Artemisina amlia Lehnert, Stone & Heimler, 2006, sp. nov.

Artemisina amlia sp. nov.

(Figs 1 a–b, 2 a–f)

Material

Holotype: 6221­2B­6 (51°54’49.1’’N, 173°53’8.3’’W, 15 km south of Amlia Island, 119 m depth). The holotype is deposited at the National Museum of Natural History, Washington, D.C., U.S.A. under the registration number USNM 1082993.

Description

The sponge is stalked with a subhemispherical, conical body. The stalk widens gradually from 4 to 25 mm over a distance of approximately 9 cm and is not sharply separated from the subhemispherical body (Fig. 1 a,b). Surface wartlike, with slightly elevated circular oscules (Fig. 1a), 2 mm in diameter; in ethanol oscules not visible. Texture soft and elastic, easily torn. Exterior colour in life golden­yellow; in preservative the ectosome is translucent with a yellowish choanosome shining through.

Skeleton. The ectosome of the upper sphere is composed of a meshwork of polyspicular tracts of small styles with a meshsize of 350–750 µm, single tracts 55–175 µm in diameter. This large mesh is subdivided by a finer net of strands of spongin embedded isochelae. The finer net has a mesh size of 45–90 µm, single, translucent strands are 15–25 µm in diameter. The ectosome of the stalk is thinner and consists of a dense, unispicular layer of tangentially arranged, parallel oriented thick styles. In the choanosome of the stalk, ascending polyspicular tracts of thick styles are connected by paucispicular tracts and single spicules, comparable to the choanosome of the sphere where the choanosomal tracts are more irregular, less dense, in places halichondroid.

Spicules. Large, smooth styles (Fig. 2 a), 400–520 x 20–25 µm, small styles (Fig. 2 b) with one prominent apical tooth (Fig. 2 c), occasionally some smaller additional spines are present (Fig. 2 d) 330–550 x 10 µm. Microscleres are smooth toxa (Fig. 2 e), 110–170 µm and isochelae (Fig. 2 f), 10–13 µm.

FIGURE 1. Artemisina amlia sp. nov. a, holotype in situ at 119 m depth near Amlia Island. width of photo approx. 32 cm. b, holotype on deck shortly after collection. Small quadrats equal 1 cm 2.

Distribution

Known only from the type locality. Found on relatively low­relief seafloor habitat where it attaches to pebbles and small cobbles. Found in close association with Mycale carlilei sp. n. and Haliclona oblonga.

Etymology

Named after Amlia Island, near where the holotype was collected.

Discussion

There are four other species of Artemisina known from the North Pacific. Spicule types and their sizes are listed in table 1. A. apollinis (Ridley & Dendy, 1887) is not stalked, has larger choanosomal styles, smaller ectosomal styles without a prominent “tooth”, larger isochelae and has two size­categories of toxas. A. arcigera (Schmidt, 1870) may be spherical but is not stalked. In spiculation it differs in having somewhat longer, large styles which are only one third of the thickness of the large styles in A. amlia sp. nov. It has smaller dermal fusiform subtylostyles, without a prominent tooth and also differs in having toxas of a much broader size range. A. foliata (Bowerbank, 1874) is flabelliform or elongated. The small category of styles is shorter, thinner and lacks the prominent tooth. Isochelae are almost double the size and toxas are more than double the size of A. amlia sp. nov. A. stipitata Koltun, 1959 has a spherical body which tapers gradually to a stem and thus has a similar growth form as A. amlia. The small styles of A. stipitata are smaller and don´t have one prominent tooth but have acanthaceous bases and A. stipitata completely lacks toxas. The color of A. stipitata is grey to yellowish grey while A. amlia sp. nov. is golden­yellow.

stipitata Koltun, 1959 374–488 x 312–384 x none none 10–17

10–27 8–10