Craniella polyura

Craniella polyura (Schmidt, 1870)

Figure 7; Table 7

Synonymy:

Tetilla polyura Schmidt, 1870:66 pl. VI, fig 8. Vosmaer 1885: 9–10, pl. I, fig 1–3, pl. II, fig. 16, pl. V, figs 3–7. Breitfuss 1911: 213. Rezvoi 1928: 76. Koltun 1966: 60–61, fig. 31 Van Soest 2016: 322, fig. 5.

Lophurella lophura Gray, 1872: 460 –461.

Polyurella schmidtii Gray, 1870: 311 –312.

Craniella polyura: Morozov et al. 2019: 21, fig. 13. Dinn & Leys 2018: 87. Van Soest et al. 2000.

Material examined. CMNI 2018-0184, specimen in 95% ethanol, collected by Curtis Dinn by Agassiz trawl; July 15, 2017, 141 m depth (63° 38.390’ N, 68° 37.642’ W) operated from the CCGS Amundsen, Frobisher Bay, Canada.

Description. One specimen was collected in inner Frobisher Bay near Hill Island. The specimen is ovoid, 3 cm tall by 1.5 cm wide (Fig. 7A). The surface is optically smooth with small furrows, giving a somewhat dimpled appearance. A root section ~ 0.5 cm long is visible on the underside of the specimen, but this portion may have been damaged upon collection and so could be longer in life. The sponge is a light brown colour, lightening towards the root (Fig. 7A). The sponge had a soft consistency when it was collected but became hard after preservation in ethanol. The spicules consist of large oxeas that are often thicker on one end 2206 (1610–3453) x 28 (15–41) µm, and short, very thin oxeas are 441 (251–1199) x 9 (4–17) µm long. There are also protriaenes that have a shaft length of 1905 (888–5879) x 16 (8–29) µm, with one whip-like clad 105 (36–183) µm long. Protrianes can have clads of equal lengths or have one long whip-like clad. Here the two protriaene variations are considered as one spicule type. Anatriaenes are uncommon compared to oxeas and protriaenes (only one was found fully intact with a length of 7017 µm); the shaft width is 14 (8–20) µm n=20, and the clads are 77 (57–94) µm; sigmaspires with a centrotylote swelling are 13 (10–18) µm in length. (Fig. 7 B–F).

Genetic data. 28S rDNA sequences group this specimen with Cinachyra and Antarctotetilla specimens based on the D3–D5 domain sequence (GenBank accession MH394250). There are no nucleotide sequences published for this species. This species does not group with other Craniella species based on a preliminary analysis of the 28S sequences.

Taxonomic Remarks. The spicule measurements of the present specimen are similar to those given by Koltun (1966). Anatriaenes were not common in this specimen; only one was found fully intact, but several anatriaene rhabdomes were seen. Koltun (1966) suggests that the anatrianes reach maximum length of over 10,000 µm, therefore it is difficult to find this spicule unbroken. Koltun (1966) also states that the anatriaenes may be absent, suggesting that this spicule is uncommon in this species. Compared with the sympatric T. sibirica, protriaenes of various sizes, most with one long whip-like clad are more common in this specimen, while anatriaenes are more common in T. sibirica. The key diagnostic spicules for this species are the sigmaspires with a centrotylote swelling. This swelling occurs in both C and S shaped spicules and is quite apparent using light and scanning electron microscopy. The external appearance of this sponge fits Koltun’s 1966 description, with the body “egg-shaped or spherical, up to 7 cm in height”. The radially spiral skeleton and velvety surface described by Koltun (1966) is also apparent in this specimen.

Discussion. This is the first record of the species in the Northern Labrador marine ecoregion. The sponge corresponds to descriptions of C. polyura by Schmidt (1870) and Vosmaer (1885), and to a description of Tetilla polyura by Van Soest (2016). The centrotylote swelling of the sigmaspires is distinctive and separates this species from the sympatric Tetilla sibirica. It is likely that both of these species belong to a common genus, and therefore the family requires revision. Koltun (1966) describes the distribution of this species to be the Barents Sea, the Kara Sea, the Laptev Sea, Greenland waters, Norway, the Azores, and Baffin Bay with a depth distribution ranging from 25– 595 m. Vosmaer (1885) stated that this sponge has a higher Arctic and coastal Russian distribution. Cárdenas & Rapp (2015) re-identified a sponge originally considered T. sandalina collected by Brøndsted off of Labrador (314 m depth) to T. polyura, but the collection location is within the Northern Grand Banks–Southern Labrador marine ecoregion.