Haliclona (Soestella) xena -

The original distribution area of H. (Soestella) xena is unknown ^[3]. It is probably a non-indigenous species since the sponge was not present in the Dutch sponge collection – collected since 1880 – before 1977. However, after 1977, the number of H. (Soestella) xena sponges increased rapidly. Today, the species is one of the most common sponge species in the Netherlands ^[4].

First observation in Belgium

On the 6^th of November 1988, an individual of H. (Soestella) xena was found for the first time on metal pipes in the port of Zeebrugge, near the eastern breakwater. These pipes had previously been used underwater for reclamation and dredging purposes, but, at the time of the discovery, they were lying on dry land ^[5].

 

Spreading in Belgium

Nowadays, H. (Soestella) xena is one of the most common sponges in Belgium ^[6]. The alien species can be found in the port of Zeebrugge as a biofouling species, both in the marina and entry dock ^{[7, 8]}. The species is also present in the Sluice Dock of Ostend since March 2009 ^[9].

 

Spreading in neighbouring countries

In the Netherlands, the sponge was collected for the first time on the 24^th of November 1977. However, it was not until 1986 that the species got described and given a scientific name ^[2].

Today, this sponge is one of the more common sponges in Dutch coastal waters, both in Zeeland (Eastern Scheldt and Lake Grevelingen) and the Wadden Sea. This species has also been spotted in Le Havre, in the northwest of France and Helgoland, an island in northern Germany ^[6].

 

How the species got introduced remains uncertain. However, at the time of its discovery, the sponge was mainly found on oyster beds. This suggests that oyster farming – more specifically, the import of oyster broodstock for aquaculture purposes – is responsible for the introduction of this sponge ^{[2, 3]}.

One characteristic that explains the occurrence of H. (Soestella) xena is that it can attach itself to all kinds of hard substrates. Harbours with their many pontoons and other hard objects or organisms, such as mussels and oysters, facilitate the settlement of this alien species ^[3].

Like other sponges, this species can ‘repair’ itself after damage, a process called regeneration: one piece of sponge can grow into a full-fledged individual. Regeneration can ensure the asexual reproduction of the species. In combination with sexual reproduction, this enables the species to thrive ^[10].

 

In addition to living in salt water, this sponge also survives in brackish water, such as in the Sluice Dock of Ostend ^[11].

For sponges, the chance of transport with molluscs is estimated to be high, but the likelihood that this will have a significant impact on the ecosystem is rather small. To date, there are no indications that this sponge has a detrimental impact on other species. On the contrary, it even provides an attractive substrate for native tunicates ^[12].

Microbial communities living in association with H. (Soestella) xena in the North Sea were identified for the first time in 2014. These may include several new genera (from the Chlamydiae phylum), of which the functions and potential effects are not yet known ^[13].

The sponge species resembles a thick mass of purplish-red to light brown tubes located on a hard substrate in the intertidal zone and shallow water. These tubes can reach a height of 10-15 cm and a diameter of 1-2 cm. A colony can reach a total diameter of 20 cm. This species is soft and easily broken ^[3].

A sponge has numerous inflow openings through which the water – including food particles – enters, but it is mainly the outflow openings that can be seen in H. (Soestella) xena ^[3]. The water flow is generated by special cells, the collar cells, whose flagella maintain a water current ^[10].

All sponges have sexual and asexual reproduction. The most common form of asexual reproduction is regeneration, in which a part of the sponge’s body grows into a new individual, e.g. after being damaged. In sexual reproduction, both unisexual and hermaphroditic species exist ^[10]. A study showed that both types occur in H. (Soestella) xena. Sperm cells enter the sponge with the water flow, where fertilisation of the eggs occurs. Larvae of this species are released into the water column and attach quickly – after a couple of hours – to a suitable substrate ^[14].

 

[1]          World Register of Marine Species (WoRMS) (2020). Haliclona (Soestella) xena De Weerdt, 1986. [http://www.marinespecies.org/aphia.php?p=taxdetails&id=132883] (2020-11-17).

[2]          de Weerdt, W.H. (1986). A systematic revision of the north-eastern Atlantic shallow-water Haplosclerida (Porifera, Demospongiae): 2. Chalinidae. Beaufortia 36(6): 81-165. [http://www.vliz.be/en/imis?module=ref&refid=38557]

[3]          Marine Species Identification Portal (2011). Sponges of the NE Atlantic. Haliclona xena. [http://species-identification.org/species.php?species_group=sponges&id=257&menuentry=soorten] (2018-11-14).

[4]          Van Soest, R.W.M. (2011). Persoonlijke mededeling

[5]          Rappé, G. (1989). Haliclona xena De Weerdt, 1986 (Porifera, Desmospongiae), Petrobius maritimus (Leach) (Insecta, Thysanura) en enkele andere bijzondere waarnemingen van de oostelijke strekdam van Zeebrugge. De Strandvlo 9(4): 113-116. [http://www.vliz.be/en/imis?module=ref&refid=18536]

[6]          Van Soest, R.W.M.; de Kluijver, M.J.; van Bragt, P.H.; Faasse, M.; Nijland, R.; Beglinger, E.J.; de Weerdt, W.H.; de Voogd, N.J. (2007). Sponge invaders in Dutch coastal waters. J. Mar. Biol. Ass. U.K. Spec. Issue 87(6): 1733-1748. [http://www.vliz.be/en/imis?module=ref&refid=118579]

[7]          Vandercruyssen, C. (2006). Verslag van de excursie in de jachthaven van Zeebrugge op 17 juni 2006. De Strandvlo 26(2): 47-48. [http://www.vliz.be/en/imis?module=ref&refid=102474]

[8]          De Blauwe, H.; Dumoulin, E. (2009). De zeefauna en -flora uit de jachthaven van Zeebrugge, in het bijzonder de fouling-organismen van drijvende pontons. De Strandvlo 29(2): 41-63. [http://www.vliz.be/imis/imis.php?module=ref&refid=139489]

[9]          Waarnemingen afkomstig van Waarnemingen.be: een initiatief van Natuurpunt Studie vzw en de Stichting Natuurinformatie (2018). Paarse buisjesspons - Haliclona xena (De Weerdt, 1986). [https://waarnemingen.be/soort/view/27580?waardplant=0&poly=1&from=1996-07-18&to=2011-08-04&akt%5B%5D=0&method=0&rar=0&only_approved=0&maand=0&prov=0&rows=20&os=0&hide_hidden=0&hide_hidden=1&show_zero=0] (2018-11-14).

[10]        Van Soest, R.W.M. (1976). De Nederlandse mariene en zoetwatersponzen: Porifera. Wetenschappelijke Mededelingen van de Koninklijke Nederlandse Natuurhistorische Vereniging, 115. Koninklijke Nederlandse Natuurhistorische Vereniging (KNNV): Hoogwoud. 36 pp. [http://www.vliz.be/en/imis?module=ref&refid=11857]

[11]        Stichting ANEMOON (2018). Paarse buisjesspons. Haliclona (Soestella) xena De Weerdt, 1986. [http://www.anemoon.org/flora-en-fauna/soorteninformatie/soorten/id/12/paarse%20buisjesspons] (2018-11-14).

[12]        Wijsman, J.W.M.; De Mesel, I. (2009). Duurzame schelpdiertransporten. IMARES Wageningen Report. Imares: Wageningen. 111 pp. [http://www.vliz.be/nl/catalogus?module=ref&refid=207323]

[13]        Naim, M.A.; Morillo, J.A.; Sørensen, S.J.; Waleed, A.A.; Smidt, H.; Sipkema, D. (2014). Host-specific microbial communities in three sympatric North Sea sponges. FEMS Microbiol. Ecol. 90(2): 390-403.

[14]        Wapstra, M.; Van Soest, R.W.M. (1987). Sexual reproduction, larval morphology and behaviour in Demosponges from the southwest of the Netherlands, in: Vacelet, J. et al. Taxonomy of Porifera from the N.E. Atlantic and Mediterranean Sea. NATO ASI Series G: Ecological sciences, 13. Springer: Berlin: pp. 281-307. [http://www.vliz.be/en/imis?module=ref&refid=37754]

VLIZ Alien Species Consortium (2020). Haliclona (Soestella) xena. Non-indigenous species in the Belgian part of the North Sea and adjacent estuaries anno 2020. Flanders Marine Institute (VLIZ). 5 pp.