Placospongia cristata Boury-Esnault, 1973

Sandes, Joana, Moraes, Fernando & Muricy, Guilherme, 2024, Taxonomy of Placospongia Gray, 1867 from Northern and Northeastern Brazil, with description of two new species (Porifera: Demospongiae: Clionaida), Zootaxa 5405 (4), pp. 495-525 : 506-509

Placospongia cristata Boury-Esnault, 1973

( Figs. 4–6 ; Tables 2–4 and 7 )

Synonyms

Placospongia cristata Boury-Esnault, 1973: 276 ; Hechtel 1976: 253; Bispo et al. 2006: 24; David-Colón et al. 2023: 507 ; Bettcher et al. 2023: 465 .

Placospongia melobesioides sensu Arndt 1927: 142 ; Hechtel 1969: 32 (non Placospongia melobesioides Gray, 1867 ).

Placospongia sp. 1 sensu David-Colón & Marín-Casa 2020.

Placospongia ruetzleri sensu Bettcher et al. 2023: 450 (in part) (non Placospongia ruetzleri van Soest, 2017 ).

? Placospongia melobesioides sensu Schmidt 1870: 72 ; de Laubenfels 1936: 153; de Laubenfels 1953: 540; Collin et al. 2005: 658.

Material examined. Holotype of Placospongia cristata Boury-Esnault, 1973 : MNHN-IP-2015-740, formerly MNHN. LBIM.D.NBE 960 (fragment deposited in UFRJPOR 3382), R / V Calypso sta. 29, off Porto de Galinhas, Pernambuco State, Brazil (8º28’S, 34º55’W), 25 m depth, leg. R / V Calypso; MNRJ 29661, Coroa Alta reef, Santa Cruz Cabrália city, Bahia State, Brazil (16º13.200’S, 38º57.038’W), intertidal, colls. Aline Fioravanso & Marianela Gastaldi, 22 April 2019 (= Placospongia ruetzleri sensu Bettcher et al. 2023 ).

Description ( Fig. 5a ). Shape thinly encrusting, 10 x 5 x 1 mm (length x width x thickness), attached to a carbonate fragment. The surface has smooth cortical plates separated by pore-bearing grooves. The consistency is hard, but fragile. The color is whitish beige in ethanol ( Fig. 5a ).

Skeleton ( Fig. 5b–d ). The cortex is 250–400 µm thick, distinct from the choanosome ( Fig. 5b ). The inner layer of the cortex is densely packed with selenasters and the outer layer consists of randomly distributed spherasters and micro-spheroxyasters ( Figs. 5c– d ). The choanosomal skeleton is formed by sparse tylostyles tracts 90–150 µm thick which run obliquely from the substrate to the cortex ( Fig. 5b ). The micro-spheroxyasters occur abundantly in the choanosome, often in clusters, lining the choanosomal cavities. Immature selenasters and spherasters are scattered throughout the choanosome.

Megascleres ( Fig. 6a–d ; Tab. 4 ). Two categories of tylostyles, both of them straight, with blunt ends and rounded tyle ( Figs. 6b and 6d ). Tylostyles I are large and choanosomal: 430–668–910 / 6–10–13 µm, tyle width 7–12–15 µm ( Fig. 6a–b ). Tylostyles II are small and cortical: 210–283–340 / 2–6–8 µm, tyle width 7–8–10 ( Fig. 6c–d ).

Microscleres ( Figs. 6e–i , Tab. 4 ). Mature selenasters are ellipsoid to rounded, with fused spines, forming rounded or polygonal plates: total size 37–44–57 / 30–42–48 µm, hilum 4–6–9 µm in diameter ( Fig. 6e ). Three types of immature selenasters: immature selenasters I straight, slender, spiny, with spines concentrated on the ends of the shafts: 17–20–23 / 2–4–6 µm; immature selenasters II elongated, stout, with large and numerous spines: 25–28–30 / 10–13–18 µm ( Fig. 6f ); immature selenasters III ellipsoid, stout, with spines very closely set, but still recognizable in their individuality: 32–39–43 / 17–24–28 µm. Spherasters are large, smooth, with short and conical rays: 10–15–25 µm in diameter ( Fig. 6g ). Micro-spheroxyasters have smooth rays, with an irregular center: 1–2–3 µm in diameter ( Fig. 6h–i ).

Habitat. This species occurs in the intertidal zone, in a shaded microhabitat ( Bettcher et al. 2023), to 25 m depth ( Boury-Esnault 1973).

Geographical distribution ( Fig. 4 ; Tab. 2 ). Caribbean Sea: Curaçao (Ardnt 1927 as P. melobesioides ), Barbados ( Hechtel 1969 as P. melobesioides ), Colombia ( David-Colón et al. 2023). Northeast Brazil: Pernambuco State ( Boury-Esnault 1973) and Bahia State ( Bispo et al. 2006; Bettcher et al. 2023).

Taxonomic remarks. Placospongia cristata is herein characterized by the combination of two categories of tylostyles, ellipsoid to rounded mature selenasters, spherasters of the typical golf-ball shape and micro-spheroxyasters. In the original description, Boury-Esnault (1973) reported only the presence of tylostyles, selenasters and spherasters as spicular components. Our re-examination of the holotype and its spicules in SEM allowed us to confirm the presence of micro-spheroxyasters, as supposed by van Soest (2009).

Besides the type locality in Pernambuco State, P. cristata was also described from Bahia State ( Bettcher et al. 2023) and the Colombian Caribbean ( David-Colón et al. 2023), with the first in situ photographs of this species. The specimens from Bahia State are thinly encrusting and orange-brown in color ( Bettcher et al. 2023), while the Caribbean specimens are thicker, with creeping and erect lobes or branches, and dark brown to chocolate-brown in color ( David-Colón et al. 2023). The spicules of these populations conformed with the holotype re-examined here, except for the larger and thicker size of tylostyles and selenasters in the Caribbean populations and the presence of a few spirasters in one specimen from Bahia State ( Tab. 4 ). Despite these small differences, we consider the Brazilian and Colombian populations to belong to a single species, widely distributed in the Tropical Atlantic realm.

Rützler (2002) and Mothes et al. (2006) suggested that P. cristata could be a junior synonym of P. melobesioides based on the shared presence of spherasters and absence of spirasters, despite the large geographical distance between Northeast Brazil and Borneo, type locality of P. melobesioides . The two species also share the rounded shape of the selenasters and the presence of micro-spheroxyasters (cf. Becking 2013 as spherules). However, as noted by van Soest (2009), the choanosomal tylostyles of P. cristata are much smaller (430–600 µm) than those of P. melobesioides (670–1010 µm; Tab. 3 ). Furthermore, in P. cristata the spherasters are more abundant and the selenasters are slightly smaller than in P. melobesioides (37–57 vs. 45–68 µm; Tab. 3 ). Therefore, we agree with van Soest (2009) that P. cristata and P. melobesioides are different species, although closely related.

The similarity between P. cristata and P. melobesioides led van Soest (2009) to propose that the records of P. melobesioides from the Central Western Atlantic ( Schmidt 1870; Arndt 1927; de Laubenfels 1936; Gonzáles-Farías 1989) could in fact belong to P. cristata . David-Colón et al. (2023) also considered the records of P. melobesioides from Barbados ( Hechtel 1969) and Gulf of Mexico (de Laubenfels 1953) and the record of P. intermedia from Panama ( Collin et al. 2005) as belonging to P. cristata . However, the record of P. melobesioides by de Laubenfels (1936) included only selenasters and was considered unrecognizable by Hechtel (1969). Schmidt (1870), de Laubenfels (1953) and Collin et al. (2005, as P. intermedia ) did not describe the spicules of their specimens, and Sollas (1888) did not find spherasters in Schmidt’s type slides. On the other hand, van Soest (2009) reexamined the specimens of Arndt (1927) and found spherasters similar to those of P. cristata , and all the spicules described by Hechtel (1969) conform to the holotype of P. cristata . Therefore, we agree that the records of P. melobesioides from Curaçao and Barbados (Ardnt 1927; Hechtel 1969) are likely synonyms of P. cristata , but all records of P. melobesioides from the Caribbean need to be reevaluated. The records of P. melobesioides from the Gulf of Mexico (González-Farías 1989) and from North Brazil ( Mothes et al. 2006) belong to the new species Placospongia beatrizae sp. nov. ( Tab. 7 ) and are discussed below in its taxonomic remarks.

Figures

FIGURE 4 Distribution of the Placospongia species that occur in Brazil. See Table 2 for localities and references. (1) Placospongia sp. = Placospongia carinata sensu Hechtel (1976); (2) Placospongia sp. = Placospongia carinata sensu Drescher et al. (2005); and (3) Placospongia sp. = Placospongia melobesioides sensu Leonel et al. (2011).

FIGURE 5 Placospongia cristata (Holotype, MNHN-IP-2015-740, former MNHN.LBIM.D.NBE 960). a Fragment of the holotype (light brown) on a mollusc shell (yellow/orange); b Cortex and choanosome in transversal section; c Outer and inner cortex, showing a spheraster in the outer cortex (arrow); d Outer and inner cortex, showing the micro-spheroxyasters in the outer cortex (arrow).

FIGURE 6 Spicules of Placospongia cristata (Holotype, MNHN-IP-2015-740, former MNHN.LBIM.D.NBE 960). a Tylostyle I; b Tyle and end of tylostyle I; c Tylostyle II; d Tyle and end of tylostyle II; e Mature selenasters; f Immature selenaster of type II; g Spheraster; h Micro-spheroxyasters; i Micro-spheroxyaster with an elongated center.