Iophon koltuni Morozov, Sabirov & Zimina, 2019

Dinn, Curtis, Edinger, Evan & Leys, Sally P., 2019, Sponge (Porifera) fauna of Frobisher Bay, Baffin Island, Canada with the description of an Iophon rich sponge garden, Zootaxa 4576 (2), pp. 301-325 : 307-311

Iophon koltuni Morozov, Sabirov & Zimina, 2019

Figure 3 , Table 3

Synonymy:

Iophon piceus dubius Koltun, 1959: 151 –152, Fig. 107; pl. XXVI, fig. 2

Iophon cf. nigricans: Dinn & Leys, 2018: 33

Iophon koltuni Morozov, Sabirov & Zimina, 2019: 4 –7, fig. 3, 4

Material Examined. CMNI 2018-0180 , specimen in 95% ethanol and frozen, collected by Curtis Dinn by Agassiz Trawl; 15 July 2017 141 m, depth, (63° 38.390’ N, 68° 37.642’ W) . CMNI 2018-0166 , specimen in 95% ethanol, collected by Philippe Archambault by ROV hydraulic manipulator; 25 October 2015, 96 m depth, (63° 38.332’N, 68° 37.7139’W). All operations performed from the CCGS Amundsen in Frobisher Bay near Hill Island .

Comparative material examined. BELUM Mc3646 Iophon nigricans , August 16, 2006, 35.6 m depth, Annika’s pinnacle, Maidens (55° 0.5323 N, 5° 42.5858 W) . BELUM Mc5341 Iophon nigricans , July 31, 2009, 20 m depth, Bola Reef, Abercastle, North Pembrokeshire (51° 58.322 N, 5° 18.104 W) . BELUM Mc4296 Iophon nigricans , June 24, 2008, depth 29 m, NW of Cath Sgeir, Gigha, Firth of Lorn (55° 39.87 N, - 5° 47.69 W) .

External appearance ( Figure 3A, C ). The specimens consist of irregular finger-like growths that form large bushes 15–25 cm in height. Dense aggregations of the bushes were seen to occur in patches several meters in diameter. The fingers do not appear to attach to a broad base, but rather branch off a small central narrow stalk. The oscula are not obvious and are raised along the surface of the fingers, mostly near the base where neighbouring fingers join. The oscula collapse upon collection. The sponge grows in soft sediment attached to polychaete tubes and small rocks. The colour is pale yellow, with lighter almost white tips in situ , but becomes dark brown/grey on contact with air and after preservation in ethanol. The body surface is irregular and furrowed, with white distal portions that appear denser than the underlying body. A transparent membrane covers the lower portions but collapses after collection. The consistency is firm, with a soft surface texture that crumbles easily after freezing or preservation.

Spicules ( Figure 3 D–K). CMNI 2018-0180 has two types of megascleres: acanthostyles and tylotes. The acanthostyles are thin, some tylote, variably spined ( Fig. 3D,E ), often with long spines on the head ( Fig. 3 E,G ) are 277 (245–308) x 9.7 (8–12) µm. Rarely these spicules are very thin and elongate but are not abundant enough to be considered a second size category. Smooth ectosomal tylotes with swollen microspined heads ( Fig. 3F,H ) are 247 (199–266) x 7.6 (6–9) µm. Microscleres are spurred anisochelae ( Fig. 3K,L ) 19 (16.5–22) µm and large bipocilli with reduced, single, equal-sized alae and elongated teeth ( Fig. 3. I,J ) 15.4 (12.5–19.5) µm. The bipocilli are relatively large, and have long, smooth, arcuate shafts with a bend in the centre of the shaft . CMNI 2018-0166 was collected at 96 m depth and conforms to CMNI 2018-0180 in spicule complement and browning of the sponge in air and with preservation. Only small fragments of CMNI 2018-0166 were collected by ROV in 2015. Megascleres of CMNI 2018-0166 include acanthostyles 268 (232–295) x 7.6 (4–12) µm and tylotes 249 (219–277) x 6.7 (4.5–9) µm. Microscleres are anisochelae 29 (17.5–37) µm and bipocilli 18 (13.5–21) µm .

Skeleton ( Figure 3 B ). Ectosomal tylotes are arranged tangentially at the surface. Acanthostyles are arranged in the choanosome in a very loose isodictyal reticulation forming triangular or square meshes of multispicular tracts. This reticulation can often appear confused in the choanosome. Bipocilli and spurred anisochelae are scattered throughout the tissues.

1 Ackers et al., 1992 and Van Soest et al., 2000 2 Goodwin, 2017 3 Lundbeck, 1905 4 Arndt, 1935 and Van Soest et al., 2000

Taxonomic Remarks. The specimens fit the spicule description of I. koltuni from the Laptev Sea, though the bipocilla spicules are larger in the Frobisher Bay specimens yet the form is consistent. The external morphology also differs from the described holotype. Specimens from Frobisher Bay grow in an elaborate digitate form while the original description by Morozov et al. (2019) describes a leaf-shaped fragment with poorly pronounced lobes. The specimens described here were initially thought to be Iophon nigricans ( Bowerbank, 1858) briefly described by Dinn & Leys (2018) but the description of Iophon cf. nigricans by Dinn & Leys (2018) was subsequently synonymized with I. koltuni . As no images of the species were published with the original description of I. koltuni , and DNA material was not provided, this record serves to expand upon the original description. The WPD lists 38 species of Iophon , nine of which are found in the Atlantic. Iophon cheliferum Ridley & Dendy, 1886 was supposedly collected by Lambe (1896) in the Gulf of Saint Lawrence, but de Laubenfels (1949) suggested that the specimen was actually I. nigricans and Lévi (listed as a personal communication in Brunel et al. 1998) suggests that the specimens were actually I. piceum (Vosmaer, 1882) (Brunel 1998) . Lambe (1900) also suggests that I. cheliferum occurs off Vancouver, British Columbia. The type specimen of I. cheliferum is from the Cape of Good Hope, South Africa, and so it is unknown if I. cheliferum does in fact occur in eastern Canada; therefore, it is not discussed here.

There are three other species of Iophon known from the northwest Atlantic: I. dubium Koltun, 1955 which has been recorded from the Arctic Ocean, Barents Sea and the western Greenland shelf, I. nigricans , recorded from European waters and eastern Canada, and I. piceum (Vosmaer, 1882) , which has been recorded from the western Greenland shelf, Arctic Ocean, Barents Sea, Iceland, the eastern Canadian Arctic, and the White Sea. Most Atlantic Iophon species have bipocilli of a common form where one ala is round, and the other is more elongate and saucershaped with more numerous teeth. This is true for all except I. dogieli in which, in the original description, the bipocilli are more variable in shape. Iophon koltuni specimens from Frobisher Bay are notable because of the bushlike growth form, and the browning of the tissue when exposed to air, much like I. nigricans which turns black. The thin acanthostyles with large spines on the head and the large bipocilli with equally sized single alae are also distinctive. Iophon koltuni is distinguished from the Atlantic species in the following ways ( Table 3):

Iophon dogieli Koltun, 1955 ( Iceland) : Megascleres are smooth styles (not acanthostyles) and smooth, short, and thick styles with a microspined head (not tylotes). These small styles appear to be inequiended tornotes in Koltun’s description. Bipocilli are a similar length and shape, however of the three bipocilli variations in Koltun’s description, the irregular three-lobed type with clover-shaped ala was not found in these specimens. The anisochelae are also slightly smaller than in the Frobisher Bay specimens ( Koltun 1955).

Iophon dubium (Hansen, 1885) (Arctic, western Greenland): The bipocilli are much smaller and have unequal alae. This species does not turn dark in air. (Lundbeck 1905).

Iophon frigidum Lundbeck, 1905 (Barents Sea): This sponge lacks bipocilli. Acanthostyles are longer, tylotes are larger, and anisochelae are larger (Lundbeck 1905).

Iophon hyndmani ( Bowerbank, 1858) (Europe) : This species has a second category of smaller entirely spined acanthostyles and the bipocilli are smaller and have unequal alae (Ackers et al. 1985).

Iophon nigricans ( Bowerbank, 1858) (Europe) : Megascleres are shorter. This species also has two categories of anisochelae and very small bipocilli with unequal alae ( Ackers et al. 1992, Van Soest et al. 2000).

Iophon piceum (Vosmaer, 1882) (Arctic) : The acanthostyles are much longer and thicker than in the Frobisher Bay specimens, tylotes are longer and the bipocilli are smaller and have unequal alae with fine teeth (Arndt 1935, Van Soest et al. 2000).

Iophon pommeraniae Thiele, 1903 ( Norway) : The acanthostyles are longer than in the Frobisher Bay specimens, tylotes are longer, and the bipocilli are smaller and have unequal alae ( Thiele 1903).

Iophon spinulentum ( Bowerbank, 1866) (Europe) : The acanthostyles are smaller and the bipocilli are much smaller and have unequal alae. Tylote length was not given in the source ( Bowerbank 1866).

Iophon variopocillatum Alander, 1942 (North Sea): The acanthostyles are shorter, the tylotes are shorter and thinner, and there are two size categories of bipocilli with unequal alae ( Alander 1942).

Recently, an Iophon specimen not assigned to a species level was reported from the Bay of Fundy ( Goodwin 2017). This sponge has slightly shorter acanthostyles 193 (193–284) x 9.9 (7.4–11.7) µm, shorter tylotes 187 (157– 244) x 5.9 (3.4–10.4) µm, small bipocilli with unequal alae are 7.9 (6.5–8.7) µm in length and this sponge has one size category of anisochelae that are 18 (14–22) µm in length. The Bay of Fundy specimen was reported to turn black in air, similar to I. nigricans . Therefore, the Frobisher Bay specimens are similar to the Bay of Fundy specimens, in that they only have one size category of anisochelae, though they are smaller in the Bay of Fundy specimen. The two differ, however, in the form of the bipocilli, where the Frobisher Bay specimens have much larger bipocilli with equal sized alae.

In summary, most North Atlantic species of Iophon have bipocilli of the common form with unequal alae, except for I. dogieli , but that species has thick styles and smaller styles/tornotes rather than acanthostyles and tylotes as found in the present specimens. Iophon nigricans appears most similar in darkening upon exposing the specimen to air but does not have a bush-like growth form, has smaller megaslceres, has two size categories of anisochelae, and has very small bipocilli.

Discussion. This sponge forms dense aggregations in inner Frobisher Bay. It grows among large stalked ascidians and other sponges, notably Mycale lingua , which has a similar yellow colour. Halichondria sitiens was also collected at this site and has a similar growth form, but close examination of the sponge texture and skeleton easily distinguishes the two species. Arcturus baffini isopods as well as crinoids ( Heliometra sp.) were often attached to the distal portions of individual branches of I. koltuni and Tetilla sibirica sponges. The habitat of the New Siberian Shoal where the holotype was collected appears to have be similar to inner Frobisher Bay, characterized by a silty deposit area and shallow water. As this was the first attempt to collect and identify sponges in a nearshore bay in the eastern Canadian Arctic, it is possible that similar habitats in the region may also be home to I. koltuni specimens.

Genetic data. 28S sequences were obtained from the D3–D5 (GenBank accession MH394248 ) and D6–D8 (GenBank MH394251 ) regions. Single base pair differences in the D3–D5 region and the D6–D8 region were noted between these specimens and I. nigricans (GenBank accession KF018114 ), and a 13 bp difference from I. hyndmani in the D3–D5 region (GenBank accession KF018107 ).

Figures

FIGURE 3. Iophon koltuni. A. Collecting I. koltuni with ROV manipulator arms, scale bar is 6 cm. B. Skeleton showing tangential tylotes at surface (right) scale bar is 100 µm. C. Sponges after collection showing browning on contact with air. D. Acanthostyle. E. Acanthostyle with swollen head and large spines. F. Tylote. G. Acanthostyle head. H. Tylote head. I, J. Bipocilli, K, L. Spurred anisochelae.