Dceanological and Hydrobiological Studies, VOL. 51, NO. 2 | JUNE 2022 
zecord of Crossaster papposus in the Baltic Sea 
In the course of the expeditions ”EMB211” and 
’EMB269” of the German research vessel “Elisabeth 
Mann Borgese”, images of the seabed were recorded 
using a downward-facing towed camera system 
Baltic Seafloor Imaging System” as reported by 
Beisiegel et al. 2017). The camera system was vertically 
submerged over the ship’s stern to its target altitude 
of 1 m above the seafloor and was towed at a 
speed of 0.5 knots along the transect. Four vertical 
parallel lasers produced laser points on the seafloor 
and allowed an exact image scaling. Identification 
af C. papposus was based on Southward & Campbell 
(2006). 
3. Results 
Crossaster papposus was observed twice in the area 
9f the Fehmarn Belt through video imaging. On both 
accasions only one single individual was recorded. 
Since the specimens were not collected, taxonomic 
identification was based on photographs and video 
material. The two recorded specimens had 12 and 
13 arms, a disc diameter of 6-7 cm and 3.5-4 cm, 
‚espectively, as well as the typical series of single 
dorsal marginals (Fig. 2). In our cases, the specimens 
had characteristic purplish coloration with one red and 
ane whitish band along the arms. 
Regarding abiotic factors, in 2019, one specimen 
was found at a depth of 16.3 m, with a near-bottom 
water oxygen level of 7.16 mil/l and salinity of 18.4. In 
2021, the second specimen was observed at a depth of 
10.9 m, with a near-bottom water oxygen level of 6.8 
mI/l and salinity of 14.5. Both locations reported in this 
study are attributed to the so-called infaunal Arctica 
community, named after the ocean quahog (Arctica 
islandica) that dominates the biomass of the benthic 
macrofauna. Few shells of these bivalves are also 
visible in the images shown in Figure 2. 
4. Discussion 
The genus Crossaster typically features 8-15 (rarely 
16) tapering arms (Lambert 1981; Clark & Downey 1992; 
Zarlson & Pfister 1999; Southward & Campbell 2006), 
a moderate to large disc, and a single series of single 
zonspicuous marginals visible in the dorsal view (Clark 
& Downey 1992; Ringvold & Moum 2020). Although 
the coloration may vary, the predominant aboral 
zolor of Crossaster papposus is purple-red, while arms 
sometimes show one or more whitish and/or dark red 
bands (Ringvold & Moum 2020). The appearance of the 
specimens from this study is fully consistent with those 
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Figure 2 
Top view on Crossaster papposus recorded with a drop 
camera system. The specimens were found in the 
“Fehmarn Belt” MPA (Baltic Sea). 
descriptions, suggesting a taxonomic classification as 
Crossaster papposus. Crossaster squamatus is another 
closely related species of the genus. However, because 
of the purplish coloration with red and whitish bands 
along the arms, characteristic only of C. papposus, and 
not of C. squamatus, it is unlikely that the specimens 
found belong to the latter taxa. Furthermore, 
C. squamatus has never been recorded in the German 
parts of the North Sea or the Baltic Sea and results of 
several marine Ssurveillance programs (MAREANO, 
BIOICE, BIOFAR) indicate that C. squamatus occurs at 
the shelf break in colder waters at a depth of 100 to 
1600 m (Mortensen 1927; Ringvold & Moum 2020). 
In contrast, C. papposus occurs mainly at the shelf 
in temperate waters from a depth of 0 to 1200 m 
(Mortensen 1927; Clark & Downey 1992), which 
corresponds more closely to the prevailing conditions 
in the Baltic Sea and supports the taxonomic 
ournal owner: Facultv of Oceanoaraphv and Geoaraphv, Universitv of Gdanisk, Poland