Megaciella triangulata Lehnert & Stone, 2015, n. sp.

Megaciella triangulata n. sp.

(Figs. 5 & 6, Table 2)

Material examined. Holotype ZSM 20150383 and paratype ZSM 20150384 collected by Jim Stark with a research survey bottom trawl (haul #180) from the FV Ocean Explorer; 24 July 2012, 141 m depth, Buldir Reef, western Aleutian Islands, North Pacific Ocean (52°03.4140' N, 176°25.0800' E). Water temperature = 4.1°C. Complete specimens in ethanol.

Description. Habitus: Both specimens are golden brown in color on wiry stalks. The holotype (larger specimen) is 17 cm in height and 11 cm in maximum width (Fig. 5 A). The stalk of the holotype is 1.5–2 cm thick and expands after 5.5 cm into a massive triangle with sides almost symmetrical (11.5, 11 and 12 cm long) and 2.5– 3 cm in thickness. The paratype (smaller specimen) attains 14 cm in height, the stalk is 0.8 cm at the base and more irregularly shaped, it widens to 1.9 cm in diameter where it expands into a small massive triangle, the sides 4, 4.5 and 5 cm long with a thickness of 1.5 cm (Fig. 5 A). The stalk has a smooth surface without recognisable apertures; the triangle bears numerous small pores, flush with the surface and 1–2 mm in diameter. The triangle part of the sponge is much softer and more elastic than the stalk due to a higher spicule density in the stalk.

Skeletal structure: The choanosome consists of an irregular reticulation of paucispicular tracts with many microscleres in between (Figs. 5 B & C). Acanthostyles are irregularly scattered in the choanosome. The thin styles are usually coring the tracts. Ectosomal tylotes are arranged paratangentially in bundles (Fig. 5 D) or in short tracts facing in different directions. Towards the stalk the abundance and density of these tylotes increases, recognisable in a smoother surface.

Spicules: Ectosomal tylotes are fusiform, tyles have a straight, microspined end and measure, 182–346 x 8–11 µm (Fig. 5 E), choanosomal thick styles are smooth, slightly bent, 295–546 x 18–35 µm (Fig. 5 F), thin styles, 335– 452 x 8-11 µm (Fig. 5 F), acanthostyles, 340–435 x 22-25 µm (Fig. 6 A). Microscleres are two categories of toxa, large category spined at the ends and with a U-turn in the center, 290–425 µm (Fig. 6 B), thicker than the small category which measures 65–185 µm and is spined all over (Fig. 6 C) and two categories of palmate isochelae, the large category with pointed ends on top and bottom, 13–18 µm (Fig. 6 D), small category without pointed ends, 7– 10 µm (Fig. 6 E) and, finally, a tiny category of anisochelae, 5–7 µm (Fig. 6 F).

Discussion. Again, we compare this new Megaciella with the nine other species co-occurring in the North Pacific Ocean (Table 2). M. triangulata n. sp. differs from these species in the following characters: M. anisochelae: A stalked cluster of tubes with no acanthostyles or toxa.

M. fragilis: A dactylate or lobate sponge,light yellow in color, with shorter and thinner tylotes, thinner styles, no acanthostyles, only one category of isochelae, and toxa of different sizes.

TABLE 2. Spicule categories and measurements of Megaciella from the North Pacific Ocean. All measurements are in µm.

species tylotes styles echinating spicules isochelae toxa other

anisochela Lehnert et microspined ends, smooth, 490–615 x none large, 13–17, small, 6–8 none anisochelas, 4–6

, 2006c 245–380 x 4–9 18 –22

fragilis (Koltun, microspined ends, smooth, 291–364 x none 14–17 large, 124–218 x 2, small, 21– none) 176–228 x 6–8 12 –18 35 x 1

microtoxa microspined ends, acantho-, 360–540 x acanthostyles, 85–215 12.5–15 50–140 none

Dickinson, 1945)+ 190–250 x 2.5–5 17.525 x 2.5–7.5

ochotensis (Koltun, “fusiform tornotes”, acantho-, 168–252 x none 25–32 84–134 none) 151–220 x 5–9 11 –14

pituitosa Lehnert & microspined ends, smooth, 460–630 x acanthostyles, 140– 15–20 large, 120–300, small, 40– 87 x none

Stone, 2014b 144–310 x 4–6 26 –30 145 x 8–10 2–3

spirinae (Koltun, microspined ends, acantho-, 166–213 x none 23–35 136-200 x 9 none) 166–208 x 3–4 10 –13

toxispinosa Aguilar- microspined ends, acantho-, 150–315 x acanthostyles, 55–105 two categories; reduced alae, large, 35–60, small none

Camacho et al., 2014 160–215 x 2.5 2.5–- 5 x 2.5–3.5 12.5–15, alae fused with shaft, (microspined, “oxhorn- 12.5–17.5 shaped”), 3–10

zenkevitchi (Koltun, microspined ends, acantho., 405–478 x apically spined styles, 21–25 large, 178–364, small, 75–92 none) 208–343 x 7–10 33 –42 364–475 x 10–12

lobata n. sp. microspined ends, smooth & acanthostyles, 440– 22–27 two categories; large, 130–720 large smooth styles, 355–508 x 4–6 microspined 735–928 710 x 42 –55 & small, 29–47 1056–1645 x 19–32 x 42 –55

triangulata n. sp. fusiform tylotes, smooth, 295–516 x acanthostyles, 340– two categories; large, 13–18 & two categories; microspined thin styles, 335–452 x microspined ends, 18–35 435 x 22–25 small, 7–10 (different shapes?) all over, weakly bent, thin 65– 6–10, anisochelas, 5–7 182–346 x 8–11 185

microspined ends, strongly bent, thicker, 290–428

after Aguilar-Camacho et al. (2014)

M. microtoxa: A massive sponge with shorter and thinner tylotes, a choanosome with acanthostyles only, only one category of isochelae, and only one category of toxa.

M. ochotensis: A lobate to dactylate sponge with shorter and thinner tylotes, choanosome with acanthostyles only, only one category of isochelae, and only one category of toxa.

M. pituitosa: Also stalked but fan-shaped, with thinner tylotes, shorter and thinner acanthostyles, only one category of isochelae, and smooth toxa.

M. spirinae: An irregularly massive-lobate sponge with smaller tylotes, choanosome with acanthostyles only which are smaller, only one category of choanosomal styles that are larger, and only one category of toxa.

M. toxispinosa: A thinly encrusting sponge with shorter and much thinner tylotes, choanosome with acanthostyles only, different size categories of isochelae, and shorter categories of toxa.

M. zenkevitchi: A sponge with differently shaped tylotes, categories of choanosomal styles differ in shape and size, only one category of isochelae, and different size categories of toxa.

M. lobata n. sp.: A lobate sponge with longer and thinner tylotes, longer and thicker styles and acanthostyles, one category of isochelae that are larger, and smooth toxa of different size categories.

Megaciella triangulata n. sp. and M. anisochela (Lehnert et al., 2006b) both from the Aleutian Island Archipelago region are presently the only two species of Megaciella known to have a tiny category of peculiar anisochelae. Though the possession of anisochelae was unusual and only recently confirmed for the genus they had previously been documented in members of the family Acarnidae (Hooper, 2002b). With the discovery of modified anisochelae in a second species of Megaciella there is additional evidence that the occasional presence of this microsclere category is a trait within the genus.

Etymology. from the Latin triangulata—triangular, referring to the triangular shape of the main body of the sponge on top of the stalk.