Halisarca hansghanssoni Pereira, Larsson, Cárdenas & Thollesson, 2025, sp. nov.
Creators: name: Pereira, Raquel
name: Larsson, Mats
name: Cárdenas, Paco
name: Thollesson, Mikael
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Porifera
Demospongiae
Chondrillida
Halisarcidae
Halisarca
Halisarca hansghanssoni

description: Halisarca hansghanssoni sp. nov.
urn:lsid:zoobank.org:act: E7E4A2DA-CA9E-4583-A7E9-49B667220BA6
Fig. 4–5
Etymology
The species is named in memory of Hans G. Hansson (1945–2011), a marine invertebrate specialist at the University of Gothenburg’s field station at Tjärnö. He shared his knowledge and fascination for marine fauna with cohorts of students and was instrumental in the Skagerrak inventory undertaken by the Swedish Taxonomy Initiative.
Material examined
Holotype
SWEDEN • 1 spec.; 58.1345° N, 10.8012° E; 248– 206 m depth; 25 Aug. 2006; Artprojektets Skagerrak-inventering leg. [SK58 (SK37 återbesök)]; dredge; P089-111026-1; GenBank no.: OM436239 (coxI); GNM Porifera 594.
Paratype
NORWAY • 1 spec.; BIOSKAG 2006, STN6 (off Grimstad); 58.2129° N, 9.3447° E; 664– 663 m depth; muddy bottom; 25 Jun. 2006; Paco Cárdenas leg.; Sneli sledge; PC1387; GenBank nos: OR269461 (coxI), PP763168 (28S D1-D2); UPSZTY 190226.
Confer status specimen
NORWAY • 1 spec.; Skorpeodden-Korsfjord; 60.1608° N, 5.1691° E; 10 Mar. 2006; Paco Cardenas leg.; GenBank no.: PP415521 (coxI); UPSZMC 191711.
Description
The holotype is a small encrusting specimen, growing on a dead bivalve shell, with a maximum diameter of 1.70 cm and a maximum thickness of 3 mm. Surface is smooth but with the canals of the aquiferous system visible as depressions.(Fig. 4A). Consistency firm but compressible and non-friable. Preserved in ethanol, and unknown color when alive. The other two specimens examined, including the paratype, presented a natural colour of creamy pale brown when alive (Fig. 4B).
For the holotype only one osculum is visible, in the thicker area of the specimen. Its shape was slightly oval and without a visible rim, measuring 1 mm maximum diameter.The ostia were visible and uniformly scattered on the surface, measuring 554.2– 763.2 –991.4± 139 µm (N=17) in diameter (Fig. 4A). The paratype was growing on a piece of plastic while the west Norwegian specimen (UPSZMC 191711) was growing on the sponge Stelletta normani Sollas, 1880.
Micro-anatomy
The choanocyte chambers are elongated (Fig. 4C), measuring 107–133×23–32 µm (N =3). Embryos were not found in the sections of the holotype.
Remarks
The specimens were all preserved in ethanol upon collection, which prevented rigorous histological work. However, when comparing its choanocyte chamber sizes with the species described for Halisarca (Ereskovsky et al. 2011; Alvizu et al. 2013; Willenz et al. 2016), only five species are compatible with the present specimens, of which none have been reported from the northeast Atlantic (NEA) or the Mediterranean. Furthermore, all of those species have a distribution restricted to shallow waters.
The species with a similar size range of choanocyte chambers are: a) Halisarca cerebrum (Bergquist & Kelly 2010) described from Palau (West-central Pacific ocean) characterised by a convoluted surface, b) Halisarca melana de Laubenfels, 1954, also from Palau, presenting a jet-black colour alive or purple-brown when preserved in ethanol, c) Halisarca magellanica (Topsent 1901) described from southern Chilean fjords, exhibits high polymorphism, including pink or ivory colouration, encrusting morphology with ‘dripping’ outgrowths or massive encrusting, and surfaces that are smooth, slimy, or velvety, d) Halisarca sacra de Laubenfels, 1930 from Northeast Pacific (California) with a very soft consistency and elongated choanocyte chambers (140–200 µm×40 µm), and e) Halisarca laxus (Lendenfeld 1885) from Southwest Indian ocean, with a soft consistency, lobate or digitate habitus. Our specimens deviate from the abovementioned species in terms of colour (H. melana and one morphotype of H. magellanica), surface and consistency (H. magellanica - ivory white, H. sacra), and habitus (H. laxus), by presenting yellowish-grey or brown-beige coloration, a firm but compressible and non-friable consistency, and an encrusting morphology, respectively.
In the NEA and Mediterranean there are three other species, which have been reported at a similar depth range as our specimens (Arndt 1935; Lévi 1956): a) Halisarca dujardinii (Johnston 1842) is the closest in morphology but is usually found in shallow waters and has larger choanocyte chambers (120–600 × 24–90 µm for H. dujardinii) (Ereskovsky et al. 2011), b) Halisarca metschnikovi (Lévi 1953) from Brittany, France, which is described with the same choanocyte chambers than what is reported for H. dujardinii, thus possessing larger choanocyte chambers than our specimen, c) Halisarca harmelini (Willenz et al. 2016), from the Mediterranean, has choanocyte chambers that are very narrow and the specimens are thin encrusting, with natural colour either translucent or slightly opaque and with very small chimney-like osculum measuring 100–500 height× 500 diameter µm (Ereskovsky et al. 2011), a description not fitting with our specimen.
Apart from the morphology indicating the specimen examined is an undescribed species, the phylogenetic analysis of coxI (Folmer fragment) (Fig. 2) shows that our specimens are more closely related to Halisarca desqueyrouxae (Willenz et al. 2016) presenting 1.42% of sequence divergence between them (KY564211) while the dissimilarity with Halisarca dujardinii sequences is of 2.63% (five specimens from Sweden were sequenced in this study). Furthermore, the overall sequence dissimilarity within H. dujardinii is 0.70%.Given this, we conclude that the specimen P089- 111026-1 is not H. dujardinii, but rather more closely related to Halisarca desqueyrouxae (Willenz et al. 2016), described from Patagonia. The ASAP (Puillandre et al. 2021) results (Fig. 5) show that these specimens belong to the same partition apart from H. desqueyrouxae with a p-value of 0.5 (see Supp. file. 3), suggesting it to be a sister species to H. desqueyrouxae. The molecular evidence is further supported by morphology. While our specimens has an incrusting habitus, H. desqueyrouxae has a wrinkled surface, up to 2 cm thick with digitation and ridges or tubular overgrowths. Furthermore, both morphotypes of H. desqueyrouxae have elongated and convoluted choanocyte chambers that are 50–260 × 20–60 µm which is marginally larger than our measurements. After identification of this new species, two additional specimens were discovered in the private collection of co-author P. Cárdenas. The paratype (Fig. 4B) was collected deeper in the Skagerrak, off Grimstad in southern Norway, and had the exact same cox1 as the holotype. The second specimen, collected in the Korsfjord south of Bergen in western Norway, has a cox1 with 1 bp difference so we prefer to identify it as H. cf. hansghanssoni for now.
description: Published as part of Pereira, Raquel, Larsson, Mats, Cárdenas, Paco & Thollesson, Mikael, 2025, Swedish marine demosponge fauna (Porifera: Demospongiae) sampled 80 years after Jägerskiöld's inventory, pp. 1-64 in European Journal of Taxonomy 983 on pages 14-17, DOI: 10.5852/ejt.2025.983.2835, http://zenodo.org/record/15168665