Clathria (Microciona) aculeofila Aguirre, Hooker, Willenz & Hajdu, 2011, sp. nov.

Clathria (Microciona) aculeofila sp. nov.

(Figs 1–6; Tabs 1–2)

Type material. Holotype CZA 13317 (schizotypes MNRJ 13317, RBINS POR 2000, MHNG 76056) Bajo El Cardo (Punta Sal– 03°57’16.90’’S, 80°57’56.40’’W, Piura, Peru), 15 m deep, coll Y. Hooker and L.K. Aguirre, 13.Feb.2008. Paratypes CZA 11449 (schizotypes MNRJ 11449, RBINS POR 2004, MHNG 76057), Baja de Quebrada Verde (El Ñuro– 04°13’22.30”S, 81°12’24.10”W, Piura, Peru), 4–5 m deep, coll. Y. Hooker and M. Rios, 14.Oct.2007. CZA 11332 (schizotypes MNRJ 11332, RBINS POR 2001, MHNG 76058), Islote El Lagarto (Lobos de Afuera Islands– 06°56’01.20”S, 80°42’19.90”W, Lambayeque, Peru), 8.6 m deep, coll. Ph. Willenz and Y. Hooker, 04.Oct.2007. CZA 11380 (schizotypes MNRJ 11380, RBINS POR 2002, MHNG 76059), San Cristobal (Lobos de Afuera Islands– 06°54’52.50”S, 80°42’55.90”W, Lambayeque, Peru), 12.9 m deep, coll. E. Hajdu, 07.Oct.2007. CZA 11437 (schizotypes MNRJ 11437, RBINS POR 2003, MHNG 76060, Sur de Quebrada Verde (El Ñuro– 04°13’30.40”S, 81°12’31.60”W, Piura, Peru), 10.0 m deep, Y. Hooker and M. Rios, 14.Oct.2007. CZA 11453 (schizotypes MNRJ 11453, RBINS POR 2005, MHNG 76146, Baja de Quebrada Verde (El Ñuro– 04°13’22.30”S, 81°12’24.10”W, Piura, Peru), 4–5 m deep, coll. Y. Hooker and M. Rios, 14.Oct.2007. CZA 11490 (schizotypes MNRJ 11490, RBINS POR 2006, MHNG 76147), Baja de Quebrada Verde (El Ñuro– 04°13’22.30”S, 81°12’24.10”W, Piura, Peru), 8 m deep, coll. Y. Hooker and M. Rios, 18.Oct.2007. CZA 12955 (schizotypes MNRJ 12955, RBINS POR 2007, MHNG 76149), the fishermen’s pier (Máncora– 04°06’35.65”S, 81°04’02.50”W, Piura, Peru), 1.6 m deep, Y. Hooker and F. Menendez, 18.Nov.2009. CZA 12981 (schizotypes MNRJ 12981, RBINS POR 2008, MHNG 76150), Baja El Burro (Punta Sal– 03°58’34.10”S, 80°59’06.00”W, Piura, Peru), 13.2 m deep, coll. Y. Hooker and B. Ibañez, 21.Nov.2009. CZA 12982 (schizotypes MNRJ 12982, RBINS POR 2009, MHNG 76151), Balneario anchorage (Punta Sal– 03°58’04.10”S, 80°58’09.30”W, Piura, Peru), ca. 10.0 m deep, coll. Y. Hooker and C. Segami, 21.Nov.2009. CZA 12989 (schizotypes MNRJ 12989, RBINS POR 2010, MHNG 76152), (El Ñuro– 04°14’1.00”S, 81°12’46.00”W, Piura, Peru), 15.7 m deep, Y. Hooker and F. Menendez, 19.Nov.2009. CZA 13031 (schizotypes MNRJ 13031, RBINS POR 2011, MHNG 76153), the fishermen’s pier (El Ñuro– 04°13’00.00”S, 81°10’50.10”W –Piura, Peru), 4.8 m deep, coll. Y. Hooker and C. Segami, 24.Nov.2009. CZA 13066 (schizotypes MNRJ 13066, RBINS POR 2012, MHNG 76154), Chavelera (Cancas– 03°55’14.10”S, 80°54’29.90”W –Piura, Peru), 11.6 m deep, coll. Y. Hooker, 30.Nov.2009.

Diagnosis. Clathria (Microciona) sp. nov. is the only encrusting Clathria in Peru and neighboring areas, with principal megascleres mostly bearing spines only at the base, auxiliary megascleres which are either smooth or paucispined at the base, smooth toxas in one or two length categories frequently over 100 µm long, and palmate isochelae in a single category, normally smaller than 15 µm long.

Description. Habit. Sponges are usually thinly encrusting (<1 mm thick), but slightly thicker sponges can be found too (Fig. 2). They frequently occur as the main epibionts on the spines of Eucidaris thouarsii (Valenciennes, 1846) (Cidaridae, Echinoidea; CZA 11332, 11380, 11449, 12981, 12982; Fig. 2). Each spine has about 3–4 cm 2 in area epibiont coverage, and specimens were not seen stretching from one spine into another. Larger specimens were found on rocky substrate, in this case reaching over 16 x 14 cm in area (e.g. CZA 11490). Surface is hispid and texture velvety. Consistency soft, but in parts it is the hard substrate that one feels when touching the sponge. Colour in life bright–red (CZA 11332, 11380, 11437, 11449, 11453, 11490, 12981, 12955, 12989) or yellow (CZA 12982, 13031, 13066), turning into beige after preservation with ethanol. Meandering subectosomal canals are clearly visible in yellow specimens only, and scattered oscules could only be seen in the pictures taken from CZA 11490 and 12982, all of which smaller than 1 mm in diameter.

Skeleton. (Figs 3, 4). Typical Clathria (Microciona) arrangement, with a basal layer of spongin (20–30 µm across) from which short, echinated fibres arise (up to 600 µm high). Principal megascleres stand erect on the substrate, held erect by the basal layer of spongin, but also slightly above, coring or echinating the fibres. Auxiliary megascleres arranged in disorganized (sub)ectosomal bouquets, frequently piercing the surface. Spicules in these bouquets are frequently laying tangential to the surface. Microscleres of variable abundance are scattered.

Spicules. Megascleres (Fig. 5 A–R; Fig. 6 A–N, Table 1). Principal subtylostyles (Fig. 5 A–F; Fig. 6 A–H), variably stout, slightly curved, slightly fusiform, tapering gradually to a sharp apex; base slightly swollen, roundish, irregularly acanthose, with variably sharp (blunt verrucose to pointy thorn), straight or bent spines; smooth shaft. Auxiliary subtylostyles (Fig. 5 K–R; Fig. 6 I–N), smooth, slender, straight, tapering gradually to a sharp apex; base barely swollen, elliptical, smooth or bearing a crown of sharp, straight spines; smooth shaft. Accessory acanthostyles (Fig. 5 G–J; Fig. 6 F–H), variably stout, slightly curved, slightly fusiform, tapering gradually to a sharp apex; base frequently styloid, irregularly acanthose, with variably sharp (blunt verrucose to pointy thorn), straight or bent spines; shaft pauci-acanthose, with spines frequently restricted to the central portion.

comparative materials. Values are in micrometres.

Microscleres (Fig. 5 S–T; Fig. 6 O –P). Palmate isochelae (Fig. 5 T; Fig. 6 P), mostly with nearly straight, slen- der shafts, only seldom slightly twisted or curved, claws 38–45 % the entire spicule length. Toxas (Fig. 5 S; Fig. 6 O), smooth, common, V– type (gentle central curve and nearly no curves on extremities); the smallest ones are usually those with the deeper central curves.

Ecology and distribution. (Fig. 1). The sponge material was collected from 1.6 to 15.7 m depth, in water temperatures of 14 to 23°C. In Cancas, El Ñuro, Máncora, Punta Sal and Lobos de Afuera cidarid sea urchins were relatively common and these had nearly always their spines covered by the Clathria aculeofila sp. nov. Apparently most, if not all of these cidarids belong to E. thouarsii. More detailed information is presented below.

Remarks. Although there are over 300 described species of Clathria (Hooper, 1996), it is relatively easy to distinguish the Peruvian species from all others. Among the several subgenera of Clathria, only C. (Cornulotrocha), C. (Microciona) and C. (Thalysias) have comparable architecture and spicule complement when contrasted to the new species described here. Only 12 species of these subgenera are this far known from provinces adjacent to the type locality of the new species, viz. the Warm Temperate Northeast Pacific, the Tropical East Pacific, the Juan Fernández and Desventuradas, the Warm Temperate Southeast Pacific and the Magellanic provinces (Table 2). Among these, C. (T.) amabilis has no microscleres, and another five species do not have any toxas: C. (C.) polita, C. (C.) rosetafiordica, C. (M.?) brepha, C. (M.) spongigartina and C. (T.) originalis. Other important points of distinction in relation to these species are the rosettes observed in C. (Cornulotrocha) and the slightly arcuate isochelae of C. (M.?) brepha, which suggests this species is probably misidentified in C. (Microciona) (Hajdu et al., in prep.). Within the remaining six species, two do not possess chelae, and are also thus quite distinct from the new species: C. (M.) antarctica and C. (M.) californiana. The first of these, in addition, has styles up to 900 µm long, which are much larger than the largest megascleres observed here in the new species. The latter differs further through its smaller megascleres and toxas, and apparent lack of accessory acanthostyles. The four remaining species appear closer to the new one, but can also be confidently recognized as distinct, as follows.

Clathria (M.) discreta has fully spined acanthostyles as principal megascleres, relatively rare toxas, which consequently have an unknown length range [ca. 80 µm according to Thiele (1905)], and isochelae, which are smaller than those encountered in the new species. Additionally, the Chilean species was described as small round masses (Thiele, 1905) or bearing cylindrical lobes (Desqueyroux, 1972), neither recognized features of the new species.

Clathria (M.) microjoanna and C. (M.) parthena possess totally smooth principal megascleres. Furthermore, de Laubenfels (1932) did not report toxas smaller than 60 µm in the former, nor isochelae smaller than 24 µm in the latter. Finally, C. (T.) membranacea needs a revision, as Desqueyroux (1972) described materials divergent from Thiele’s (1905) original description. Thiele´s material differs from the new species by its considerably shorter principal spicules, accessory acanthostyles which appear to be absent, and toxas reported to reach only 70 µm in length. On the other hand, Desqueyroux’s sponges come closer to the new species because of their larger and stouter principal spicules, but they also have smaller toxas, and no accessory acanthostyles, and above all, the reported occurrence of anisochelae suggests better placement elsewhere, possibly in C. (Cornulotrocha). A formal decision on this matter has to await a detailed revision of all relevant material. This far, the only Chilean Clathria with anisochelae is C. (Cornulotrocha) rosetafiordica Hajdu et al. 2006 from the fjords region. This species differs from the new one, as pointed out above, and also from Desqueyroux’s sponges in having smaller anisochelae and lack of toxas. The new species appears thus well distinguished from allied forms in neighboring biogeographic provinces.

continued next page The genetic homogeneity of Clathria sponges occurring in distinct spines of the same sea urchin remains to be investigated. We preferred to be on the safe side, following the advice by van Soest (in litt.), and nominate the holotype from a single spine.

Sea urchin abundance and dimensions at Punta Sal. The three transects evaluated had a total of 377 sea urchins, thus 6.28 sea urchins/m2. The mean density ranged from 1.5 to 12 sea urchins/m2, calculated from six obtained counts (each 10 x 2 m transect had 50% evaluation by each of two divers). Test dimensions ranged from 3.2 to 5.6 cm in greatest diameter and 1.8 to 4.1 cm in height, measured from the 30 collected sea urchins.

Frequency and intensity of sponge–sea urchin association. Total number of spines for each collected sea urchin ranged from 68 to 96, with a sponge coverage percentage ranging from 18.2 to 75.7. As expected, the smallest sea urchins, presumably the younger, had the least sponge coverage, but this is not striking. Sea urchins with tests only up to 4.4 cm in diameter (N = 20) had mean sponge coverage of 45.5%, while those with tests ranging from 4.5 to 5.6 cm (N = 10) had mean coverage of 49.5%. Nevertheless, densely covered small sea urchins were also observed (4 cm test, 75.7% coverage), as well as slight coverage of large individuals (5.6 cm test, 18.9% coverage). This suggests that factors other than sea urchin age also play an important role in shaping this association. An important assumption here is that larger sea urchins are older.

Etymology. The species name aculeofila is derived from the Latin word 'aculeus' (= thorn, sting, prickle) and the Greek word 'philos' (= love), and refers to the species observed abundance as an epibiont on cidaroid spines.