Energetic aspects of crustacean larval development have become a field of increasing scientific interest (for recent. * Present address: Departamento de ...
Marine Biology 87, 173-180 (1985)
Marine , Biology ...............
9 Springer-Verlag1985
Growth and respiration during the larval development of Hyas coarctatus (Decapoda: Majidae) C. C. Jacobi * and K. Anger ** Biologische Anstalt Helgoland, Meeresstation; D-2192 Helgoland, Federal Republic of Germany
Abstract
The spider crab Hyas coarctatus Leach was reared in the laboratory from hatching to metamorphosis, and growth and respiration were measured in all larval stages at regular intervals of time. Growth, measured as dry weight (W), carbon (C), nitrogen (N), hydrogen (H), and energy (E; calculated from C), can be described in the zoeal stages by a power function, and as a non-linear (quadratic) regression equation of time (t; days) in the megalopa. C, H, and E showed higher growth rates than W or N during the zoeal stages, suggesting accumulation mainly of lipids rather than protein. Respiration (R; expressed as /~g O89h-i individual-1) increased as a linear function of t in the zoeal stages. From this simple relationship and the above power function for increase in w, equations describing the relationships between R and W and between QO2 (~g O2 h -I mg-1), t, and W were derived for zoeal development. Both R and Q 0 2 first decreased during megalopa postmoult, then increased for a short period, before decreasing again toward metamorphosis. No descriptive models were proposed for these changes in the ultimate larval stage. The total amount of energy lost by zoeal respiration was less than their net gain by body growth, whereas the megalopa respired almost 14 times the amount of energy eventually gained. This means that net growth efficiency is far lower in the megalopa than in the zoeal stages of H. coarctatus.
Introduction
Energetic aspects of crustacean larval development have become a field of increasing scientific interest (for recent * Present address: Departamento de Fisiologia, Instituto de Bioci6ncias, Caixa postal 11.461,Universidade de Silo Paulo; 05421 Silo Paulo, Brasil ** To whom offprint requests should be addressed
review of literature see e.g. Dawirs, 1983; Anger, 1984 c). Mostly studied were growth and respiration of decapod larvae in relation to their stage of development and to environmental- factors, such as temperature and salinity (reviewed by Schatzlein and Costlow, 1978; Dawirs, 1983, 1984) or pollutants (e.g. Capuzzo and Lancaster, 1981; Laughlin and Neff, 1981). Only a few investigators, however, have considered changes in larval biomass or metabolism during single moult cycles (McNamara et al., 1980; Anger and Dawirs, 1982; Dawirs, 1983; Anger and Jacobi, in press). The present paper reports on changes in dry weight, elemental composition (C, N, H), energy content, and respiration rate during the larval development of the little known, though widely distributed spider crab Hyas coarctatus, which was reared in the laboratory from hatching to metamorphosis. The only previous experimental studies on this species were made by Christiansen (1973), who first successfully reared its larvae and described their morphology, and by Anger (1984 a), who gave a preliminary account of larval and postlarval growth. Materials and methods
Obtaining and handling of larvae Ovigerous female Hyas coarctatus Leach were dredged during the winter of 1983/84 from ca 20 to 50 m depth near the island of Helgoland (German Bight, North Sea) and maintained in the laboratory at a constant 6 ~ Freshly hatched larvae were transferred to mass cultures and reared at 12 ~ as described in detail by Anger et al. (1983). Growth Larvae having the same age within a given instar were sampled from the culture bowls every second day (for number of replicate analyses and total number of larvae
174
C.C. Jacobi and K. Anger: Growth and respiration in Hyas coarctatus larvae
analysed, see Tables 1 to 3). Dry weight (W), carbon (C), nitrogen (N), and hydrogen (H) were measured by standard techniques (Anger and Dawirs, 1982). Energy content (E; in Joules, J) was calculated from C (Salonen et al., 1976). Larval growth was followed in this way from the day o f hatching o f the zoea I until imminent metamorphosis o f the megalopa to the first juvenile stage. Our description of growth patterns within the larval stages is based on a total of 319 analyses. Biomass values in Tables 1 to 3 were given in/~g to avoid the use of excessive decimals, but in mg for regression equations and figures, in order to allow direct conversion to the weightspecific terms of respiration and energy.
concentration in the experiments was usually ca 5 to 8%, which did not affect larval respiration (Belman and Childress, 1973; Dawirs, 1983), and which permitted accurate measurement of oxygen consumption. The standard error in replicate blank analyses was + 0.2 to 0.5% of the mean value. Respiration rate (R) was expressed as/zg 02 h -1 individual < , and weight-specific metabolic rate (QO2; based on dry weight, W) as/zg 02 h -l mg -1. Energy loss by heat dissipation was calculated using the generalized oxycaloric equivalent, 14.06 J (mg O2) -1, given by Gnaiger (1983).
Results
Respiration Respiration was measured every two days in zoeae, and every four days in megalopa larvae using the Winkler method (Grasshoff, 1976; Dawirs, 1983) at 12~ Depending on their weight, three (megalopa) to ten (zoea I) larvae were confined in a Winkler bottle (ca 55 cm 3) containing Mill,ipore-filtered (0.25/~m) seawater. Prior to the experiment, the larvae had been held for 2 h in bowls of filtered seawater (without food) to allow for defaecation. Eight replicate experiments and four replicate blanks (without larvae) were run for 15 h. The decrease o f oxygen
Growth Growth data for the larval stages of H y a s coarctatus are compiled in Tables 1 to 3. A number of different models were tested to describe growth patterns within these stages. In both zoeal stages and for almost all measures of biomass accumulation, the consistently best fit of predicted and measured values was found in the general growth equation: tn y = b + m " tn (t + 1)
Table 1. Hyas coarctatus, zoea I. Growth during development: Dry weight (W), carbon (C), nitrogen (N), hydrogen (H) (all in/~g; C, N, H also in % of W), C / N a n d C / H ratios, energy content (in Joule, J) per individual and per mg W; 2, _+: arithmetic mean, standard deviation; n: number of replicate analyses; n' total number of individuals analysed Time of development (d) 0
w
~g)
c
(%)
+ -l-
(.g) `2 N
(%) `2 -{-
~g) `2 -I-
H
(~) (~g) `2 -]-
C/ N
"2
C/H
`2 _+ `2 _+
J individual -~ J mg -1 n nt
`2 ___
2
4
6
8
10
12
43.6 1.5
67.4 3.9
81.5 1.9
95.6 3.2
100.3 2.2
103.2 2.5
112.7 3.8
32.9 1.3 14.2 0.3
32.7 1.8 22.2 2.0
32.8 0.3 ~.8 0.6
33.3 0.9 31.8 0.7
37.1 0.4 37.7 0.8
38.5 0.6 39.7 1.0
38.5 0.8 43.4 2.2
8.4 0.3 3.6 0.1
6.8 0.3 4.6 0.3 5.1 0.3 3.4 0.3 4.9 0.3
6.6 0.2 5.3 0.2 4.4 0.3 3.6 0.3 5.0 0.1
6.7 0.2 6.4 0.1 4.7 0.2 4.5 0.2 5.0 0.1
7.4 0.1 7.4 0.2 5.0 0.2 5.0 0.2 5.0 0.I
7.9 0.1 8.2 0.2 5.4 0.1 5.6 0.2 4.9 0.1
8.1 0.2 9.1 0.4 5.6 0.2 6.3 0.4 4.7 0.1
6.5 0.1 0.75 0.08 11.0 0.9 13 130
7.6 0.4 0.90 0.~ 11.0 0.1 14 112
7.1 0.2 1.07 0.03 11.2 0.4 11 88
7.5 0.2 1.31 0.03 13.1 0.2 13 78
5.1 0.3 2.2 0.1 3.9 0.1 6.4 0.2 0.48 0.02 11.0 0.6 12 120
7.1 0.2 1.42 0.04 13.8 0.3 12 72
6.9 0.2 1.56 0.~ 13.8 0.4 13 78
(1)
O 0
I-oo0
I
4~
Do 0
oo
o
O"
0
O" O"
0
0
0
P
~n
.o.~
.o.~
.o-~
.o.~.o.~
.~.~ .o.~ .o.~ .o.~ . o . ~ . o . ~
.o.~
.--~.o.~
.o.~.o.oo ~ . ~ . o . ~
.o.o.o~
~.~
.~.~
0
P~
0
0
o
m"
C~
b~ 0
~a
C.C. Jacobi and K. Anger: Growth and respiration in Hyas coarctatus larvae
176 or
y = e b" (t + 1) m
0
(2)
where y is biomass (W, C, N, H ) o r energy (E) per individual, t is the time o f d e v e l o p m e n t (d) within a given stage, and b and m are fitted constants. Since b is the intercept with the ln y axis o f Eq. (1), the expression e b represents an estimate o f the initial (day 0) biomass or energy
i
y = a o + a~ 9 t + a 2 t 2,
Again, the course o f change in d r y weight is shown as an example for the pattern Of growth (Fig. 2, lower graph), The fitted constants for all y are given in Table 5.
0.12- -~
Zoea II
V
e b
m
t"
e b
m
0.0445 0.368 0.0139 0.438 0.0033 0.362 0.0021 0.394 0.46 0.460
0.996 0.997 0.974 0.986 0.994
0.1229 0.0445 0.0096 0.0063 1.56
0.286 0.342 0.308 0.358 0.368
i
i
i
i
i
;13
o" c~
R=0.%35 + 0.0073-t r=0.970
-2.B ~" -2.6 ~.o -2L
:T,
2.0- ~
-29
,
-3.0 ~o
0.10-
0.10 1
0.0a-
*
9 "
a /
0.06./
9
I ~
0.08 g
I0
W=O.OL/`5" (t+l) 0 3 68
I 06 ~" c~
004- " ~ " 0
J-O.Ot, 2
~ 6 8 10 12 Time of development (days}
Fig. 1. H yas coarctatus, zoea 1. Change of dry weight (W), weightspecific (Q02), and individual respiration rate (R) during time (t) of development. Symbols for W and R: mean + standard deviation (vertical bars), range (vertical lines); Q02 : mean and confidence limits (see text for explanation)
0i
2i
Time of development (doys) /`i 6i 8I 10 12 1/, 16 16 20i 22 i i i i i .2
.
7 ~ 1.0 -xzu
~.;:o .o & ~ _ 0.8
0.8 c~.
~
0.6 - ~ "
Q
r ew
W C N H E
i
3.0- 1\ c , ~ _ m ~ o ~ . n ~ / . ~ 1~I~-0.368 2.6- , , ,.,~,~-,.~.,-,o-~,.,,~,.-,,-,,-,,\ " 2.6- ~ 2./,- ~
Table 4. Hyas coarctatus. Fitted constants of Eq. (2) for growth in t h e zoeal stages*.y: biomass (W, C, N, H), in rag, or energy (E), in Joule (J); for symbols see Table 1. r: correlation coefficient; in all cases significantly different from zero (p < 0.001) Zoea I
i
-0.20 s 9 909 2s 9 -0.12 -Z~
where y and t are defined as above, and ao, al and a2 are fitted constants. The theoretical initial biomass or energy is (5)
I
~ 0 20.~ 0.16o _
(4)
a0 = y0.
i
i
-0.2/, ~-~ . o
(3)
T h e symbol m designates the slope (regression coefficient) in this and the following equations. It is related to a particular d e p e n d e n t variable (y) by referring to it as my (mw, mc etc.). The typical shape o f a zoeal growth curve [Eq. (2)] is shown in Fig. 1 (lower graph) with y = W. The parameters o f the regression equations for all measures o f larval biomass and for both zoeal stages are given in Table 4. G r o w t h in the m e g a l o p a stage was found to follow a different, arc-shaped pattern, which can be described b y a non-linear regression model:
i
Time of development (doys) 4 6 8 10 12
== 0.2~
figure:
e ~ = Yo = W0, Co, No, H0 (in m g ) , or Eo (in J ) .
i
2
0.999 0.990 0.982 0.995 0.983
"-J
0.6
~i
~. o&
i
1
i
i
i
I
I
i
I
i
3.0 5- o
3.0
2.0
5o
2.0 4
1.0
1.0
* Calculated from values in Tables 1 and 2
[
/`0 g
.0.50
Table 5. Hyas coarctatus. Fitted constants of Eq. (4) for growth in the inegalopa stage*, y." see Table 4. r2: coefficient of determination Y W ao al a2 r2
o00t
i0o
"6 0.35 9
C
N
H
E
0.2919 0.1061 0.0220 0.0125 3.7 0.02565 0.00991" 0.00189 0.00172 0.35 -0.001078 -0.000418 -0.000072 -0.000068 -0.015 0.687 0.71 t 0.694 0.725 0.688
* Calculated from Table 3
D
0.30
-0.35 ~ g
W= r2=0'687 0"292+0"0256' t-OO ' 108"t2
T
0.30 ~
-~ }.
~ ~ 1'0 1'2 1'~ 1'6 1'8 ~0 22 Time of development (doys)
Fig. 2. Hyas coarctatus, megalopa. Change of W, Q02, and R during time (t) of development (see Fig. 1)
C. C. Jacobi and K. Anger: Growth and respiration in Hyas coarctatus larvae Relative elemental composition (C, N, H as % of W) and weight-specific energy content (E as J mg -1) also varied during larval development and growth. The proportions of C and H increased during both zoeal stages, and consequently also the energy content per unit of weight (Tables 1 and 2). Since the fraction of N was practically constant, the C / N ratio also showed a clearly increasing tendency. This pattern suggests that lipids were accumulated to a far higher degree than the major source of N, i.e. protein, and is also reflected in the slopes (m) of the regression equations (Table 4), where C, H, and E increase at much higher rates than either W and N. The relative composition of the megalopa remains fairly stable (Table 3), and differs from the increasing percentage figures of the zoeal stages (Tables 1 and 2). The C / N ratio suggests that the increasing portion of the growth curve (Fig. 2) may be chiefly due to lipid accumulation, followed by a period of loss in the same constituent. High individual variation, however, and the unusual growth pattern in this stage hamper interpretation of these results.
177
In the megalopa stage, R follows a more complicated pattern than in the zoea (cf. Figs. 1 and 2, upper graphs, respectively). No attempt was made to describe this curve with non-linear regression equations, since we feel that the energetics of the ultimate larval stage needs further research before it can be incorporated in a model. From the general definition of weight-specific metabolic rate
QO2= R . W-l~
(7)
further relationships can be derived for the zoeal stages. By. substituting in Eq. (7) for W from Eqs. (2) and (3), and for R from Eq. (6), QO2 can be described as a function of time (t, days) in the given zoeal stage:
QO2 = (Ro+ mR" t) 9 Wo 1" (t + 1) - ' ~ .
(8)
Substituting the parameters from Eqs. (6 a) and (6 b), and for W0 and mw from Table 4 into Eq. (8), we obtain for the zoeal stages: Zoeal: Q02= (3.225+0.164-t). ( t + l ) -0"368 (8a) Zoea II: Q02 = (1.924 + 0.182- 0 9 (t+ 1) -0.286 . ( 8 b )
Respiration The shape of the relationship generalized in Eq. (8) is shown in Fig. 1 (middle graph) using Eq. (8a) as an example. The corresponding curve (eye-fitted) for the megalopa stage is shown in Fig. 2 (middle graph). Since R and W were measured in aliquot samples, no standard deviation or any other commonly used measure for variation can be given for Q02. However, since the change of respiration during development was quite different in the megalopa as opposed to the zoeal stages, an attempt was made to estimate some confidence limits for the Q02 values found in this study. From the standard deviations and numbers of replicates given for W in Tables 1 and 3, and for R in Table 6, 95%-confidence limits were calculated. In the next step, the upper limit for R and the lower limit for W were taken to calculate the maximum Q02 which can be expected within the confidence limits for R and W. Minimum Q02 was obtained in the opposite way,
Respiration rates per individual (R) and per unit of dry weight (QO2) during larval development of Hyas coaretatus are given in Table 6. Respiration, as with growth, showed a clear relation to larval age in the zoeal stages, but not in the megalopa. Oxygen consumption per zoea (R) increased as a linear function of its time (t, days) of development in the given stage (Zoea I and II): R = R0+mR" t,
(6)
where the intercept (R0) is an estimate of initial R (on Day 0), and mR is the specific slope (regression coefficient). Inserting the fitted parameters, the following regression equations are produced: Zoea I: R =0.1435 + 0.00734. t ; r = 0.970
(6a)
Zoea II: R = 0.2365 + 0.02232 - t ;
(6b)
r = 0.970.
Table 6. Hyas coarctatus. Individual (R) and weight-specific (Q02)* respiration rate, in/~g 02 h -1 individual -~ and/~g 02 h -1 mg -x, respectively, during larval development. ~, ___:arithmetic mean, standard deviation (n = 8) Stage
Zoea I
ZoeaII
Megalopa
Age (d)
R
~ _+
Q02 R 2 -tQ02 R 5c -tQ02
0
2
4
6
8
10
12
16
0.139 0.012 3.16 0.260 0.020 2.11 1.046 0.082 4.10
0.155 0.007 2.31 0.283 0.009 1.67
0.172 0.016 2.12 0.320 0.025 1.65 0.786 0.040 1.84
0,199 0,014 2.07 0,349 0.028 1.65
0.213 0.018 2.13 0.391 0.032 1.68 0.621 0.094 1.43
0.208 0.029 2.02 0.445 0.019 1.84
0.227 0.012 2.01 0.545 0.040 2.10 1.183 0.076 2.69
0.774 0.510 0.073 0.058 1.74 1.25
* Dry weight taken from Tables 1 to 3
20
178
C.C. Jacobi and K. Anger: Growth and respiration in Hyas coarctatus larvae
i.e. by dividing the lower limit for R by the upper limit for W. To give some idea of variation (individual variation plus inaccuracy of measurements), these "confidence limits" are shown as vertical bars in Figs9 1 and 2 (middle graphs, respectively). They suggest that the deviating pattern of change in Q 0 2 of the megalopa cannot be explained by random variation of samples. The relationship between respiration and weight is usually expressed as: R = R'. Wm
(9)
and Q02 = R"
W ~-~
(10)
From actual growth patterns and individual respiration in the zoeal stages (Fig. 1), and much more obviously from those in the megalopa, it can be concluded that these general models cannot concur with our present findings. In fact, only intermoult respiration during the zoeal stages can be described by Eqs. (9) and (10) which, by regression analysis, become: R = 1.06 -
W
; r = 0.996
0'714
(9a)
and Q02=
1.06" W -~
.
(10a)
Respiration was higher than predicted by these equations in the freshly hatched Zoea I, in the freshly moulted and premoult Zoea II, and during most part of the megalopa stage. For the last stage, no attempt was made to find a descriptive model for the relationship between respiration and weight. From Eqs. (2) and (3), t can be expressed as:
Fig. 3 (upper graph) shows the predicted curve from Eq. (13 a) and the observed data. The present data on growth and respiration allow an estimation of energy lost by metabolic heat production and a comparison with energy accumulated by larval body growth. The total amount of oxygen consumed during the zoeal stages was obtained by integration of Eqs. (6 a) and (6b) assuming durations of 12 and 13 d, respectively, for development in these stages (Anger, 1984a). For the megalopa, an average respiration rate of 0.82#gh -1 individual-I (Table 6) and a development of 22 d (Table 3) were assumed. Total oxygen consumption was converted to energy loss by 14.06J (mgO2) -~ (Gnaiger, I983). Growth was estimated in all stages by subtracting E0 and the energy content on the day of moulting to the next stage as calculated from Eqs. (2) and (4) and the parameters given in Tables 4 and 5. These growth figures include the production of exuviae. The results of these calculations are shown in Table 7. The total amount o f energy lost due to respiration increases considerably during larval development, whereas the amount accumulated in biomass shows a clear maximum in the second zoeal stage, and an equally clear minimum in the megalopa. Both zoeal stages accumulate ca 1.4 to 1.5 times more energy than they lose in metabolic heat. The megalopa, in contrast, has both a much lower gross and net growth efficiency than the zoeae, since its
0.04
0.05 ,
l
0.06 *
~
Dry weight (rag) 0.07 0.08 0.09 l
l
l
T
l
- 1
(11)
|
0.10
0~11
w
.3.2
3.2-
L.LL "W 1"718
3.0-
t = \W00]
l
.39 0
9
`7
E 2.8.
into Eq. (8), obtaining by rewriting: R = Ro - mR + m R " W o wm~" W wm~.
o ~
-2.6 ~.o
~_c 2.6.
D"
(12)
Inserting the parameters from Table 4 and Eqs. (6a) and (6 b), zoeal respiration rates can be described as: Zoea I: R = 0.136 + 34.44. W T M
(12a)
Zoea II: R = 0.214 + 34.00
(12b)
9 ~ V 3"496 .
92 . 8
-2.L
:~ 2.4. o TM
o
-2.2
22.
-2.0
2.0 ,
I
,
I
:
l
:
l
:
I
'
I
i
:
A
Predicted and observed R values are shown, as an example, for the first zoeal stage in Fig. 3 (lovOer graph). Substituting Eq. (12) into the weight-specific metabolic rate given by Eq. (7), we get: Q o 2 = (Ro - m e ) 9 W -1 + m R " W ( l/mw" W ( 1 / m ~ - l ) .
"7 -~ 0.22
