Carposporangia

Carposporangia are specialized sporangia found in red algae (Rhodophyta) that produce carpospores. They are borne on the carposporophyte, a diploid generation that develops from a fertilized egg and remains attached to the female gametophyte during development.

In most florideophyte red algae, reproduction follows a triphasic life cycle. The haploid female and male gametophytes produce eggs and sperm, respectively. Fertilization yields a zygote that stays attached to the parental tissue and differentiates into the carposporophyte. The carposporophyte bears numerous carposporangia, each containing many carpospores. When mature, carpospores are released and germinate to form the diploid tetrasporophyte, which then produces haploid tetraspores via meiosis, continuing the cycle.

Structure and function: Carposporangia are typically embedded in the tissue of the carposporophyte and can appear as spherical or ellipsoidal bodies arranged singly or in clusters along the carposporophyte surface. They inventory and protect carpospores until release, facilitating the spread of the next generation.

Taxonomic context: The carposporangium stage is a hallmark of Florideophyceae within red algae and is not present in all red algal groups. Its presence reflects the characteristic triphasic life cycle of florideophytes, which contrasts with the simpler diplontic or haplontic cycles found in other red algae lineages.