NOTE Grana-Raffucci and Appeldoorn: Age determination of larval strombid gastropods 
859 
Table 1 
Mean statolith diameter (pm ± SD), mean number of increments (1 SD) 
hatching) for Strombus costatus and S. gigas. n = 20 for each day. META = 
and mean shell length (pm ± SE) by age (days after 
day of metamorphosis, data not available. 
Age 
(d) 
Strombus costatus 
Strombus gigas 
Statolith 
diameter 
Number of 
increments 
Shell length 
Statolith 
diameter 
Number of 
increments 
Shell length 
0 
13.35 ± 0.48 
6.00 1 0.65 
345.00 ± 32.60 
14.65 ± 0.80 
6.70 1 0.73 
325.00 ± 35.36 
1 
14.05 ± 0.22 
7.06 ± 0.64 
390.00 1 13.69 
15.05 ± 0.59 
7.30 ± 0.66 
375.00 ± 40.82 
2 
15.30 ± 0.56 
8.80 ± 0.70 
440.00 ± 13.69 
15.70 ± 0.71 
7.25 1 0.79 
387.501 17.68 
3 
15.50 ± 0.50 
8.75 ±0.50 
470.00 ± 18.71 
16.45 ± 0.50 
8.00 1 1.03 
408.25 ± 14.43 
4 
15.93 ± 0.46 
9.57 ± 1.28 
625.12 ± 17.83 
— 
— 
— 
5 
— 
— 
16.35 1 0.51 
10.72 ± 0.46 
443.00 ± 18.32 
6 
16.14 ± 0.64 
11.71 ± 0.73 
625.80 ± 21.77 
17.40 ± 0.97 
12.35+ 1.26 
458.25 ± 28.87 
7 
15.65 + 0.91 
12.65 ± 1.04 
635.00 ± 15.69 
17.15 + 0.57 
13.45 ± 1.28 
461.35 ± 15.22 
8 
16.50 + 0.67 
14.85 1 0.99 
641.75 ± 30.28 
— 
— 
— 
9 
— 
— 
18.10 ± 0.30 
15.55 ± 2.63 
466.75 ± 14.43 
10 
16.35 ± 0.57 
15.15 1 2.03 
650.00 ± 14.42 
17.93 ± 0.46 
17.07 ± 1.59 
475.80 ± 13.67 
12 
17.33 ± 1.55 
18.33 ± 1.15 
700.67 + 24.32 
19 
27.60 ± 0.82 
24.35 1 0.75 
1160.001 31.75 
20 
27.90 ± 0.55 
26.05 ± 0.83 
1177.501 40.00 
21 
META 
META 
META 
22 
28.15 ± 1.39 
26.75 + 4.28 
1340.001 44.50 
23 
30.45 1 1.10 
29.40 ± 1.10 
1655.00 1 83.25 
Individual statolith increment counts and the 
magnitude of corresponding standard deviations 
(Tables 2 and 3) indicate that observed variability 
may be due to errors in measurement, not to vari- 
ability in increment deposition. Nested ANOVA of 
subsamples of each species supported this hypoth- 
esis (Table 4), showing significant variability only at 
the level of readings between age groups. 
Within each species, the relation between age (A) 
and statolith diameter (D, pm) was more variable 
than that between age and increment count (S. 
costatus : D = 14.21 + 0.26A, r 2 = 0.80; S. gigas: D - 
14.93 + 0.34A, r 2 = 0.93). Similarly, the relation be- 
tween age and shell length (L, pm) was more vari- 
able than that between age and increment count but 
was similar to that between statolith diameter and 
age ( S . costatus: L = 397.6 + 29. 2A, r 2 =0.83; S. gigas : 
L = 356.7 +13.7A, r 2 =0.89). 
Significant regressions occurred between shell 
length and statolith diameter ( S . costatus: L = -1015 
+ 100.4D, r 2 =0.85; S. gigas: L = -237 +39.9D, r 2 =0.90). 
Data for S. gigas obtained from the Turks and Caicos 
hatchery did not, however, fit this relation, suggest- 
ing that 1) environmental or genetic factors influ- 
ence the relative growth of these structures, or 2) 
the relation is not linear over the entire larval and 
postmetamorphic period. 
Larvae of S. costatus subjected to starvation 
showed no unusual pattern in region 2; mean num- 
ber of increments between seven-day-old starved 
(12.09 ± 0.74 SD) and nonstarved (12.65 ± 1.04 SD) 
larvae were not significantly different R 18 =0.262; 
P>0.05). Mean statolith diameter was also similar 
in the two groups ( 15.65 ± 0.91 SD pm for nonstarved 
larvae; 14.83 ±0.75 SD pm for starved ones) 
(£ 18 =1.414; P>0.05). 
Discussion 
Statoliths of strombid larvae have a distinctly rec- 
ognizable structure at hatching. Region 1 consists of 
a primordial granule surrounded by four increments. 
Three regions within the statolith result from 
changes in density of increments caused by abrupt 
changes in increment width at times of hatching and 
metamorphosis. Large transitions in incremental 
width may be caused by differences in metabolism 
during normal larval growth and development, in- 
cluding variable mineral deposition in the larval shell 
(Maeda-Martinez, 1987). 
In both S. costatus and S. gigas , the rate of incre- 
ment formation is constant after hatching. Variabil- 
ity found in incremental deposition was due largely 
to errors in measurement, not variation in deposi- 
tional rate. A two-day period of starvation did not 
produce any noticeable structural change or precise 
mark. Starved veligers may have continued growing 
on stored energy reserves (Rodriguez Gil, 1995), ne- 
gating differences between treatments. That starved 
