Myxilla (Burtonanchora) araucana Hajdu, Desqueyroux-Faundez, Carvalho, Lobo-Hajdu and Willenz 2013
Creators: name: Hajdu, Eduardo
name: Desqueyroux-Faúndez, Ruth
name: Carvalho, Mariana De Souza
name: Lôbo-Hajdu, Gisele
name: Willenz, Philippe
Publisher: name: Zenodo
Year: 2013
Subjects: Biodiversity
Taxonomy
Animalia
Porifera
Demospongiae
Poecilosclerida
Myxillidae
Myxilla
Myxilla araucana

description: Myxilla (Burtonanchora) araucana Hajdu, Desqueyroux-Faúndez, Carvalho, Lôbo-Hajdu and Willenz sp. nov.
(Figs. 6G, 10R–V; Tab. 9)
Myxilla araucana Hajdu et al. (2009, nomen nudum, in part) in Willenz et al. (2009: 130, in part-bottom left and bottom right in situ photos, A–F SEM; non upper in situ photo, = Stelodoryx sp.)
Type material. Holotype. IZUA-POR 149, northern side of the entrance of Quintupeu Fjord (42º09’49.32”S – 72º26’40.32”W, Chilean Patagonia), 20 m depth, coll. E. Hajdu, G. Lôbo-Hajdu and Ph.Willenz, 21 April 2004 — fragments from the holotype: RBINSc-IG 32231-POR 8220 and MNRJ 8220. Paratypes. MNRJ 7283, 7287, Quintupeu Fjord (cross refs. (63) 710022–3 and (63D) 710022–3, respectively; Chilean Patagonia), coll. C.A. Viviani (ORPLAN), 26 April 1971. MNRJ 8222, northern side of the entrance of Quintupeu Fjord (42º09’49.32”S – 72º26’40.32”W, Chilean Patagonia), 24 m depth, coll. E. Hajdu, G. Lôbo-Hajdu and Ph.Willenz, 21 April 2004 — fragment from the paratype: RBINSc-IG 32231- POR 8222.
Comparative material. Myxilla (Burtonanchora) asigmata (Topsent, 1901) — RBINS POR 038 (holotype)
Myxilla (B.) gracilis Lévi, 1965 - MNHN LBIM DCL 330, microscopic preparation of dissociated spicules from holotype
Myxilla (B.) myxilloides Lévi, 1960 — MNHN LBIM DCL 782, microscopic preparation of dissociated spicules from holotype
Myxilla (B.) sigmatifera (Lévi, 1963) — MNHN LBIM DCL 528, microscopic preparation of dissociated spicules from holotype
Diagnosis. Myxilla (B.) araucana sp. nov. is the only species in the subgenus to possess only a single category of anchorate isochelae <80 µm in length as microscleres, next to terminally microspined ectosomal subtylote megascleres always <300 µm.
Description (Fig. 6G). Erect sponge, inverted-conical or fusiform with deep longitudinal grooves, soft, with a smooth surface. The holotype was approximately 3 x 1.5 cm (height, largest diameter). Oscula, 3–5 mm in diameter, apical, occasionally with small perioscular membranes. Subdermal canals visible in situ. Live-colour is light-yellow to whitish, becoming beige in ethanol.
Skeleton (Fig. 10R). Ectosomal skeleton, slightly divergent tufts of subtylotes and abundant isochelae, which form crusts at some parts. Choanosome plumo-reticulated, with ascending primary paucispicular tracts of styles connected nearly at right angles mostly by single styles. Isochelae very common in choanosome.
Spicules (Figs. 10S–V, Table 9). Megascleres, straight or slightly curved, smooth styles (Figs. 11S), 378–504 µm long and 12–22 µm thick, with sharp apex; terminally microspined ectosomal subtylotes (Figs. 10T–U), 155– 233 µm long and 3.6–7.2 µm thick. Microscleres, anchorate isochelae with three or four fully formed alae (Figs. 10V), 43–74 µm long.
Distribution and ecology. So far known only from its type locality in the Chilean fjords region, ca. 42ºS (Quintupeu Fjord). On nearly vertical rocky substrate, between 10 and 24 m depth.
Etymology. The name ‘araucana’ is a noun in apposition, which honours the native Americans settled in a large fraction of Chile territory, the Araucanos [Spanish name for the Mapuche people].
Remarks. Only 12 species are currently accepted within Myxilla (Burtonanchora) according to the World Porifera Database (van Soest et al., 2013), all of which are compared to the new species described above (Table 10). We decided to add another one, M. (B.) magna, on the basis of arguments recently raised by Rios and Cristobo (2007). It appears to us that a clear understanding of monophyletic species groups within the Myxillidae may not have been reached yet, as apparent from the ping-pong assignment of species to and out from synonymies. This is due in part to different interpretations of supposedly highly polymorphic species (e.g. M. mollis Ridley & Dendy, 1886 vs. M. magna), where not even subgeneric assignment is well settled.
Myxilla (B.) asymmetrica was up to now, the single species known from the SE Pacific in the subgenus. It differs from the new species notably by the lack of terminal spination in its ectosomal megascleres, as well as the smaller size of its anchorates and possession of sigmas. Within the remaining 12 species in Table 10, eight species can be easily distinguished from the new one, either because their choanosomal megascleres are much larger [M. (B.) asigmata, M. (B.) hastata, M. (B.) lissostyla] or much smaller than those of the new species [M. (B.) crucifera, M. (B.) gracilis, M. (B.) lacunosa, M. (B.) myxilloides, M. (B.) ponceti]. With the exception of M. (B.) asigmata and M. (B.) lissostyla, the other six species have additional microsclere categories, which add further on their distinctiveness.
Myxilla (B.) asigmata, M. (B.) hastata, and M. (B.) lissostyla, on the other hand, have considerably larger tornotes and, in the case of the latter, much larger anchorates too. M. (B.) lissostyla sensu Desqueyroux (1975) should be revised as the isochelae drawn appear arcuate, not anchorate. This would render the species best assigned to Lissodendoryx. We were unable to recover any preparations from this material in the MHNG sponge collection. However, the sponge collection at the Museo Zoologico of Universidad de Concepcion (Chile) has one specimen holding (3976) from Brabante Island, which is likely to be the specimen reported upon by Desqueyroux (1975). We were unable to access this collection in time for the present study. Further suggestion of non-conspecificity of Desqueyroux’s (1975) and Burton’s (1938) sponges is derived from the former much smaller isochelae.
Myxilla (B.) araucana sp. nov. differs from three of the remaining four species because it has only a single category of anchorates as microscleres, as opposed to the anchorates and raphides observed in M. (B.) pistillaris, and the two categories of anchorates and two categories of sigmas observed in M. (B.) magna and M. (B.) sigmatifera. Topsent (1916) described the tornotes in M. (B.) pistillaris as being curved, a trait observed only seldom in the new species.
Both African species described by Lévi (1960, 1963), viz. M. (B.) myxilloides and M. (B.) sigmatifera, respectively, so closely resemble each other that the hypothesis of non-conspecificity has been reevaluated here from reexamination of dissociated spicule slides from both holotypes (Table 10). The only points of distinction seen were the relatively larger dimensions of megascleres and sigmas I in M. (B.) sigmatifera. It is worth noting that the studied microscopic preparation of the South African species is contaminated by a reasonable number of arcuate chelae, which are nearly as abundant as the large anchorate ones. From scanning Lévi’s (1963) descriptions of poecilosclerid sponges, it becomes apparent that the arcuates come from Phorbas dayi (Lévi, 1963; as Anchinoe d.). Nevertheless, the remaining spicules of the latter species were not observed along side the arcuate isochelae.
Myxilla (B.) pedunculata as originally described by Lundbeck (1905) might be the closest known relative of the new species, albeit its widely distant occurrence in the Boreal eastern Atlantic. All spicule categories have comparable dimensions, and only a single category of anchorates constitutes all the microscleres present in both species. Slight exceptions to this overall similarity are the mucronate terminations of tornotes, in M. (B.) pedunculata, instead of being basally microspined; the pedunculate habit of Lundbeck’s sponge; and the possible occurrence of acanthostyles [referred to as “stylus from embryo”, in Lundbeck (1905)]. Koltun (1959) further reported on acanthostyles being present in M. (B.) pedunculata, but as a variation within the main style category, rather than an additional megasclere category. In any case, these observations by Lundbeck (1905) and Koltun (1959) on the likely occurrence of acanthostyles in their Boreal species strengthens the argument for nonconspecificity of both species. It appears thus there is no species possibly so close to the new species that doubts might be shed on its validity.
description: Published as part of Hajdu, Eduardo, Desqueyroux-Faúndez, Ruth, Carvalho, Mariana De Souza, Lôbo-Hajdu, Gisele & Willenz, Philippe, 2013, Twelve new Demospongiae (Porifera) from Chilean fjords, with remarks upon sponge-derived biogeographic compartments in the SE Pacific, pp. 1-64 in Zootaxa 3744 (1) on pages 50-51, DOI: 10.11646/zootaxa.3744.1.1, http://zenodo.org/record/5271084