Alien Biospheres: Part 7 - Return to the Water

Biblaridion・2 minutes read

Alien organisms on the planet have evolved over 150 million years, diversifying into various clades to adapt to different niches. The food webs in the ancient oceans are sustained by microscopic phototrophs and chemotrophs, with various species evolving specialized feeding strategies and swimming techniques to thrive in their environments.

Insights

  • Alien organisms on the planet have diversified into various clades, adapting to different land niches over 150 million years, showcasing a long evolutionary history and the ability to thrive in diverse environments.
  • The evolution of specialized predators like Acanthivorous odontognathans, with needle-like teeth and efficient swimming, highlights the unique adaptations required for survival in an ecosystem lacking traditional fish, showcasing the creativity of evolution in response to environmental challenges.

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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.

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Summary

00:00

Evolution of Alien Organisms in Ancient Oceans

  • Alien organisms on the planet have diversified into various clades, adapting to different land niches over 150 million years.
  • The oceanic food webs are sustained by microscopic phototrophs and chemotrophs, with zooplankton feeding on them.
  • Pelagic nekton niches are mainly occupied by acanthopods, evolving from early polypods with anguilliform swimming.
  • Sub-carangiform swimming is more efficient for speed than anguilliform swimming, leading to the evolution of hadrorhachids.
  • Hadrorhachids specialize in feeding on plankton, growing large due to abundant food sources.
  • The size of hadrorhachids is limited by respiration through gills, with an upper limit around 15 meters.
  • Giant filter-feeding hadrorhachids, known as ptilopods, become the largest animals in the ancient oceans.
  • Teleopterids, evolving from hadrorhachids, become dominant pelagic predators with streamlined bodies and countershading.
  • Dorypods, a clade of teleopterids, specialize in hunting small nekton with streamlined harpoons and sharp spines.
  • Temnopods, another clade of teleopterids, evolve thunniform swimming to become macropredators with powerful bites.

12:59

Reef-dwelling orthorhachids evolve unique adaptations.

  • Some reef-dwelling orthorhachids may re-evolve limb-driven swimming, developing fins into seven pairs of paddles.
  • Reef-dwelling fish exhibit laterally compressed bodies and enlarged fins for better turning control.
  • Adaptation to reef life may lead to coloration changes for orthorhachids to blend with surroundings.
  • Basal orthorhachids, tanypterids, rely on anthostomes for protection, while remipterids use agility to evade predators.
  • Different modes of swimming evolve independently in various clades, similar to unrelated fish groups on Earth.
  • Marine tentaclostomes, lithostracans, may thrive in benthic environments, hiding among anthostomes for protection.
  • Shell-less tentaclostomes, anostracans, may lose shells for flexibility and ambush prey in reefs.
  • Marine sarcopods, coelopods, burrow beneath sand to avoid predators, with setae detecting water vibrations.
  • Predatory coelopods, trichopods, may compete with anostracans for prey, leading to potential specialization.
  • Freshwater native tentaclostomes, myzostomes, may be omnivorous, grazing on vegetation along riverbeds.

25:53

Evolution of Crocodilian Body Plan in Predators

  • Crocodilian body plan evolved multiple times among unrelated clades, ideal for semi-aquatic ambush predators.
  • Signature feature: long, robust jaws for efficient swimming and powerful bites to restrain prey.
  • Different jaw structures in osteopods and deinognathans, latter preadapted for semi-aquatic ambush predation.
  • Deinognathans' eyes may move upward to sense prey above waterline, spiracles repositioned for underwater concealment.
  • Odontognathans dominate freshwater habitats, diversify into specialized forms, initially as macropredators.
  • Trachygnathans evolve to feed on acanthopods, termed "Acanthivores" due to lack of fish on alien planet.
  • Acanthivorous odontognathans adapt mouthparts for aquatic feeding, evolving needle-like teeth and slender mandibles.
  • Odontognathans develop swimming efficiency similar to remipterids, using back-and-forth limb strokes.
  • Dolichognathans, smaller than trachygnathans, become prolific predators of acanthopods, expanding into coastal shallows.
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