Asbestopluma caribica, Hestetun, Jon T., Pomponi, Shirley A. & Rapp, Hans Tore, 2016

Hestetun, Jon T., Pomponi, Shirley A. & Rapp, Hans Tore, 2016, The cladorhizid fauna (Porifera, Poecilosclerida) of the Caribbean and adjacent waters, Zootaxa 4175 (6), pp. 521-538 : 525-527

Asbestopluma caribica sp. nov.

( Figure 4 ; Table 1 )

Type material. Holotype: USNM 30433; paratype USNM 1417730, R/V “Bartlett” (1981–10–28, Beata Ridge, Caribbean Sea, st. 40, 15°08'N, 069°13'W, 4007 m).

Etymology. The species is named after the Caribbean Sea, where it was collected.

Diagnosis. Erect, very fine single-stem Asbestopluma with an upper stem carrying two oppositely arranged rows of filamentous projections. Megascleres are mycalostyles and subtylostyles; microscleres are anisocercichelae, palmate anisochelae and sigmancistras.

Description. There are two specimens of this sponge, designated here as the holotype and paratype. Both are fine, single stems with some abrasive damage from collection. The holotype is 83 mm tall, and the paratype is 109 mm tall. Both stems are divided into a bare lower part and filament-bearing upper part. The filament-bearing part is 21 mm and 27 mm in the holotype and paratype respectively. The stems are around 1 mm in diameter at the basal end, gradually diminishing to 0.5 mm in diameter before expanding back to around 1 mm in diameter at the filament-bearing portion. The upper parts of both stems are translucent to white, while the lower stems, due to a very thin cover of fine sediment, are partly light brown. The lower ends of both stems are broken. Filaments are found in two opposite rows spaced approximately every 1 mm. They are in almost all cases reduced to stumps <1 mm long and are probably damaged ( Fig. 4 A–B).

Skeleton. The stem is made up of longitudinally arranged mycalostyles with apical tips. The skeleton of the filaments is anchored perpendicularly into the stem, pointing slightly upwards, and is made up of subtylostyles ( Fig. 4 C). Microscleres are found at the stem surface, with anisocercichelae confined to the filament-bearing part. The acanthotylostyles are found at the surface of the basal part of the stem.

Spicules. Mycalostyles, straight and fusiform, 990–(1194)–1426 µm long and 18–(23)–33 µm wide ( Fig. 4 D).

Subtylostyles, straight and slightly fusiform, with faint, slightly elongated tyle, 320–(550)–660 µm long, 8– (12)–14 µm wide ( Fig. 4 E).

Acanthotylostyles, curved, in the basal stem sheath, 74–(114)–194 µm long ( Fig. 4 F)

Anisocercichelae, with weakly arched shafts and one central extension tooth or extension in each end, with rudimentary alae or fimbria-like structures in the upper end and covered with minute spines. The spines are not clearly visible using a light microscope. The upper edge is about two thirds of the total length and the lower edge is about 20% of total length. In the upper stem and filaments, 52–(64)–74 µm ( Fig. 4 G–H).

Palmate chelae, with strongly arched shafts and alae 80% of the total length of the spicule, 8–(10)–12 µm ( Fig. 4 I–J).

Sigmancistras, straight or contorted, with the concave edge flattened, 19–(26)–34 µm ( Fig. 4 K).

Remarks. The spicule complement is mostly typical for Asbestopluma , with one category each of mycalostyle and subtylostyle, basal stem acanthotylostyles, palmate anisochelae and sigmancistras. The major diagnostic character feature of A. (A.) caribica sp. nov. is that the alae of the larger type of palmate anisochela common in the genus have been reduced, accentuating a long projection at either end, and featuring minute spines. Our interpretation is that this spicule represents a transformation of a palmate anisochela in a probably separate, but analogous event to the transformation from isochela or abyssochela to cercichela in Cercicladia australis Ríos, Kelly & Vacelet, 2011 . Thus, we have chosen to use the term anisocercichela here.

The only other Asbestopluma known from the area is Asbestopluma (A.) gracilior ( Schmidt, 1870) , which has a stalked, ovoid body, lacks the large category of anisochela, and was collected at ~ 600 m rather than 4000 m as is the case with A. (A.) caribica . The pennate morphology of A. (A.) caribica is common in the genus, as is the general features of its spicule complement, but the unique presence of anisocercichelae makes it difficult to identify particular close relatives.

Figures

FIGURE 4. Asbestopluma caribica sp. nov. A) The holotype (left) and paratype (right), B) detail of the filament-bearing upper stem, C) filaments and stem detail, D) mycalostyle, E) subtylostyle, F) acanthotylostyle, G – H) anisocercichela side and back views, I – J) palmate anisochela front and back views, K) sigmancistra.

Tables

TABLE 1. Individual spicule measurements from the Asbestopluma (A.) caribica sp. nov. holotype and paratype.

Specimen	Holotype USNM 30433	Paratype USNM 1417730
Mycalostyles	990–(1162)–1290 x 20–(26)–33	1066–(1227)–1426 x 18–(21)–24
Subtylostyles	320–(571)–660 x 8–(12)–14	327–(528)–645 x 9–(12)–14
Acanthotylostyles	86–(115)–194	74–(114)–171
Anisocercichelae	52–(60)–68	60–(67)–74
Palmate anisochelae	9–(10)–11	8–(10)–12
Sigmancistras	24–(25)–28	19–(27)–34