Development of the gastropod Trochita pileus (Calyptraeidae) in the sub-Antarctic Southwestern Atlantic

Characterization of the complete mitochondrial genome of Desmaulus extinctorium (Littorinimorpha, Calyptraeoidea, Calyptraeidae) and molecular phylogeny of Littorinimorpha

For the purpose of determining the placement of Calyptraeidae within the Littorinimorpha, we hereby furnish a thorough analysis of the mitochondrial genome (mitogenome) sequence of Desmaulus extinctorium. This mitogenome spans 16,605 base pairs and encompasses the entire set of 37 genes, including 13 PCGs, 22 tRNAs and two rRNAs, with an evident AT bias. Notably, tRNASer1 and tRNASer2 lack dihydrouracil (DHU) arms, resulting in an inability to form a secondary structure. Similarly, tRNAAla lacks a TΨC arm, rendering it incapable of forming a secondary structure. In contrast, the remaining tRNAs demonstrate a characteristic secondary structure reminiscent of a cloverleaf. A comparison with ancestral gastropods reveals distinct differences in three gene clusters (or genes), encompassing 15 tRNAs and eight PCGs. Notably, inversions and translocations represent the major types of rearrangements observed in D. extinctorium. Phylogenetic analysis demonstrates robust support for a monophyletic grouping of all Littorinimorpha species, with D. extinctorium representing a distinct Calyptraeoidea clade. In summary, this investigation provides the first complete mitochondrial dataset for a species of the Calyptraeidae, thus providing novel insights into the phylogenetic relationships within the Littorinimorpha.

Relationship between over-crowding within egg capsules of the marine gastropod Acanthina monodon and prospects for juvenile success

Encapsulated development with extraembryonic yolk may lead to competition for nutrients within egg capsules. In this research, different degrees of competition among embryos in subtidal egg capsules of Acanthina monodon resulted in considerable differences in hatching size. For newly hatched juveniles, individuals hatching from less crowded egg capsules showed better survival, larger SL, higher rates of oxygen consumption, and higher rates of food consumption. However, by 28 days after hatching, the largest surviving juveniles were the best-performing individuals, regardless of the initial embryo density within the capsules. In summary, more crowded egg capsules resulted in poorer survival. These findings may help to explain the variability seen in juvenile success in some field populations; much of that variation may reflect stressful experiences that the new recruits have had during the early stages of their encapsulated development.