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The effect of temperature and salinity on
the larval development of Stenorhynchus
seticornis (Brachyura: Inachidae) reared
in the laboratory
jesu
’
s e. herna
’
ndez
1
, jose
’
luis palazo
’
n-ferna
’
ndez
2
, gonzalo herna
’
ndez
1
and juan bolan
~
os
1
1
Universidad de Oriente, Escuela de Ciencias Aplicadas del Mar, Boca del Rı
´
o, Isla de Margarita, Venezuela,
2
Universidad de
Oriente, Instituto de Investigaciones Cientı
´
ficas, Boca del Rı
´
o, Isla de Margarita, Venezuela
Larvae of Stenorhynchus seticornis were reared in the laboratory in a factorial experiment employing three temperatures (22,
25 and 288C) and three salinities (30, 35 and 40‰) to determine the effects of these variables on the survival and duration of
the larval stages. Larvae from five females were subdivided in six groups of 10 and reared in glass bowls containing 125 ml
filtered and UV-irradiated seawater at different temperature–salinity combinations. Larvae were transferred daily to clean
bowls with newly hatched Artemia nauplii, and the number of moults and mortality within each bowl was recorded.
Complete larval development of S. seticornis occurred under all experimental conditions, except at temperature 288C and
salinity 35‰. Salinity affected percentage survival of the two zoeal stages, but not that of the megalopa. Survival of the
second zoeal stage, the megalopa, and the complete development to the first crab was affected by temperature, with the greatest
survival occurring at 258C. Duration of the two zoeal stages, the megalopa, and development to the first crab stage showed a
gradual reduction with increasing temperature. Development from hatching to the first crab stage required 17 to 31 days and
was inversely related to temperature, averaging 26.9 days at 228C, 21.0 days at 258C and 19.7 days at 288C. Salinity affected
the duration of the first zoeal stage only.
Keywords: larval development, temperature, salinity, Stenorhynchus seticornis
Submitted 9 June 2009; accepted 8 March 2010; first published online 5 July 2010
INTRODUCTION
In recent years, the marine ornamental industry has experi-
enced exponential growth which has created a high demand
for many species of fish, corals and crustaceans. The marine
ornamental industry relies heavily on wil d-collected speci-
mens, mainly from coral reefs. This, combined with the preva-
lence of destructive harvesting techniques, has increased
anthropogenic pressure on these fragile ecosystems (see
Rhyne et al., 2005 for references).
Along with corals, marine tropical decapod crustacean s are
among the most popular invertebrate species in the aquarium
trade industry (Calado et al., 2003). In recent years, research-
ers have begun a worldwide effort to minimize the growing
pressure on natural populations of marine ornamental
species and to promot e the sustainable use of these highly
valued resources (Corbin, 2001). Nevertheless, this goal will
only be achieved if wild specimen collection is significantly
replaced by the artificial rearing of these species (Calado
et al., 2003). Aquaculture is thus a viable long-term alternative
to wild collection , allowing the aquarium trade’s future to
become independent from natural resources (Lin & Shi,
2002; Rhyne et al., 2005), and minimizing the negative
impacts on the natural environment (Lin & Shi, 200 2).
Studies on the larval development of decapod crustaceans
have received great attention because they provide not only
valuable information on the larval morphology that helps in
the identification and general classification of larvae and
species, but provide knowledge on the effects of environ-
mental factors such as temperature, salinity, water quality,
antibiotics, culture systems, feeding, etc. on the larval develop-
ment of species with biological and/or economic interests
(Boschi & Scelzo, 1969; Bolan
˜
os, 1992; Nagaraj, 1992;
Gonc¸alves et al., 1995). Raising larvae to juveniles also
provides opportunities for detailed studies in physiology,
biochemistry, genetics and behaviour (Sastry, 1970).
Early stages of development are the most sensitive phase in
the complex life cycle of marine invertebrates, and to maxi-
mize their survival, larvae should be reared close to optimal
conditions (Zacharia & Kakati, 2004). Defining these
optimal conditions for culture of euryhaline marine species
is fundamental to develop optimal rearing protocols for
these species (Sastry, 1970; Zacharia & Kakati, 2004).
Larval development in Crustacea occurs within a well
defined range of environmental conditions characteristic to
a species. Of the environmental factors that affect crustacean
development, temperature and salinity have received great
Corresponding author:
J.L. Palazo
´
n-Ferna
´
ndez
Emails: juis.palazon@icman.csic.es; jose.palazon@ne.udo.edu.ve
505
Journal of the Marine Biological Association of the United Kingdom, 2012, 92(3), 505–513. # Marine Biological Association of the United Kingdom, 2010
doi:10.1017/S0025315410000809
attention because they significantly affect survival and the
extent of larval life (Costlow & Bookhout, 1968; Hicks,
1973; Anger, 1983; Gonc¸alves et al., 1995; La
´
rez et al., 2000;
Li & Hong, 2007). Differences in tolerance to these factors
have been observed depending, in part, on the stage of devel-
opment, the species and its habitat (Dı
´
az & Bevilacqua, 1986).
Within a tolerated range, temperature mostly affects dur-
ation of larval stages, and these in turn affect dispersal and
gene flow interacting with coastal physical processes (Crisp,
1976). Salinity influences many physiological functions and
is therefore important in regulating the distribution of estuar-
ine and marine organisms (Ehlinger & Tankersley, 2004).
Larval survival is thus strongly affected by temperature and
salinity (Sandifer, 1973; Paula et al., 2001) although each
species tolerance will be specific for its degree of adaptation
to the environmental gradients of coastal systems (Paula
et al., 2003).
In the field, environmental factors such as temperature and
salinity frequently affect organisms in an interactive way.
Therefore, it is important to investigate responses to the com-
bined effects of temperature and salinity in order to under-
stand, at least in part, the significance of these factors on
survival during early larval development and the problems
involved in recruitment in the natural enviro nment, as well
as the possibility of its successful culture (Mene et al., 1991;
Zacharia & Kakati, 2004).
The arrow crab, Stenorhynchus seticornis (Herbst, 1788) is
a common species in eastern Venezuelan coastal waters.
It lives in a variety of bottoms—rocks, corals, pebbles, sand,
or sand mixed with broken shell, wharf piling and rock
jetties—from the intertidal zone to 188 m in depth
(Williams, 1984) and ranges alo ng the west Atlanctic coasts,
from North Carolina to Argentina (Melo, 1996). It is com-
monly associated with sponges, stony corals, soft corals, gor-
gonians, anemones and echinoderms (Hayes et al., 1998).
The species is appreciated by aquarists owing to its extremely
long legs which resemble those of a spider. As stressed by
Rhyne et al. (2005) for the majoid crabs, the abbreviated
larval development of the species (two zoeae and one mega-
lopa) should be appealing for commercial culture if high
larval survival can be obtained.
Few studies have been conducted on the biology of S. seti-
cornis. Larval development was described by Yang (1976).
Quintero (1986) tested animal and vegetal based diets on
larval development; Herna
´
ndez et al. (1999) tested the
effects of starvation on the larvae; Cobo (2002) and
Okamori & Cobo (2003) studied some reproductive traits.
The purpose of the present work was to determine the
effects of various temperature–salinity combinations on the
survival and duration of the larval stages of S. seticornis
under laboratory conditions.
MATERIALS AND METHODS
Ovigerous females of S. seticornis were collected from El
Morro beach, south-east coast of Margarita Is land,
Venezuela (10857
′
15
′′
N63848
′
30
′′
W), and brought to the lab-
oratory in aerated containers with seawater from the site of
collection. The animals were maintained in individual
aquaria at temperatures of 25–278C and salinities of 36 –
38‰, and fed with Artemia, Mysidacea, and/or filamentous
green algae.
Five females with eggs near hatching (following the general
criteria given by Boschi, 1981) were selected, and isolated.
After hatching of their eggs, the females were removed from
the aquaria, and the larvae were subdivided into groups of
10 and transferred into glass bowl s containing 125 ml filtered
(5 m m) and UV-irradiated (1.5 l. min
21
) seawater at the
experimental temperatures and salinities. Only vigorously
swimming, apparently healthy larvae were used.
Selected larvae were reared in each of nine temperature (22,
25 and 288C) and salinity (30, 35 and 40‰) combinations.
The ranges of temperature and salinity used were chosen so
as to span the ranges found in coastal waters near Margarita
Island where the ovigerous females were collected. Each
rearing was carried out in six replicates (bowls with 10
larvae) per female. A total of 2700 larvae (540 per female)
were used in the experiment. Bowls were covered to reduce
evaporation, and/or contamination. All larvae were exposed
to a photoperiod of approximately 10 hours light and 14
hours dark. As a precaution against possible thermal shock,
larvae were acclimated to the experimental temperatures by
gradually reducing or increasing temperatures (approximately
1 degree/hour) within the bowls until the experimental con-
ditions were reached. Experimental temperatures were
obtained by placing the experimental bowls in temperature-
controlled water baths.
Forty ppt salinity was obtained by mixing locally-obtained
seawater with hypersaline water (147‰) from Boca Chica
Lagoon, Margarita Island. Both waters were previously fil-
tered, and UV-irradiated. Low salinities were obtained by
diluting filtered and UV-irradiated seawater with distilled
water.
Larvae were fed daily on newly hatched Artemia nauplii
(Great Salt Lake, Utah), (approximately 5 nauplii per ml), as
recommended by Quintero (1986). In order to avoid salinity
changes in the experimental bowls, nauplii were previously
screened and rinsed with filtered seawater at the experimental
salinities. Artemia cysts were decapsulated in a hypochlorite
solution (Ortiz et al., 1991).
The number of moults and mortality within each bowl was
recorded daily. Remaining larvae were transferred to clean
bowls with filtered and UV-treated seawater at the same temp-
erature and salinity, and newly hatched Artemia nauplii were
added. The experiment was concluded when all larvae had
moulted to the first crag stage or died.
Differences between survival (arcsin-transformed percen-
tages) and duration for each stage and for the complete devel-
opment were assessed by means of a factorial, model I,
analysis of variance (ANOVA) (Sokal & Ro
¨
hlf, 1981).
Females were treated as blocks. In the case of duration of
the first zoeae, bowls were considered as a possible source of
variation and treated as a nested factor. The Student–
Newman–Keuls (SNK) multiple range test was used to con-
trast means when treatment differences were significant
(Sokal & Ro
¨
hlf, 1981). Perc entage survival for each stage
was calculated with respect to the number of larvae reaching
that stage.
RESULTS
As in other majoids, the early postembryonic development of
S. seticornis consists of two zoeal stages before attaining the
506 jesu
’
se.herna
’
ndez et al.
megalopa. The experimental conditions used in the present
work did not affect this pattern of development.
Survival
Day to day survival from hatching to the first crab stage at
different experimental temperature–salinity combinations is
illustrated in Figure 1. The rate of survival shows a steeper
decline at 288C at all salinities.
Complete larval development occurred in all experimental
conditions, except at 288 C, 35‰, even though only 1% of
the larvae in the experiment reached the first crab stage. The
highest mean survival from hatching to the first crab stage
(4.5%) occurred at 258C; 30‰. At this temperature –salinity
combination some recipients showed survivals as high as
26.6%, At 228C larvae required longer times (27–35 days)
to complete development to the first crab (Figure 1).
first zoea
Mean survival at this stage was ≤61% under all experimental
conditions, and was influenced by salinity (F ¼ 3.43; P ,
0.05), but not by temperature (F ¼ 2.02; P . 0.05). The
effect of temperature–salinity interaction was not significant
(F ¼ 0.32; P . 0.05) so the effects were considered as inde-
pendent. Only 30 and 35‰ differed in percentage survival.
Highest mean survival (61.3%) occurred at 288C, 30‰, the
lowest survival (49.3%), was at 258C, 35‰ (Figure 2).
second zoea
Mean survival at this stage varied from 26% at 288C, 35‰ to
59.6% at 258C, 30‰. Analysis of variance showed differences
due to different salinities (F ¼ 3.65; P , 0.05), and tempera-
tures (F ¼ 20.55, P , 0.001). The effect of temperature–sal-
inity interaction was not significant (F ¼ 0.59, P . 0.05).
The SNK test indicated that there was no difference in percen-
tage survival between 22 and 258C, which had the highest
survival. The observed differences are due to the considerable
reduction in survival at the highest temperature (288C), at all
salinities (Figure 2). Only extreme salinities differed in percen-
tage survival. The higher mean survi val was observed at 30‰
(Figure 2) .
megalopa
This stage showed the highest mortality during the exper-
iment. Percentage survi val was lower than 12% under all
experimental conditions. No megalopa moulted to the first
crab under 288C, 35‰, and only 1% larvae moulted at
288C, 40‰. The highest mean survival rate (12.2%) occurred
at 258C, 30‰ (Figure 2).
Percentage survival in megalopae differed significantly
within temperatures (F ¼ 4.41; P , 0.05) but not within
salinities (F ¼ 1.55; P . 0.05). Interaction between these two
parameters was not significant (F ¼ 1.93; P . 0.05).
Extreme temperatures (22 and 288C) resulted in decreased
percentage survival.
cumulative survival fr om hatching
to the first crab stage
Survival was low under all experimental conditions. The
highest mean survival (3.0%) occurred at 258C, 30‰ and
the lowest (0%) at 288C , 35‰.
Analysis of variance showed significant differences due to
temperatures only (F ¼ 4.19; P , 0.05). A SNK test indicated
differences between 25 and 28 8C, which showed the
maximum and minimum survival, respectively.
Rate of development
As shown in Figure 3, the duration of the two zoeal stages, the
megalopa and total time required for development to the first
crab stage were influenced to some extent by different sali-
nities and temperatures, with the effect of temperature being
greater. Times of development showed a gradual reduction
from low to high temperature.
Fig. 1. Percentage of survival from hatching to the first crab stage in
Stenorhynchus seticornis larvae reared in different salinities at 22, 25, and 288C.
temperature--salinity effects on s. seticornis larvae 507
first zoea
The time required by first zoeae to moult to the second stage
varied between 3 and 5 days (Figure 4A). At 25 and 28 8C the
first moult began at day 3, while at 228C it began at day 4. At
higher temperatures, all larvae completed ecdysis in a three
day period while at 228C it extended to five days. Regardless
of salinity, at 25 and 288C more than 60% of the larvae com-
pleted ecdysis during day 4 while at 228C the percentage of
moulting larvae on this day was reduced to ,2%.
Two-way ANOVA showed that temperatu re (F ¼ 1437.30;
P , 0.001) had a considerably greater influence than salinity
(F ¼ 12.22; P , 0.001). The temperature–salinity interaction
was not significant (F ¼ 2.11; P . 0.05) indicating that the
effects of both variables were independent. The rate of devel-
opment increased with increasing temperature. Mean dur-
ation of first zoeae was 5.5 days (range 4–8 days) at 228C;
4.3 days (range 3– 6 days) at 258C and 4.1 days (range 3–5
days) at 288C. In relation to salinity, duration was significantly
higher at 40‰, while no difference between 30 and 35‰
could be detected.
second zoea
Duration of this stage varied between 3 and 6 days (Figure 4B).
As in the former stage, the time required by the larvae to
moult to the megalopa stage declined with increasing temp-
eratures. Except for those larvae reared at 258C, 40‰, which
started to moult at day 8, at 25, and 288C, larvae started to
moult at day 7. At 228C ecdysis began at day 10 whereas the
majority of the larvae at 25, and 28 8C had completed ecdysis.
Analysis of variance showed differences in mean time
required to moult between temperatures (F ¼ 255.07; P ,
0.001) but not between salinities (F ¼ 2.88; P . 0.05).
Temperature–salinity interaction was not significant (F ¼
0.25; P . 0.05). The SNK test indicated a significant decrease
in time for moulting with increasing temperature. On the
average, larvae required 6.5 days at 228C, 4.7 days at 258C
and 4.3 days at 288C.
megalopa
The persistent lag and the tendency for each moult to require a
greater period of time at the lower temperature continued in
Fig. 2. Mean (+SE) percentage survival of zoea and megalopa stages of Stenorhynchus seticornis reared at different salinities and temperatures. zoea I;
zoea II; megalopa.
Fig. 3. Comparison of time required for the development from hatching of
larvae of Stenorhynchus seticornis reared at different salinities and
temperatures. Vertical lines represent total range, blocks represent standard
deviation and horizontal lines are mean values.
508 jesu
’
se.herna
’
ndez et al.
the megalopae. In all test salinities, larvae reared at 288C
moulted to the first crab stage before those maintained at
228C began to moult. At 288C megalopae moulted to the
first crab between days 18 and 22 (5 days), but at 228C they
did not begin to moult until day 24, and needed 8 days for
all to complete ecdysis. At 258C, ecdysis began at day 17
and some larvae did not mo ult until day 27 (Figure 4C).
The ANOVA showed a significant effect of temperature
(F ¼ 3.55; P , 0.05), while no effect of salinity (F ¼ 0.06;
P . 0.05) was evident. Multiple comparison of means
showed a reduction in the duration of the megalopa stage at
25 and 288C, requiring on the average, 15.0 days at 228C,
12.2 days at 258C and 11.9 days at 288C.
cumulative rate of development from
hatching to the first crab stage
Depending on the experimental conditions, S. seticornis
required 17 to 31 days to complete development to the first
crab. The shortest time required to complete development
to the crab stage was, on average, 19.7 days (range 18 to 22
days) at 288C, 21.0 days (range 17 to 27 days) at 258C,
Fig. 4. Comparison of time of moult for (A) first zoeae; (B) second zoeae; (C) megalopae of Stenorhynchus seticornis reared at different salinities and temperatures.
228C; 258C; 288C.
temperature--salinity effects on s. seticornis larvae 509
while at 228C, the same stage was attained at an average time
of 26.9 days (range 24 to 31 days).
The ANOVA indicated a significant effect of temperature
only (F ¼ 14.07; P , 0.001). Larvae reared at 228C showed
an increased duration of larval development while no differ-
ence between 25 and 28 8C could be detected.
DISCUSSION
It is generally recognized tha t temperature, acting either inde-
pendently or simultaneously with other environmental
factors, is one of the major physical factors affecting survival,
duration of stages and growth of decapod larvae (Ong &
Costlow, 197 0; Nagaraj, 1993; La
´
rez et al., 2000; Zacharia &
Kakati, 2004). We found evidence that survival and duration
of the individual stages and the complete development to
the first crab of Stenorhynchus seticornis were affected by
the temperatures and salinities used; temperature having a
more pronounced effect than salinity.
Survival
The highest survival rates obtained for the first and second
zoeae (61.3% and 59.6%, respectively) were high compared
with those obtained by Quintero (1986) (34%, and 50%,
respectively) for the same species at 22–248C; 36 – 38‰,
and similar feeding conditions. This author found a high mor-
tality during the first zoeal stag e and stated that during devel-
opment some stages require better care and/or better quality
or a special kind of food. However, those survival rates were
lower tha n that observed by Yang (1976) at 17–298C; 32–
36‰ (ZI: 77.8%, ZII: 64.3%). The differences obtained in
both cases may be due to the different temperature–salinity
regimes and/or explained according to Costlow (1967),
Quintero (1986) and La
´
rez et al. (2000) who stated that survi-
val is extremely variable in eggs masses obtained from differ-
ent female crabs (genetic quality), differences in the natural
environment from which the ovigerous females were collected
and/or in eggs hatched at different times of the year.
High survival obtained in the zoeal stages could have been
favoured, to some extent by: (i) food supply. It is known that
the lack of food of proper size and nutritional value during the
period when larvae first begin feeding cause extensive mortal-
ities in some species (Sastry, 1983). Larvae of S. seticornis were
fed immediately after eclosion as recommended by Herna
´
ndez
et al. (1999) who tested the effects of starvation on S. seticornis
larvae, and found that only larvae fed immediately after eclo-
sion were able to moult to the second zoeal stage; (ii) water
quality. All water used in the experiment was previously fil-
tered and UV-irradiated in order to reduce harmful microor-
ganisms such as bacteria and protozoa; (iii) nutritional quality
of food and/or the fact that the Artemia cysts were decapsu-
lated using a hypochlorite solution, thus preventing the con-
tamination of the culture media with micro-organisms
(New & Singholka, 1984); and (iv) the larvae were transferred
daily to clean bowls, containing seawater at the same exper-
imental conditions avoiding thermal or sali nity shock.
In the present study, a reduction in the effect of salinity,
both in survival and duration of development with each suc-
cessive stage of development was observed; this suggests, as
stressed by Nagaraj (1993), that salinity tolerance increases
with each successive stage and euryhalinity may be attained
in the juvenile phase of the life history. Additionally,
Charmantier (1998) stated that the osmoregulatory capability
develops throughout the larval sequence of stages and com-
monly the tolerance ranges of larval stages to temperature
and salinit y are narrower than those of adults.
The highest survival rate in the megalopa stage, although
low, was higher than that obtained by Yang (1976) and
Quintero (1986) (7.4% and 6%, respectively). Yang (1976)
stated that the major cause of mortality in the megalopa
stage of S. seticornis in his experiment seemed to have been
a failure to complete moult into the crab stage because of an
inability of the animals to ext ract the lengthy pereopods.
Poor megalopal survival has been observed in other
majoids (Quintero, 1986; Harms & Seeger, 1989; La
´
rez et al.,
2000; Rhyne et al., 2005), as well as in other Decapoda
(Costlow et al., 1960; Mene et al., 1991; Luppi et al., 2003),
and has been attributed, in part, to a shift in the food prefer-
ences and/or in nutritional requirements, to the necessity of
an adequate substrate for settlement, and cannibalism.
According to Williams (1984), adults of S. seticornis are
omnivorous, while its zoeal stages are carnivorous. Maybe
megalopae of S. seticornis shift from the carnivorous diet
typical of the zoeae to an omnivorous diet typical of the
adults and, therefore, would require a mixed (animal and veg-
etable) food supply not necessarily of planktonic origin or
maybe they have higher energy requirements to fulfil meta-
bolic costs and/or growth, as well as preparation of the organ-
ism for metamorphosis as demonstrated in other decapods
(see Barros & Valenti, 2003 for reference s).
Although only 1% of the larvae in the experiment reached
the first crab stage, at 258C–30‰ survival of megalopae was
as high as 12.2%. In nature, larval survival is generally very
low, often ,1% (Thorson, 1950; Morgan, 1995), and
decreases exponentially with time when mortality sources
such as predation or the likelihood of encount ering harsh
environmental conditions are relativel y constant over the
lifespan of a larva (Thorson, 1950; Morgan, 1995). The low
survival in the development to the first crab stage was due
to the high mortality in the megalopa stage, so the successful
completion of the life history of S. seticornis in the laboratory
appears to depend largely on the succes sful rearing of the
megalopa. The reasons for the high mortality of megalopae
of S. seticornis remain unsolved. This could be tested in
future studies focused on megalopae feeding and settlement
cues using the combination of temperature and salinity
(258C, 30‰) which yielded the higher survival rate (12.2%)
as reference.
On the other hand, the traditional water exchange of
rearing systems often requires larval manipulation and can
induce stress, so larvae could be raised to the megalopa and
then moved to an alternative rearing system that allow high
prey densities, good water quality, suspension of the larvae
in the water column (thus avoiding clumping), and where
settlement induction could be better achieved. This kind of
system was used succe ssfully by Rhyne et al. (2005) for
rearing Mithraculus forceps (A. Milne-Edwards, 1875) and
M. sculptus (Lamarck, 1818) larvae.
Rate of development
Although the rate of larval development may be genetically
determined (Sastry, 1983; Gonc¸alves et al., 1995), it may be
modified by environmental factors within the tolerance
510 jesu
’
se.herna
’
ndez et al.
limits for the species, and as well as by the quality and quantity
of available food (Sastry, 1983).
With the exception of the first zoeae, the duration of the
stages of development of S. seticornis was not affected by
the range of salinities used. The mean duration of the zoeal
stages, as well as the megalopa, was inversely related to temp-
erature. This last result is consistent with the general trend for
most other crustaceans including majoids (Wilson et al., 1979;
Scotto & Gore, 1980; Rengel et al., 1993; La
´
rez et al., 2000) and
other decapod larvae (Ong & Costlow, 1970; Goy et al., 1981;
Mene et al., 1991; Nagaraj, 1993; Paula et al., 2003; Zacharia &
Kakati, 2004), in which an inverse relationship between temp-
erature and duration of development has been also found.
Gonc¸alves et al. (1995) stated that, within certain limits,
higher temperatures shorten larval development, and that
this is important for the life history of the species since a shor-
tened developmental time increases the chance of reaching
maturity.
The effect of temperature on zoeal duration can have
important consequences to recruitment success. The length
of zoeal duration can affect dispersal, as well as total survival
to settlement based on the length of time zoeae are subjected
to predation. There could also be effects on survival and
growth based upon prey availability and energetics (Sulkin
& McKeen, 1994).
In crustaceans, moulting is a complex and continuous
process affected by metabolic activities controlled by
enzymes and moulting hormones (Passano, 1960; Chang,
1985; Skinner, 1985). As found for Mithrax caribbaeus
Rathbun, 1920 (La
´
rez et al., 2000), and Crangon uritari
Hayashi & Kim, 1999 (Li & Hong, 2007), the decrease in
the length of the intermoult period in S. seticornis at 288C
could be explained as the result of an increase in metabolic
rate along with an increase in the activity of enzymes and hor-
mones involved in the moulting process all as a consequence
of the increase in temperature within the tolerable physiologi-
cal limits for the species.
As observed by La
´
rez et al. (2000) for Mithrax caribbaeus,
the range of salinities used in the present work did not affect
significantly the time of development of the different stages of
S. seticornis. However, in other majoids a gradual increase in
larval life with decreasing salinity has been found (see La
´
rez
et al., 2000 for references). This may indicate that the effects
of salinity would be related to the physiological and adaptive
capacities and evolutionary history of each species.
Although laboratory experiments cannot exactly represent
natural conditions, they allow the analysis of the responses of
larvae to environmental variables in relation to adult habitats
and have greatly enhanced the understanding of the ecology
of pelagic crustacean larvae. They can also represent approxi-
mate environmental limits and how these variables affect
survival and rate of development of the larvae in nature
(Sastry, 1983).
Previous studies on the effects of temperature and salinity
on the larval development of Brachyura have fitted the
observed duration and mortality to a response surface, consid-
ering temperature, salinity and their interaction effects as pre-
dictor variables (Costlow et al., 1960; Costlow, 1967; Laughlin,
1983; Nagaraj, 1993; La
´
rez et al., 2000; Paula et al., 2003; Li &
Hong, 2007). We tried to fit a response surfa ce of these charac-
teristics to our data using a quadratic model. In all the cases,
the fitted model did not represent the data adequately.
Probably a greater number of temperature–salinity
combinations, a higher order surface or the use of additional
variables must be included in the model.
As observed in the megalopa stage of other decapods
(Felder et al., 1985; Rodrı
´
guez et al., 1990; Stevens, 2003;
Suprayudi et al., 2004; Rhyne et al., 2005) moult frequency
and time of dev elopment of S. seticornis megalopae should
have been affected by factors other than salinity and tempera-
ture, such as nutrition, the absence of an appropriate substrate
and/or other settlement cues.
A longer period as megalopae increases the individual’s
probability to spread and reach an appropriate substrate
prior to metamorphosis (Jac kson & Strathmann, 1981).
Extension of the duration of late larval stages might allow
the species to colonize new areas or repopulate already colo-
nized ones, and enha nce the possibilities of gene flow
among local populations (Dı
´
az & Bevilacqua, 1986); neverthe-
less, a longer larval development period is correlated with a
rise in mortality, so its advantages are not obvious (Luppi
et al., 2003).
In order to make S. seticornis an ideal candidate for aqua-
culture, further studies are needed to address the nutritional
and substrate issues in order to improve the larval survivor-
ship and settlement of megalopae. Further research is also
needed to develop mass larvae rearing protocols as well as a
grow-out system for juveniles. This will allow the production
of quality animals at a low cost, enabling the commercial
production of the species.
ACKNOWLEDGEMENTS
We thank Dr Andrew Gannon and the anonymous referees
for assistance with revision of the manuscript, appreciative
comments and constructive criticism. This study received
financial support from the Consejo de Investigacio
´
ndela
Universidad de Oriente, Venezuela.
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Correspondence should be addressed to:
J.L. Palazo
´
n-Ferna
´
ndez
Universidad de Oriente
Instituto de Investigaciones Cientı
´
ficas
Boca del Rı
´
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Venezuela
emails: juis.palazon@icman.csic.es; jose.palazon@ne.udo.edu.ve
temperature--salinity effects on s. seticornis larvae 513