Spinning a Marine Silk for the Purpose of Tube-Building

Abstract

A B S T R A C TAmphipod silk is a fibrous, self-secreted, adhesive substance employed in tube-building by amphipod species within the Corophiidea, Ampeliscoidea and Aetiopedidea. In the present study we provide a detailed characterisation of a novel, marine-based silk production system situated in pereiopods 3 and 4 in the corophioid Crassicorophium bonellii and the aorid Lembos websteri. The silk material is a mixture of protein and mucopolysaccharides. Ultrastructural and histological analyses revealed that silk in both species is produced in several rosette-type glands, presumed to be of two different types. These glands are distributed among all limb articles apart from the coxa but mainly in the basis and merus of pereiopods 3 and 4. Secretion commences in the basis and a thread-like secretion product leaves the glandular pereiopod through a cuticular pore near the dactylar tip. The silk's physical and chemical properties most likely change while moving through the dactylar duct, which subdivides into several small ductules and terminates in a spindle-shaped chamber. This chamber, which communicates with the exterior, may be considered a silk reservoir in which the silk appears fibrous. For the first time an independently evolved, marine arthropod silk processing and secretion system is described.

Sequence basis of Barnacle Cement Nanostructure is Defined by Proteins with Silk Homology

“…Aquatic arthropods such as caddisfly larvae256 and certain amphipods67 have recently been found to employ silks as mortar to construct their protective housing underwater. Caddisfly (e.g., H. consimilus and H. occidentalis ) belong to the more evolutionary distant insects while amphipods (e.g., C. bonellii ) are closer neighbors, divergent from barnacles by four ancestors57.…”

“…Despite inspiring scientific inquiry for more than a century3 and impeding maritime operations even today4, the permanent bond of adult barnacles is among the least understood. In contrast to marine organisms that use glues to fabricate protective shelters (e.g., sand-castle worm tubes5, case-maker fly larva retreats2, and amphipod tubes67) or tie themselves to rocks, (e.g., mussel byssus threads89) adult barnacles produce their adhesive interface in a sequential process hidden under their base as a part of their normal growth cycle1011. The recent finding that barnacle adhesive is nanostructured and held together as an amyloid-like material121314 further distinguishes it from archetypal marine adhesives processed into solid foams1915 or spun threads26.…”

Aspects of mast building and the fine structure of “amphipod silk” glands in Dyopedos bispinis (Amphipoda, Dulichiidae)

“…Dyopedos bispinis proximal glands (D1) are multicellular and have a strongly elongated form (i.e., "pseudotubular" glands, see discussion below in sections 5.4-5.6 and Fig. 9D-H), as has been observed in most other corophiid species (Nebeski, 1880;Neretin, 2016), likely with the exception of Crassicorophium bonellii and Lembos websteri (Kronenberger et al, 2012b). It is not clear whether the distal glands (D2) or Dyopedos bispinis are multicellular like the proximal glands (D1) or whether each D2 secretory cell has an individual duct.…”

“…Compositions of the pereopod 3-4 glandular complex are similar in Dyopedos bispinis and tube-building species. All studied corophiid species have two gland groups, proximal and distal, a common cuticular chamber and a single excretory opening (Nebeski, 1880;2012b;Neretin, 2016, and Fig. 5A).…”

“…The glands of another distal group can be unicellular or similar to the proximal glands. Kronenberger et al (2012b) inves-tigated silk glands in Crassicorophium bonellii and Lembos websteri Bate, 1857 and found that the proximal gland group presents rosette glands, while the distal group presents lobed glands. Thus, the structure of amphipod silk glands varies in different species but has never been studied in mast-building amphipods.…”