Functional morphology of the sperm-containing chambers of the sea slug Okenia polycerelloides in the context of sexual selection.

Sea slugs are interesting models to study post-copulatory sexual selection in simultaneous hermaphrodites due to the enormous variation of their reproductive systems. However, the knowledge of the functional morphology of their reproductive system is limited to few species, and it is rarely discussed in the context of sexual selection theory. In this study, we investigated the functional morphology of the sperm-containing chambers (i.

The grass squid Pickfordiateuthis pulchella is a paedomorphic loliginid.

The wide disparity in adult body size observed both within and among animal taxa has long attracted widespread interest, with several general rules having been proposed to explain trends in body size evolution. Adult body size disparity among the cephalopod mollusks is remarkable, with adult body sizes ranging from a few centimeters to several meters. Some of the smallest cephalopods are found within Pickfordiateuthis, a group comprising three described species of squid found in the western Atlantic and tropical eastern Pacific.

Gonadal histology of box jellyfish (Cnidaria: Cubozoa) reveals variation between internal fertilizing species Alatina alata (Alatinidae) and Copula sivickisi (Tripedaliidae).

Cubozoans (box jellyfish) are gonochoristic cnidarians with distinct reproductive strategies. This comparative histological study examines the gonad organization of Alatina alata and Copula sivickisi, two box jellyfish species that exhibit different modes of internal fertilization. A.

Exoskeletons of Bougainvilliidae and other Hydroidolina (Cnidaria, Hydrozoa): structure and composition.

The exoskeleton is an important source of characters for the taxonomy of Hydroidolina. It originates as epidermal secretions and, among other functions, protects the coenosarc of the polypoid stage. However, comparative studies on the exoskeletal tissue origin, development, chemical, and structural characteristics, as well as its evolution and homology, are few and fragmented.

Inferring muscular ground patterns in Bivalvia: Myogenesis in the scallop Nodipecten nodosus.

Background: Myogenesis is currently investigated in a number of invertebrate taxa using combined techniques, including fluorescence labeling, confocal microscopy, and 3D imaging, in order to understand anatomical and functional issues and to contribute to evolutionary questions. Although developmental studies on the gross morphology of bivalves have been extensively pursued, organogenesis including muscle development has been scarcely investigated so far.

Results: The present study describes in detail myogenesis in the scallop Nodipecten nodosus (Linnaeus, 1758) during larval and postmetamorphic stages by means of light, electron, and confocal microscopy.

Mantle margin morphogenesis in Nodipecten nodosus (Mollusca: Bivalvia): new insights into the development and the roles of bivalve pallial folds.

Background: Despite extensive knowledge on bivalve anatomy and development, the formation and differentiation of the mantle margin and its associated organs remain largely unclear. Bivalves from the family Pectinidae (scallops) are particularly promising to cast some light on these issues, because they exhibit a complex mantle margin and their developmental stages are easily obtained from scallop farms. We investigated the mantle margin of the scallop Nodipecten nodosus (L.

Spermatophoric reaction reappraised: novel insights into the functioning of the loliginid spermatophore based on Doryteuthis plei (Mollusca: Cephalopoda).

During copulation, spermatophores produced by male coleoid cephalopods undergo the spermatophoric reaction, a complex process of evagination that culminates in the attachment of the spermatangium (everted spermatophore containing the sperm mass) on the female's body. To better understand this complicated phenomenon, the present study investigated the functional morphology of the spermatophore of the squid Doryteuthis plei applying in vitro analysis of the reaction, as well as light and electron microscopy investigation of spermatangia obtained either in vitro, or naturally attached on females. Hitherto unnoticed functional features of the loliginid spermatophore require a reappraisal of some important processes involved in the spermatophoric reaction.