Mesozoic origin of coleoid cephalopods and their abrupt shifts of diversification patterns.

Coleoids are the most diverse group of cephalopod mollusks. While their origin is date during the Mesozoic, the diversification pattern is unknown. However, two hypotheses have been proposed.

A phylogenetic approach to understand the evolution of reproduction in coleoid cephalopods.

A central question in the evolution of life-histories is whether organisms reproduce once or repeatedly. For cephalopods, the main differences between semelparous and iteroparous are based on ovulation pattern and spawning type. The different reproductive strategies in coleoid cephalopods could be related to the habitat in which the species dwell (coastal vs.

Environmental and ecological factors mediate taxonomic composition and body size of polyplacophoran assemblages along the Peruvian Province.

Intertidal communities' composition and diversity usually exhibit strong changes in relation to environmental gradients at different biogeographical scales. This study represents the first comprehensive diversity and composition description of polyplacophoran assemblages along the Peruvian Province (SE Pacific, 12°S-39°S), as a model system for ecological latitudinal gradients. A total of 4,775 chitons from 21 species were collected on twelve localities along the Peruvian Province.

Sexual Selection and the Evolution of Male Reproductive Traits in Benthic Octopuses.

Competition between same-sex organisms, or intra-sexual selection, can occur before and after mating, and include processes such as sperm competition and cryptic female choice. One of the consequences of intra-sexual selection is that male reproductive traits tend to evolve and diverge at high rates. In benthic octopuses, females often mate with more than one male in a single reproductive event, opening the venue for intra-sexual selection at multiple levels.

Thorson's rule, life-history evolution, and diversification of benthic octopuses (Cephalopoda: Octopodoidea).

Here, we evaluate the so-called Thorson's rule, which posits that direct-development and larger eggs are favored toward the poles in marine organisms and whose validity been the subject of considerable debate in the literature, combining an expanded phenotypic dataset encompassing 60 species of benthic octopuses with a new molecular phylogeny. Phylogenetic reconstruction shows two clades: clade 1 including species of the families Eledonidae, Megaleledonidae, Bathypolypodidae, and Enteroctopodidae, and clade 2 including species of Octopodidae. Egg size, development mode, and all environmental variables exhibited phylogenetic signal, partly due to differences between the two clades: whereas most species in clade 1 inhabit cold and deep waters, exhibit large eggs and hatchling with holobenthic development, species from clade 2 inhabit tropical-temperate and shallow waters, evolved small eggs, and generally exhibit merobenthic development.

Updated molecular phylogeny of the squid family Ommastrephidae: Insights into the evolution of spawning strategies.

Two types of spawning strategy have been described for ommastrephid squids: coastal and oceanic. It has been suggested that ancestral ommastrephids inhabited coastal waters and expanded their distribution into the open ocean during global changes in ocean circulation in the Oligocene. This hypothesis could explain the different reproductive strategies in oceanic squids, but has never been tested in a phylogenetic context.