Eocyzicus argillaquus

Hethke, Manja & Weeks, Stephen C., 2020, Fig. 25 in Fig. 20. Sesarmops mora n in Paralbunea dayriti, Zoological Studies 59 (33), pp. 1-11 : 9-10

Eocyzicus argillaquus

Population survival

Standardized densities of replicates in Eocyzicus argillaquus did not diverge much ( Fig. 8 , Table 1B). Survival remained at 100% until 10 days after hydration. Population densities first started to decrease in cups 15.1 and 15.2 eleven days after hydration, followed by cups of lower densities 13 days after hydration. We decided to end the experiment when mortality rate increased dramatically 16 days after hydration. To ensure a statistically relevant sample size, we pooled replicates 3, 5, 7, and 10 for further analyses (e.g., only one individual remaining in cup 3.2).

Eocyzicus argillaquus

Size

PC1 and PC2 explain 76.0% and 12.6% of the variance in the log-transformed size dataset. Figure 9A shows that single-individual cups (in red) occupy positive scores on PC1 while all other densities overlap, which is corroborated by NPMANOVA ( Table 5A). Pairwise comparisons separate single-individual cups from cups with initial densities higher than three. Cup 3 is distinct from cups 5 and 15.2. All other cups cannot be distinguished based on size variables. So, in contrast to Eulimnadia texana , the population density effect on size in E. argillaquus mostly affects very-low density cups rather than density extremes. Further studies might reveal whether densities higher than 14 inds/400 ml yield distinct size patterns. All linear variables have positive loadings on PC1 (size variable), and size in higher-density cups is generally smaller than in single-individual cups. PC2 is driven by variable c. High c values often indicate aberrant forms, such as the specimen illustrated in figure 10D.

The analysis of the five variables that were easiest to obtain ( Table 5B) provides similar results, which shows that it is not essential to worry about variability in linear variables during data acquisition. Also, PC1 (as a measure of size) by population density is best fitted by a logarithmic relationship in E. argillaquus ( Fig. S1 ).

Figures

Fig. 8. Population survival of Eocyzicus argillaquus. Five days after hydration, individuals were transferred into 400 ml cups and survival was monitored daily. Population densities remained initially stable and started to decline in cups 15.1 and 15.2 eleven days after hydration. We ended the experiment when raw densities dropped notably (29 of 84 individuals dead on 11 October 2017). Numbers in the legend represent standardized population densities 16 days after hydration.

Fig. 9. Population density effect on size and shape in Eocyzicus argillaquus. A, Biplot of principal component scores and variable vectors (loadings) on PC1 and PC2 of a set of log-transformed linear measurements. Outlines scaled to size. B, Population density effect on shape in Eocyzicus argillaquus based on Fourier shape analysis. Outlines represent shape only.

Fig. 1. Linear carapace variables used for A, Eocyzicus argillaquus and B, Eulimnadia texana, following Defretin-Lefranc (1965) and Tasch (1987):A, most anterior point of the valve; B, most posterior point of the valve; C, most ventral point of the valve; D, anterior extremity of the dorsal margin; E, posterior extremity of the dorsal margin; U, midpoint of the larval valve (located on the umbo, but not necessarily the midpoint of the umbo). a, vertical distance of A to A'; b, vertical distance of B to B'; c, horizontal distance of C to A''; Arr, horizontal distance of E to B'; Av, horizontal distance of D to A'; Ch, length of the dorsal margin; Cr, horizontal distance of U' to A'; u, vertical distance of Ch to highest point of the umbo; L, valve length; H, valve height.