Ovigers

Ovigers are specialized leg-like appendages found in male sea spiders (Pycnogonida). They are modified walking legs used to carry and brood eggs during reproduction. Each male typically possesses a pair of ovigers, located toward the front of the body, which bear eggs along their distal segments.

Function and role in reproduction: After mating, fertilized eggs are transferred onto the distal portions of the ovigers and are carried there by the male until hatching. The ovigers provide a surface for the eggs and allow the male to aerate and protect the developing embryos. In many species, the eggs hatch into free-swimming larval forms while still attached to the ovigers, or shortly after detaching from them.

Anatomy and variation: Ovigers are entirely absent in females and are a distinctive feature of many pycnogonid families. Their length, robustness, and the number of segments involved can vary widely among species, with some having highly developed ovigers and others more rudimentary structures. The structure of the ovigers, including any specialized hooks or setae, is often used in taxonomic identification within Pycnogonida.

Evolution and significance: The presence of ovigers illustrates paternal care in pycnogonids, a notable example of parental investment in arthropods. The evolution of these appendages may influence mating systems and life history strategies in sea spiders.

See also: Pycnogonida, sea spiders, parental care in arthropods.