Nakata NN and Emlet RB (2023), Having cake and eating too: The benefits of an ...

ECB-ART-51757

Ecol Evol 2023 Jul 17;137:e10298. doi: 10.1002/ece3.10298.

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Having cake and eating too: The benefits of an intermediate larval form in a brittle star Amphiodia sp. opaque (Ophiuroidea).

Nakata NN , Emlet RB .

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Most marine invertebrate larvae either obligately feed or depend on maternally provided reserves during planktonic development. A small number of species have the capacity to do both, in a mode of development known as facultative planktotrophy. We describe facultative feeding in a larva from the Oregon coast, and identify it as being an undescribed species in the genus Amphiodia, which we refer to as Amphiodia sp. opaque. We quantified the effects of food on larval and juvenile quality by culturing larvae, collected as embryos, with and without microalgal food at 15°C. The resulting juveniles were monitored under conditions of starvation. A cohort of juveniles of larvae caught as plankton was subjected to the same starvation treatment for comparison with our laboratory-reared larvae. We observed benefits to offspring that received food: larvae provided with microalgae developed more quickly and metamorphosed at higher rates. Furthermore, juveniles resulting from fed larvae were larger and were able to avoid starvation for longer after metamorphosis. Our results varied across two experimental years, suggesting that provisions provided by parents vary between populations and years. Juveniles from planktonic larvae exhibited sizes not statistically different from larvae cultured in the absence of food, but died from starvation more quickly.

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	FIGURE 1. Amphiodia sp. opaque (a) fertilized egg, (b) unhatched blastula, (c) gastrula, (d) early pluteus 3 days post spawn (dps), (e) reduced pluteus 6 dps from no‐food treatment, with mouth (m) and empty stomach (st), (f) reduced pluteus 6 dps from food treatment, with algal food visible in the stomach (arrowheads), (g) pluteus at 10 dps from no‐food treatment, with three pairs of arms: anterolateral (al), postoral (po), and posterolateral (pl), (h) pluteus 10 dps from food treatment, with juvenile rudiment (r), (i) juvenile from no‐food treatment with disk diameter (dd), and (j) juvenile from food treatment. Scale bars are 100 μm; same scale for (a–f) and for (g–j).
	FIGURE 2. Maximum likelihood tree of COI sequences from adult and larval Amphiurid spp. in the northeastern Pacific, constructed using the PhyML plug‐in in Geneious. Sequences from GenBank (*) and BOLD are labeled with accession number (and see Table 2). Development modes are indicated on the right, with characteristic larvae depicted. Bootstrap values are shown next to nodes.
	FIGURE 3. Cumulative sum of juveniles over time by treatment and year: (a) 2020 and (b) 2021. Each year had the same initial number of larvae in each treatment (2020 n = 110 per treatment, 2021 n = 120). Final time points represent date of discovery of the last juvenile in that treatment.
	FIGURE 4. Bar plots of percent metamorphosis (= no. juveniles/initial no. larvae) averaged across experimental bowls for years 2020 (initial larvae n = 220/22 bowls) and 2021 (n = 240/14 bowls). Error bars represent standard error (SE). Lowercase letters above bars represent significant differences in pairwise comparisons.
	FIGURE 5. Boxplot of juvenile aboral surface area (SA) at metamorphosis by food treatment, pooled across years. Lowercase letters above boxplots represent significant differences in pairwise comparisons.
	FIGURE 6. Scatterplots of (a) planktonic duration by juvenile size, and (b) juvenile aboral surface area (SA) by time to juvenile starvation. Points are mean values for replicate finger bowls (larval culture containers) and bars are standard error. Treatment is coded by color (food: dark gray, no‐food: white, wild: “w”) and experimental year by shape (2020: circle, 2021: triangle, wild: “w”).
	FIGURE 7. Kaplan–Meier survival curves for Amphiodia juveniles according to larval food treatment and year. No juveniles were censored as they were followed until the time of the event, death. Lowercase letters below survival curves indicate significantly different pairwise comparisons.

References [+] :

Allen, Intermediate modes of larval development: bridging the gap between planktotrophy and lecithotrophy. 2007, Pubmed