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Crabs

This reading profile brings together 14 source-linked articles that reference crabs.

Explore Fauna’s source-checked field guides and research articles covering crabs, or search the species catalog below for individual species profiles.
Across Fauna

Source-linked reading

  1. Field guideHow crabs molt and growBecause a hardened crab shell cannot stretch, growth comes in steps. The crab prepares a larger cuticle underneath, leaves the old shell, expands while the new one is soft, and then mineralizes and strengthens it.
  2. Field guideFollowing tidal wildlife rhythmsPlan observations by predicted high or low water and rising or falling phase, record actual conditions and habitat exposure, compare equal windows relative to tide, and add lunar spring-neap stage and weather.
  3. Field guideObserving spiders without handlingSpiders can be studied closely without capture. Use magnification, patient angles, web architecture, posture, habitat, and time of activity as evidence, while treating each clue as suggestive rather than decisive on its own.
  4. Field guideHow kelp forests support animalsHoldfasts, stipes, blades, and floating canopies add surfaces and shelter from seafloor to sea surface. Grazers consume kelp and epiphytes, detritus feeds animals inside and beyond the forest, and fish and invertebrates use the structure as nursery, feeding, and refuge habitat. Predators can indirectly protect kelp by limiting grazers in some regions.
  5. Field guideReading an estuaryEstuaries are partly enclosed waters influenced by coastal water and freshwater. Their depth, exposed area, currents, salinity, and wildlife access shift with tides, river flow, weather, and season.
  6. Field guideTidepooling without harmLow tide opens a temporary window into the intertidal zone. The best visit is timed conservatively, made from stable bare ground, and leaves every organism in its exact place.
  7. Field guideUsing a quadrat for biodiversityChoose an area suited to the organisms, place replicated quadrats by a declared random or systematic rule, use one edge convention, record the same response each time, and limit conclusions to the sampled design.
  8. Field guideCoevolution and evolutionary arms racesA host defense can favor parasite countermeasures, and those countermeasures can favor new host defenses. Pollinators and flowers can also impose reciprocal selection. The evolutionary response may escalate, cycle, stabilize, vary across landscapes, or involve many species, so a close fit between partners is not by itself proof of a two-species arms race.
  9. Field guideFood webs and trophic levelsA food chain is one pathway through a feeding network; a food web joins many such pathways. Trophic levels summarize distance from primary production, but omnivores, detritus, changing diets, and cross-habitat subsidies make real organisms harder to place than a simple pyramid suggests.
  10. Field guideHow sea stars regrow armsSea-star regeneration is slow coordinated reconstruction, not a detached limb simply stretching back. Wound closure is followed by cell migration, proliferation, patterning, and the rebuilding of several integrated organ systems.
  11. Field guideHow sharks sense electric fieldsSharks sample tiny voltage differences through the ampullae of Lorenzini. Arrays of surface pores connect to sensory chambers, letting the nervous system compare signals across space and distinguish external fields from some self-generated activity.
  12. Field guideHow snails build shellsA snail does not move into a larger shell. Its living mantle adds material at the aperture and can thicken inner surfaces, so the shell records continuous accretion from the tiny oldest apex to the newest outer lip.
  13. Field guideMaking useful citizen-science recordsA useful record preserves what you encountered, where and when you encountered it, and honest evidence that another person can evaluate.
  14. Field guideWhy sea otters use toolsA hard object can act as a hammer, a portable chest anvil, or a fixed anvil, letting an otter pry loose or fracture prey that teeth and paws alone handle less efficiently. The behavior is flexible rather than compulsory, and it is especially associated with hard-shelled snails and bivalves.