How do sea fleas look? - briefly
Sea fleas are translucent, oval‑shaped crustaceans about 0.5–2 mm long, possessing a segmented body and a pair of large, clawed appendages for clinging to marine hosts. Their lightly armored exoskeleton gives them a faint, moving speck appearance in plankton samples.
How do sea fleas look? - in detail
Sea fleas, members of the order Harpacticoida, are microscopic crustaceans that inhabit marine surface films and intertidal zones. Their bodies are typically elongated, ranging from 0.2 mm to 2 mm in length, and exhibit a segmented construction divided into a cephalothorax and an abdomen.
The cephalothorax is covered by a rigid, translucent carapace that often appears glassy or slightly amber in hue. This shield protects the head region, which bears a pair of short, stalked eyes and two prominent antennae. The antennae consist of several articulated segments, ending in fine setae that function as sensory organs.
The abdomen consists of five to six freely articulated segments, each bearing a pair of biramous swimming legs. These legs terminate in slender, feather‑like setae that generate water currents for locomotion and feeding. The overall coloration is generally pale, ranging from almost colorless to faintly yellowish, allowing the organism to blend with the surrounding water film.
Key morphological traits include:
- Carapace: transparent, convex, often with a slight amber tint.
- Eyes: small, stalked, composed of simple ommatidia.
- Antennae: multi‑segmented, ending in sensory setae.
- Legs: biramous, with setose exopods for swimming.
- Setae: dense, plumose structures on legs and antennae for filtration.
- Body segmentation: distinct cephalothorax and abdomen, each with clear articulation.
Variations among species affect size, the degree of carapace pigmentation, and the length of antennal and leg setae, but all share the fundamental plan of a compact, translucent body equipped for a planktonic lifestyle in the thin water layers at the sea surface.