundity in each trial (I–VI) varied between 13240 and
31960. The absolute fecundity (the
total number of mature eggs in an ovary) of H. brachysoma is however
higher (20472±20542) (Padmakumar et al. 2011; Bindu et al. 2012) than those
reported for most catfishes (3000 to 20000) (Thakur & Das 1985; Szyper et
al. 2001; Bindu et al. 2009), especially for species which do not exhibit
parental care (Chaudhari & Singh 1984). The fertilized eggs of H. brachysomawere spherical, golden yellow in colour, with a diameter of 1.61±0.051 mm. These eggs are larger than that of Clarias
batrachus, Ompok pabda, Heteropneustes fossilis, Mystus cavasius andClarias dussumieri (Thakur & Das 1985; Rao et al. 1994; Kohinoor et al.
1997; Sreedhar & Haniffa 1999; Rahman et al. 2004; Aneesh et al.
2013). Fertilized eggs were
non-adhesive, but free and demersal, and could be easily transferred to
incubation tanks. This may be
linked to the natural occurrence of bagrid catfishes in downstream slow flowing
habitats in river systems (Arratia et al. 2003). More than 90% of fertilization and
23–95 % hatching was achieved in the experimental trials. In trial VII, conducted at the end of
the breeding season (September), female fish was utilized for the second time
for spawning in the very same season (utilized for the first time in June). Even though the spawning fecundity was
lesser the same female produced viable eggs and larvae pointing out the
possibility of multiple spawning in H. brachysoma.
Stages
of embryonic development are summarised in Table 2. At 1HPF, the chorion separated from the
spherical yolk (Image 1a). Embryonic development commenced with the formation of the blastoderm at
the animal pole region, leaving a large yolk at the vegetal pole. This was followed by cell division,
reaching 16-celled stage after 30min (Image 1b). A clear blastocoel began to appear at
about 3:30 HPF (Image 1c) and the blastula appeared as a cap of cells over the
yolk. By 4 HPF, the
diameter of the fertilized egg was 1.82±0.04 mm. During the late blastula stage (5:30
HPF) the blastoderm flattened and migrated over the yolk. An embryonic shield appeared in the
gastrula stage (Image 1d). The
germinal ring then migrated equidistantly around the yolk and constricted
it. Gradually, epibolic germ layers
spread to the equator of the spherical yolk surface, and at 7:30 HPF (Image 1e),
the germinal ring accounted for three quarters of the total egg volume after
which the yolk plug appeared. The
formation of the embryonic shield (Image 1f) represents the early induction of
the formation of embryo (Islam 2005). As the blastopore closed, the yolk plug becomeprojected and the head rudiment is seen lifted up (Image 1g). The optic rudiment
gradually became differentiated into a vesicle by 11 HPF. A head fold could be seen at the
proximal end of the embryo and myomeres became clear. At 12 HPF (Image 1h) the tail bud
appeared and the embryo was seen encircled over the yolk, reaching nearly three
quarters of its circumference. The
tail bud elongated in an antero-posterior direction by 14 HPF and the brain
differentiation was evident. Distinct
paired somites were observed at 15:30 HPF (Image 1i). Development of lenses and auditory
placodes were observed at 18–19 HPF. The caudal fin fold became elongated and the embryo appeared ‘C’ shaped
encircling the yolk. Twitching
movements of the muscular somites at intervals were observed at this stage
(Image 1j). By 20 HPF, the heart
appeared anterior to the yolk and embryonic movement became rapid. At 21 HPF, tail became free and the
embryo encircled almost 90% of the yolk mass. Gradually, the heart exhibited a
rhythmic beat and the chorion became soft and wrinkled. As the development advanced the embryo
appeared more and more elongated (Image 1k). Pectoral fin folds were formed and a
pair of otoliths was observed in the auditory vesicle. The myomeres became prominent and the
embryo at this stage started to twitch and roll within the chorion. The protruding embryo was seen to
violently beat inside the eggshell, trying to rupture the shell within 1h of
hatching. A similar movement has
also been reported in other catfishes such as H. fossilis (Bindu et al.
2009), C. batrachus (Thakur 1980) and Pangasius sutchi (Islam
2005). Gradually the pulsation of
the heart also became regular at 100–102 beats min-1. The chorion ruptured and the tail
emerged first, followed by the head.
Hatching occurred at 24 HPF (Image
1l). The embryonic stages of H.
brachysoma are similar to other tropical catfishes (Thakur & Das 1985;
Arockiaraj et al. 2003; Islam 2005). Hatching time in catfishes vary widely between 16 HPF and 75 days
(Thakur & Das 1985; Arratia et al. 2003; Padmakumar et al. 2004; Bindu et
al. 2009; Aneesh et al. 2013). In
the present experiment the hatching time varied between 22 and 27 hr at
24–26 0C. The
hatching period of P. sutchi ranges from 24–36 hr at 22–32 0C
(Islam 2005) and that of C. gariepinus 21–26 hr at 20–32 0C
(Bruton 1979). A water pH of
6.5–7.0 (mean 6.93±0.55) was found to be suitable for hatching and larval
rearing of H. brachysoma in the laboratory conditions. At a higher pH (7.6–7.8) hatching
was delayed, all the developmental stages were arrested, while eggs succumbed
at a pH higher than 8.5 (Bindu 2006).
Yolk-sac larvae period
The newly hatched
larvae (3.94±0.112 mm) retained the remnant yolk on the ventral side. The
hatchlings were slender and transparent with unpigmented eyes, and without a
distinct mouth (Image 2a). They
were laterally compressed and curved around the circular yolk sac with the
downward protrusion of the head. The notochord and myomeres were more
prominent. The hatchlings gradually
straightened with lashing tail movements and were congregated in the tank
corners. Anal fin fold extended
from the postero-dorsal end to the ventral region. Size of the hatchlings varied between
3.8 and 4.1 mm similar to C. gariepinus (3.4–4.0 mm), but larger
than Mystus montanus, M. cavasius, P. sutchi and H. fossilis(Arockiaraj et al. 2003; Rahman et al. 2004; Islam 2005; Bindu et al. 2009).
Pigmented eyes
and functional mouth parts formed in the 2 DPH
larvae. Two pairs of barbels became
visible and the auditory vesicles were more distinct (Image.2b). The pulsating,two chambered heart and the streaming of larval blood
circulation to the caudal fin became perceptible at this stage. The body thickened and increased in
length. The length of the larvae
ranged between 4.75 and 5.25 mm (5.08 ± 0.164 mm). At this time, the mean diameter of
the yolk sac was 1.39±0.067 mm. At
3 DPH, the size of the larvae varied between 5 and 5.75 mm (5.52±0.571
mm). The absorption of the yolk sac
started from the mouth region and by the end of 3 DPH, 90% of the yolk was
absorbed and the yolk sac was 1.35±0.08 mm in diameter. The upper and lower jaws were well developed. Four pairs of barbels were clearly
visible. Melanophores were observed
along the head and dorsal surface of the body. The pelvic fin became visible, and the
fin fold appeared to be continuous, extending dorsally from behind the head, up
to the postero-ventral margin of the yolk. The larvae started to move actively in the water.
Post yolk-sac larvae period
The
yolk was fully absorbed four days after the completion of embryonic development
(Image 2c) and the diameter of the yolk sac reduced to 1.1±0.065 mm. the length of
the larvae ranged from 5.5–6.3 mm (5.9±0.307 mm). The head appeared broad and well
differentiated with denser pigmentation. Barbels became elongated; the maxillary pair was perceptibly longer than
the others. Pectoral fin rays
became well differentiated with their characteristic spines. In H. brachysoma, the hatchlings
subsisted on endogenous nutrition from the yolk till 4 DPH, and accepted
exogenous feeding from the 5 DPH at which stage they were fed on powdered yolk
of boiled egg. The hatchlings
could gradually be weaned to powdered pellet feed also. The gape size of the larvae became
appropriate to feed on the live plankton in 4–5 DPH, and the jaw bones became stronger. At this time, the tip of the caudal fin
bifurcated and caudal fin rays became clearly visible. The characteristic black humeral ocellus
became more prominent, and the fry grew to an average size of 6.75±0.49 mm
(range: 6.0–7.5 mm) in a week. They were subsequently transferred to fry nursing hapas and cement tanks
for further rearing.
Juvenile Period
The
fry attained a size of 26.2±2.39 mm in a month, when fed at the rate of 10% of
biomass. Feed management,
especially exogenous feeding of the newly hatched larvae, is considered to be a
major constraint in fish larviculture (Sorgeloos & Leger 1992; Wittenrich
et al. 2007). The observation that
larvae of H. brachysoma accept and relish commercial feed at a very
early stage, as is evident from 50–75 % survival in fry nursing, is of
great significance. The larvae
achieved 58–65 mm in 85 days (Table 3) (Image 3). In addition to the naturally available
plankton, fish fry were also fed with rice bran and ground
nut oil cake. Probably this
mixed feeding behavior in the early life history stages of H. brachysomaappears to be a factor that favors smooth weaning of the early larvae to
artificial diets.
Conclusion
Horabagrusbrachysoma, is
found to be a potential candidate for diversification of aquaculture due to its
hardy nature, omnivorous feeding behaviour (Sreeraj et al. 2006; Padmakumar et
al. 2009) as well as high fecundity (Bindu et al. 2012). Anthropogenic impacts including overfishing
(Prasad et al. 2012), habitat loss and delayed monsoon could result in large scale depletion of wild populations of this threatened
species. Mass seed production
through induced breeding would therefore help in stock enhancement and ranching
in our natural water bodies facilitating the conservation and management of H.
brachysoma wild populations. However significant improvements in larval rearing technology will need
to be achieved for popularization of rearing and culture techniques. The results of the present study provide
baseline information for further investigations regarding multiple spawning behavior, larval rearing and pond culture of this endemic
and threatened species.
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