Ontogenetic-habitat-shift
Guides
Pleuroncodes planipes
pelagic red crab, tuna crab, squat lobster, langostilla, benthic anomuran red crab
Pleuroncodes planipes is a pelagic and benthic anomuran red crab distributed across the eastern Pacific Ocean, from California to Panama. The species exhibits a complex life cycle with both pelagic and benthic phases: larvae and small individuals occupy open waters, while larger adults become exclusively benthic. It forms exceptionally dense aggregations on seamounts, with recorded densities up to 78 crabs/m² at depths of 355–385 m. The species tolerates hypoxic conditions (0.04 ml/l oxygen) and serves as a major prey item for large pelagic predators including yellowfin and skipjack tuna.
Pseudiron centralis
White Sand-river Mayfly
Pseudiron centralis is a predaceous mayfly species endemic to sandy freshwater river habitats in North America. It exhibits a univoltine summer life cycle with an extended egg stage lasting 9–10 months. Larvae are active epibenthic predators specialized for feeding on psammophilous chironomid larvae, with distinct microhabitat shifts during development: early instars occupy marginal sands, while later instars inhabit shifting sand dunes in main channel areas. The species shows low population density but also low mortality, with random dispersion patterns in mature larvae.