Zeuxo holdichi -

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SCIENTIFIC NAME

Zeuxo holdichi Bamber, 1990

2021 - present Oorsprongsgebied

Unknown

Aquaculture - importing live animals Unknown

Current distribution Zeuxo holdichi Bamber, 1990 (49 OBIS-datapoints, 96 GBIF-datapoints)

The origin of the tanaid Zeuxo holdichi is currently unknown, but it is presumed to be a non-native species to Western Europe and is likely introduced to European waters through shellfish aquaculture. In 2023, the species was first spotted in the Sluice Dock of Ostend. To date, this remains the only location in Belgium where it has been found, although the organism has been detected in several marine and brackish locations in the Netherlands.

Original spreading

The species was initially described (1990) in the Bay of Arcachon (Southwest France) ^[2], but it is assumed to be a non-native species whose natural distribution range remains unknown to date (cryptogenic) ^[3].

First observation in Belgium and current spreading

First observation in Belgium

In July 2023, several live specimens of the brackish water isopod were found in samples from the Sluice Dock in Ostend ^[4].

Distribution in Belgium

Zeuxo holdichi has so far only been found in the Sluice Dock in Ostend ^[4].

Distribution in neighbouring countries

In 1990, this species was described from the Bay of Arcachon (Southwest France) ^[2]. Subsequently, Zeuxo holdichi was reported along the western coast of Portugal up to Northern Brittany and Southwest England ^[5]. In 2012, the species was also found along the Channel coast of Northern France ^[6] and in the Dutch Eastern Scheldt ^[3]. Recently, specimens were also discovered in the Netherlands near Katwijk (North Sea), in the Grevelingenmeer, and in the Western Scheldt ^[7,8]. In 2022, Zeuxo holdichi was also found in the Venice Lagoon ^[9].

Way of introduction

Given the intensive shellfish farming in the Bay of Arcachon, it is strongly suspected that the species was introduced via aquaculture. The further secondary spread to both northern and southern regions (all known for shellfish farming and the presence of marinas) is attributed to both shellfish transport and recreational boating ^[3,6].

Factors making this species so successful in our area

Zeuxo holdichi thrives in both brackish and marine environments ^[4,8] and can be found on various substrates: among and on (oyster) shells, on sandy/muddy bottom sediment, and among red seaweeds ^[3-5]. The species occurs from the intertidal zone down to a depth of 60 meters ^[6], with a preference for the nearshore sublittoral zone ^[5].

Factors that influence the spreading

The order of Tanaids (small crustaceans) has a sedentary lifestyle and lacks a planktonic larval stage. As a result, the potential for secondary natural dispersal is limited.

(Potential) effects and measures

No effects or measures are known to be associated with the presence of Zeuxo holdichi.

Specific features

This small tanaid measures approximately 5 mm and has an elongated body with five free pleon segments without a dorsal row of upright setae. The uropod consists of seven segments. The left coxa has a distinctive tooth on the medial side. The right mandible features a large molar with four teeth in a row ^[2].

References

[1] World Register of Marine Species (WoRMS) (2024). Zeuxo holdichi Bamber, 1990. https://www.marinespecies.org/aphia.php?p=taxdetails&id=416601 (2024-10-18).

[2] Bamber, R.N. (1990). A new species of Zeuxo (Crustacea: Tanaidacea) from the French Atlantic coast. J. Nat. Hist. 24(6): 1587-1596. [https://www.vliz.be/en/imis?module=ref&refid=393639]

[3] Faasse, M. (2013). Northward dispersal of the tanaid Zeuxo holdichi to the Netherlands (Crustacea: Tanaidae). Ned. Faunist. Meded. 39: 95-98. [https://www.vliz.be/en/imis?module=ref&refid=393638]

[4] Jonckheere, I.; Kerckhof, F. (2024). Waarnemingen gedaan tijdens de SWG-excursie naar de Spuikom van Oostende op 9 juli 2023 met vondsten van verschillende nieuwe geïntroduceerde soorten voor de Belgische fauna. De Strandvlo 44(2): 33-41. [https://www.vliz.be/nl/imis?module=ref&refid=394050]

[5] Bamber, R.N. (2011). The marine fauna and flora of the Isles of Scilly. Tanaidacea (Crustacea: Peracarida). J. Nat. Hist. 45(29-30): 1801-1815. [https://www.vliz.be/en/imis?module=ref&refid=393626]

[6] Foveau, A.; Pezy, J.-P.; Bauxi, N.; Baffreau, A.; Bachelet, Q.; Chouquet, B.; Dancie, C.; Ruellet, T.; Dauvin, J.-C. (2018). Range extension of the tanaidid Zeuxo holdichi (Bamber, 1990) along the northern coasts of France? Cah. Biol. Mar. 59(4): 329-333. [https://www.vliz.be/en/imis?module=ref&refid=393624]

[7] waarnemingen.nl. Zeuxo holdichi Bamber, 1990. https://waarneming.nl/observation/294033938/ (2024-04-03)
[8] Gittenberger, A.; Rensing, M.; Wesdorp, K.H. (2017). Uitheemse mariene soorten in Nederland. GiMaRIS Rapport, 19. GiMaRIS: Leiden. 39 pp. [https://www.vliz.be/en/imis?module=ref&refid=393505]

[9] Del Pasqua, M.; Bernarello, V.; Esquete, P.; Cornello, M.; Cacciatore, F.; Oselladore, F.; Ponis, E.; Boscolo Brusà, R. (2022). First records of the tanaid species Zeuxo holdichi and Apseudopsis tridens (Crustacea: Peracarida) from the Venice Lagoon (Italy, Northern Adriatic Sea). Thalassas 38(1): 417-430. [https://www.vliz.be/en/imis?module=ref&refid=393623]

How to cite

VLIZ Alien Species Consortium (2024). Zeuxo holdichi. Introduced alien species of the Belgian part of the North Sea and adjacent estuaries anno 2024. Flanders Marine Institute (VLIZ). 4 pp.