2.4. Degree of preservation of A. salina nauplii.
Small portions of the sediment with carcasses were put in the Petri
dish, diluted with ASW, and investigated under optical microscope (Zeiss
Stemi SV11) to count the nauplii and assess the degree of their
preservation. We categorized the remains in five groups according to the
presence of morphologically recognizable limbs and gut and the general
body shape. The procedure and the characteristics of the five
preservatonal groups are described in detail in Naimark et al., 2018c.
Group 1 comprised carcasses with all limbs, gut and body shape well
preserved. Specimens in group 2 had well preserved limbs and body shape
but no traces of the gut. Unlike freshly killed specimens or specimens
from other preservational groups, the group 2 specimens were rigid and
did not tend to fold in wrinkles when placed on a hard surface. Group 2
was rare in sediment-free controls but common in sediments. Groups 3-5
comprised specimens with preservation gradually deteriorating from only
moderately damaged cuticle, gut and limbs in group 3 to separate limbs
or limbless bodies in group 5 (Naimark et al., 2018c). The overall
degree of preservation was estimated as the ratio of the well-preserved
groups 1 and 2 to the poorly preserved groups 3, 4, and 5.