Alien Biospheres: Part 7 - Return to the Water

Recent questions

• What are the main niches occupied by alien organisms?

  Alien organisms on the planet have diversified into various clades, adapting to different land niches over 150 million years. These organisms have evolved to occupy niches such as pelagic nekton, reef-dwelling habitats, and freshwater environments. Each niche has unique characteristics that have influenced the evolution and specialization of these alien organisms over time.

• How do hadrorhachids obtain their large size?

  Hadrorhachids specialize in feeding on plankton, which provides them with abundant food sources necessary for growth. Their large size is a result of this specialized feeding behavior, allowing them to thrive in the ancient oceans. However, the size of hadrorhachids is limited by their respiration through gills, with an upper limit around 15 meters. This balance between food availability and respiratory constraints shapes the evolution and size of these organisms.

• What are the key features of teleopterids?

  Teleopterids, evolving from hadrorhachids, become dominant pelagic predators with streamlined bodies and countershading. They have evolved to be efficient hunters in the ocean, with adaptations such as streamlined bodies for speed and countershading for camouflage. Within the teleopterids clade, there are subgroups like dorypods and temnopods, each specializing in different hunting strategies and prey types. These features have allowed teleopterids to become successful predators in the marine environment.

• How do orthorhachids adapt to reef life?

  Some reef-dwelling orthorhachids may re-evolve limb-driven swimming, developing fins into seven pairs of paddles. This adaptation allows them to navigate the complex reef environments with agility and precision. Additionally, reef-dwelling fish exhibit laterally compressed bodies and enlarged fins for better turning control, aiding in their maneuverability among coral structures. Coloration changes may also occur in orthorhachids to blend with their surroundings, enhancing their ability to camouflage and evade predators in the reef ecosystem.

• What are the characteristics of odontognathans in freshwater habitats?

  Odontognathans dominate freshwater habitats and diversify into specialized forms, initially as macropredators. These organisms have adapted to feed on acanthopods, as there is a lack of fish on the alien planet. Odontognathans have evolved mouthparts suited for aquatic feeding, with needle-like teeth and slender mandibles for capturing prey efficiently. They have developed swimming efficiency similar to remipterids, using back-and-forth limb strokes to navigate freshwater environments. Additionally, dolichognathans, a subgroup of odontognathans, have become prolific predators of acanthopods, expanding their presence into coastal shallows for hunting opportunities.