Asbestopluma monticola Lundsten & Reiswig & Austin 2014, sp. nov.

Asbestopluma monticola sp. nov.

Figs. 2 & 3

Type material. Holotype: CASIZ 192095; MBARI 941 -A1; January 27, 2006, Davidson Seamount off central California, USA; latitude: 35.722787, longitude: -122.722553, depth: 1280 m. The holotype was recovered from the summit of Davidson Seamount using the MBARI’s ROV Tiburon.

Paratype: CASIZ 194901; MBARI V3745 - A1, Monterey Canyon, November 14, 2013; latitude: 36.72559, longitude: -122.01423, depth: 1323.28 m. The paratype was recovered from steep rock outcrop of the Monterey Canyon.

Type locality. Holotype: Davidson Seamount, California, USA. Paratype: Monterey Canyon, USA.

Etymology. The species name (Latin mont = mountain + - cola = dweller), mountain dweller, is descriptive of the type locality, where dense stands of this beautiful sponge thrive.

Diagnosis. Branching Cladorhizidae with three size classes of megasclere styles and three microsclere types of a single size class including acanthose tylostyles, sigmas, and palmate anisochelae.

Description. Holotype : an arborescent, dichotomously-branching sponge with bottle-brush arrangement of filaments 19.37 cm tall and 13 cm wide, but was likely wider as several branches were broken off before measuring (Fig. 2A–E). Filaments are 1–9 mm in length (Fig. 4A). At the base, the stalk is 7 mm wide and branches all taper to approximately 1 mm width distally. Attached to hard substrate via conic holdfast disk, 1.3 cm in width. Sponge is white in situ and in preserved state. Paratype: matching description above for holotype, 28 cm tall, 9 mm wide at conical base, 6 mm stalk width, and 2 mm branch tip width, tapering distally.

Spicules. Large styles 1 (Fig. 3A, Table 1), fusiform, straight, often with pointed end rounded, in axes of branches and stem: L 751 ± 46 µm (n=53), W 25.5 ± 1.4 µm (n=53). Large styles 2 (Fig. 3B), fusiform, straight or slightly curved, in filaments and their inserts in branch axes: L 687± 69 µm (n=103), W 17.5 ± 2.8 µm (n=66). Large styles 3 (Fig. 3C), fusiform, thick, strongly bent, mainly in basal cone: L 462.1± 79.7 µm (n=85), W 39.97 ± 7.7 µm (n=67). Microacanthotylostrongyle (Fig. 3D) thin, rough, mostly curved, occurs in basal cone and sparsely throughout branch axes: L 98.1 ± 10.7 µm (n=50), W 1.7 ± 0.4 µm (n=50). Sigma (Fig. 3E) robust, contort, without profile discontinuity near ends (not clearly sigmancistroid), occurs throughout specimen: L 22.9 ± 1.5 µm (n=50). Palmate anisochelae (Fig. 3F) foot with frontal tooth bearing two broad lateral flukes and distal medial spine extending toward spicule center, lateral wings short and never meet the frontal tooth; without spurs; occurs throughout the specimen: L 11.8 ± 0.5 µm (n=50).

Habitat and associated fauna. Asbestopluma monticola was first observed while conducting ROV dives at Davidson Seamount off central California in 2002. A single specimen was collected in 2006 while surveying Davidson Seamount once more. A dense population of A. monticola was observed there and they were noted as living attached to both the seafloor and, also, dead hexactinellid sponges. Since 2006, hundreds of additional observations of this species have been made. They are abundant in Monterey Canyon off northern California and central Oregon, a range of ~ 1000 km. They co-occur with numerous species of sponges (Staurocalyptus sp., Farrea sp., Chonelasma sp.), corals (Anthomastus ritteri Verrill, Paragorgia arborea Linnaeus, Keratosis sp., Corallium sp., Clavularia sp.), crustaceans (lithodid crabs, pandalid shrimps, amphipod), echinoderms (comatulid crinoids, Gorgonocephalus sp. ophiuroids, Hippasteria sp. asteroids), and vertebrates (Careproctus sp., egg case of Rajiformes, and Psychrolutes phrictus Stein & Bond). Small crustaceans like the pandalid shrimp were observed to be actively climbing upon and around the branches of A. monticola. The average depth of observation was 1236 m (±211; n=428). Oxygen concentration is low (0.85 ±0.3 ml/L; n=428) and temperature averages 3.18 °C (±0.54; n=428). Small crustacean prey were observed in various states of decomposition on A. monticola (Fig. 4A–D).

Remarks. Among the 42 known species of Asbestopluma, eight species branch. These are compared with A. monticola below. Asbestopluma monticola differs from A. formosa (Vacelet 2006), in that it lacks the characteristic embryo-containing branching enlargements, they differ in branching patterns— A. formosa has fan shapedbranches that divide dichotomously three or four times in a single plane with long, thin, and parallel terminal branches, and A. monticola also lacks microstrongyles. Asbestopluma monticola resembles A. desmophora (Kelly and Vacelet, 2011), however, it lacks desmas and sigmancistras and has bent fusiform styles in its basal cone. Asbestopluma monticola differs from A. bitrichela (Lopes et al., 2011) in a lack of desmas and anchorate/ unguiforate anisochelae. This new species differs from A. delicata (Lopes et al., 2011) in the absence of microstrongyles and palmate isochelae. Asbestopluma monticola d iffers from A. magnifica (Lopes et al., 2011) in being much smaller (~50% less) in total length, in having a single size class of anisochelae, and having a microtylostrongyle. When compared to A. furcata (Lundbeck, 1905), A. monticola has larger megascleres and only one size class of anisochelae (A. furcata has two size classes of anisochelae). Asbestopluma monticola is very similar to A. ramosa Koltun, however, A. ramosa has a flabelliform branching pattern, with vertical branches emanating from a single point and much thicker branches averaging 1.2 cm. Asbestopluma ramosa has larger spicules, especially when comparing anisochelae (Koltun, 1959; Stone et al., 2011). Asbestopluma ramosa also does not appear to have the robust, bent fusiform styles of A. monticola. Asbestopluma monticola superficially resembles A. rickettsi (described below), however, A. monticola differs in having only one size class of anisochelae. In situ, A. rickettsi is more transparent and much more delicate looking than A. monticola. A comparison of spicule data for all known Asbestopluma species through 2011 is published in Lopes et al. (2011).