Plakina coerulea Cedro & Hajdu & Correia 2013, sp. nov.
Creators: name: Cedro, Victor R.
name: Hajdu, Eduardo
name: Correia, Monica D.
Publisher: name: Zenodo
Year: 2013
Subjects: Biodiversity
Taxonomy
Animalia
Porifera
Homoscleromorpha
Homosclerophorida
Plakinidae
Plakina
Plakina coerulea

description: 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.
description: Published as part of 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, pp. 2151-2174 in Journal of Natural History 47 (33 - 34) on pages 2153-2158, DOI: 10.1080/00222933.2013.792962, http://zenodo.org/record/5197504