Eulimnadia texana (Packard, 1871)

Hethke, Manja & Weeks, Stephen C., 2020, Fig. 25 in Fig. 20. Sesarmops mora n in Paralbunea dayriti, Zoological Studies 59 (33), pp. 1-11 : 4-5

Eulimnadia texana

Carapace length

According to the growth models in figures 2B and 3, the expected length in single-individual cups is 7.3 mm, while individuals of cup 15 reach considerably smaller expected lengths of 5.1 mm. The superimposition of growth curves in figure 2B shows that maximal carapace lengths are ranked according to population density 16 days after hydration. Both, standardized population density and modelled maximal lengths are best fitted using natural log regression ( Fig. 4A ). In general, expected lengths decrease while population density increases. Also, the number of growth bands increases while length increases ( Fig. 4B ).

Length at maturity

A number of Eulimnadia texana hermaphrodites started carrying eggs on 25 September (seven days after hydration; Fig. 3 ). Two of three hermaphrodites were mature in cups 1.1–1.5, six of nine hermaphrodites in cups 5.1 and 5.2, and six of 15 hermaphrodites in cups 10.1 and 10.2 ( Fig. 3 ). None of the clam shrimp in cup 15 were mature that day, implying a population density effect on earliest maturation time. Two days later, there was only one non-mature hermaphrodite in cup 15.

At earliest maturation time, average hermaphrodite lengths were 4.7 mm, 4.3 mm, 4.9 mm, 4.7 mm and 4.8 mm at 1.0, 4.4, 5, 10 and 8.2 inds/400 ml, respectively. On the same day, immature clam shrimp (hermaphrodites and males) of cup 15 yielded distinct average lengths of 4.1 mm. Nine days after hydration, hermaphrodites of cup 15 reached 4.7 mm (density: 13.43 inds/400 ml). At maturity, hermaphrodite length of different population densities cannot be statistically distinguished ( Table S5). These data suggest average hermaphrodite body lengths of 4.7 mm at earliest maturation time (n = 23; at 24°C), based on a resolution of two days.

Figures

Fig. 4. A, Bivariate fit of max. y (estimated from von Bertalanffy equation) by standardized population density 16 days after hydration. Natural log regression provides the best fit. B, Bivariate fit of mean length by mean number of growth bands (per cup).

Fig. 3. Eulimnadia texana experiment, n = 282. Growth model curves follow the von Bertalanffy equation y = a(1-be-cx). The value of a represents an estimation of maximal length (max. y). Colours represent hermaphrodites (red), males (blue), and juvenile or unclear (black). Numbers in upper left corner represent initial population density and replicate.