Plakina arletensis, Ruiz & Muricy & Lage & Domingos & Chenesseau & Pérez, 2017

Ruiz, César, Muricy, Guilherme, Lage, Anaíra, Domingos, Celso, Chenesseau, Sandrine & Pérez, Thierry, 2017, Descriptions of new sponge species and genus, including aspiculate Plakinidae, overturn the Homoscleromorpha classification, Zoological Journal of the Linnean Society 179 (4), pp. 707-724 : 711-714

PLAKINA ARLETENSIS SP. NOV.

FIGS 2, 3

Material examined

Holotype: MNHN DJV177 , Grotte Chauve-Souris at 12 m depth, Anse Noire, La Martinique (14 ° 32.024 0 N, 61 ° 05.278 0 W). Collector : T. Perez , 10 December 2013. Slides and a fragment of the holotype were deposited in the sponge collection of the Museu Nacional of Universidade Federal do Rio de Janeiro, Brazil ( MNRJ 18460 ).

Paratype: MNHN DJV178 , Grotte Chauve-Souris at 11 m depth, Anse Noire , La Martinique. Collector : T. Perez , 6 March 2014 .

Other specimens examined

150530-GU6-TP04, Grotte Amedien at 12 m depth, La Guadeloupe (16 ° 30.033 0 N, 061 ° 28.774 0 W). Collector: T. Perez, 30 May 2015 .

150516- MT8 -CR03, Anse Fortune at 7 m depth, La Martinique (14 ° 30.377 0 N, 61 ° 05.850 0 W). Collector: C. Ruiz, 16 May 2015 .

Comparative material examined

Plakina jamaicensis Lenhert & van Soest, 1998 . RBINS POR 70, Chalet Caribe caves, West of Montego Bay, Jamaica (18 ° 27.246 0 N, 77 ° 58.287 0 W). Collector P. Willenz and A. Ereskovsky.

Etymology: Plakina arletensis refers to the little village ‘Les Anses d’Arlet’, close to the cave where this sponge was first found, which is one of the most beautiful places in La Martinique. This is also a special dedication to the kind and warm inhabitants of this village.

Diagnosis: Thin encrusting and white Plakina , with a rugose folded surface, a skeleton made of monolophose, trilophose and tetralophose calthrops, actines with and without terminal spines. Diods and triods are absent. Well-developed mesohyl with a high abundance of prokaryotic symbionts.

Description

Small crust, about 2 – 15 cm in size, 0.2 – 0.5 cm thick. White colour in vivo, becoming slightly cream or light brown in alcohol ( Fig. 2A, B). The consistency is cartilaginous and the surface is rugose and irregularly folded. Oscules are circular, 1 – 2 mm in diameter, with a slightly elevated rim.

Skeleton: The skeleton is dense, especially at the surface which is pierced principally by trilophose calthrops. The choanosomal skeleton has an alveolar arrangement formed by all spicule types ( Fig. 2C).

Spicules: Diods and triods are absent. Calthrops are irregular, abundant, their actines (20 – 30 lm long) being with or without spines. Spines (1 – 4) are short and conical, usually at the basis of each actine ( Fig. 2D, E). Monolophose calthrops are abundant (13 – 28 lm actines long). The lophose actine is distally ramified by 2 – 4 short conical rays with sharp endings ( Fig. 2F). Trilophose calthrops are common; lophose actines ramify close the base in 2 – 3 rays, distally in 2 – 4 smaller rays with terminal spines (ramification pattern 1 proximal, 2 distal, terminal spines; for the terminology of ramification patterns, see Muricy & Dıaz, 2002). The non-lophose actines are 10 – 30 lm long ( Fig. 2G). Tetralophose calthrops are heterolophose and the less abundant spicule type. The three apical actines ramify distally in 3 – 4 rays, then distally in 2 – 5 short rays with terminal spines. The basal actine ramifies distally in two rays, and then distally again in 2 – 3 short rays with terminal spines (ramification pattern 1 distal, 2 distal, terminal spines). The actine length is 5 lm on average ( Fig. 2H; Table 1).

Tissue general organization: The ectosome is 15 – 30 lm thick, separated from the choanosome by subectosomal cavities (15 – 40 lm) with a well-developed system of inhalant/exhalant canals (25 – 140 lm wide). The aquiferous system is leuconoid ( Fig. 3A, B ). Choanocyte chambers, 47 – 78 lm in diameter, are spherical and diplodal ( Fig. 3B, C ).

Cytology: Choanocytes are 3 – 7 lm wide and 4 – 6 lm high, their collar, 40 – 50 lm in diameter, is composed of about 50 microvilli. The choanocyte nucleus is spherical and located on the apical area of the cell (4 – 5 lm in diameter). Their cytoplasm is dense, often with one to five phagosomes of about 1.0 – 1.5 lm ( Fig. 3B, C ). The exo- and endopinacocytes are flat or ovoid (15 – 27 lm long and 7 – 11 lm large), with several vacuoles observed in their cytoplasm ( Fig. 3B – D ). Their nucleus is also flattened (4 – 5 lm in diameter). Choanocytes and pinacocytes are flagellated, underlined by a basement membrane ( Fig. 3C, D ). Few archaeocytes were observed. They have an irregular form with a spherical nucleus 2 lm in diameter ( Fig. 3D, E ).

Symbiotic prokaryotes: Plakina arletensis sp. nov. can be considered as a high microbial abundance (HMA) sponge. Three main morphotypes were easily detected, all three being extracellular and randomly dispersed in most of the mesohyl ( Fig. 3E, F ). The first morphotype corresponds to an abundant ovoid cell (1.5 – 1.8 lm long; 0.4 – 1 lm high), with a more or less dense periplasm. We consider most of the small spherical forms as a perpendicular view of morphotype 1 ( Fig. 3E, F ). The second morphotype, less abundant, has a rod-like to irregular shape (2 – 3 9 0.3 – 0.8 lm) with several translucent vacuoles. The third morphotype, less abundant, has the same ovoid form and dense periplasm as the first morphotype, but is bigger (3 – 5 9 1 – 1.7 lm) ( Fig. 3E, F ).

Ecology: Plakina arletensis sp. nov. is found only in shallow water caves, where it forms a white crust with a patchy distribution on vertical walls. No indications of epibiosis or predation were observed.

Taxonomic remarks

Plakina arletensis sp. nov. has a growth-form typical of the ‘true’ Plakina species. It has mono-, tri- and tetra-lophose calthrops like the Mediterranean species P. trilopha Schulze, 1880 , P. jani Muricy, Boury-Esnault, Bezac & Vacelet, 1998 , P. endoumensis A, abundant; C, common; R, rare (see Muricy et al., 1998 for a description of the ramification patterns). Muricy, Boury-Esnault, Bezac & Vacelet, 1998 and P. weinbergi Muricy, Boury-Esnault, Bezac & Vacelet, 1998 or like P. jamaicensis from the Caribbean Sea or P. coerulea Cedro, Hajdu & Correia, 2013 from northeastern Brazil. In contrast to these two sponges, the new species does not possess diods or triods ( Table 1). The tetralophose calthrops are heterolophose, but not candelabra-like as in Corticium . The basal actin is best described as bifurcated, with different ramification patterns in comparison with the apical actines. This type of heterolophose calthrops can be observed in other Plakina species such as P. jani and P. endoumensis ( Muricy et al., 1998) .

Plakina arletensis sp. nov. has a well-developed mesohyl, with subectosomal cavities similar to P. trilopha , P. jani and P. kanaky Ruiz & Perez, 2015 ( Table 2). As with most Plakina species, the new species does not have vacuolar cells in the mesohyl, but prokaryote symbionts are abundant ( Muricy et al., 1999). In addition to the similarities in morphological traits, the assignment of the new species to Plakina is also highly supported by phylogenetic analyses. The CO1 sequences for our new species show it clustering with other Plakina species and also show it to be a distinct species (see below).

PLAKINA NATHALIAE ( ERESKOVSKY, WILLENZ &

Figures

Figure 3. A, general soft tissue organization of Plakina arletensis sp. nov. B, detailed view of the mesohyl, showing the aquiferous system. C, transmission electron micrograph of a choanocyte chamber. D transmission electron micrograph with archeocytes and pinacocytes. E, transmission electron micrograph showing the abundance of prokaryotic cells inside the mesohyl and the three main morphotypes (1–3). F, transmission electron micrograph with a detailed view of the prokaryote symbionts (1–3). Ar, archeocytes; cc, choanocyte chamber; Ch, choanocyte; en, endosome; EC, exhalant canal; Mb, basement membrane; M, mesohyl; ph, phagosome; Pi, pinacocytes; Pk, prokaryotes.