Characterization of the first invasive population of sea spiders (Pycnogonida)
Flandroit, F.; Simon, L.; Decoux, B.; Geerinckx, N.; Eeckhaut, I.; Caulier, G. (2025). Characterization of the first invasive population of sea spiders (Pycnogonida). Manag. Biol. Inv. 16(3): 787-822. https://dx.doi.org/10.3391/mbi.2025.16.3.10
In: Management of Biological Invasions. Regional Euro-Asian Biological Invasions Centre (REABIC): Helsinki. ISSN 1989-8649; e-ISSN 1989-8649, meer
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Cycles > Life cycle
Monitoring
Phenology
Ammothea hilgendorfi (Böhm, 1879) [WoRMS]; Ammotheidae Dohrn, 1881 [WoRMS]; Pantopoda [WoRMS]
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- Flandroit, F., meer
- Simon, L., meer
- Decoux, B.
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| Abstract |
Pycnogonids, or sea spiders, are ubiquitous arthropods present in most marine ecosystems. However, because of their usually low population densities, they remain understudied by zoologists despite presenting numerous unique biological features. The species Ammothea hilgendorfi (Böhm, 1879), native to the Northern Pacific Ocean, was introduced in Europe in the late 1970s and its presence has now been reported in several seas. Recordings of the species in Europe are sporadic and mostly do not exceed a handful of specimens. Hence, the populations have only been considered as introduced in the invasion process. The goal of this study is to investigate the first population of A. hilgendorfi at the Belgian coast (North Sea) during a 24-month monitoring through different proxies (phenology, biometry, developmental cycle). For the first time, our results demonstrate that this population of pycnogonids can be considered as established as it is able to complete its entire life cycle, including all larval instars, which are ectoparasites of hydroids. Moreover, it has developed in very high densities of individuals and has outnumbered by far the native sea spiders, which have almost disappeared, so it can also be considered as invasive sensu stricto. Their average density increased from the first year to the second, which indicates that the invasion has likely not reached its capacity yet. Since research on sea spiders has been very limited, this work emphasizes the importance of studying these animals, especially when the lack of knowledge undermines the assessment of their impact and their invasiveness potential. |
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