Family PYCNOGONIDAE Wilson, 1878

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Introduction

Pycnogonidae is world-wide family characterised by a robust, compact body and short legs. It includes Pycnogonum, with nearly 70 species (Arango & Wheeler, 2007), and Pentapycnon, peculiar 10-legged forms occurring in Antarctica and the Caribbean (see Arnaud & Bamber, 1987).

The current phylogeny suggests this lineage can be one of the most primitive, but the phylogenetic affinities of Pycnogonidae are to be explained from the morphological and anatomical point of view (see Arango & Wheeler 2007). This lineage shows some particular features such as rough cuticle characterised by high density of mucous cells and complex arrangements to be described. Aspects of the biology of Pycnogonidae are known due to studies on P. litorale Strom, 1762 from the Northern Seas, the most studied species of sea spiders (see King 1973 and Arnaud & Bamber 1987 for older literature; Vilpoux & Waloszek 2003; Ungerer & Scholtz 2009, for more recent studies on development).

Diagnosis

Animals almost always compact, with short legs. Chelifores and palps lacking; ovigers reduced in size, 6- to 9-segmented, with large terminal claw, without strigilis, sometimes lacking in males, rarely entirely absent; legs knobbly, most without auxiliary claws. Cement gland(s) usually not visible. The family includes 10-legged forms.

General References

Arango, C.P. & Wheeler, W.C. 2007. Phylogeny of the sea spiders (Arthropoda, Pycnogonida) based on direct optimization of six loci and morphology. Cladistics 23: 255-293

Arnaud, F. & Bamber, R.N. 1987. The Biology of Pycnogonida. pp. 1-96 in Blaxter, J.H.S. & Southward, A.J. (eds). Advances in Marine Biology. London : Academic Press Vol. 24.

King, P.E. 1973. Pycnogonids. London : Hutchinson Hutchinson and Co.

Ungerer, P. & Scholtz, G. 2009. Cleavage and gastrulation in Pycnogonum litorale (Arthropoda, Pycnogonida): morphological support for the Ecdysozoa? Zoomorphology (Berlin) doi: 10.1007/s00435-009-0091-y

Vilpoux, K. & Waloszek, D. 2003. Larval development and morphogenesis of the sea spider Pycnogonum litorale (Strom, 1762) and the tagmosis of the body of Pantopoda. Arthropod Structure & Development 37: 349-383

Wilson, E.B. 1878. Report on the Pycnogonida of New England and adjacent waters. Report of the United States Commission on Fish and Fisheries 1878: 463-506, pl. I-VII

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