Histology and biochemical composition of the autotomy mantle of Ficus ficus (Mesogastropoda: Ficidae)

Abstract

When the foot of the figsnail Ficus ficus is mechanically stimulated, a portion of the mantle on the side of the inner lip, recognized as the autotomy tissue, swells then autotomizes. Studies of the behaviour and population dynamics of mantle autotomy in F. ficus have previously been reported, but here, a detailed description of the structure of the autotomy tissue is presented for the first time. Whether or not this autotomy tissue has the secondary function of a storage compartment was also investigated through analysis of its biochemical composition. Figsnails were collected from the coast of Kaohsiung, Taiwan. Histological observations indicated that the most obvious feature of the autotomy tissue is the extensive network of muscle fibres and connective tissues. In the swollen autotomy tissue, not only do the epithelia rupture, but the connective tissue expands threefold on the dorsal side and 15‐fold on the ventral side. Chemical analysis of body composition indicated that the average contents of protein, lipid, carbohydrate and ash in the foot, mantle and autotomy tissue are in the range of 55.6–76.5%, 0.6–14.1%, 2.0–27.9% and 6.5–13.5%, respectively, with the caloric value ranging from 4.7 to 5.5 kcal g−1 dry wt. The content of carbohydrate in the autotomy tissue is much less than that in the foot and mantle, i.e. 2.0–6.8% vs. 13.0–27.9%. There is no indication that the autotomy tissue serves as an energy reserve. Hence, it is suggested that the autotomy tissue functions only as a defensive weapon.

Leave it all behind: a taxonomic perspective of autotomy in invertebrates

“…The shelled sacoglossan Lobiger serradifalci casts off parapodia (lateral extensions) in defence when disturbed (Marín & Ros, 2004). The Mesogastropoda Ficus ficus and the pulmonate gastropod (Stylommatophora) Prophysaon foliolatum autotomise a portion of their mantle when mechanically stimulated (Deyrup‐Olsen, Martin & Paine, 1986; Liu & Wang, 2002). The mantle shows a well‐developed autotomy response: the autotomy tissue swells in response to provocation and autotomises due to intrinsic muscular contraction (Liu & Wang, 2002).…”

“…The Mesogastropoda Ficus ficus and the pulmonate gastropod (Stylommatophora) Prophysaon foliolatum autotomise a portion of their mantle when mechanically stimulated (Deyrup‐Olsen, Martin & Paine, 1986; Liu & Wang, 2002). The mantle shows a well‐developed autotomy response: the autotomy tissue swells in response to provocation and autotomises due to intrinsic muscular contraction (Liu & Wang, 2002). For Prophysaon foliolatum, the mantle also acts as a storage organ (comprising 11% of total body mass, Deyrup‐Olsen et al , 1986), whilst in Ficus ficus the mantle appears to serve primarily in defence (it does not act as an energy reserve; Liu & Wang, 2002).…”

“…The mantle shows a well‐developed autotomy response: the autotomy tissue swells in response to provocation and autotomises due to intrinsic muscular contraction (Liu & Wang, 2002). For Prophysaon foliolatum, the mantle also acts as a storage organ (comprising 11% of total body mass, Deyrup‐Olsen et al , 1986), whilst in Ficus ficus the mantle appears to serve primarily in defence (it does not act as an energy reserve; Liu & Wang, 2002).…”

Cost of autotomy drives ontogenetic switching of anti-predator mechanisms under developmental constraints in a land snail

“…For example, spiny mice autotomize the skin of the tail from the underlying muscles to survive predation, resulting in a naked wound and subsequent necrosis of the tail [18]. The definition of autotomy is especially loose in molluscs [17], partly because breakage planes are not evident in tissues of molluscs that are regarded to perform autotomy [28,29] unlike in musculature segments of lizard tails and in hinges of arthropod appendages. The keys to defining autotomy as an anti-predator mechanism in molluscs are the unsuitability of the predator's feeding apparatus to separate prey body parts and the adaptive significance of the body-part loss induced by predators.…”