Porifera of Greece: an updated checklist

Abstract Background The checklist of Porifera of Greece was created in the framework of the Greek Taxon Information System (GTIS), an initiative of the LifeWatchGreece Research Infrastructure (ESFRI) that has resumed efforts to compile a complete checklist of species recorded from Greece. An updated checklist of Porifera was created on the basis of a list of the Aegean Demospongiae and Homoscleromorpha published one decade ago. All records of species known to occur in Greek waters were taxonomically validated and cross-checked for possible inaccuracies and omissions. Then, all recent publications were reviewed and the species recorded from 2006 to date were added to the list. New information The updated checklist of Porifera of Greece comprises 215 species, classified to 111 genera, 65 families, 24 orders, and 4 classes. In total, 34 new additions were made to the previous species list (8 Calcarea, 17 Demospongiae, 1 Hexactinellida, and 6 Homoscleromorpha) with Calcarea being listed for the first time from the area. The demosponge orders Poecilosclerida, Dictyoceratida, Tetractinellida, Haplosclerida, and Suberitida have the highest number of species covering 62% of the known Greek sponge species richness. It is worth mentioning that 8 species have been first described from Greek waters, 7 of which are considered endemic to this area. Our bibliographic overview also revealed knowledge gaps with regard to specific habitats typically rich in sponge diversity, and marine sectors of Greece.


Introduction
The history of sponge science is directly linked to Greek civilization, since the older written references to sponges are found in Homer's Epics, and their scientific knowledge has been established by the Greek philosopher, and first marine biologist, Aristotle in his zoological works (Voultsiadou 2007).
In modern times, research on Porifera of the Greek seas started early in the 20 century with the study of bath sponges, i.e., the members of the family Spongiidae (Szymanski 1904, Arndt 1937. In the subsequent decades, up to the 1980s, a series of scattered records of sponge species followed, which can be traced either in faunistic papers (Pérès andPicard 1958, Tortonese 1947) or in more general works on Porifera (Topsent 1920, Vacelet 1969, Griessinger 1971, Pulitzer-Finali 1983. The systematic research on Greek Porifera started in the 1990s when the Laboratory of Zoology, Aristotle University of Thessaloniki, presented a series of publications on the Aegean sponge taxonomy, ecology and biogeography. New species were described (Voultsiadou-Koukoura and van Soest 1991a, Voultsiadou-Koukoura and van Soest 1991b, Voultsiadou-Koukoura et al. 1991, species lists presented Koukouras 1993, Voultsiadou-Koukoura andvan Soest 1993), and the associations of sponges with other invertebrates investigated (Koukouras et al. 1996 and references therein). A checklist of all Aegean sponge species reported up to 2005 and an overview of the relevant literature was provided by Voultsiadou (2005a) and followed by two publications on the distribution of Aegean and Levantine Porifera in the Mediterranean context (Voultsiadou 2005b, Voultsiadou 2009).
The aforementioned literature addresses mainly the classes Demospongiae and Homoscleromorpha. No research on Hexactinellida of the Greek seas has been carried out th (but see Boury-Esnault et al. 2014), while few species of Calcarea have been recorded mostly in general faunistic publications (e.g. Pansini et al. 2000, Gerovasileiou et al. 2015.
The aim of the present work was to present an updated, annotated checklist of Porifera of the Greek seas. For this purpose, older lists of the classes Demospongiae and Homoscleromorpha were updated according to the recent literature and taxonomic status, and a first attempt to provide a catalogue of Calcarea was made.

Materials and methods
The Checklist of Porifera of Greece (Suppl. material 1) was created in the framework of the Greek Taxon Information System (GTIS), an initiative of the LifeWatchGreece Research Infrastructure (ESFRI) that has resumed efforts to compile a complete checklist of all species reported from Greece (Bailly et al. 2016). In that publication, a methodology is described to produce Preliminary Checklists only. However, in the present case of Porifera, the status of the list for Greece was quite advanced, and the recent primary literature was exhaustively searched for this work: the present list is thus considered as an updated, annotated, and archived checklist.
The checklist of Demospongiae and Homoscleromorpha was constructed based on a previous inclusive list of the Aegean sponges published by Voultsiadou (2005a Hooper, 1993, andTimea mixta (Topsent, 1896)] were not included in the present checklist, since they have been to date reported only from the Turkish coast of the Aegean Sea, but not from the Greek waters. Then, all recent publications were reviewed and the species recorded from 2006 to date have been added to the list. The records of freshwater species from Greece were derived from the catalogue published by Pronzato and Manconi (2001).

Discussion
A total of 215 species, classified to 111 genera, 65 families, 24 orders, and 4 classes makes the updated checklist of Porifera of Greece. Demosponges and Homoscleromorpha make up the bulk of Porifera of Greece, while only 8 species of Calcarea are listed for the first time from the area. As it can be seen from the list, the orders Poecilosclerida, Dictyoceratida, Tetractinellida, Haplosclerida, and Suberitida have the highest number of species comprising 62% of the known Greek sponge species richness.
The majority of species included in the present checklist were already known as elements of the Greek fauna (Voultsiadou 2005a), while 34 new additions were made in the course of this study (Table 1). These additions include 8 species of Calcarea, 17 species of Demospongiae, 1 species of Hexactinellida, and 6 species of Homoscleromorpha. Two more, freshwater species, Ephydatia fluviatilis and Eunapius carteri, were also added as elements of the Greek fauna.
The list of sponges of Greece compiled for the needs of the present study is the most comprehensive list of Porifera in the Eastern Mediterranean. There is another list presenting 131 sponge species from the Turkish coasts (Topaloğlu and Evcen 2014) and various scattered sources of information on the sponges of the remaining Levantine coasts (see Voultsiadou 2005b). However, a major gap of our knowledge on the sponge species richness from the Greek seas is obvious since practically the entire bibliography on Greek sponges concerns the Aegean Sea, while very few and scattered information is available from the Ionian coasts of Greece (e.g. Schuffner 1877, Laborel 1960). Finally, it should be mentioned that several species reported from the Turkish coasts of the Aegean have not been yet found in Greek waters. Given that both Turkish and Greek coasts are part of the broader ecoregion of the Aegean Archipelago (Spalding et al. 2007), it is reasonable to assume that it is a matter of time before these species are recorded as elements of the Greek fauna as well.