08/11/2024
What Are Polyclad Flatworms?
🌊 🥿 🪱
This wonderful infographic by the Marine Biodiversity of Yucatán (BDMY) provides a heap of information combined with great visual representations of these worms and their world.
🌊 🥿 🪱
Polyclad flatworms, also called marine flatworms are members of the order Polycladida in the phylum Platyhelminthes. Polyclad get their name from their many-branched digestive system (derived from the Greek "Polus"(numerous) and "klado" (branch).
🌊 🥿 🪱
Polyclads outward appearance could make a fashion designer envious, as they are some of the most vibrantly colored and visually striking groups of marine invertebrates. The vivid patterns and coloration, reminiscent of nudibranchs, can serve as a warning to predators or as camouflage among corals and other colorful invertebrates and algae.
🌊 🥿 🪱
The majority of polyclads are marine organisms. A few species have even adapted to brackish environments, and even fewer to freshwater. The free- living marine species can be found from the intertidal zone down into the deep-sea at depths exceeding 1000 meters (3300 ft.). Polyclads are benthic organisms, typically living close to the seafloor where they glide over the seafloor propelled by cilia on a carpet of mucus. Some are also capable of swimming by undulating their bodies.
🌊 🥿 🪱
Ecologically, polyclads act as both predators and prey. Voracious carnivores, these flatworms feed primarily on small invertebrates, such as mollusks, crustaceans, and other worms. Many polyclads have a close association with sessile organisms such as bivalves, tunicates, sponges, and corals. Polyclads may be using these animals as a refuge from predators, or acting as predators on their associated hosts.
🌊 🥿 🪱
They feed through a muscular tube, called a pharynx that is thrust outside of their bodies. With their pharynx everted, polyclads can extend part of their digestive system out of their bodies to engulf or pe*****te prey. This allows them to feed on animals that are difficult to access or to digest the prey externally before absorbing the nutrients.
🌊 🥿 🪱
Polyclad flatworms can be prey to fish and larger invertebrates, although they have several effective defense mechanisms. Some species produce toxic chemicals, while others rely on their ability to regenerate damaged tissue. Their bright colors and patterns might also serve as warning of their bad taste to potential predators. Additionally, polyclads are good at evasion, as their thin, soft bodies with abundant mucus glands are difficult to grasp and easily slide into small crevices where larger predators can't follow.
🌊 🥿 🪱
Polyclads exhibit remarkable reproductive strategies. They are hermaphroditic, meaning individuals possess both male and female reproductive organs. Mating can involve elaborate behaviors, such as "p***s fencing," where two flatworms duel with their copulatory organs, each attempting to inseminate the other. Once fertilized, polyclads lay clusters of eggs, with some species hatching as miniature adults, while others emerge as Müller's larvae and complete their development in the plankton before settling to the seafloor to metamorphose into adults.
🌊 🥿 🪱
Hernández, A., Ugalde, D., & Simoes, N. (2022). Polyclads. Zenodo.
Versión Español https://doi.org/10.5281/zenodo.7309009
Versão em Português https://doi.org/10.5281/zenodo.7325205
