What Exactly Is: Sea Spider | The "All-Legs"

If you are afraid of spiders, then you’re not even safe under the sea. Except these ones are a lot “nicer” and technically not even spiders. Meet the sea spiders, aka pycnogonids, aka pantopods. They are known as the “all-legs” because their axial body is so reduced it became barely noticeable. Inside these legs lies biological wonders that you might not even think are possible.


Timestamps
0:00 Opening Thought
0:46 Taxonomy and General Information
3:37 Morphology
9:08 Lifestyle and Behaviour
13:19 Fossil Records


References
Bamber, R.N.; El Nagar, A.; Arango, C.P.; Sabroux, R. (Eds) (2025). Pycnobase: World Pycnogonida Database. https://www.marinespecies.org/pycnobase. doi:10.14284/360

Ballesteros, J. A., Setton, E. V. W., Santibáñez-López, C. E., Arango, C. P., Brenneis, G., Brix, S., Corbett, K. F., Cano-Sánchez, E., Dandouch, M., Dilly, G. F., Eleaume, M. P., Gainett, G., Gallut, C., McAtee, S., McIntyre, L., Moran, A. L., Moran, R., López-González, P. J., Scholtz, G., Williamson, C., … Sharma, P. P. (2021). Phylogenomic Resolution of Sea Spider Diversification through Integration of Multiple Data Classes. Molecular biology and evolution, 38(2), 686–701. https://doi.org/10.1093/molbev/msaa228

Wang, J. J., Huang, D. Y., Lin, R. C., & Zheng, X. Q. (2013). A new species of Austrodecus Hodgson, 1907 (Arthropoda, Pycnogonida, Austrodecidae) from the Southwest Indian Ridge. ZooKeys, (349), 73–79. https://doi.org/10.3897/zookeys.349.6170

Brenneis, G., Frankowski, K., Maaß, L., & Scholtz, G. (2023). The sea spider Pycnogonum litorale overturns the paradigm of the absence of axial regeneration in molting animals. Proceedings of the National Academy of Sciences of the United States of America, 120(5), e2217272120. https://doi.org/10.1073/pnas.2217272120

Dietz, L., Dömel, J. S., Leese, F., Lehmann, T., & Melzer, R. R. (2018). Feeding ecology in sea spiders (Arthropoda: Pycnogonida): what do we know?. Frontiers in zoology, 15, 7. https://doi.org/10.1186/s12983-018-02...

Richards, P.R. & Fry, W.G. (1978). Digestion in pycnogonids: a study of some polar forms. Zoological Journal of the Linnean Society, 63(1-2): 75-97. https://doi.org/10.1111/j.1096-3642.1...

Woods, H. A., Lane, S. J., Shishido, C., Tobalske, B. W., Arango, C. P., & Moran, A. L. (2017). Respiratory gut peristalsis by sea spiders. Current biology : CB, 27(13), R638–R639. https://doi.org/10.1016/j.cub.2017.05...

Lehmann, T., Heß, M., & Melzer, R. R. (2014). Common littoral pycnogonids of the Mediterranean Sea. Zoosystematics and Evolution, 90(2): 163–224. https://doi.org/10.3897/zse.90.7520

Lucena, R. A. & Christoffersen, M. L. (2022). Pycnogonida (Arthropoda) from Museu de Ciências Naturais, Rio Grande do Sul, Brazil. Zoosystematics and Evolution, 98(2): 305–312. https://doi.org/10.3897/zse.98.83671

Alexeeva, N. & Tamberg, Y. (2023). Ultrastructure of the female pedal gonad in Phoxichilidium femoratum (Chelicerata, Pycnogonida). Arthropod Structure & Development, 76, 101295. https://doi.org/10.1016/j.asd.2023.10...

Moran, A. L., Lobert, G. T., & Toh, M. W. A. (2024). Spawning and larval development of Colossendeis megalonyx, a giant Antarctic sea spider. Ecology, 105(3), e4258. https://doi.org/10.1002/ecy.4258

Sabroux, R., Garwood, R. J., Pisani, D., Donoghue, P. C. J., & Edgecombe, G. D. (2024). New insights into the Devonian sea spiders of the Hunsrück Slate (Arthropoda: Pycnogonida). PeerJ, 12, e17766. https://doi.org/10.7717/peerj.17766


Outro
The Soundlings - Silent Night (Youtube Library)


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