Fine structure of the tubes of Maldanidae (Annelida)

Abstract

Many marine annelids are active tube builders. Several polychaete families make agglutinated tubes by fixing sediment particles with specific secretions from their epithelial glands. The fine structure of the tubes of six species of Maldanidae from five genera (Nicomache minor, N. lumbricalis, Maldane sarsi, Praxillella praetermissa, Axiothella catenata, Rhodine gracilior) was examined by scanning electron microscopy. These species exhibit different lifestyles. Nicomache minor and N. lumbricalis inhabit massive hard tubes attached to stones. Other species live in the sediment, Rhodine in rigid organic tubes, Praxillella, Axiothella and Maldane in sand or mud tubes. All the examined maldanid tubes have a similar basic structure. The inner sheath of the tubes is made of a hardened organic lining secreted by the worm. Fibres from the inner sheath fasten sediment particles of the agglutinated layer. In Nicomache the tube surface is covered with a fibrous outer layer. All tube layers contain variously arranged organic fibres, which form a 3D network in the agglutinated layer and fabric-like linings in the inner sheath and outer layer. The tubes of Maldanidae may be important for taxonomy, and useful for identification of fossils.

Devonian agglutinated polychaete tubes: all in all it's just another grain in the wall

“…Finally, and possibly most importantly, none of the above-mentioned groups show flanged tubular morphologies, besides annelids. Indeed, many extant polychaete families are capable of building tubular constructions with agglutinated material (some with high capacity of particle selectivity), including Sabellariidae [38], Pectinariidae [39], Oweniidae [10], Terebellidae [40], Maldanidae [41], Sabellidae [42], Capitellidae [43], Cirratulidae [43], Spionidae [44], Ampharetidae [45], Eunicidae [46], Fabricidae [47], Onuphidae [48], Nereididae [49], Trichobranchidae [50] and possibly even Phyllodocidae [51]. However, most of these groups produce agglutinated tubes that are simple cylindrical forms, without complex morphologies.…”

“…Some Maldanidae species (i.e. Nicomache lumbricalis) can even show an increase in particle size from the inner to the outer portions of the wall [41]. Despite the fact that this is also the case for the sabellariids Sabellaria alveolata and Phragmatopoma caudata (electronic supplementary material, figure S12), their tube morphologies Taking together, the comparisons with modern groups strongly suggest an annelid affinity to A. mutveii, with possible relationships to the family Maldanidae.…”

Worms’ Antimicrobial Peptides

“…Recently, nicomicin-1 and -2 were identified in the artic polychaeta Nicomache minor [110]. This worm lives in the cold water, inhabiting hard tubes attached to stones [111]. Nicomicins consist of 33 residues (Table 1), containing BRICHOS domain in the sequences of their prepropeptide.…”

Linking properties of an orb‐weaving spider's capture thread glycoprotein adhesive and flagelliform fiber components to prey retention time

“…Animals use adhesives for many purposes. For example, insects glue their eggs to both wet and dry surfaces (Gaino & Mazzini, ; Li, Huson, & Graham, ), mussels and barnacles attach to marine substrates (Dickinson et al, ; Kamino, ; Naldrett, ; So et al, ; Waite, ), caddis fly larvae and some polychaete annelids build tubes from sand and gravel (Mackay & Wiggins, ; Shcherbakova, Tzetlin, Mardashova, & Sokolova, ; Wang, Svendsen, & Stewart, ), and sea cucumbers expel adhesive Cuvierian tubules for defense (Baranowska, Schloßmacher, McKenzie, Müller, & Schröder, ; Flammang & Becker, ; Flammang, Ribesse, & Jangoux, ). After being secreted as low viscosity solutions, these adhesives stiffen to resist crack propagation that leads to failure.…”