Kalachev A.V.1, Yurchenko O.V.1, Osten V.G.2 2018. Phenotypic plasticity in pre-feeding larvae of sea urchins, Mesocentrotus nudus and Strongylocentrotus intermedius // Invertebrate Zoology. Vol.15. No.4: 420–433 [in English].
1 National Scientific Center of Marine Biology, Far Eastern Branch of the Russian Academy of Sciences, 17 Palchevskogo str., Vladivostok, 690041, Russia. E-mail: email@example.com
2 Far Eastern Federal University, Vladivostok, 690090, Russia
ABSTRACT: Experimental studies showed that in echinoids egg size of a species affects magnitude of phenotypic plasticity in larvae of the species. Here we tested whether any difference in magnitude of plasticity exists in pre-feeding larvae of two sea urchins, Mesocentrotus nudus (A. Agassiz, 1864) and Strongylocentrotus intermedius (A. Agassiz, 1864). These species are closely related by their phylogenetic position, have overlapping ranges, and differ by size of their eggs. Our results indicate that by the end of pre-feeding development (4 d after fertilization) the larvae from high algae treatment (8 000 cells 1 ml–1) had shorter post-oral arms as compared to their siblings of the same age from no algae treatment (0 cells 1 ml–1). In spite the egg volume of M. nudus was approximately 2-times bigger than that in S. intermedius, relative difference in post-oral arms length in no algae and high algae conditions in S. intermedius was approximately 1.5 times larger. Our results support the assumption that the degree of phenotypic plasticity in the larvae, developing from smaller eggs with lower maternal investment, is higher than in the larvae, developing from bigger eggs. We propose that pre-feeding larvae of S. intermedius are more phenotypically plastic than the larvae of M. nudus.
KEY WORDS: Sea urchins, larvae, development, phenotypic plasticity, maternal investment.