Reproductive pattern of Trochita pileolus (d' Orbigny, 1841) (Gastropoda: Calyptraeidae) and different types of intracapsular development in Trochita species of South America

PENCHASZADEH, PABLO E.; TESO, VALERIA; ARRIGHETTI, FLORENCIA; ALDEA, CRISTIAN

POLAR BIOLOGY

SPRINGER

Lugar: Berlin; Año: 2021

0722-4060

Several types of development are reported in the Family Calyptraeidae which is widely distributed around the world. In species with direct development embryos can grow from large eggs or they can feed on nurse eggs, nurse embryos, or other intracapsular nutritional resources. For a better understanding of the role of egg size it is necessary to address further questions as to how biochemical composition varies among egg size, type of development and embryos. Adults and broods of Trochita pileolus were collected from 2 stations during one cruise off Tierra del Fuego and nearby Burdwood Bank at depth ranges of 96-151 m. A total of five brooding females and 37 egg capsules of Trochita pileolus were collected. The mean shell diameter of brooding females was 16.3 ± 2 mm. The number of egg capsules observed in brooding females ranged from 5 to 9. The number of egg capsules per brood was 5-9. In egg capsule 7-10 embryos develop from uncleaved eggs of about 500 µm in diameter. Neither nurse eggs nor other kinds of extraviteline food sources were recorded. No oophagy, adelphophagy, or late intracapsular cannibalism was observed. The mean shell diameter of protoconch of adults is 1.2 ± 0.2 mm (1.0-1.4). Additionally, differences between egg size and energy content between the three species of Trochita were studied to understand the evolutionary patterns in reproduction. The development mode of T. pileolus closely resembles the giant T. trochiformis from Chile, in which both species obtain energy for developing embryos from large fertile eggs. T. trochiformis presented eggs with higher lipid content than the other two species, and this eggs are more energy-dense that eggs glycogen-enriched. On the other hand, the energetic content of T. pileus eggs are similar to T. pileolus, despite the egg size of T. pileus is lower. This is possible because in T. pileus it has been proved the presence of nurse eggs and adelphophagy.