Tradeoffs explain scaling, sex differences, and seasonal oscillations in the remarkable weapons of snapping shrimp (Alpheus spp.)
- Department of Biology, Duke University, United States
Figures
Figure 1
Snapping claw length and abdomen length increased with rostrum-to-telson length across the three alpheid species.
Residuals from these lines were used to test for weapon expenditures and tradeoffs in subsequent analyses. Shaded regions represent 95% confidence intervals for linear regressions. A scaled dorsal view of an Alpheus angulosus individual is shown in panel g (distal toward the top of the page; the left claw is the snapping claw). Slopes of each scaling relationship are presented in Supplementary file 1, Table 1. F-test sample sizes and p-values are shown above each graph.
Figure 2
In all three analyzed species, there was a tradeoff between snapping claw residuals and abdomen residuals.
Individuals with greater snapping claw residuals had lower abdomen residuals in (a) Alpheus heterochaelis, (b) Alpheus angulosus, and (c) Alpheus estuariensis. Regressions were calculated from both sexes because sex and the sex × snapping claw residual interaction were not significant predictors in any model. Shaded regions represent 95% confidence intervals for linear regressions. F-test sample sizes and p-values are shown above each graph.
Figure 3
The tradeoff between snapping claws and abdomens varied by size in Alpheus heterochaelis males.
The tradeoff between snapping claw residuals and abdomen residuals was steepest for the smallest individuals in Alpheus heterochaelis males (a) but not females (b). Lines represent model predictions for standardized carapace lengths of −3, –2, –1, 0, 1, 2, and 3. A standardized carapace length of 0 represents an individual with the mean carapace length, and each increment of 1 represents one standard deviation. F-test sample sizes and p-values are shown above each graph. The interaction term was significant for males (t-test, n=329, p=0.00209) but not for females (t-test, n=348, p=0.932).
Figure 4
Alpheus heterochaelis females exhibited tradeoffs between weapon size and egg mass volume, average egg volume, and egg count.
As carapace length increased, (a) egg mass volume increased, (b) average egg volume remained constant, and (c) egg count increased. As snapping claw residuals increased, (d) egg mass volume residuals decreased, (e) average egg volume decreased, and (f) egg count residual decreased. F-test sample size and p-values are shown above each graph.
Figure 5
Smaller Alpheus heterochaelis females (blue) exhibited steeper tradeoffs between snapping claw residuals and average egg volume compared to larger females (yellow).
Lines represent model predictions for standardized carapace lengths of −2, –1.5, −1, –0.5, 0, 0.5, 1, and 1.5. A standardized carapace length of 0 represents an individual with the mean carapace length, and each increment of 1 represents one standard deviation.
Figure 6
Male Alpheus heterochaelis benefited from positive snapping claw residuals through pairing in a way that females did not.
(a) Paired Alpheus heterochaelis males had greater snapping claw residuals than unpaired males, but there was no such trend in females. Sample sizes are shown below each jittered dot plot. p-value for the statistically significant t-test is shown above the graph. (b) Males with more positive residuals paired with relatively larger pair mates, but there was no such trend in females. F-test sample sizes and p-values are shown above each graph. (c) The probability of being paired was positively correlated with snapping claw residuals (but not carapace length) for males. Meanwhile, the same probability was correlated with carapace length (but not snapping claw residuals) for females. 1 indicates paired individuals, and 0 indicates unpaired individuals. Z-test sample sizes and p-values are shown above each graph. Shaded regions in regressions are 95% confidence intervals.
Figure 7
Male Alpheus heterochaelis shifted investment from their abdomen to their snapping claws during the breeding season, whereas female weapon scaling slopes decreased during the breeding season.
During the breeding season, males had (a) reduced abdomen residuals and (b) increased snapping claw residuals. Females did not exhibit significant morphological shifts. (c) Female Alpheus heterochaelis scaling slopes were significantly shallower during the breeding season compared to the nonbreeding season. Male scaling slopes did not significantly change seasonally, but during the breeding season, there was an upward shift in snapping claw lengths across all rostrum-to-telson lengths. Shaded regions are 95% confidence intervals. F-test sample sizes and p-values are shown above each graph. **p<0.01 ***p<0.001.
Additional files
-
MDAR checklist
- https://cdn.elifesciences.org/articles/84589/elife-84589-mdarchecklist1-v2.docx
-
Supplementary file 1
Abdomen length and snapping claw length scaled positively with rostrum-to-telson length.
- https://cdn.elifesciences.org/articles/84589/elife-84589-supp1-v2.docx
Download links
A two-part list of links to download the article, or parts of the article, in various formats.
Downloads (link to download the article as PDF)
Open citations (links to open the citations from this article in various online reference manager services)
Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)
Tradeoffs explain scaling, sex differences, and seasonal oscillations in the remarkable weapons of snapping shrimp (Alpheus spp.)
eLife 12:e84589.
https://doi.org/10.7554/eLife.84589
