Artemisina flabellata, Lehnert, Helmut & Stone, Robert P., 2015

Lehnert, Helmut & Stone, Robert P., 2015, New species of sponges (Porifera, Demospongiae) from the Aleutian Islands and Gulf of Alaska, Zootaxa 4033 (4), pp. 451-483 : 464-468

Artemisina flabellata n. sp.

( Figs. 8 & 9 , Table 3)

Material examined. Holotype: ZSM 20150387, collected by Jay Orr with a research survey bottom trawl (haul #135) from the FV Ocean Explorer; 11 July 2012, 99 m depth, Petrel Bank, central Aleutian Islands, Bering Sea (52°15.9960' N, 179°54.0060' E). Water temperature = 4.3°C. Complete specimen in ethanol.

Description. Habitus: Large, light brown to gold colored, fan-shaped to flabellate sponge, starting from an almost circular base with a maximum diameter of 7 cm and a height of 26.5 cm, the upper rim approximates a quarter-circle, 25.8 cm in width ( Fig. 8 A). The thickness of the blade is quite variable, the thickest part is 9 cm while other parts are less than 1 cm in thickness. There is a hole in the center of the blade, possibly from tissue necrosis ( Fig. 8 B). No oscules are visible. The consistency of the base is hard and inelastic, softer and more elastic but, still resilient, towards the top.

Skeletal structure: The ectosome is a relatively thick veneer of densely packed thin ectosomal styles primarily in a tangential arrangement, single bundles of ectosomal styles may stand perpendicular to the surface and consequently the thickness varies between 200 and 700 µm. The choanosome is halichondroid and consists of vague tracts with many spicules in between. Plumose tracts are irregular and there are many spicules in between.

Spicules: are thick choanosomal styles, finely spined apically, 648–1630 x 25–33 µm ( Figs. 8 C & E), occasionally strongylote or weakly microspined all over, apically spined ectosomal styles, 453– 1152 x 9–16 µm ( Figs. 8 D & E), small acanthostyles, 157–248 x 15–18 µm ( Fig. 8 F), cleistochelae with a peculiar central plate on the shaft and the alae fused or open with a small gap, 13–18 µm ( Figs. 9 A & B), thin, smooth toxa, 90–1150 µm ( Fig. 9 C).

Discussion. The skin-like ectosome and halichondroid choanosome warrant assignment in the genus Artemisina . Again we compare Artemisina flabellata n. sp. with eight species occurring from the North Pacific and North Atlantic Oceans ( Table 3) and with the other new Artemisina described above. Artemisina flabellata n. sp. differs from these species in possessing cleistochelae and the following characters:

A. amlia : A stalked, subhemispherical or conical sponge with shorter ectosomal styles, shorter choanosomal styles, and shorter smooth toxa.

A. apollinis : A massive to funnel-shaped sponge with shorter and thinner ectosomal styles, shorter choanosomal styles, and two categories of toxa.

A. archegona : A thinly encrusting sponge, bright orange color in life, white in ethanol, with shorter and much thinner ectosomal styles, and shorter and thinner choanosomal styles.

A. arcigera : A massive to spherical or stalked and tube-shaped (central Aleutian Islands) sponge, only 5.5 cm high, with shorter ectosomal styles, shorter and much thinner choanosomal styles, and microspined toxa but no smooth toxa.

A. erecta : A small (11 mm x 5 mm x 3 mm), white colored sponge with shorter and thinner ectosomal styles, shorter choanosmal styles, and microspined toxa but no smooth toxa.

species ectosomal styles choanosomal styles smooth toxa microspined toxa isochelae other

amlia Lehnert et al. , 330–550 x 9–11 400–520 x 20–25 110–170 none 10–13 none

2006a

apollinis (Ridley & 290–457 x 5–9 500–842 x 13–21 85 –280 291–468 14–18 none

Dendy, 1886)

archegona Ristau , 120–340 x 2.5 185–240 x 7–20 105–520 x none 18–21 toxiform oxeas, 450–800

1978 0.5–1.0 x 3–6

Topsent did not provide measurements in the text. Sizes of isochelae were measured by us from Topsent´s plate IX, Fig. 7 .

A. stipitata: Massive to spherical or flabellate (central Aleutian islands) sponge with shorter ectosomal styles, shorter choanosomal styles, and no toxa.

A. transiens : A stalked, white-colored sponge with shorter ectosomal styles, choanosomal styles not different from ectosomal styles, and shorter smooth toxa.

A. clavata n. sp.: A club-shaped sponge with shorter and thinner ectosomal styles, shorter choanosomal styles, and microspined toxa but no smooth toxa.

Artemisina flabellata n. sp. is the only species of Artemisina discussed that has a third category of megasclere in addition to the ectosomal and choanosomal styles; the latter two styles being the longest within the genus. These acanthostyles were found irregularly distributed, singly or in groups, in sections of the choanosome. It could be discussed if these are really proper to the sponge. The irregular distribution might be an argument for a foreign inclusion but, as they were found quite often in different sections we think it far more probable they are proper to the sponge. Validity of this new species is independent from the presence of these acanthostyles as there are three more unique characters which separate A. flabellata from all other congeners: It has two unusually long categories of styles and peculiar cleistochelae which separate this species from all others.

Etymology. from the Latin flabellum—fan, referring to the habitus of this sponge.

Figures

FIGURE 7. Artemisina clavata n. sp. A. Holotype. Grid marks are 1 cm. B. Paratype, grid marks are 1 cm. C. Choanosomal thick styles (upper left to lower right) among ectosomal subtylostyles with acanthose heads. Scale bar is 100 µm. D. Ectosomal subtylostyle (upper left to lower right) with microspined head. Scale bar is 20 µm. Inset at upper right corner shows microspined head of ectosomal subtlostyle. Scale bar is 2 µm. E. Palmate isochela. Scale bar is 1 µm. F. Toxas with microspined ends (lower left to upper right). Scale bar is 20 µm.

FIGURE 8. Artemisina flabellata n. sp. A. Holotype. Grid marks are 1 cm. B. Close-up of surface of holotype. Note thin organic ectosome. Grid marks are 1 cm. C. Choanosomal style (upper left to lower right). Scale bar is 100 µm. D. Ectosomal thinner style (upper left to lower right). Scale bar is 100 µm. E. Microspined end of ectosomal thinner style on very slightly microspined head of choanosomal style. Scale bar is 10 µm. F. Acanthostyle among isochelas. Scale bar is 30 µm.

FIGURE 9. Artemisina flabellata n. sp. A. Cleistochela with peculiar central plate and almost closed alae. Scale bar is 2 µm. B. Cleistochelae with completely closed alae from different angels. Scale bar is 2 µm. C. Thin toxon among cleistochelas. Scale bar is 20 µm.