Sycon ancora, Klautau, Imesek, Azevedo, Plese, Nikolic & Cetkovi, 2016

Klautau, Michelle, Imešek, Mirna, Azevedo, Fernanda, Pleše, Bruna, Nikolić, Vedran & Ćetković, Helena, 2016, Adriatic calcarean sponges (Porifera, Calcarea), with the description of six new species and a richness analysis, European Journal of Taxonomy 178, pp. 1-52 : 32-39

Sycon ancora sp. nov.

urn:lsid:zoobank.org:act:F39F5C07-44BF-4AC4-822D-77AA1155B018

Figs 14–15 ; Table 11

Etymology

From the Latin ancora , meaning anchor, for the presence of anchor-like spicules for attachment.

Material examined

Holotype

ADRIATIC SEA: Island of Pag , 44°28'34.96" N, 15°02'39.74" E, 1 m, collected by V. Nikolić, 14 Feb. 2011 ( PMR 17809 = UFRJPOR 8345, in ethanol).

Paratype

ADRIATIC SEA: near Split, 43°30'27.57" N, 16°23'20.55" E, 5–10 m, collected by V. Nikolić, 15 Aug. 2011 ( IRB-SD 12 = UFRJPOR 8347, in ethanol).

arrows atrium.

= subatrial triactines). F. Tangential section of the atrial skeleton. Abbreviation: at =

Colour

White in life and in ethanol.

Description

The body is vase-shaped (1.1 × 0.8 cm), with a single apical osculum surrounded by a crown of trichoxeas ( Fig. 14A ) and diactines supported by sagittal tetractines. These tetractines are arranged parallel to each other and their unpaired actines are basipetally directed. The unpaired actine is longer and thinner than the paired ones and the apical actine is curved towards the osculum aperture. The paired actines are slightly curved. There is no suboscular region. The aquiferous system is syconoid and the atrium is central. The radial tubes are coalescent ( Fig. 14B ). Diactines and trichoxeas protrude through the distal cones; consequently, the surface is very hispid. These diactines (ca 10 to 15) penetrate only a little into the sponge surface ( Fig. 14C ). The unpaired actine of some triactines also protrudes through the cones.

The tubar skeleton is articulated, but not so well organised as in most sycons ( Fig. 14D ). It is composed of rows of sagittal triactines that point their unpaired actines to the surface. These tubar triactines are larger than those of the distal cones and the paired actines are frequently curved. The subatrial skeleton is composed of sagittal triactines and tetractines ( Fig. 14E ) with very thin actines. The unpaired actine is much longer than the paired ones and the longest ones are frequently localized among the choanocyte chambers. They point their unpaired actines towards the distal cones. Some of the subatrial triactines are similar to pseudosagittal spicules. The atrial skeleton is composed of two categories of tetractines tangentially organized ( Fig. 14E ). They frequently have long, unpaired and short, paired actines. One of the paired actines is commonly shorter than the other; however, the three basal actines can have the same size ( Fig. 14F ). When one of the paired actines is shorter than the other, it frequently penetrates an exhalant canal. The main difference between the two categories of atrial tetractines is in the apical actine. Tetractines with thinner apical actines project these actines mainly into the canals, while thicker and curved apical actines penetrate into the atrium ( Fig. 14E ). Few anchor-like tetractines are present at the sponge base and project their basal actines into the substrate.

Spicules ( Table 11)

DIACTINES. Almost fusiform, but the tip outside the sponge is a little thicker ( Fig. 15A ). Size: 537.8/ 16.1 µm.

TRICHOXEAS. Very thin, long and straight. They were always broken.

ANCHOR- LIKE TETRACTINES. The basal actines are very short and curved, while the apical one is very long. Frequently there are spines on the apical actine, but near the basal ones. They vary from four to seven, but seven spines are more common ( Fig. 15B ). Size:> 1000.0/25.0 µm.

TRIACTINES OF THE CONES. They are smaller than the tubar triactines. The unpaired actine protrudes through the cones and it is shorter than the paired ones, which are curved. Actines are slightly conical and sharp ( Fig. 15 C–D). Size: 112.3/ 6.9 µm (paired actine); 78.6/7.0 µm (unpaired actine).

TRIACTINES OF THE TUBES. Subregular to sagittal. The unpaired actine is a little longer or has the same length of the paired ones. The paired actines are straight or slightly curved. Actines are slightly conical and sharp ( Fig. 15 E–G). Size: 168.2/13.0 µm (paired actine); 188.1/ 12.4 µm (unpaired actine).

SUBATRIAL TRIACTINES AND TETRACTINES. The subatrial spicules are very thin. They are sagittal or, sometimes, similar to pseudosagittal spicules. Actines are slightly conical and sharp. The unpaired actine is longer than the paired ones ( Fig. 15H ). The apical actine of the tetractines is conical, sharp, smooth, shorter than the basal ones and curved in the direction of the atrium. Size: 97.9/ 5.4 µm (paired actine); 212.4/6.0 µm (unpaired actine).

ATRIAL TETRACTINES I AND II AND TRIACTINES. There are two categories of atrial tetractines and the triactines are very rare. They are sagittal or subregular. The unpaired actine is frequently longer than the paired ones ( Fig. 15I ). It is also common to find one of the paired actines shorter than the other (63.5– 109.3(±64.7)–155.0/10–11.3(±1.8)– 12.5 µm (n=2); Fig. 15J ). This shorter, paired actine is frequently projected inside the exhalant canal. Actines are cylindrical and sharp. Sometimes, the tip of the unpaired actine is thicker ( Fig. 15I ). The main difference between the two categories of tetractines is in the shape and size of the apical actines, which are straight and thinner in one and curved and thicker in the other. Size (tetractine I): 153.5/ 10.8 µm (paired actine); 219.4/ 10.7 µm (unpaired actine); 123.8/ 11.4 µm (apical actine). Size (tetractine II): 162.5/ 6.3 µm (paired actine); 137.5/ 6.3 µm (unpaired actine); 77.1/ 5.6 µm (apical actine).

Ecology

Specimens were collected on a semi-vertical hard limestone bottom. They were found among Cystoseira macroalgae.

Remarks

Currently there are 12 accepted species of Sycon in the Mediterranean Sea, 10 of which have already been reported for the Adriatic. We compared our specimens to all known species of Sycon and even more carefully to the Mediterranean ones, yet we could not find a perfect match.

The main characteristic discerning Sycon ancora sp. nov. from other species is the shape of the atrial triactines and the presence of anchor-like tetractines at the base. If we exclude these characteristics, this species would be mostly comparable to S. raphanus ; however, there are several important differences between them.

Sycon raphanus was originally described from the Adriatic Sea by Schmidt (1862). Unfortunately, his description was not detailed enough. According to him, S. raphanus has a bulb shape and a peduncle. He even considered these characteristics to distinguish S. raphanus from S. ciliatum (Fabricius, 1780) , a species from the English Channel which he believed to be present in the Adriatic Sea.

Haeckel (1872) disagreed with the possibility of S. ciliatum occurring in the Mediterranean Sea and considered that all specimens called S. ciliatum were, in fact, S. raphanus . He also mentioned that he analysed all the specimens from Schmidt’s collection identified as S. raphanus and found a potpourri of species, including Leucandra aspera , Sycon humboldti , Sycon setosum and “the real S. raphanus ”. Therefore, he made a detailed description of this species, which has since then been considered as the official description of S. raphanus . According to his description, S. raphanus is morphologically very variable, solitary or not, with or without peduncle. The skeleton is composed of tufts of 5–10 cylindrical diactines ( var. tergestina ) to 20–50 diactines ( var. procumbens ) and the size of the diactines varies from 400–800/ 20–30 µm up to 1000–2000/ 20–40 µm, rarely attaining 3000 µm. Analyzed specimens of S. ancora sp. nov. have tufts of 10–15 diactines measuring 378+1500/ 10.8–18.9 µm. Sycon raphanus has triactines with curved paired actines in the distal cones and in the tubar skeleton. The tubar triactines are 100–180/ 10–12 µm (paired) and 150–250/ 10–12 µm (unpaired), which are thinner than in S. ancora sp. nov. The subatrial skeleton of S. raphanus has triactines (paired: 100–180/ 5–8 µm; unpaired: 150– 250/ 5–8 µm), while S. ancora sp. nov. has triactines and tetractines. The atrial skeleton of S. raphanus shows subregular to regular (rarely sagittal) triactines and tetractines (basal: 150–250/ 8–10 µm; apical: 60–120 µm), while our species has tetractines with two types of apical actines (there is a variation in the thickness and position), a long unpaired actine and paired actines with different sizes. Haeckel (1872) also mentioned the presence of only triactines supporting the oscular crown, while S. ancora sp. nov. has only tetractines.

Although we believe the entire genus Sycon is in urgent need of revision, the characteristics we found in our specimens strongly indicate the presence of a new species.

Other calcarean species from the Adriatic Sea

Apart from the species described here, we also recorded and molecularly analyzed specimens of Clathrina blanca (Miklucho-Maclay, 1868) , C. clathrus ( Schmidt, 1864) , C. rubra Sarà, 1958 and Paraleucilla magna Klautau, Monteiro & Borojević, 2004 . These species are not redescribed here, since specimens from the Adriatic Sea have already been recorded and described in earlier works ( Cvitković et al. 2013; Imešek et al. 2014). In the present study, C. blanca was recorded near Selce (45°09'07.8" N, 14°43'15.0" E), about 1 m deep and C. rubra was recorded near the Island of Čiovo (43°28'58.5" N, 16°21'25.6" E), about 5m deep on a shaded hard bottom. In August and November 2010 they were quite abundant, always only a few millimeters in size and often found on bryozoans. C. clathrus was found in numerous locations along the coast (e.g., Prapratno Cove, 42°48'36.8" N, 17°40'38.4" E; near the Island of Čiovo, 43°28'58.5" N, 16°21'25.6" E) and the cryptogenic species P. magna was found in large numbers in on aquaculture installations in Grška Cove on the Island of Brač and in the Port of Ploče.

Molecular analysis

The number of sites used for the final alignments (gaps included) was as follows: 513 for ITS Calcinea, 1434 for 28S Calcinea, 734 for ITS Calcaronea and 846 for 28S Calcaronea. Both markers revealed the same tree topology in both analyses (but see Fig. 19 ), yet the Bayesian analysis rendered much better support values than ML in all cases. However, the Adriatic species nested within the respective genera with high bootstrap (BS) and posterior probability (PP) values, thereby confirming the results of morphological analysis ( Figs 16–19 ).

Once more the presence of diactines did not show any phylogenetic signal ( Rossi et al. 2011; Klautau et al. 2013). Furthermore, we found former guanchas with only triactines reunited in a monophyletic clade in the ITS analysis, with high support values inside the Clathrina group (0.99 PP and 0.84 BS; Fig. 16 ). In the 28S calcinean tree ( Fig. 17 ) we recovered a clade where Levinella represents a sister group to Ascandra with high support values (1.00 PP and 0.99 BS), which confirms the results of Voigt et al. (2012). We also recovered a clade comprising the genera Murrayona and Ascaltis in both analyses; however, the support values were less good (0.71 PP and 0.54 BS). The molecular analyses also confirmed the presence of P. magna in the Adriatic Sea ( Figs 18–19 ). Besides, we recovered a calcaronean clade with high support (1.00 PP and 0.99 BS in ITS analysis; 0.95 PP and 0.64 BS in 28S analysis) formed only by Paraleucilla species. The genus Paraleucilla formed a highly supported clade with Leucandra nicolae , while Leucandra spinifera sp. nov. is a sister species of L. aspera ( Fig. 19 ). Sycon ancora sp. nov. represents a sister species of S. raphanus ( Fig. 19 ). We confirmed the paraphyly of the genera Sycon and Leucandra ( Voigt et al. 2012) .

Species richness

Considering previous data, together with our present results based on morphological and molecular analyses, we found a total of 13 species of Calcinea ( Table 12) and 26 of Calcaronea in the Adriatic Sea ( Table 13). Taking into account the species richness by sectors ( Fig. 20 ), the richest sector is the Central Adriatic, where 34 species were found, followed by the Northern Adriatic with 18, and the Southern Adriatic with only 5 species. Most of the species present in the Adriatic Sea are also present in other Mediterranean areas, yet, altogether we recorded six species provisionally endemic for the Adriatic, two calcinean and four calcaronean.

Figures

Fig. 14. Sycon ancora sp. nov., holotype (PMR 17809 = UFRJPOR 8345). A. Specimen in ethanol. B. Cross section. C. Detail of the distal cone. D. Tubar and subatrial skeletons. E. Atrial skeleton (white

Fig. 15. Sycon ancora sp. nov., holotype (PMR 17809 = UFRJPOR 8345). A. Cortical diactine. B–C. Anchor-like tetractines. D–E. Triactines of the cones. F–H. Tubar triactines. I. Subatrial triactine. J. Atrial triactine. K. Atrial tetractine. Scale bar D–K = 100 µm.

Fig. 19. Maximum likelihood tree based on partial 28S rDNA sequences of Calcaronea. Bayesian posterior probabilities (PP) and bootstrap values (BS) are given near the branches (PP/BS; when>0.50). Adriatic specimens are written in bold. Adriatic specimens obtained in this study are marked with an asterisk. The detached tree shows the only difference in the topology of the ML and Bayesian analyses.

Fig. 16. Maximum likelihood (ML) tree based on ITS1-5.8S-ITS2 rDNA sequences of Calcinea. Bayesian posterior probabilities (PP) and bootstrap values (BS) are given near the branches (PP/BS; when>0.50). Adriatic specimens are written in bold; *Adriatic specimens obtained during this study; **Mediterranean specimens of Borojevia cerebrum; ***Brazilian specimens of Clathrina conifera.

Fig. 17. Maximum likelihood tree (ML) based on partial 28S rDNA sequences of Calcinea. Bayesian posterior probabilities (PP) and bootstrap values (BS) are given near the branches (PP/BS; when>0.50). Adriatic species are written in bold.Adriatic specimens obtained in this study are marked with an asterisk.

Fig. 18. Maximum likelihood tree based on ITS1-5.8S-ITS2 rDNA sequences of Calcaronea. Bayesian posterior probabilities (PP) and bootstrap values (BS) are given near the branches (PP/BS; when>0.50).

Fig. 20. Species richness in the Adriatic Sea divided by sectors.: 1–9 species;: 10–17 species;: 18–26 species.