Trikentrion muricatum

Field: Agricultural and Biological Sciences (Life Sciences)

Trikentrion muricatum (Linnaeus, 1759) Figs 20A–E Spongia muricata Linnaeus, 1759: 1348, sp. 8; Pallas 1766: 389, sp. 237 (including Boddaert 1768: 490 and Wilkens 1787: 225, pl XXII fig. 72); Linnaeus 1767: 1298, sp. 10; Esper 1790: pl. III (not: pl. VII fig. 1 = Callyspongia (Cladochalina) aculeata, cf. above), 1794: 185 (text); Gmelin in Linnaeus 1791: 3821, sp. 10. Trikentrion muricatum; Van Soest et al. 2012: 41, figs 17A–D, 18A–E, 19A–D, 20A–D (with further references, synonyms and extensive discussions). Original description: ‘ Spongia ramosissima, poris cylindricis subulatis prominentibus aequalibus multifidis hispidis’ (i.e. a strongly branched sponge with cylindrical pores and with prominent spines and equal multifid hispidations). Type material: Van Soest et al. (2012) proposed BMNH 1872.10.19.1 from Ghana, Volta River, Fantee, approximate coordinates 5.7°N 0.667°E, as neotype for Spongia muricata. This locality is close to the assumed type locality of Elmina. Unfortunately, this is a dried specimen, but so far no ‘wet’ specimens of this species are known to exist in museum collections, nor have there been recent fresh collections of the species. Molecular sequences: none. Remarks: This species was extensively discussed in Van Soest et al. (2012). These authors concluded that authorship for the species should go to Pallas (1766), but they overlooked the additional information cited in Linnaeus’ pre-1759 works. Linnaeus’ 1759 description was copied from Linnaeus (1753a: 118, pl. XI fig. 1, abbreviated as ‘ Spongia hispida’). The full description was also copied to Linnaeus 1753b: 1170, in which the source was given as ‘Mus. Tess. Habitat in India’, but this locality was not mentioned in the original 1753a text, so it is unclear where this information came from. The 1753a paper was authored by Linnaeus but the frontispiece lacks his name, instead of which the publication is usually referred to as ‘Museum Tessinianum’ concerning a collection owned by Carl Gustav Tessin from Sweden, which was catalogued by Linnaeus. The image shown in this publication (here reproduced in Fig. 20A) more or less resembles what is currently understood as Trikentrion muricatum (see e.g. Van Soest et al. 2012, with more convincing illustrations copied from Seba, Ellis and Esper, not repeated here, but see above for the references). Pallas (1766: sp. 237) did not acknowledge Linnaeus as having described the species. He referred to Seba (1758: 188, pl. XCIX fig. 7, ‘ Spongia ramis crassiusculis tenax tota superficie apiculis tenuibus, mollibus, dense consita’ (i.e. a sponge with thick tenacious branches the entire surface of which is densely planted with thin soft spikes), who reported the specimen from Elmina, West Africa, with a clear image in his pl. 99 fig.7 (see Van Soest et al. 2012: fig. 17). Later authors, Ellis (1766) and Esper (1790, 1794), confirmed that the species originated in West Africa, not as Linnaeus was initially led to believe, from the Indian Ocean. The German translation of Pallas’ work by Wilkens (1787: 225, pl. XXII fig. 72) listed Spongia muricata (as ‘Der Stachelschwamm’) and he copied the habitus from Seba, here reproduced as Fig. 20B. Importantly, Wilkens extended (p. 226 ‘Zusatze’) the references with Linnaeus’ 1753a record of ‘ Spongia hispida’ from Museum Tessinianum, which was omitted by Pallas, and also referred to a ‘new’ author, Kundmann (1737: 162, pl. IX fig. 12, as ‘ Fucus marinus’, here reproduced as Fig. 20C), not treated earlier by Van Soest et al. (2012). Van Soest et al. (2012) argued that Pallas should be the author of the species, because Linnaeus’ original description was unrecognizable. However, these authors were not aware of the image in Linnaeus (1753a: pl. XI fig. 1), which is sufficiently similar to Seba’s, Ellis’ and Esper’s images to postulate that Linnaeus is the valid author and that Pallas should have acknowledged that. Accordingly, Trikentrion muricatum (Linnaeus, 1759) is the proper author-year for this combination. Species diagnosis: (after Van Soest et al. 2012: 41, figs 17A–D, 18A–E, 19A–D, 20A–D). (Groups of) Thick cylindrical branches densely covered with flattened papillae rise up from a small and low holdfast. Groups may have a shared holdfast or divide into groups from a single very thick short stalk. Branches divide twice or three times into slightly thinner branches ending roundly or sometimes more pointedly. The neotype consists of two groups of branches with in total 12 branches, but additional specimens may have up to 20 branches. The height of an entire specimen may be up to 20 cm, with branch thickness 2–5 cm. The papillae are 1–4 mm in size. Consistency hard in dried condition, no live or wet specimens are known. Colour is also only known from dried specimens, reddish brown, but if colour plates of Seba and Esper are based on on-deck specimens the species is orange-brown. Skeleton a wide-meshed reticulation of thick irregular tracts of robust oxeas, with loose polyactines concentrated at the surface, intermingled with trichodragmas. Oxeas fusiform, 222–528 x 13–21 µm; polyactines Y-or T-shaped, with basal clade having hooked spines in the lower half, the upper half and both lateral clades smooth; overall size of basal clade 79–156 x 12–27 µm, lateral cladi 42–84 x 12–27 µm; trichodragmas 57–102 x 4–18 µm. No recent fresh collections of this species have been made. A photo of the neotype reproduced from Van Soest et al. (2012) is here reproduced in Fig. 20D. Distribution (Fig. 20E): The species is only known from the Gulf of Guinea, tropical West Africa.