Hymedesmia dujardinii ( Bowerbank, 1866 )

Hymedesmia dujardinii ( Bowerbank, 1866) View in CoL

Fig. 17 View Fig

Hymeniacidon dujardinii Bowerbank 1866: 224–225 .

Stylopus coriaceus Fristedt, 1885: 28–29 View in CoL , pl. II fig. 8a–g.

Stylopus dujardini ( Bowerbank, 1866) View in CoL — Levinsen 1893: 419. — Arndt 1935: 64.

Stylopus dujardini var. coriaceus View in CoL – Topsent 1928: 283.

Hymedesmia dujardini View in CoL – Lundbeck 1910: 101–104, pl. X fig. 5. — Stephens 1917: 11; 1921: 40. — Hentschel 1929: 962.

Hymedesmia brondstedi Burton, 1930 View in CoL – Ackers 2007: 99.

Material examined (7 specimens)

SWEDEN • 1 spec.; Saltbacken; 59.0832° N, 11.2242° E; 40–25m depth; 1 Oct. 2019; Mats Larsson leg. [MM-191001-1]; SCUBA; LAR-191001-PA010087, 0089; voucher: GNM Porifera 1068 GoogleMaps • 1 spec.; Lunneviken; 59.0546° N, 11.1690 °E; 40–25 m depth; 2 Nov. 2019; Mats Larsson leg. [MM-191102- 2]; SCUBA; LAR-191102-PB020269, 71–72; GenBank no.: OM415619 (28S D3-D5); voucher: GNM Porifera 1046 GoogleMaps • 1 spec.; same collection data as for preceding; LAR-191102-PB020285, 87, 89; GenBank no.: OM415622 View Materials (28S D3-D5); voucher: GNM Porifera 1069 GoogleMaps • 1 spec.; same collection data as for preceding; LAR-191102-PB020302–03; GenBank no.: OM415641 View Materials (28S D3-D5) GoogleMaps • 1 spec.; same collection data as for preceding; LAR-191102-PB020339–41; GenBank no.: OM415575 View Materials (28S D3-D5); voucher: GNM Porifera 1120 GoogleMaps • 1 spec.; same collection data as for preceding; LAR-191102- PB020344–45; GenBank no.: OM415574 View Materials (28S D3-D5); voucher: GNM Porifera 1121 GoogleMaps • 1 spec.; Gåseklovan ; 58.3099° N, 11.5389° E; 40–25m depth; 10 Oct. 2015; leg. [Gåseklovan, 151010]; ROV; P110-151015-1; voucher: GNM Porifera 1070 GoogleMaps .

Description

All specimens presented a thin encrusting habitus and were growing on clean rock, algae or Chaetopterus norvegicus polychaete tubes. The surface is smooth. The colour alive was translucent white-cream; white-pink ( Fig. 17A–B View Fig ) or light-brown colour changing to pale beige when preserved in ethanol. Pores were visible and regularly distributed and without pore-sieve. Oscula were present on a slightly elevated ‘chimney’ ( Fig. 17B View Fig ).

Skeleton

The skeleton conformation was hymedesmoid, with acanthostyles erected with base attached in the substrate, and surface smooth tornotes. Megascleres are one class size of acanthostyles spined mostly at the base but somewhat extending along the shaft, measuring 50.0– 124.5– 207.5 ±47.69 ×1.3– 5.1 – 8.8± 1.80 µm (N=65), and smooth spicules that can be tylotes, anisotornotes or strongyles, measuring 72.5– 196.6 –242.5 ± 35.5 ×1.3– 2.8– 3.8± 0.80 µm (N=31) ( Fig. 17C View Fig ).

Ecology and distribution

This species presents ample geographical and bathymetrical distributions, with reports from the Arctic to northern Africa and the Mediterranean, and from shallow waters to 1200 m depth. Additionally, specimens of this species have been observed on various substrates, including rock, brachiopod shells, and Chaetopterus tubes. Given the wide distribution, lack of substrate preference, and spicules variability, it is likely that H. dujardinii represents a species complex. The type locality for H. dujardinii is North Yorkshire, UK, and the specimen was growing on brachiopod shells. In spite of that, it is worth noting that this species is currently considered in the WPD a synonym of H. coriacea ( Fristedt, 1885) (see Remark below), which was firstly described in Bohuslän, Sweden, by Fristedt (1885) growing on Chaetopterus tubes (as in present study).

Remarks

Bowerbank (1866) introduced the name Hymeniacidon dujardinii for this species; however, under the mistaken assumption that it was the same as Halisarca dujardinii ( Johnston, 1842) . This led Burton (1930) to dismiss Bowerbank’s name as unavailable and also introduce the replacement name Hymedesmia brondstedi . This rejection of Bowerbank’s name was maintained by Alander (1942), who also identified Stylopus coriaceus Fristedt, 1885 as an available senior synonym to Hymedesmia brondstedi . We find, however, that Burton’s conclusion was not justified according to the current International Code of Zoological Nomenclature (henceforth, the Code) (ICZN 1999), even though, it is certainly not a clear-cut case. Our argument is the following: a) Bowerbank (1866) provided a detailed description (by his contemporary standards) of the species and listed the specimen on which this was based, b) he used a new binomial for this sponge (not opening problems of homonymy), c) he headed his description ‘ Hymeniacidon Dujardinii, Bowerbank ’, stating that he was the first to use this binomial for this species d) although he did not claim to describe a new species, he explicitly differentiated his sponge from Johnston’s Halisarca dujardinii and, e) the Code (ICZN 1999) prescribes in Art. 16 ‘intention of authors to establish new nominal taxa to be explicit’ only for names proposed after 1999. This leads us to conclude that Hymeniacidon dujardinii Bowerbank, 1866 is an available name for nomenclatorial purposes. This does not necessarily imply that it should be used as the valid name, for example if Art. 23.9 of the Code could be applied. However, the name has been used by several authors after 1899; some are listed under synonyms, see above, and, e.g., as Leptosia dujardini by Topsent (1901; 1904) or as Stylopus dujardini by Topsent (1925, 1928), thus disqualifying application of Art. 23.9 (ICZN 1999).

We conclude that the name Hymedesmia (Stylopus) dujardinii ( Bowerbank, 1866) is the valid name for this species hypothesis and hence that it should be reinstated. Consequently, H. (S.) coriaceus ( Fristedt, 1885) becomes a junior synonym of H. (S.) dujardinii .