Loxorhynchus grandis, commonly known as the ‘large Pacific spider crab‘ or ‘Pacific spiny crab‘, is a species of decapod crustacean belonging to the family Epialtidae, within the order Decapoda. The genus name ‘Loxorhynchus‘ comes from the Greek ‘loxos‘, meaning skewed or crooked, and ‘rhynchos‘, meaning snout, in reference to the shape of its shell. The specific epithet ‘grandis‘ means large in Latin, describing its relatively large size compared to other spider crabs. Loxorhynchus grandis is distributed along the Pacific coast of North America, from Alaska to Baja California, Mexico. It mainly inhabits temperate and cold waters, being found in rocky bottoms, reefs, and sandy areas, at depths ranging from 6 to 300 meters.
In terms of morphology, Loxorhynchus grandis is one of the largest spider crabs in the Pacific, with a carapace that can reach up to 20 centimeters wide and a leg span of up to 60 centimeters. Its carapace is oval, elongated and teardrop-shaped, with the back part wider and rounded, tapering to the tip of the snout. On the snout, there is a strongly downward curved preorbital spine. The entire carapace is covered with spines (called tubercles) of different sizes, which give it a rough appearance and natural camouflage among rocks and seaweed. This spiny texture and its variable coloration, ranging from reddish brown to greenish gray, allow it to blend in effectively with its environment. Four pairs of legs and a pair of pincers (chelipeds) emerge from the carapace. The legs and chelipeds are moderate in size compared to the body, but robust and strong, used for movement, feeding and defense. The second pair of legs are the longest of all, being even longer than the shell itself. The crabs of this genus differ from other similar ones, such as Pugettia producta, by their larger size, the more elongated shape of their carapace and the arrangement of the spines, which in Loxorhynchus grandis are more prominent and less uniform.
Loxorhynchus grandis is omnivorous, feeding on a wide variety of marine organisms. Its diet includes algae, sponges, small molluscs, echinoderms (such as sea urchins and starfish), annelids, and other invertebrates. It uses its chelipeds to capture and manipulate its food, crushing the hard shells of its prey or tearing off fragments of softer organisms. This crab is also an opportunist that feeds on organic debris and carcasses, playing an important role in recycling nutrients in its ecosystem. Its ability to consume a wide range of foods makes it a key component of the seafloor, contributing to the control of various invertebrate populations and the cleanliness of the seafloor.
In terms of reproduction, Loxorhynchus grandis follows a sexual reproductive cycle typical of crabs. Mating usually occurs after the female molts, when her shell is softer, facilitating copulation. Fertilized females carry the eggs under their abdomen, attached to their pleopods (swimming legs), until they hatch. During this period, females are less active and hide to protect their developing young. The larvae, known as zoeae, are planktonic and go through several stages of development in the water column before settling to the seafloor as juveniles. This pelagic larval process allows for wide dispersal of the species and a high rate of colonization of different habitats.
A curious fact about Loxorhynchus grandis is its decorating behavior, a common habit among spider crabs. It uses algae, sponges, and other materials from the environment to decorate its shell, using specialized hooks on its exoskeleton to attach these items. This behavior not only enhances its camouflaging ability, protecting it from predators such as large fish and octopuses, but can also deter other organisms that might try to settle on it. Furthermore, despite its relatively large size, Loxorhynchus grandis is a slow-moving and rarely aggressive crab, relying on its camouflage and tough spiny armor as its primary form of defense.
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