Biochemical analyses of the cement float of the goose barnacleDosima fascicularis– a preliminary study

Abstract

The goose barnacle Dosima fascicularis produces an excessive amount of adhesive (cement), which has a double function, being used for attachment to various substrata and also as a float (buoy). This paper focuses on the chemical composition of the cement, which has a water content of 92%. Scanning electron microscopy with EDX was used to measure the organic elements C, O and N in the foam-like cement. Vibrational spectroscopy (FTIR, Raman) provided further information about the overall secondary structure, which tended towards a β-sheet. Disulphide bonds could not be detected by Raman spectroscopy. The cystine, methionine, histidine and tryptophan contents were each below 1% in the cement. Analyses of the cement revealed a protein content of 84% and a total carbohydrate content of 1.5% in the dry cement. The amino acid composition, 1D/2D-PAGE and MS/MS sequence analysis revealed a de novo set of peptides/proteins with low homologies with other proteins such as the barnacle cement proteins, largely with an acidic pI between 3.5 and 6.0. The biochemical composition of the cement of D. fascicularis is similar to that of other barnacles, but it shows interesting variations.

Chemical characterization of the adhesive secretions of the salamander Plethodon shermani (Caudata, Plethodontidae)

“…While the salamander secretion contains slightly more polar groups (e.g. Tyr) than other marine species ( Asterias , Dosima , Megabalanus , Balanus and Phragmatopoma ) 37 , 42 , 43 , 47 , 48 , the secretions of the terrestrial Notaden and Euperipatoides are rather unpolar. There are again similarities regarding the quantity of hydrophobic amino acids given for most animals, including Plethodon , and only the two goose-barnacles Dosima and Lepas appear to be clearly higher (>40%), while the sandcastle worm Phragmatopoma is lower (21%).…”

“…Values beyond 90% have even been demonstrated in other species, i.e. 92% for the sponge-like cement of the marine goose barnacle Dosima 37 and 98% for the prey capture threads of the New Zealand glowworm larvae Arachnocampa luminosa 38 . The water evaporation and thereby the hardening of the secretion in Plethodon appears to be faster compared to either water alone or a water-based wood adhesive.…”

“…Holothuria , Littorina) 39 , 40 or higher than 84% (i.e. Lepas , Megabalanus , Dosima ) 37 , 41 – 43 have been measured, demonstrating a wide and diverse range.…”

“…In most other glue-producing species, however, the proteins are also smaller than 200 kDa: i.e. Holothuria = 220 kDa 39 ; Dosima = 205.0 kDa 37 ; Littorina = 118 kDa 44 ; Mytilus = 110 kDa 45 and Megabalanus = 100 kDa 7 .…”

“…Holothuria , Littorina ) there is a high carbohydrate fraction (15–40%) 39 , 40 , 46 , while in most others (e.g. Dosima , Lepas , Notaden , Euperipatoides ), the carbohydrate content is relatively low (<3% dry weight) 35 , 37 , 41 . In the Plethodon secretions, a low carbohydrate concentration (0.41%) could likewise be measured, although the secretory content of both gland types as well as the isolated secretion show a high affinity for sugar residues such as mannose (from the mucous gland) or L-fucose and N-acetyl-d-glucosamine (from the granular gland) 23 .…”