Semisuberites cribrosa

Semisuberites cribrosa (Miklucho-Maclay, 1870)

(Figure 4, Table 3)

Original description: Veluspa polymorpha var. cribrosa Miklucho-Maclay, 1870. 6–7, Fig. 12, 13.

Synonyms: Auletta elegans Vosmaer, 1882, Axinella variabilis (Vosmaer, 1882), Cribrochalina sluiteri Vosmaer, 1882, Cribrochalina variabilis Vosmaer, 1882, Cribrochalina variabilis var. crassa Vosmaer, 1882, Cribrochalina variabilis var. salpingoides Vosmaer, 1882, Reniera infundibuliformis Hansen, 1885, Semisuberites arctica Carter, 1877, Siphonocalypta elegans (Vosmaer, 1882), Stylissa stipitata de Laubenfels, 1961, Veluspa cribrosa Miklucho- Maclay, 1870, Veluspa flabelliformis Miklucho-Maclay, 1870, Veluspa polymorpha var. cribrosa Miklucho-Maclay, 1870, Veluspa polymorpha var. flabelliformis Miklucho-Maclay, 1870, Veluspa polymorpha var. infundibuliformis Miklucho-Maclay, 1870.

Material Examined

Gulf of St. Lawrence: IML 3004, 48.350N, 64.460W; IML 3005 collected in Baie des Chaleurs; IML 11897, 48.5891N, 63.8339W, 163 m depth. Additional collected specimens are noted in Table 3.

External appearance (Figure 4A–C)

Semisuberites cribrosa (Miklucho-Maclay, 1870) is variable in size, but is often a trumpet shaped sponge with a long stalk that forms a holdfast, sometimes with visible roots. The diameter of the cup can approach 35 cm and the sponge can extend up to 25 cm in height. The surface is velvety with a very soft consistency. Larger specimens may have more elaborate forms where more than one stalk may intertwine and give rise to two vases. The distal lip of the sponge is often frayed after collection. Specimens are white to brown or grey in colour. The stalk may have epibionts growing down its length, giving a dark brown or muddy appearance.

Spicules and skeleton (Figure 4D–E)

The spicules are exclusively styles that are highly variable in size 186– 390 –540 x 6– 10 – 14 µm. Some authors separate the spicules into two categories (Van Soest 2016; Van Soest & Hajdu 2002), but it is unclear whether this is consistent across all specimens. Styles from the Gulf of St. Lawrence specimens did not have obvious swollen heads, nor did they appear mycalostyle-like, although this is reported to be common (Van Soest & Hajdu 2002). The chonaosomal skeleton is formed by loose longitudinal tracts aligned parallel to the surface. The ectosomal skeleton consists of dense spicule brushes forming a loose palisade near the surface. Single spicules are loosely placed throughout the skeleton, mostly perpendicular to the surface.

Distribution and ecology

Semisuberites cribrosa (Miklucho-Maclay, 1870) was mostly collected in the southern Gulf of St. Lawrence from 34– 289 m. It has also been reported from Arctic and northern boreal waters (Van Soest et al. 2019). It appears to grow mainly in soft sediment environments where the stalk is somewhat submerged beneath the substrate.

Remarks

This is the first record of the species from the Gulf of St. Lawrence and it represents the southernmost extent of its known distribution in the North Atlantic. The species is often confused with, and sometimes reported as, Phakellia ventilabrum (Linnaeus, 1767) in eastern Canada. Specimen IML 3004 was originally labelled as P. ventilabrum in the museum’s collection. The description of P. ventilabrum from the Gulf of St. Lawrence by Lambe (1896) does not include strongyle spicules, but rather flexuous styles. It is therefore probable that the specimens collected by Lambe (1896) do not belong to the genus Phakellia due to the lack of strongyles, but instead could be S. cribrosa; however Lambe’s specimens were not reviewed for this present work.