Pycnogonid Courtship, Mating Behavior, and Parental Care

Pycnogonids are one of the few groups of animals in which the males exclusively care for the developing eggs and young and the ovigerous legs play a major role in these activities. Male pycnogonids appear to use their ovigerous legs during courtship to induce egg laying by the female (Nakamura and Sekiguchi, 1980). Then, following courtship, the female begins to lay the eggs and the male fertilizes them while the female holds them on her ovigerous legs (Cole, 1901a; Nakamura and Sekiguchi, 1980). After fertilization, depending on ovigerous leg type (Bain, in press), the male either gathers the eggs one by one onto his ovigerous legs (Nakamura and Sekiguchi, 1980) or hooks his ovigerous legs into the egg mass (held by the female) and, in one motion, gathers most of the eggs into a single mass on his ovigerous legs (Cole, 1901a). The eggs then remain on the ovigerous legs for variable amounts of time depending on species and geographic location (Cole, 1901b; Thompson, 1909; Hedgpeth, 1948; Nakamura, 1981). While most pycnogonids carry the eggs only until they hatch, some Arctic species of Nymphon and Boreonymphon continue to carry the juveniles after they hatch until the juveniles are one third the size of the adult. (Thompson, 1909).

Pycnogonid Preferred Foods and Feeding Behavior

We currently know very little about pycnogonid feeding habits. Some pycnogonids, such as Anoplodactylus californicus and Anoplodactylus carvalhoi are generalized predators which feed on hydroids, polychaetes, nudibranchs and other small invertebrates (Bain, 1991; Piel, 1991) while others, like Achelia pribilofensis, are scavengers (B. Bain, personal observation). Others, like Pycnogonum litorale and Pycnogonum rickettsi feed by inserting the proboscis into a sea anemone and sucking out its internal fluids. The pycnogonid then drops off and wanders away when satiated. This type of feeding behavior rarely results in the death of the anemone unless the pycnogonid is as large or larger than the anemone (B. Bain, personal observation).

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