Halichondria panicea

Halichondria panicea (Pallas, 1776) Fig. 25 Spongia panicea Pallas, 1766: 388. Amorphina panicea – Fristedt 1885: 26. Halichondria panicea – Levinsen, 1893: 415–416. — Alander 1942: 28, pl. 6. Material examined (21 specimens) SWEDEN • 1 spec.; Svartejan; 59.1102° N, 11.3219° E; 30 m depth; 11 Oct. 2018; Mats Larsson leg. [MM-180911-1]; SCUBA; LAR-180911-7191, 7194; GenBank no.: OM436248 (coxI); voucher: GNM Porifera 1003 • 1 spec.; same collection data as for preceding; 25 Oct. 2018; Mats Larsson leg. [MM-180925-1]; SCUBA; LAR-180925-7457, 7460, 7463; GenBank nos: OM436249 (coxI), OM415607 (28S D3-D5); voucher: GNM Porifera 1009 • 1 spec.; same collection data as for preceding; 4 Dec. 2018; Mats Larsson leg. [MM-181204-1]; SCUBA; LAR-181204-8186–8188; GenBank nos: OM436281 (coxI), OM415649 (28S D3-D5); voucher: GNM Porifera 1010 • 1 spec.; same collection data as for preceding; LAR-181204-8189–8191; GenBank nos: OM436228 (coxI), OM415594 (28S D3-D5); voucher: GNM Porifera 1011 • 1 spec.; Gullmaren; 58.2550° N, 11.4446° E; 1 Apr. 2012; dredge; P016-230414-7; GNM Porifera 1007; • 1 spec.; same collection data as for preceding; P088-120403-1; GNM Porifera 1016; • 1 spec.; Gullmaren; 58.2667° N, 3.5812° E; 28 Apr. 2018; P088-180425-2; GNM Porifera 1018; • 1 spec.; Gullmaren; 58.2667° N, 3.58125° E; 24 Apr. 2018; dredge; P088-180425-2; GNM Porifera 1018; • 1 spec.; same collection data as for preceding; P088-180425-3; GNM Porifera 1019 • 1 spec.; Lunneviken; 59.0546° N, 11.1690° E; 30 m depth; 18 Sep. 2018; LAR-180918-7245–7246; GNM Porifera 1004 • 1 spec.; Bergylteskär; 58.8210 °N, 11.0831° E; 9 Dec. 2018; Mats Larsson leg. [MM-181209-1]; SCUBA; LAR-181209-8193, 8197–8198; GenBank no.: OM415600 (28S D3-D5); voucher: GNM Porifera 1012 • 1 spec.; same collection data as for preceding; LAR-181209-8205, 8207–8208; GenBank nos: OM436242 (coxI), OM415603 (28S D3-D5); voucher: GNM Porifera 1013 • 1 spec.; Trindeknubben; 58.7829° N, 10.9962° E; 24 Jun. 2019; Mats Larsson leg. [MM-190624-1]; SCUBA; LAR-190624-9497; voucher: GNM Porifera 1005 • 1 spec.; Yttre Vattenholmen; 58.8754° N, 11.1056° E; 16 Nov. 2019; Mats Larsson leg. [MM-191116-1]; SCUBA; LAR-191116-PB160514–16; voucher: GNM Porifera 1006 • 1 spec.; Kosterhavet; 58.8833° N, 11.0833° E; 1 Nov, 2001; Fredrik Pleijel leg. [TML-01]; dredge; P002-011112-1; voucher: GNM Porifera 1014 • 2 specs; 58.0723° N, 11.3267° E; 11- 30 m depth; 23 Sep. 2009; Artprojektets Skagerrak-inventering leg. [201]; dredge; P088-111026-1; GNM Porifera 585; Skagerrak; 58.0651° N, 11.3234° E; 2326 m depth; 24 Sep. 2009; Artprojektets Skagerrak-inventering leg. [212]; dredge; P088-111026-2; GNM Porifera 586 • 1 spec.; Gullmarens inlopp; 8 May 2012; staff and students of courses 1BG217 and 1BG394 cohort 2012 leg. [Gullmarens inlopp, 120508]; dredge; P088-120410-1; GNM Porifera 1017 • 1 spec.; Gullmaren, Långgap, 58.2577° N, 11.4262° E; 18 m depth; 20 Apr. 2016; students and staff of course 1BG217, cohort 2015 leg. [1BG217-2015-25]; dredge; P088-160505-1; GNM Porifera 1008 • 1 spec.; Gullmaren, Långgap; 58.2550° N, 11.4447° E; 12 m depth; 21 Apr. 2016; staff and students of course 1BG217 cohort 2016 leg. [1BG217-2016-5]; dredge; P002-160504-1; GNM Porifera 1015 • 1 spec.; Gullmaren, Flatholmen; 14 m depth; 23 Apr. 2019; staff and students of course BG393 cohort 2019 leg. [Flatholmen, 190423 [34]] P088-190424-1; GNM Porifera 1021. Description Specimens presented morphologies from thin sheets to thick encrusting or even branching (Fig. 25A–C). However, the most common form is thick encrusting (Fig. 25C). The oscula are elevated on chimneys, scattered evenly across the surface. The colour alive varied from green to dark yellow turning to beige/ cream in ethanol. The surface is smooth, easy to peel off and with tracts of the aquiferous system observable even in living specimens. Skeleton The skeleton has a confused skeleton arrangement except for the ectosome (i.e., halichondrioid skeleton). The ectosome is reticulated (Fig. 25D–E). The specimens presented only curved oxeas as megascleres, measuring 391.2– 256.4– 128.2 ± 47.26× 12.3.4– 4.7– 2.3± 2.17 µm (N =167). Ecology and distribution Halichondria panicea is a common species, found from the intertidal/subtidal down to 500 m. In shallow waters it often grows on boulders and brown algae. In Sweden it can be found from the intertidal to 569 m depth (Alander 1942). Remarks The different morphotypes that this species can present are attributed to different water regimes (Palumbi 1986; Barthel 1991). This species is sympatric with Halichondria bowerbanki Burton, 1930 and the two species can be easily confused.However, specimens of H.panicea have a peelable ‘skin-like’ surface, and can have a green colour, which H. bowerbanki never has. Additionally, the specimens of H. bowerbanki rarely yield an amplicon when using the standard coxI primers. The H. panicea presents a very wide distribution ranging from the northeast Pacific (Bering Sea) to the southwest Atlantic but the Pacific reports of H. panicea probably refer to a distinct species (Erpenbeck et al. 2004).). Six coxI sequences were obtained, corresponding to three haplotypes (1–2 bp differences). Still more studies need to be done to test if the NEA H. panicea is a species complex.