Larvae of the pycnogonids Ammothea gigantea Gordon, 1932 and Achelia cuneatis Child, 1999 described from archived specimens
2012
John A. Fornshell | Frank D. Ferrari
The larvae of two species of Pycnogonida are described from archived collections. Achelia cuneatis Child, 1999 is an example of a typical protonymphon larva in having three pairs of three segmented appendages, cheliphores, palps and ovigerous appendages. Ammothea gigantea Gordon, 1932 is an example of a lecithotrophic protonymphon larva, having the three pair of appendages plus buds of the first walking legs. Ammothea gigantea is the third species known to have this larval type. The Achelia cuneatis protonymphon larvae is oval, 150 um long and characterized by a relatively long spinneret spine arising at the distal end of the first segment of each cheliphore. Spines also arise from the distal end of the first segment of the second and third limbs. This typical protonymphon larva of Achelia cuneatis has few yolk granules. The lecithotrophic protonymphon of Ammothea gigantea lacks a spinneret spine on the cheliphore; the larva is oval in shape, but much larger than Achelia cuneatis with a length of 700 um. Its second limb is much larger than the third limb on the first post-embryonic stage, and the third limb is further reduced to a spine-like structure on the second post-embryonic stage. This lecithotrophic protonymphon larva has a large number of yolk granules.
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