Xenocarid

Xenocarids are small shrimp-like organisms that serve as generalists in a variety of habitats. Different species exist in different sizes and colours better suited for different habitats, but beyond that their general morphology remains unchanged. Xenocaris agilis thrives among sandy sediments as a scavenger, picking up retinalphytes, carrion, and the occasional small prey from the seabed with their feeding appendages. Their mandibles at the base of the head allows them to consume a wide range of foods. They are highly maneuverable and moderately fast, suitable for escaping large predators in compensation for lack of protective armour. Here two xenocarids are pictured swimming around each other, perhaps preparing to mate. [Creature design by Squiddum]

Basic Information

Anatomy

This clade of xenosegmatans first arose when a descendant of Xenoeuly kirbyii developed tagmosis of the first three and last two segments, dividing the body into distinct head/abdomen/tail regions. The head possesses three pairs of feeding appendages (modified from swimming appendages) and three pairs of mandibles (modified from gill fronds). The mandibles are serrated and reinforced with keratin. Three pairs of compound eyes sit atop the head, with the front two pairs being the most well developed and facing the front. The head contains a relatively denser network of ganglia compared to the other segments, forming a primitive brain-like organ. Each segment of the abdomen contains a pair of large swimming flippers, with a gill frond sitting underneath each flipper. Flippers move in undulating unison along the abdomen, swimming in a similar fashion to Anomalocaris. Motion of the flipper during swimming pushes water through the gill, increasing efficiency in oxygen uptake. Each segment has retained a pair of reduced dorsal eyespots. The lengthened abdomen houses a lengthened digestive tract and a simple stomach for each abdominal segment.

Genetics and Reproduction

As sequential hermaphrodites, xenocarids can simply morph into the other sex whenever there is imbalance of sex in the current population. The gill fronds of the tail are modified into gonopods, which males and females use to latch onto each other during copulation. The male sits on top of the female, and both release their gametes simultaneously in such close proximity to increase fertilization success. This produces a large number of fertilized eggs per successful mating attempt, which are left to float among zooplankton until they drift down into the sediment.

Ecology and Habitats

Xenocarids are generalist omnivores, having access to a great dietary range due to their highly adaptable mandibles. As opportunists, they forage in shallow waters for potential meals, searching for retinalphyte matter as well as carrion and small prey.

Dietary Needs and Habits

Feeding appendages grab onto food then bring it to the mandibles. The mandibles chew up the food into chunks which are then manipulated into the mouth.

Additional Information

Geographic Origin and Distribution

Can be found in all shallow waters of tropical to temperate warmth. Present anywhere with moderate biodiversity.

Perception and Sensory Capabilities

Compound eyes of the head can distinguish size, shape and color of objects. Due to arrangement of eyes on head, depth perception is achieved to some extent. Abdominal eyespots are only used for distinction of shadows/time of day.

EXTINCT

Genetic Ancestor(s)