Post by MADMIKE on Jul 12, 2007 12:12:51 GMT -5
The fry patterns in the South American catfish genus Corydoras
(Pisces, Siluriformes, Callichthyidae)
Ian Fuller
ABSTRACT
The fry pattern of aquarium-bred species of the South-American catfish genus Corydoras,
contribute to discriminate between species of the so-called 'acutus'- group, showing a greyish
adult colour pattern.
INTRODUCTION
Identifying many of the Corydoras species can be extremely difficult and none more so
than the long-snouted members in, the sosh adult colour patterns. Although there are
about twenty species within this group, seven species were successfully bred under
controlled aquarium conditions. It is demonstrated that the colour patterns change during
the fry's three to four month period to adulthood and maturity. It was thought that
juvenile colour patterns might be an additional character with which to differentiate
between the different species. This was demonstrated earlier with two of the short-
snouted species of Corydoras: C. rabauti (La Monte, 1941) and C. zygatus (Eigenmann
& Allen, 1942). They were considered as one species by many authors, until breeding
experiments by the author (Fuller, 1983a) revealed that these two species possessed
totally different body colour patterns during their larval stages.
MATERIAL
The seven species involved are: C. acutus (Cope, 1872): 4 males-2 females, C. blochi
blochi (Nijssen, 1971): 2 males-4 females, C. septentrionalis (Gosline, 1940): 3 males-2
females, C. treitlii (Steindachner, 1906): 2 males-2 females, C. amapaensis (Nijssen,
1972): 3 males-i female, C. ellisae (Gosline, 1940): 3 males-3 females, and C.
stenocephalus (Eigenmann & Allen, 1942): 2 males-2 females, all obtained from
aquarium fish importers. The fry colour patterns are recorded in line drawing form, and
were made when the fry had reached the age seven days and twenty-eight days
respectively, and at the time when they reached the pattern of an adult female.
The adult female pattern was chosen as the datum point at which fry are deemed to have
reached their adult coloration. (Figs. 1-7).
METHODS
All seven species were bred in aquariums of similar size (length 45cm, width 35cm,
height 30cm), with similar furnishings. All seven species spawned in a very similar way
following a pre-determined sequence of events.The sexual activity starts with a male of
the species actively pursuing one of the females until she submits to his attentions, at
which point she reverses rolls and pursues the male. The male then takes on a quivering
arched sideways stance, allowing the female to push headfirst into the side of his body, at
a point just above and slightly in front of the ventral fins. At the moment of contact the
male grips the female by clamping across her barbels with his pectoral fin spine, holding
her firmly against the side of his body. The grip is maintained until the male has stopped
quivering, this grip being referred to as the 'mating clinch'. Both fish then separate with
the female actively cleaning various sites around the aquarium before depositing her
eggs, the male being in close attendance all the time and ready to mate. During the
mating clinch which may take place at all levels in the aquarium from the substrate, in
amongst the plants and spawning mops to mid water, the female will deposit her eggs
into a pouch made by pressing her ventral fins together. When a pair of fish mate in mid
water and after the male has stopped quivering, they drift to the substrate where they may
rest for several seconds before separating. No method has yet been devised to
successfully determine how and at what point the eggs are fertilised.
In each of the seven species spawning activities the none participating fish were left in
the aquariums with the spawning pairs and in all seven cases the none participating
females showed no interest at all. The males however persisted with their attempts to
mate with the active female, in all seven cases the first male selected by the female made
sure that he was always between her and the other pursuing males. With all seven species
after spawning activity had ceased the adult fish were removed.
Figs. 1 - 7. Adult females of seven long-snouted species of Corydoras: C. acutus, C.
blochi blochi, C. septentrionalis, C. treitlii, C. amapaensis, C. ellisae, C. stenocephalus.
Table I.
Water conditions of the tanks during the time of spawning of seven Corydoras species.
pH (Pondus hydrogenii) = acidity! alkalinity; neutral measurement = 7.
GH (General hardness = total hardness, measured in degrees dH) is a measure of all
dissolved salts. 0-5 = soft, 6–10 = medium, 11-20 = medium hard = medium hard.
KR (Carbonate hardness) a measure of (bi)carbonates.
Temperature recorded in degrees Celsius
pH GH (dH) KH Temp
Corydoras acutus 7.2 12 2 21.1
Corydoras amapaensis 7.4 14 1 23.3
Corydoras blochi blochi 6.8 10 3 25.5
Corydoras ellisae 7.0 9 1 23.3
Corydoras septentrionalis 7.4 8 1 23.8
Corydoras stenocephalus 6.8 10 3 25.5
Corydoras treitlii 7.4 12 2 22.2
CONDITIONS
None of the seven species (Table I) showed preference as to the level at which to deposit
their eggs, with eggs being deposited close to the substrate and to within twenty
millimetres of the surface.
The fry of all seven species take from between eighty-five to one hundred hours to hatch
(Table II) depending on the water temperature. Although the temperature is not a
controlling factor it does have a slight bearing on the developing embryos. For example,
C. acutus that spawned at 21,1 deg C. and took between ninety and one hundred hours for
all of the fry to emerge. When spawned at 23,9 deg C. they would hatch in eighty-five to
ninety five hours, but at 26,5 deg C. they still take between eighty-five and ninety five
hours to hatch.
Of the seven species bred five, - # C. acutus, C. ellisae, C. septentrionalis, C.
stenocephalus, and C. treitiii, # preferred to deposit their eggs in either Java Moss or the
woollen spawning mops. The remaining two, C. amapaensis, and C. blochi blochi
divided their eggs evenly between the tank sides and the clumps of Java Moss.
The growth rates shown in the following table are an average taken from ten specimens
to the nearest 0.5 mm.
By the seventh day after hatching the fry of all the seven species have developed their
own distinctive colour patterns. (Figs. 8-14). Five of the species (C. acutus, C.
amapaensis, C. blochi blochi C. septentrionalis and C. stenocephalus) show patterns that
are rather similar to each other. C. ellisae and C. treitili have exactly the same patterns as
each other, differing from the other live species by having no markings along the sides of
the body.
As the fry of the seven species grow and develop, their colour patterns are constantly
changing and reach a maximum intensity by the time they are four to six weeks old. The
pigmentation forms into irregular markings that cover most of the fishes body, giving all
seven species a dark blotchy appearance especially when viewed from above, as shown in
Figs. 15-21. From six weeks onward the ever changing colour patterns of the fry, start to
develop into the more recognisable patterns of the adult female.
By the time the fry of all seven species are aged between eight and ten weeks old, they
will all have attained the colour pattern shown by adult females, as demonstrated in Figs.
1-7.
The effect of water temperature on all the fry's growth rates, is very much the same as on
egg development. More importantly water quality does have a positive effect on growth
rates. Water quality that had been allowed to deteriorate through contamination from
excess build up of the fry's waste matter effectively retarded growth, it is thought that
permanent growth damage would occur if conditions were allowed to prevail for any
length of time. To maintain maximum fry growth rates daily 30% water changes were
made.
DISCUSSION
Adult female coloration was chosen as the time at which fry were deemed to have
reached adulthood. This was because with other species of Corydoras e.g. C. barbatus
(Quoy & Gaimard, 1824) that have been bred - where there are known colour differences
between the sexes - the males of some of these species can take a further eight or even as
long as twelve weeks to mature and develop their adult colours. (Fuller, 1983b).
Figs. 8 – 14
Table II.
Details of egg production of seven Corydoras species. Per column: total number of eggs,
diameter, number of eggs laid at a time, adhesion, and time to hatch. The adhesion (how
well they stick) is a value of personal rating out of 10.
Number
per
female
Diameter
in mm
Number
laid at a
time
adhesion Time to hatch
C. acutus 40 1.5mm 2 - 4 4 4 days/90-100hrs
C. amapaensis 150 1.5mm 3 - 8 5 4 days/90-100hrs
C. blochi blochi 50 1.3mm 2 - 4 7 4 days/90-100hrs
C. ellisae 65 1.0mm 2 - 5 3 3-4 days/85-100hrs
C. septentrionalis 110 1.6mm 2 - 4 4 3-4 days/85-100hrs
C. stenocephalus 60 1.3mm 3 - 5 7 4 days/90-100hrs
C. treitlii 55 1.3mm 2 - 5 5 3-4 days/85-95hrs
Table 111.
Fry growth rates of seven Corydoras species, showing their total lengths per period of
time.
7 days 1 month 2 months 3 months Adult colour
reached in
C. acutus 4.0mm 7.0mm 14.0mm 22.0mm 8-10 weeks
C. amapaensis 4.5mm 8.0mm 15.0mm 22.0mm 10-12 weeks
C. blochi blochi 5.0mm 9.0mm 16.0mm 23.0mm 7-8 weeks
C. ellisae 4.5mm 8.5mm 15.5mm 23.0mm 8-9 weeks
C. septentrionalis 5.0mm 9.0mm 14.5mm 21.5mm 10-12 weeks
C. stenocephalus 5.5mm 9.5mm 15.0mm 20.5mm 8-10 weeks
C. treitlii 4.5mm 8.5mm 15.0mm 22.0mm 9-10 weeks
With the seven species so far bred from the 'acutus' group there were no discerning colour
differences between the sexes that could be readily recognised. The first visual signs of
maturing males are in the fin spines, the pectoral and ventral fins being the most
prominent; becoming thicker and more elongated. In mature males of the seven species
spawned the ventral fins are possibly the most reliable indicator of sex, as these become
elongated and pointed compared to the rounded tan shaped fins of the temales.
As with most animals, growth rates can vary tremendously. Corydoras fry are no
exception, and caused some concern when one or two of the faster growing quicker
developing males became dominant and were observed chasing and bullying smaller less
mature specimens. The aggression became so intense preventing the smaller fry from
feeding altogether.
To further assist and improve the survival rate of the smaller male fry, large clumps of
Java Moss were placed in all the fry rearing tanks. This had the effect of giving all the fry
a secure refuge, and enabled the smaller males to avoid the bullying by the larger ones. It
also had the effect of reducing the amount of squabbling between males of equal size,
enabling the majority to reach adulthood (between sixty and seventy percent of the fry of
all seven species reached adulthood).
Long-term observations have shown that female Corydoras fry grow at a faster rate than
males, as twenty percent. With the seven species bred from the 'acutus' group there is a
difference of between ten and fifteen percent in standard length after ten months. Despite
growth variation within each of the sexes, after ten to twelve week's males and females
can be separated with relative ease:
REFERENCES
Fuller, I. 1983a. Lookalikes unmasked. Practical Fishkeeping January: 32-33.
Fuller, I. 1983b. Spawning Corydoras barbatus. Freshwater and marine aquarium 6 (12):
24-25, 67-68.
Nijssen, H. & I.J.H. lsbrücker, 1980. A review of the genus Corydoras Lacepede, 1803
(Pisces, Siluriformes, Callichthyidae) Bijdr. Dierk. 50(1): 190-220.
(Pisces, Siluriformes, Callichthyidae)
Ian Fuller
ABSTRACT
The fry pattern of aquarium-bred species of the South-American catfish genus Corydoras,
contribute to discriminate between species of the so-called 'acutus'- group, showing a greyish
adult colour pattern.
INTRODUCTION
Identifying many of the Corydoras species can be extremely difficult and none more so
than the long-snouted members in, the sosh adult colour patterns. Although there are
about twenty species within this group, seven species were successfully bred under
controlled aquarium conditions. It is demonstrated that the colour patterns change during
the fry's three to four month period to adulthood and maturity. It was thought that
juvenile colour patterns might be an additional character with which to differentiate
between the different species. This was demonstrated earlier with two of the short-
snouted species of Corydoras: C. rabauti (La Monte, 1941) and C. zygatus (Eigenmann
& Allen, 1942). They were considered as one species by many authors, until breeding
experiments by the author (Fuller, 1983a) revealed that these two species possessed
totally different body colour patterns during their larval stages.
MATERIAL
The seven species involved are: C. acutus (Cope, 1872): 4 males-2 females, C. blochi
blochi (Nijssen, 1971): 2 males-4 females, C. septentrionalis (Gosline, 1940): 3 males-2
females, C. treitlii (Steindachner, 1906): 2 males-2 females, C. amapaensis (Nijssen,
1972): 3 males-i female, C. ellisae (Gosline, 1940): 3 males-3 females, and C.
stenocephalus (Eigenmann & Allen, 1942): 2 males-2 females, all obtained from
aquarium fish importers. The fry colour patterns are recorded in line drawing form, and
were made when the fry had reached the age seven days and twenty-eight days
respectively, and at the time when they reached the pattern of an adult female.
The adult female pattern was chosen as the datum point at which fry are deemed to have
reached their adult coloration. (Figs. 1-7).
METHODS
All seven species were bred in aquariums of similar size (length 45cm, width 35cm,
height 30cm), with similar furnishings. All seven species spawned in a very similar way
following a pre-determined sequence of events.The sexual activity starts with a male of
the species actively pursuing one of the females until she submits to his attentions, at
which point she reverses rolls and pursues the male. The male then takes on a quivering
arched sideways stance, allowing the female to push headfirst into the side of his body, at
a point just above and slightly in front of the ventral fins. At the moment of contact the
male grips the female by clamping across her barbels with his pectoral fin spine, holding
her firmly against the side of his body. The grip is maintained until the male has stopped
quivering, this grip being referred to as the 'mating clinch'. Both fish then separate with
the female actively cleaning various sites around the aquarium before depositing her
eggs, the male being in close attendance all the time and ready to mate. During the
mating clinch which may take place at all levels in the aquarium from the substrate, in
amongst the plants and spawning mops to mid water, the female will deposit her eggs
into a pouch made by pressing her ventral fins together. When a pair of fish mate in mid
water and after the male has stopped quivering, they drift to the substrate where they may
rest for several seconds before separating. No method has yet been devised to
successfully determine how and at what point the eggs are fertilised.
In each of the seven species spawning activities the none participating fish were left in
the aquariums with the spawning pairs and in all seven cases the none participating
females showed no interest at all. The males however persisted with their attempts to
mate with the active female, in all seven cases the first male selected by the female made
sure that he was always between her and the other pursuing males. With all seven species
after spawning activity had ceased the adult fish were removed.
Figs. 1 - 7. Adult females of seven long-snouted species of Corydoras: C. acutus, C.
blochi blochi, C. septentrionalis, C. treitlii, C. amapaensis, C. ellisae, C. stenocephalus.
Table I.
Water conditions of the tanks during the time of spawning of seven Corydoras species.
pH (Pondus hydrogenii) = acidity! alkalinity; neutral measurement = 7.
GH (General hardness = total hardness, measured in degrees dH) is a measure of all
dissolved salts. 0-5 = soft, 6–10 = medium, 11-20 = medium hard = medium hard.
KR (Carbonate hardness) a measure of (bi)carbonates.
Temperature recorded in degrees Celsius
pH GH (dH) KH Temp
Corydoras acutus 7.2 12 2 21.1
Corydoras amapaensis 7.4 14 1 23.3
Corydoras blochi blochi 6.8 10 3 25.5
Corydoras ellisae 7.0 9 1 23.3
Corydoras septentrionalis 7.4 8 1 23.8
Corydoras stenocephalus 6.8 10 3 25.5
Corydoras treitlii 7.4 12 2 22.2
CONDITIONS
None of the seven species (Table I) showed preference as to the level at which to deposit
their eggs, with eggs being deposited close to the substrate and to within twenty
millimetres of the surface.
The fry of all seven species take from between eighty-five to one hundred hours to hatch
(Table II) depending on the water temperature. Although the temperature is not a
controlling factor it does have a slight bearing on the developing embryos. For example,
C. acutus that spawned at 21,1 deg C. and took between ninety and one hundred hours for
all of the fry to emerge. When spawned at 23,9 deg C. they would hatch in eighty-five to
ninety five hours, but at 26,5 deg C. they still take between eighty-five and ninety five
hours to hatch.
Of the seven species bred five, - # C. acutus, C. ellisae, C. septentrionalis, C.
stenocephalus, and C. treitiii, # preferred to deposit their eggs in either Java Moss or the
woollen spawning mops. The remaining two, C. amapaensis, and C. blochi blochi
divided their eggs evenly between the tank sides and the clumps of Java Moss.
The growth rates shown in the following table are an average taken from ten specimens
to the nearest 0.5 mm.
By the seventh day after hatching the fry of all the seven species have developed their
own distinctive colour patterns. (Figs. 8-14). Five of the species (C. acutus, C.
amapaensis, C. blochi blochi C. septentrionalis and C. stenocephalus) show patterns that
are rather similar to each other. C. ellisae and C. treitili have exactly the same patterns as
each other, differing from the other live species by having no markings along the sides of
the body.
As the fry of the seven species grow and develop, their colour patterns are constantly
changing and reach a maximum intensity by the time they are four to six weeks old. The
pigmentation forms into irregular markings that cover most of the fishes body, giving all
seven species a dark blotchy appearance especially when viewed from above, as shown in
Figs. 15-21. From six weeks onward the ever changing colour patterns of the fry, start to
develop into the more recognisable patterns of the adult female.
By the time the fry of all seven species are aged between eight and ten weeks old, they
will all have attained the colour pattern shown by adult females, as demonstrated in Figs.
1-7.
The effect of water temperature on all the fry's growth rates, is very much the same as on
egg development. More importantly water quality does have a positive effect on growth
rates. Water quality that had been allowed to deteriorate through contamination from
excess build up of the fry's waste matter effectively retarded growth, it is thought that
permanent growth damage would occur if conditions were allowed to prevail for any
length of time. To maintain maximum fry growth rates daily 30% water changes were
made.
DISCUSSION
Adult female coloration was chosen as the time at which fry were deemed to have
reached adulthood. This was because with other species of Corydoras e.g. C. barbatus
(Quoy & Gaimard, 1824) that have been bred - where there are known colour differences
between the sexes - the males of some of these species can take a further eight or even as
long as twelve weeks to mature and develop their adult colours. (Fuller, 1983b).
Figs. 8 – 14
Table II.
Details of egg production of seven Corydoras species. Per column: total number of eggs,
diameter, number of eggs laid at a time, adhesion, and time to hatch. The adhesion (how
well they stick) is a value of personal rating out of 10.
Number
per
female
Diameter
in mm
Number
laid at a
time
adhesion Time to hatch
C. acutus 40 1.5mm 2 - 4 4 4 days/90-100hrs
C. amapaensis 150 1.5mm 3 - 8 5 4 days/90-100hrs
C. blochi blochi 50 1.3mm 2 - 4 7 4 days/90-100hrs
C. ellisae 65 1.0mm 2 - 5 3 3-4 days/85-100hrs
C. septentrionalis 110 1.6mm 2 - 4 4 3-4 days/85-100hrs
C. stenocephalus 60 1.3mm 3 - 5 7 4 days/90-100hrs
C. treitlii 55 1.3mm 2 - 5 5 3-4 days/85-95hrs
Table 111.
Fry growth rates of seven Corydoras species, showing their total lengths per period of
time.
7 days 1 month 2 months 3 months Adult colour
reached in
C. acutus 4.0mm 7.0mm 14.0mm 22.0mm 8-10 weeks
C. amapaensis 4.5mm 8.0mm 15.0mm 22.0mm 10-12 weeks
C. blochi blochi 5.0mm 9.0mm 16.0mm 23.0mm 7-8 weeks
C. ellisae 4.5mm 8.5mm 15.5mm 23.0mm 8-9 weeks
C. septentrionalis 5.0mm 9.0mm 14.5mm 21.5mm 10-12 weeks
C. stenocephalus 5.5mm 9.5mm 15.0mm 20.5mm 8-10 weeks
C. treitlii 4.5mm 8.5mm 15.0mm 22.0mm 9-10 weeks
With the seven species so far bred from the 'acutus' group there were no discerning colour
differences between the sexes that could be readily recognised. The first visual signs of
maturing males are in the fin spines, the pectoral and ventral fins being the most
prominent; becoming thicker and more elongated. In mature males of the seven species
spawned the ventral fins are possibly the most reliable indicator of sex, as these become
elongated and pointed compared to the rounded tan shaped fins of the temales.
As with most animals, growth rates can vary tremendously. Corydoras fry are no
exception, and caused some concern when one or two of the faster growing quicker
developing males became dominant and were observed chasing and bullying smaller less
mature specimens. The aggression became so intense preventing the smaller fry from
feeding altogether.
To further assist and improve the survival rate of the smaller male fry, large clumps of
Java Moss were placed in all the fry rearing tanks. This had the effect of giving all the fry
a secure refuge, and enabled the smaller males to avoid the bullying by the larger ones. It
also had the effect of reducing the amount of squabbling between males of equal size,
enabling the majority to reach adulthood (between sixty and seventy percent of the fry of
all seven species reached adulthood).
Long-term observations have shown that female Corydoras fry grow at a faster rate than
males, as twenty percent. With the seven species bred from the 'acutus' group there is a
difference of between ten and fifteen percent in standard length after ten months. Despite
growth variation within each of the sexes, after ten to twelve week's males and females
can be separated with relative ease:
REFERENCES
Fuller, I. 1983a. Lookalikes unmasked. Practical Fishkeeping January: 32-33.
Fuller, I. 1983b. Spawning Corydoras barbatus. Freshwater and marine aquarium 6 (12):
24-25, 67-68.
Nijssen, H. & I.J.H. lsbrücker, 1980. A review of the genus Corydoras Lacepede, 1803
(Pisces, Siluriformes, Callichthyidae) Bijdr. Dierk. 50(1): 190-220.