Page 2 - Deniz_et_alii2017

Natural and Engineering Sciences 74

Introduction

Sea hares are almost shell-free marine Opisthobranchs because they do not have an outer protective
shell, but only a small, degenerate and inner shell (Derby, 2007; Kamiya et al., 2006), and also they
use a chemical mixture for defense and communication (Kicklighter et al., 2005).
A. dactylomela is a sea hare, belonging to the order Opisthobranchia, subclass Gastropoda.
A.dactylomela, a spotted sea hare, up to 40 cm long, with body shades of green, brown, and cream.
Its mantle has shapes of black rings with cream spots which are connected by a network of black
lines. Mantle usually has large black rings. It is sheltered eulittoral and shallow sublittoral (Worms,
2017).
A. dactylomela distributes worldwide in tropical to warm temperate waters (Vairappan et
al., 2007; Ioannou et al., 2009). It is usually found in sea grass beds where it feeds (Barnes, 1963).
A. dactylomela feeds on red and green algae. It uses its jaws to grasp the algae and its radula to pull
the algae into its buccal cavity. The crop in A. dactylomela is lined with chitinous plates and acts
like a gizzard to aide in the digestion of the larger seaweeds that it eats. Foods
eaten; Chondrococcus hornemanni, Ulva reticulata, Laurencia spp., Martensia
fragilis and Spyridia filamentosa (MacFarland, 1909; Wilbur & Yonge, 1966). It is thought that A.
dactylomela consumes algae and produces secondary metabolites from algae and stores these
metabolites in its digestive glands and uses them as a defense mechanism against predators
(McPhail et al., 1999).
When feeling threatened A. dactylomela will elicit a quick downward movement of its
parapodia over its back. It may also release foul fluids from both the opaline gland and the purple
dye cavity. Purple color (aplysioviolin) of the secretion is derived from pigments (phytoeritrobilin)
found in the red algae (Rüdiger, 1967; Chapman and Fox, 1969; MacColl et al., 1990). The idea
that A. dactylomela releases ink and opaline in defensive situations is widely held (Barnes,
1963; Tobach, et al., 1989; Wilbur & Yonge, 1966). The most peculiar feature of these
invertebrates is their secretion, which is rich in bioactive proteins. Many of these proteins belong
to a family of L-amino acid oxidases (L-AAOs) (Tallita et al., 2011). A chemically defended animal
not only avoids being eaten by using its chemical arsenal, but it also avoids predators by detecting
chemicals released by attacked conspecifics and subsequently producing evasive behaviors. These
conspecific chemicals, called alarm signals, are known from many species (Blum, 1996; Wisenden,
2000; Wyatt, 2003).
In this study, the specimen of the A. dactylomela was photographed in a rock poll which
covered with algae during feeding and also its size was measured.

One specimen of A. dactylomela was photographed at the infralittoral zone of the Bay
(36°07'32.5"N 33°36'31.6"E) on 26 March, 2017, at a depth of 1 m in a rock pool together with Padina
pavonica (Linnaeus) and other algae (Figure 1).