Supplementary material
Supplementary text A:
The Adriatic Sea was formed with the final rise of the Alps 20 Million Years ago (Ma).
At the same time, the Apulian Plate collided with the Adriatic Plate (Battaglia et al.
2004). 10 Ma ago, there was still a connection between the Eastern and the Western
Mediterranean Sea which was closed, before the Messinian crisis occurred. During
the Messinian age (7.2-5.3 Ma), the Mediterranean Sea almost dried up because of
the closure of the Strait of Gibraltar (Hsü et al. 1973, Hsü 1974). At the beginning of
the following Pliocene (5.3 Ma), the Strait of Gibraltar reopened which resulted in a
flooding of the Mediterranean Sea (Hsü 1974, McKenzie 1999, Bianchi and Morri
2000) and a re-immigration of species from the Atlantic Ocean. These species are
assumed to be the basic forerunners of the current Mediterranean benthos, which
presents a strong similarity with that currently populating the Eastern Atlantic Ocean
(for review see Boudouresque 2004).
Supplementary text B:
Patterns of speciation and histories of colonization of certain Mediterranean basins
are obviously unique for any taxon. As these colonizations took place at different
times and interacted in a highly complex way, it appears often difficult or even
impossible to reconstruct the ancestral courses of immigration and final isolation of
putative stem species from which the recent stock of Mediterranean endemics
evolved. Nevertheless, there are more examples of Mediterranean macrozoobenthic
‘neo-endemics’, besides spadellid Chaetognatha. In principle, some boreal
immigrants of the Pleistocene survived periodic warming of epipelagic and neritic
waters by sticking to bathybenthic grounds. One example for this deep-sea migration
is the recent presence of the gastropod Buccinum undatum in the Western
Mediterranean basin on muddy sediment below 1.000 m depth (Por and Dimentman
2006). Many other taxa, among them brachiopods and deep-water fishes, had same
habitat segregation strategies, but became however extinct and can be found in
deposits of the Pleistocene Mediterranean (e.g., Álvarez and Emig 2000, Girone
2002). Changes in thermal conditions of the Mediterranean Sea are also known to
drive the reorganization and fragmentation of populations in other benthic fully or
moderately boreal metozoans, such as stylasterid hydrozoans (Zibrowius and Cairns
1992), scleractinian anthozoans (Zibrowius and Cairns 1992), polychetes (Arvanitidis
et al. 2002), decapod crustaceans (e.g., Almaca 1985), brachiopods (Por and
Dimentman 2006, cf. Logan 1979), holothurian echinoderms (Tortonese 1985), and
fishes (Tortonese 1985, Rahel and Hubert 1991, Ben Rais Lasram and Mouillot
2009, Ben Rais Lasram et al. 2010).
Captions supplementary movies:
Suppl. movie 1. Structure and macrozoobenthic inhabitants of the type locality of S.
valsalinae sp. nov. at Valsaline Bay, Pula (Croatia), as filmed with a HD underwater
camera. The Bay of Valsaline is known to house some interesting but rather bizarre
hard substrate biocoenoses the classification of which appears rather problematic,
since equivalents are hard or even impossible to find in common textbooks dealing
with marine biota of the Mediterranean Sea (e.g. the Cystoseira amentacea –
paguroid – Gobius facies: see account of Müller and Schubart 2007). The lack of a
broad belt of Posidonia oceanica meadows - a species which normally represents a
dominant component of the Mediterranean infralittoral - causes direct converging and
mixing of faunal elements of the upper and lower infralittoral macrozoobenthos.
Some species identified in the investigated habitat, such as the Pilgrim’s Scallop
Pecten jacobeus (Linnaeus, 1758) or the hermit crab Paguristes eremita (Linnaeus,
1767) (see also Fig. 1C), usually indicate muddy or silty bottoms below depth levels
of at least 30 metres (e.g. Poppe and Goto 1993, d’Udecem d’Acoz 1999), belonging
to the ‘coastal detritic assemblage’ in the sense of Pérès (1985). Other species found
in the type locality, such as the lancelet Branchiostoma lanceolatum (Pallas, 1774),
are typical inhabitants of coarse sandy sediments in the upper infralittoral (e.g. Ros et
al. 1985, Heß 2002). When also regarding Vatova`s (1935) classification of
Mediterranean marine zoocoenoses modified for the unique conditions along the
coastal waters of the Istrian Peninsula, it can be stated that S. valsalinae sp. nov.
belongs to a soft bottom facies combining elements of the ‘Branchiostoma’ (also
called ‘Amphioxus sand’) and ‘Venus verrucosa’ type.
Suppl. movie 2. Living specimen of Spadella valsalinae sp. nov. collected in the Bay
of Pula (Croatia) in July 2009. The movie was shot through one ocular of a stereo
light microscope (40 times magnification). At first the head is shown by zooming
through the transparent animal from dorsal (sharp vision of the eyes and corona
cilata) to ventral surface (sharp vision of oesophagus and mouth cuticle). The hood
(praeputium) covers the head, the grasping spine apparatus is compact and located
at either side of the head. Afterwards, the camera zooms along the trunk and tail
region, the again starting from dorsal surface. Peristaltic movements of the midgut
are well visible. Please note that the lateral fins appear somewhat damaged and that
the small, thin posterolateral protuberances on the head are missed, what is most
probably a sampling artefact. The seminal vesicles are emptied and therefore appear
rather inconspicuous, but the clear separation from tail and lateral fins is still visible.
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