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Keywords:

  • Cliona parenzani;
  • Clionaidae;
  • Eastern Mediterranean;
  • Porifera

Abstract

  1. Top of page
  2. Abstract
  3. Problem
  4. Material and Methods
  5. Results
  6. Discussion
  7. Conclusions
  8. Acknowledgements
  9. References

An excavating sponge, which covers extensive areas of limestone rock, has been found at several locations of the Eastern Mediterranean Sea. This zooxanthellate clionaid, brown with yellow oscula, may have an extension of several square meters under the β-form, similar to what has been described in coral reef areas. It has been observed at 3–30 m depth, generally in clear water in the Ionian Sea, Crete, Cyprus and Lebanon. The gross morphology and the spicule characters are described from all the collected specimens. The spicule complement, with variable tylostyles and rare, sometimes absent, thin spirasters, is compared with that of Cliona parenzaniCorriero & Scalera-Liaci 1997 from the Apulian coast (Ionian Sea, Mediterranean Sea), and of several Caribbean and Indo-Pacific clionaid species, which display the same morphology and rather similar spicule characters. The sponge is tentatively identified as C. parenzani, although there are some differences with the type specimens in the highly variable spiculation, suggesting that it may represent a species complex similar to what is known for other species in the Caribbean and Indo-Pacific areas. Although the sponge appears to be closely related to large brown spreading clionaids from tropical areas and was previously practically overlooked in the Eastern Mediterranean, it does not appear to be a recent introduction. It is suggested that it could be a survivor in the warmer area of the Mediterranean of an ancient thermophilous fauna, which did not survive in the colder Western Basin during glacial episodes of the Pleistocene.


Problem

  1. Top of page
  2. Abstract
  3. Problem
  4. Material and Methods
  5. Results
  6. Discussion
  7. Conclusions
  8. Acknowledgements
  9. References

In the Caribbean as well as in tropical Pacific areas, coral reefs, and rocky limestone in general, are frequently excavated by highly destructive clionaid sponges, which may impressively cover several square meters (Rützler 2002; Zea & Weil 2003). These sponges, associated with zooxanthellae, are dark brown, and often with conspicuous yellowish oscula. In the Pacific, they are known as Cliona orientalis Thiele, 1900 (Vacelet 1981; Schönberg 2000, 2001b, 2003) and Cliona albimarginata (Calcinai et al. 2005), and probably each represent a species complex. In the Caribbean, they have been referred to as the species complex of Cliona caribbaea Carter, 1882–Cliona aprica Pang, 1973–Cliona tenuis (Zea & Weil 2003; López-Victoria & Zea 2005). The resemblance in gross morphology, ecology and spicule characteristics between these two geographically widely separated species complexes (Caribbean and Pacific), and the increase in these clionaids over the past few decades in the coral reefs of the Caribbean, suggested to Zea & Weil (2003) that these species complexes may be related, the Caribbean species possibly having been introduced from populations of C. orientalis from the Pacific. This hypothesis, however, remains highly speculative.

To date, these clionaids are localized in tropical coral reef areas and were not clearly recorded from the Mediterranean. Alpha and β forms (respectively with excavating chambers communicating through external papillae, and encrusting growth form because of merging of papillae) of Cliona celata and Cliona viridis are well known in the Mediterranean, but their morphological characters and the surface area they cover are notably different. A clionaid of the C. viridis group, Cliona parenzani has been described from the Ionian Sea (Apulian coast, Italy) by Corriero & Scalera-Liaci (1997) in the β stage with a surface cover of up to 2500 cm2, and according to the authors’ description, more closely resembles the tropical forms. However, C. parenzani was not compared with its possible tropical relatives. Here, we report the presence at various locations in the Eastern Mediterranean of sponges displaying a highly variable spiculation that are very similar in shape, color, habit and extension to tropical clionaids. The record of these conspicuous clionaid sponges in the Eastern Mediterranean raises several problems of biogeography and taxonomy.

Material and Methods

  1. Top of page
  2. Abstract
  3. Problem
  4. Material and Methods
  5. Results
  6. Discussion
  7. Conclusions
  8. Acknowledgements
  9. References

The localizations where the species was recorded in the Eastern Mediterranean are reported in Fig. 1.

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Figure 1.  Location map showing records of Cliona parenzani.

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Specimens were observed and collected by SCUBA diving. Photographs were taken in situ using Nikonos and underwater digital cameras. The samples were preserved in formalin or in ethanol generally a few hours after collection.

For the study of spicules by both light and scanning electron microscopy (SEM), a small piece of sponge tissue was boiled in a few drops of nitric acid on a microscopic glass slide, as described in Vacelet (2006). The slide was then either mounted in Araldite® for light microscopy or sputter-coated with gold–palladium, then observed under a Hitachi S570 SEM. Spicule size was measured using light microscopy on 50 spicules, or less for microscleres, which were very rare. Spicules dimensions are presented as range (mean ± SD); the number of measurements was indicated when different from 50.

The histology and skeletal architecture were studied by light microscopy on thick polished sections obtained by sawing small pieces of specimens stained in toto in acid fuchsine and embedded in Araldite® with a low speed saw using a diamond wafering blade, and wet-ground on polishing discs.

Results

  1. Top of page
  2. Abstract
  3. Problem
  4. Material and Methods
  5. Results
  6. Discussion
  7. Conclusions
  8. Acknowledgements
  9. References

General description

Brown clionaid sponges covering extensive surface areas were observed in several places in the Eastern Mediterranean Sea (Table 1). At all locations, the sponge occurred under full light conditions on sub-horizontal rocky areas in relatively pristine areas, apparently not in the vicinity of sewage or any other source of organic pollution. The covered area varies from a few square centimeters to an impressive cover of several square meters (Fig. 2). The cover is complete on large surfaces, except for some specimens from Lebanon III (Ramkine Island, Table 1), which display a variable amount of lacunae (Fig. 2F). The limestone substratum is excavated to a depth of 5–15 mm, with cavities 1–2 mm in diameter (Fig. 3B) bearing excavation scars 27–63 μm in diameter (Fig. 6A). The colour varies from brown to deep brown in surface, and is dull yellow inside, uniformly dark brown in preservative. The oscula, 1.6–2 mm in diameter with a spacing of approximately 20 mm, are prominent for their yellow raised margin, 1.6–1.8 mm high (Fig. 3A). The surface is mammillate, with roundish processes corresponding to pore sieves, irregular and poorly differentiated in specimens incompletely covering the substratum, more regular and in the shape of low mammillate processes in specimens entirely covering the substratum. The skeleton is made of tylostyles arranged in an irregular palisade in the pore-sieves and around the oscules, with a poorly defined radial arrangement at the surface and dispersed without order in the inner parts (Fig. 4). The spirasters, always few in number, and not seen in several specimens, are mostly located around the canals. Rare flexuous oxea, 560–600 × 5–6 μm, probably belonging to the sponge, have been observed in the samples from Cyprus II and Crete. The histology has only been observed in specimens from Zakynthos Island and from Cyprus II (Fig. 4). The choanocyte chambers are 24–30 μm in diameter. The choanosome and superficial tissue contain numerous zooxanthellae, 7.5–8 μm in diameter (Fig. 4B), and large amoeboid cells, up to 24 × 18 μm, full of small granules 1–2 μm in diameter.

Table 1.   Mean spicule size (in μm ± SD) in the various specimens. Measurements on n = 50 spicules unless otherwise stated.
 location and datetylostyle lengthtylostyle diametertylostyle shapespiraster lengthspiraster diametersmooth spirasters
Ionian SeaC. parenzani, from  Corriero & Scalera-Liaci 1997300–500 (424.5 ± 50.0)7.5–15 (12.3 ± 2.3)Head globular, sharp long point25–50 (38.4 ± 6.2)1–2 (2 ± 0.7)2–60 × 1–2
Zakynthos (Ionian Sea)Off Zakynthos Island near Agios Nikolaos June 1959185–480 (370.5 ± 53.9)6–11 (9.1 ± 1.4)Head globular, tip short, acerate7.5–45 (25.8 ± 9.7) n = 251.2–2.2 (1.4 ± 0.3), n = 25 
Cyprus IIBaths of Aphrodite, May 2005235–505 (407.08 ± 54.6)5–9 (5.6 ± 1.0)Head poorly inflated7.5–42.5 (25.1 ± 8.6) n = 151.25–1.6 (1.3 ± 0.1) n = 15 
RhodesKallithea Bay, September 2005235–450 (362.4 ± 52.7)5–10 (6.6 ± 1.3)Head globular, tip acerate   
Lebanon IChak El Hatab, July 2003260–450 (381.8 ± 39.7)5–10.1 (7.3 ± 1.4)Head globular, tip acerate7.5–42.5 (23.1 ± 7.9) n = 301.2–2 (1.3 ± 0.2), n = 30 
Lebanon IISelaata, near Batroun July 2003230–800 (455.9 ± 102.4)5–12.5 (8.7 ± 1.8)Head globular, tip acerate7.5–37.5 (26 ± 8.2), n = 201.2–2 (1.4 ± 0.2), n = 20 
Lebanon IIIRamkine Island, near Tripoli July 2003185–375 (281.7 ± 49.3)2–5 (4.2 ± 0.9)Variable, frequently ill-formed10–30 (18.7 ± 7.2), n = 61.18–2 (1.3 ± 0.3), n = 6 
Crete IWest coast, near Elafonissi, October 2006190–320 (256.1 ± 39.4)2–7 (3.7 ± 1.2)Head globular, tip blunt   
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Figure 2.  Underwater photographs of Cliona cf. parenzani. A: Cyprus I (Cape Pyla), 15 m. B: Cyprus I (Cape Pyla), 3 m. C: Cyprus I (Cape Pyla), 15 m. D: Lebanon II (Selaata), 5 m. E and F: Lebanon III (Ramkine Island), 6 m.

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Figure 3.  A: Underwater photograph of Cliona cf. parenzani from Crete. B: Collected specimen from Zakynthos Island, Greece.

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Figure 6.  A–D: Specimen of Cliona from Lebanon I (Chak El Hatab). A: Excavation scars. B: Tylostyle. C: Malformed head of tylostyle. D: Spiraster. E–H: Specimen from Lebanon II (Selaata). E: Tylostyle. G, H and I: Spirasters. I–M: Specimen from Lebanon III (Ramkine Island). I–L: Tylostyles. M: Spiraster.

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Figure 4.  Polished section of a Cliona specimen and substratum from Zakynthos Island, Greece. A: General view. B: Enlarged view of the same slide.

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Sponge features in different locations

In the Ionian Sea, off Zakynthos Island near Agios Nikolaos (37°54 N, 20°42 E), Greece, an encrusting brown Cliona with prominent yellow oscula was observed and collected on 22 June 1959 (preserved in formalin) (collected by JV). The sponge was covering surfaces of several square meters on sub-horizontal calcareous rock between 10 and 30 m in depth and was excavating the limestone to depths of several millimeters (Fig. 3B; Fig. 4) The spicules are tylostyles and very rare spirasters (Fig. 5A–C). The slightly curved tylostyles are highly variable, generally with a well marked, round head and an acerate point. The head may be trilobate or reduced to a faint oval swelling, and the tip may be mucronate or shortly conical. Size 185–480 (370.5 ± 53.9) × 6–11 (9.1 ± 1.4) μm. The spirasters are thin, feebly curved, with a few short, simple spines. Size 7.5–45 (25.8 ± 9.7) n = 25 × 1.2–2.2 (1.4 ± 0.3), n = 25 μm.

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Figure 5.  A–C: Specimen of Cliona from Zakynthos. A, B: Tylostyles. C: Spirasters. D: Specimen from Crete I, tylostyles. E: Specimen from Rhodes, tylostyle. F and G: Specimen from Cyprus II. F: Tylostyle. G: Spiraster.

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In Lebanon, a similar clionaid has been observed and collected at three localities:

  • I)
    In Chak El Hatab (34°17′64′′N, 35°40′26′′ E), on 5 July 2003, numerous specimens of the sponge, brown with yellow oscula were covering the sub-horizontal rocky bottom at 5 m depth (preserved in formalin) (collected by JV, TP, HZ, GB). The spicules (Fig. 6A–D) are similar to those of the Zakynthos Island sample, having tylostyles 260–450 (381.8 ± 39.7) × 5–10.1 (7.3 ± 1.4) μm, generally with a well-marked head, and rare spirasters with a few spines 7.5–42.5 (23.11 ± 7.91) × 1.2–2 (1.35 ± 0.2), n = 30 μm.
  • II)
    In Selaata (north of Batroum, 34°17′05′′ N, 35°39′55′′ E), on 6 July 2003, a brown Cliona encrusting large areas of subhorizontal rocks (Fig. 2D) was fairly common between 3 and 6 m depth (preserved in formalin) (collected by JV, TP, HZ, GB). The spicules (Fig. 6E–H) are tylostyles slightly larger, 230–800 (455.9 ± 102.4) × 5–12.5 (8.7 ± 1.9) μm, with rare spirasters with spines generally simple but sometimes dichotomous, 7.5–37.5 (26 ± 8.2) × 1.2–2 (1.4 ± 0.2), n = 20 μm. At the same location, typical specimens of Cliona viridis of the β form have been collected.
  • III)
    In Ramkine Island (Rabbit Island), north-west of Tripoli (34°29 N, 35°46 E, on 14 July 2003, between 3 and 9 m depth, a brown Cliona sp. was spread over rocky surfaces (Fig. 2E and F) (preserved in formalin) (collected by JV, TP, HZ, GB). The covering of the rock was more or less complete depending on individual specimens. Some were irregularly spread over coarse sediment (Fig. 2F). The tylostyles (Fig. 6I-L) are shorter and thinner 185–375 (281.7 ± 49.3) × 2–5 (4.2 ± 1.0). The tylostyle head, generally spherical or ovoid, is frequently ill-formed, trilobate or shifted along the shaft, and the tip frequently displays a sudden narrowing. The spirasters (Fig. 6M) are very rare, with a few short simple spines: 10–30 (18.7 ± 7.2) × 18–2 (1.3 ± 0.3), n = 6.

In Cyprus, large spreading clionaids have been observed at two locations:

  • I)
    Near Cape Pyla on the south coast (34°56.9′ N, 33°51.5′ E), 30 October 1989 and 31 October 1989, the sponge was covering surfaces of several square meters on horizontal surfaces in a dense facies of the macroalgae Cystoseira sp. and Sargassum sp., 15–17 m depth (Fig. 2A and C) (collected by JV). In the same place, large areas were also covered on sub-horizontal and sub-vertical, anfractuous rocks at 2–3 m depth (Fig. 2B). No specimens were collected.
  • II)
    Near ‘Baths of Aphrodite’ on the west coast (35°03 N, 32°21 E), 3 m depth, similar specimens were observed and collected on 31 May 2005 (preserved in alcohol) (collected by HZ). The megascleres (Fig. 5F) are mostly styles, more rarely tylostyles with a faintly marked head, sometimes substrongyles: 235–505 (407.0 ± 54.6) × 5–9 (5.6 ± 1.0). The spirasters (Fig. 5G) are very rare, with a few spines simple or divided in bouquet: 7.5–42.5 (25.1 ± 8.6) × 1.2–1.6 (1.3 ± 0.1) n = 15.

In Rhodes, Kallithea Bay (36°25′ N, 28°15′ E), 6 m depth, 10 September 2005, (preserved in formalin) (collected by HZ), the sponge was common on sub-horizontal rock surfaces. The spicules (Fig. 5E) are very variable tylostyles, often with a well-marked head and an acerate tip, 235–450 (362.4 ± 52.7) × 5–10 (6.6 ± 1.3). Spirasters have not been observed.

In Crete, specimens have been observed in three locations:

  • I)
    Specimens covering approximately 1600 cm2 were collected on 2 October 2006 on the West coast near Elafonissi (35°22′43′′ N, 23°32′00′′ E), 5 m depth (preserved in alcohol) (collected by TD). The spicules (Fig. 5D) are tylostyles with a variable head and most often a blunt point, 190–320 (256.1 ± 39.4) × 2–7 (3.7 ± 1.2). Spirasters have not been observed.
  • II)
    Another specimen (Fig. 3A) with the same external characters has been observed but not collected in Elounda region (35°15′10′′ N, 25°45′31′′ E) on 11 December 2006, 11 m depth, covering a flat surface of approximately 800 cm2 on a vertical wall.
  • III)
    A third specimen was observed without collection at Agia Pelagia (35°24′18′′ N, 25°02′02′′ E) on 19 May 2007, occupying almost entirely an irregular rock on the bottom, at 25 m depth. Total surface cover was approximately 750 cm2.

In Syria, the sponge has been observed without collection (GB) at three localities: Ras Samra (5 August 2003); El Hamam Island (12 August 2003); Lattakia (11 August 2003).

Although the gross morphological characters appear rather constant in all these specimens, the shape and size of the spicules, mainly of the megascleres, appear highly variable (Table 1, Fig. 7). Most tylostyles have similar size, but the shape of the head, and the proportion of styles or substrongyles are inconsistent. The specimen from Cyprus II-Bath of Aphrodite is distinct by the poorly marked head of the tylostyles, which are rather styles or substrongyles (Fig. 5F). The specimen from Lebanon III-Ramkine Island is distinct in having, in addition to a few normal tylostyles, very slender tylostyles and styles with an acerate end (Fig. 6I–L). In this specimen, the tylostyle head is highly variable, with numerous malformations and a granular silica. The head could be absent or reduced to a terminal enlargement, ovoid, globular up to 8 μm in diameter for a shaft 2 μm thick, or globular mucronate. The point is often mucronate or with a sudden narrowing. These variations are observed in several parts of the sponge body, and are not specific to the growing area of this specimen.

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Figure 7.  Variation in size of Cliona cf. parenzani tylostyles in seven studied sites (Tukey boxes, n = 350, 50 measurements per sampling).

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Discussion

  1. Top of page
  2. Abstract
  3. Problem
  4. Material and Methods
  5. Results
  6. Discussion
  7. Conclusions
  8. Acknowledgements
  9. References

The taxonomic identification of these clionaids is rather problematic. They are closely related by the spicule complement to the β stage of the common sponge which is called, depending on the author, Cliona viridis (Rosell & Uriz 1991, 2002), or Cliona nigricans (Schmidt, 1862) (Rützler 1973; Bavestrello et al. 1996). The genetic identity of C. viridis with C. nigricans has recently been established (Barucca et al. 2007). It is well known that C. viridis has a highly variable spiculation. However, our specimens clearly differ, in color and gross morphology from this common species. They are brown instead of green to whitish green. They are not massive, but thinly encrusting on large surfaces, most often completely covering the substratum and they do not display large exhalant papillae and conspicuous inhalant papillae as in C. viridis. Typical specimens of C. viridis sympatric with the brown clionaids from the Lebanese coasts and collected in the same places also show some differences in the spirasters, which are more numerous, slightly shorter and thicker. However, the variability of the spicule complement both in C. viridis and in our specimens prevents an accurate distinction based only on spicule characters.

All specimens closely resemble in gross morphology Cliona parenzani (Corriero & Scalera-Liaci 1997) from the Ionian Sea, and the tropical clionaids of the Cliona orientalis and Cliona caribbaeaCliona apricaCliona tenuis species complexes. As the specimens occur in sympatry with C. parenzani, identification to this species would seem coherent. However, the spicule complement of our specimens appears to be very variable and does not always matches that described for C. parenzani. All our specimens were devoid of the smooth spirasters, which were considered as a distinctive character of this species (Corriero & Scalera-Liaci 1997). The spicules of the specimens from Zakynthos Island, Rhodes, and Lebanon Chak El Hatab and Selaata are rather similar in shape and size, with tylostyles generally displaying a well-marked globular head as in C. parenzani. These specimens, however, differ from C. parenzani by thinner tylostyles (Table 1) and by the absence of smooth spirasters. The specimens collected from Cyprus differ by tylostyles having a poorly marked head, most often styles. The sample from Lebanon Ramkine Island differs by shorter and thinner tylostyles with a large inflated head irregular in shape and a frequently ill-formed tip, similar to the abnormal spicules, possibly immature, described in some clionaids (Schönberg 2001a) (Fig. 2F). These peculiarities are evident in several preparations from different parts of the specimens, not specifically in growing areas. Another hypothesis could be that there is a local deficiency in the silica content of the sea water, which affects spicule development. Two other sponge species from the same location in Ramkine Island display deficient spiculation. A Plakina sp. has ill-formed spicules, and several specimens of Merlia normani lacking a microsclere category have been found at this site (unpublished data of JV and TP). It has been shown that a deficiency in silica content could influence the spicule complement of demosponges (Maldonado et al. 1999). The identification of all the specimens here studied with C. parenzani is acceptable on the basis of gross morphology, color and spreading habit, but only if one assumes that the spicule complement may be highly variable in this species, as it is frequent in this group of clionaids.

The problem is even more complex, if we compare these sponges with their tropical relatives. The morphology, color and habit of these brown, spreading clionaids from the Eastern Mediterranean are similar to those of the excavating sponges that have been reported as the species complex of C. caribbaeaC. apricaC. tenuis in the Caribbean (Zea & Weil 2003), and C. orientalisCliona albimarginata in the Indo-Pacific (Vacelet 1981; Schönberg 2000, 2001b, 2003; Calcinai et al. 2005). These highly destructive zooxanthellate sponges excavate large surfaces of limestone and coral skeleton, extending up to several square meters. They display the same morphological characteristics: thinly encrusting, brown–black to amber–brown with clearer, most often, yellowish oscular rim and endolithic tissue extending up to 1–2 cm beneath the surface. The morphological similarity is especially evident with C. caribbaea as redescribed by Zea & Weil (2003), and with C. orientalis as redescribed by Schönberg (2000). The Mediterranean clionaid sponges, however, differ from the Caribbean species by thinner tylostyles, with a maximum shaft diameter of 12.5 μm instead of 14–19 μm (but up to 15 μm in the type specimens of C. parenzani), and from C. orientalis by longer and thicker tylostyles (Table 2). The spirasters from the Mediterranean species also generally display simple spines, whereas those of the Caribbean and the Indo-Pacific species are more profusely spined, with frequently bouquet-like divided spines. These differences in spicule complement are rather subtle and probably not very important given the variability of the spicule shape and size in the Mediterranean specimens as well as in those from the tropical areas. However, it is preferable to consider the Mediterranean specimens as a different species rather than identifying them to a geographically very distant species, either from the Caribbean or from the Indo-Pacific. We thus tentatively identify these clionaids as C. cf. parenzani, although keeping in mind that their taxonomic status remains problematic. They may belong to a complex of species having a distinct pattern of distribution, similar to that evidenced in the Caribbean (López-Victoria & Zea 2005). This cannot be determined from the present data, and would need a more methodical sampling combined with a genetic analysis. It may be noted, however, that in contrast to the Caribbean species, no significant difference in gross morphology has been observed at the various locations. Only the specimens from Ramkine Island are somewhat distinct by an incomplete cover of the substratum, a resemblance with C. aprica from the Caribbean (Zea & Weil 2003).

Table 2.   Spicule dimensions (in μm) of several related Cliona species.
 tylostylesspirasters
Cliona viridis (from Rosell & Uriz 2002)80–600 × 1–11 190–520 × 1–11 β stage13–30 × 4–5 and 10–53 × 1–4
Cliona copiosa (=Cliona viridis) from (Sarà 1959)238–455 × 7–10.57–55 × 1–2.6
Cliona aprica (from Zea & Weil 2003)132.427 × 3.8–1912.6–38.5 × 0.4–1.7
Cliona caribbaea (from Zea & Weil 2003)271–465 × 4.7–14.314.9–47 × 0.3–1.5
Cliona tenuis (from Zea & Weil 2003)199.380 × 3.3–14.311–39 × 0.5–1.3
Cliona orientalis (from Schönberg 2000)270 × 725 × 1

It is remarkable to find in the Eastern Mediterranean, a clionaid still unrecorded from other Mediterranean areas and which is similar to several highly destructive species whose populations apparently increased in tropical coral reef environments over the past few decades (Rützler 2002; Zea & Weil 2003). The possibility of a recent introduction into the Eastern Mediterranean should be considered, as the introduction of a similar clionaid from the eastern Pacific to the Caribbean had been hypothesized (Zea & Weil 2003). An arrival via the Suez Canal (Lessepsian migrant) is unlikely, because no spreading brown clionaid has been recorded from the Red Sea, and because specimens referable to C. cf. parenzani were recorded by one of us at its western-most location of the Eastern Mediterranean, Zakynthos Island, as early as 1959 (see Results). Given the high variability of the spicule complement and the possible presence of a species complex, no conclusive evidence can be obtained at present from the skeletal characters. The early presence of large specimens in the Ionian Sea indicates that a putative introduction into the Mediterranean could not be a very recent event. It is possible that the occurrence of such spreading brown clionaids in the Eastern Mediterranean has been previously overlooked, probably because of taxonomic confusion with C. viridis. A recent increase of abundance of a previously more discrete species cannot be excluded. In the Mediterranean, such a hypothetical increase is not correlated with mass mortalities of coral reefs, an event that in tropical seas provided large amount of new substrate to similar clionaids (Rützler 2002; Ward-Paige et al. 2005). Our records in the Eastern Mediterranean are from pristine locations, suggesting that, as in the Caribbean, Mediterranean large clionaid sponges are not associated with organic pollution.

Conclusions

  1. Top of page
  2. Abstract
  3. Problem
  4. Material and Methods
  5. Results
  6. Discussion
  7. Conclusions
  8. Acknowledgements
  9. References

A large clionaid sponge, with a marked variability in spicule characters and resembling highly destructive zooxanthellate counterparts in Caribbean and Indo-Pacific coral reefs, is widely distributed in the Eastern Mediterranean. Although conspicuous by its large surface cover and its limestone destructing capacity, it has been described only recently as Cliona parenzani, without any reference to its tropical counterparts. This species, or species-complex, does not seem to be a recent introduction, but its abundance may have increased recently. This is another example of sponges with tropical or subtropical affinities that in the Mediterranean are restricted to the eastern part (Pansini & Longo 2003; Perez et al. 2004). Such sponge species, for which a Lessepsian origin appears unlikely, may be survivors of an ancient thermophilous Mediterranean fauna, which did not survive in the colder Western Basin during glacial episodes of the Pleistocene.

Acknowledgements

  1. Top of page
  2. Abstract
  3. Problem
  4. Material and Methods
  5. Results
  6. Discussion
  7. Conclusions
  8. Acknowledgements
  9. References

We acknowledge the help of Chantal Bézac and Christian Marschal, Centre d’Océanologie de Marseille, for their technical help, and Teresa Abaurea for her help in spicule measurements. Field work in Lebanon was possible thanks to the French-Lebanese cooperation program CEDRE.

References

  1. Top of page
  2. Abstract
  3. Problem
  4. Material and Methods
  5. Results
  6. Discussion
  7. Conclusions
  8. Acknowledgements
  9. References
  • Barucca M., Azzini F., Bavestrello G., Biscotti M.A., Calcinai B., Canapa A., Cerrano C., Olmo E. (2007) The systematic position of some boring sponges (Demospongiae, Hadromerida) studied by molecular analysis. Marine Biology, 151, 529535.
  • Bavestrello G., Calcinai B., Cerrano C., Pansini M., Sarà M. (1996) The taxonomic status of some Mediterranean clionids (Porifera: Demospongiae) according to morphological and genetic characters. Bulletin de l’Institut Royal des Sciences naturelles de Belgique, Biologie, 66, 185195.
  • Calcinai B., Bavestrello G., Cerrano C. (2005) Excavating sponge species from the Indo-Pacific Ocean. Zoological Studies, 44, 518.
  • Corriero G., Scalera-Liaci L. (1997) Cliona parenzani n. sp. (Porifera, Hadromerida) from the Ionian Sea. Italian Journal of Zoology, 64, 6973.
  • López-Victoria M., Zea S. (2005) Current trends of space occupation by encrusting excavating sponges on Colombian coral reefs. Marine Ecology, 26, 3341.
  • Maldonado M., Carmona M.C., Uriz M.J., Cruzado A. (1999) Decline in Mesozoic reef-building sponges explained by silicon limitation. Nature (London), 401, 785788.
  • Pansini M., Longo C. (2003) A review of the Mediterranean sea sponge biogeography with, in appendix, a list of the demosponges hitherto recorded from this sea. Biogeographia, 24, 5990.
  • Perez T., Vacelet J., Bitar G., Zibrowius H. (2004) Two new lithistids (Porifera: Demospongiae) from a shallow Eastern Mediterranean cave (Lebanon). Journal of the Marine Biological Association of the United Kingdom, 84, 1524.
  • Rosell D., Uriz M.J. (1991) Cliona viridis (Schmidt, 1862) and Cliona nigricans (Schmidt, 1862) (Porifera, Hadromerida): evidence which shows they are the same species. Ophelia, 33, 4553.
  • Rosell D., Uriz M.J. (2002) Excavating and endolithic sponge species (Porifera) from the Mediterranean: species descriptions and identification key. Organisms Diversity & Evolution, 2, 5586.
  • Rützler K. (1973) Clionid sponges from the coast of Tunisia. Bulletin de l’Institut océanographique et de la Pêche de Salammbô, 2, 623636.
  • Rützler K. (2002) Impact of crustose clionid sponges on Caribbean reef corals. Acta Geologica Hispanica, 37, 6172.
  • Sarà M. (1959) Specie nuove di Demospongie provenienti da acque superficiali del golfo di Napoli. Annuario dell’Istituto e Museo di Zoologia della Università di Napoli, 11, 122.
  • Schönberg C.H.L. (2000) Bioeroding sponges common to the central Australian Great Barrier Reef: descriptions of three new species, two new records, and additions to two previously described species. Senckenbergiana maritima, 30, 161221.
  • Schönberg C.H.L. (2001a) New mechanisms in demosponge spicule formation. Journal of the Marine Biological Association of the United Kingdom, 81, 345346.
  • Schönberg C.H.L. (2001b) Small-scale distribution of Great Barrier Reef bioeroding sponges in shallow water. Ophelia, 55, 3954.
  • Schönberg C.H.L. (2003) Substrate effects on the bioeroding demosponge Cliona orientalis. 2. Substrate colonisation and tissue growth. Marine Ecology, 24, 5974.
  • Vacelet J. (1981) Algal-sponge symbioses in the coral reefs of New Caledonia: a morphological study. In: GomezE.D., BirkelandC.E., BuddemeierE.W., JohannesR.E., MarshJ.A., TsudaJ., TsudaR.T. (Eds), Proceedings of the IV th International Coral Reef Symposium. Marine Science Center, University of the Philippines, Manila: 713719.
  • Vacelet J. (2006) New carnivorous sponges (Porifera, Poecilosclerida) collected from manned submersibles in the deep Pacific. Zoological Journal of the Linnean Society, 148, 553584.
  • Ward-Paige C.A., Risk M.J., Sherwood O.A., Jaap W.C. (2005) Clionid sponge surveys on the Florida Reef Tract suggest land-based nutrient inputs. Marine Pollution Bulletin, 51, 570579.
  • Zea S., Weil E. (2003) Taxonomy of the Caribbean excavating sponge species complex Cliona caribbaeaC. apricaC. langae (Porifera, Hadromerida, Clionaidae). Caribbean Journal of Science, 39, 348370.