Plakina coerulea, Cedro & Hajdu & Correia, 2013

Cedro, Victor R., Hajdu, Eduardo & Correia, Monica D., 2013, Three new intertidal sponges (Porifera: Demospongiae) from Brazil’s fringing urban reefs (Maceió, Alagoas, Brazil), and support for Rhabderemia’s exclusion from Poecilosclerida, Journal of Natural History 47 (33 - 34), pp. 2151-2174 : 2153-2158

Plakina coerulea sp. nov.

Holotype

MNRJ 14295 (cross ref. EH–056), Piscina dos Amores Reef (09 ◦ 40 ′ 35 ′′ S, 035 ◦ 42 ′ 07 ′′ W), Maceió (AL, Brazil), intertidal, coll. E Hajdu, VR Cedro and MD Correia, 1 February 2010. Schyzoholotype, UFAL – POR 0621 .

Diagnosis

Plakina coerulea sp. nov. is the only Plakina combining azure-blue live colour, and a spicule complement of diods up to 90 µm, triods up to 60 µm and tetralophose calthrops as the only category of lophose calthrops.

Description

Small single specimen found, encrusting, c. 2 cm in greatest diameter ( Figure 2A ), slightly compressible and crumbly, surface microtuberculated. Single circular oscule (approx. 0.5 mm in diameter), encircled by thin, slightly contracted, transparent membrane, suggesting that oscule attains larger dimension. Reticulation formed by subectosomal canals visible on close-up photographs. Colour alive: azure-blue, slightly faded in alcohol.

Skeleton ( Figure 3A ). Ectosomal skeleton microhispid, pierced by abundant spicules of every category. Choanosome, dense, with alveolar arrangement masked by abundant criss-crossed spicules. Larger canals or lacunae also present, more conspicuous closer to the base of the sponge, and in subectosomal area.

Spicules ( Table 1). Diods ( Figure 3B, C ), common, usually fusiform, slightly curved in one or both actines, centrotylote-like, with variously developed central swelling (frequently up to three or four thorns in a whorl), and sharp ends. Length 63– 78.8 –90 µm, width 3– 5.6 –7 µm. Triods ( Figure 3D ), very variable on actine size and thickness, commonly regular–trigonal or y-shaped, rarely diod-like. Diameter 44– 50.3 –61 µm. Calthrops ( Figure 3E, F ), strikingly variable in development of actines, ranging from diod-like to triod-like forms, sometimes with one or two rounded/bulbous undeveloped actines. Diameter 41– 45.3 –55 µm, width 5– 6.5 –9 µm. Tetralophose calthrops ( Figure 3G–I ), regular, with well-developed lophose actines with three to five ramifications, ending on trifurcated or tetrafurcated pointed ends. Diameter 15– 17.7 – 20 µm. Microrhabds ( Figure 3J ), single spicule found and considered allochthonous.

Ecology

A single specimen was found in our surveys of the sponge fauna of Maceió City’s coastal reefs. It occurred in a shallow crevice on the underside of a medium-sized coral boulder, beside Spirastrella hartmani Boury –Esnault et al., 1999 ( Spirastrellidae ) and a didemnid tunicate.

Distribution

The species is a provisional Brazilian endemic, so far known only from its type locality (intertidal Maceió’s urban reefs – Piscina dos Amores, Figure 1A ).

(Continued) P. trilopha Schulze, 1880 d , 40–88 10–35 ml, 20–30

(sensu Muricy et al. t, 12–33 dl, 20–35

1998) tl, 16–27

ttl, 10–25

White pinkish – East and west Mediterranean, Azores

P. weinbergi Muricy et al. d, 29– 37.1 –52/3–5 16– 20.8– 36/3–4 ml, 41– 44.5 –50/3–4 Light-yellow – East

1998 t, 17– 28.5 –41/3–5 dl, 42– 44.2 –46/3–4 Mediterranean

tl, 22– 33.2 –47/3–4

ttl, 19– 29.3 –35/3–3.5

Remarks

Plakina coerulea sp. nov. is one of the few Plakina spp. bearing tetralophose calthrops, formerly known from Plakina endoumensis , P. jani , P. jamaicensis , P. reducta , P. tetralopha , P. tetralophoides , P. trilopha and P. weinbergi ( Muricy et al. 1998) . Plakina endoumensis , P. jani , P. trilopha and P. weinbergi possess additional categories of calthrops and are therefore easily distinguishable from the new species. Plakina reducta and P. tetralopha possess considerably larger tetralophose calthrops, respectively up to 60 µm and up to 30 µm, and are therefore also easily differentiated from the new species. Plakina jamaicensis possesses considerably larger diods (up to 120 µm) and P. tetralophoides considerably smaller diods (up to 40 µm) when contrasted with the new species, which is therefore clearly set apart from all the possibly closer species of Plakina .

Figures

Figure 1. Map showing South America and Brazil, with Alagoas state in black (upper left), an expanded Alagoas state with Maceió city in black (upper middle), and the collecting localities off Maceió ((A) Piscina dos Amores; (B) Riacho Doce; (C) Ponta do Meirim; (D) Ponta do Prego).

Figure 2. In situ photographs of the new species described in this study. (A) Plakina coerulea sp. nov. (holotype, MNRJ 14295 at Piscina dos Amores); (B) Rhabderemia meirimensis sp. nov. (holotype, MNRJ 14275 at Ponta do Meirim); (C) Mycale (Aegogropila) rubra sp. nov. (paratype, MNRJ 14050 at Praia do Francês). Scale bars: 1 cm.

Figure 3. Plakina coerulea sp. nov. (holotype, MNRJ 14295). (A) Transverse section of skeleton. (B–J) Scanning electron micrographs of the spicule complement: (B, C) diods; (D) triod; (E) calthrops; (F) reduced calthrops; (G, H) tetralophose calthrops; (I) tetralophose calthrops in G in greater detail; (J) rugose microrhabd. Scale bars: A, 500 µm; B–H, 20 µm; I, J, 5 µm.