Characterisation of a skin secretion with adhesive properties in the ground frog Eupsophus vertebralis (Alsodidae)

Some skin secretions with adhesive properties allow frogs to distract predators and escape; their nature is poorly studied. Here, we report the sticky skin secretion released by the Patagonian frog Eupsophus vertebralis when stressed. This secretion contained ~ 50% proteins spanning 25–250 kDa and required a fast setting time to turn into strong adhesive, which worked well on synthetic and biological materials. Lap-shear assays with Eupsophus glue secretion showed average shear strength of 3.34 MPa, comparable to cyanoacrylate (5.47 MPa). These properties suggest its biotechnological value for practical applications in industrial and medical sectors.

SNAP-24, a Drosophila SNAP-25 homologue on granule membranes, is a putative mediator of secretion and granule-granule fusion in salivary glands

Fusion of vesicles with target membranes is dependent on the interaction of target (t) and vesicle (v) SNARE (soluble NSF (N-ethylmaleimide-sensitive fusion protein) attachment protein receptor) proteins located on opposing membranes. For fusion at the plasma membrane, the t-SNARE SNAP-25 is essential. In Drosophila, the only known SNAP-25 isoform is specific to neuronal axons and synapses and additional t-SNAREs must exist that mediate both non-synaptic fusion in neurons and constitutive and regulated fusion in other cells. Here we report the identification and characterization of SNAP-24, a closely related Drosophila SNAP-25 homologue, that is expressed throughout development. The spatial distribution of SNAP-24 in the nervous system is punctate and, unlike SNAP-25, is not concentrated in synaptic regions. In vitro studies, however, show that SNAP-24 can form core complexes with syntaxin and both synaptic and non-synaptic v-SNAREs. High levels of SNAP-24 are found in larval salivary glands, where SNAP-24 localizes mainly to granule membranes rather than the plasma membrane. During glue secretion, the massive exocytotic event of these glands, SNAP-24 containing granules fuse with one another and the apical membrane, suggesting that glue secretion utilizes compound exocytosis and that SNAP-24 mediates secretion.

Feeding behaviour and prey choice in Macroperipatus torquatus (Onychophora)

Macroperipatus torquatus feeds nocturnally on crickets and a few other invertebrates on the floor of the Trinidadian rain forest. Prey are inspected by gentle application of the antennae and, if suitable, are captured by entangling them in proteinaceous glue squirted from the oral papillae. Entangled prey are bitten through an arthrodial membrane and immobilized by injected saliva, which may also partly digest the flesh. Ingestion of the flesh takes several hours, comprising some 90% of total handling time, and normally only one prey item is eaten per night. The deplected carcass is discarded. Fully charged glue reserves amount to about 11% of body mass and after exhaustion are replenished in about 24 days. The quantity of glue used in an attack increases up to about 80% of reserve capacity for larger prey. Glue adhering to the prey is ingested, but some attached to the substratum is always lost. Squirting glue may therefore be costly for two reasons. Firstly, depleted glue reserves render peripatus less capable of attacking further prey or of defending themselves; secondly, unrecovered glue together with the metabolic cost of glue secretion will detract from the energetic yield of the prey. Small prey will scarcely repay the cost of glue used whereas larger ones are more likely to escape; consequently the energetically optimal prey are relatively large, but somewhat smaller than those potentially available. Accordingly, adult peripatus preferred larger prey and grew better when fed on them in the laboratory, whereas juveniles grew better on smaller prey. The size distribution of prey in the forest was heavily biased towards smaller types and it seemed likely that the productivity of large peripatus would be limited by the availability of profitable prey.