The bearded fireworm, Hermodice carunculata, is a common species in the marine annelid taxon Amphinomidae. It has a widespread distribution throughout the Atlantic, Gulf of Mexico, the Caribbean, Mediterranean and Red Seas. We review its environmental tolerances, defence mechanisms and feeding habits to evaluate its potential to survive in changing ocean conditions, to increasingly emerge as a nuisance species and to invade new geographic areas. Hermodice carunculata tolerates a wide range of environmental conditions, including temperature, salinity, oxygen saturation and various types of pollution. It has few natural predators because it is protected by its sharp chaetae and probably by toxins. Hermodice carunculata is best known for consuming live cnidarians, and has been implicated in transmitting coral pathogens, but it also feeds non-selectively on detritus. In the short term, we predict that H. carunculata will be able to withstand many future ecological challenges and possibly contribute to coral reef decline. In the long term, ocean acidification may negatively impact its defence mechanisms and survival. Its invasive potential may be significant. We highlight the gaps in our knowledge about the reproduction and development of this species, the nature and origin of its toxins and role of microbes in their feeding behaviour and defensive strategies.

Larvae of ~100 species of benthic invertebrates were obtained from the vicinity of Tomales Bay and Dillon Beach, California, over a 6-year period (1971–1977). This study reports on larvae of 14 species in eight families of polychaetes: Micronereis nanaimoensis, Nereis vexillosa, Sthenelais fusca, Nephtys caecoides, Nephtys californiensis, Boccardia berkeleyorum, Polydora pygidialis, Polydora spongicola, Dipolydora cardalia, Mediomastus californiensis, Ampharete labrops, Phragmatopoma californica, Sabellaria cementarium and Pectinaria californiensis. Some species were cultured from embryos obtained from laboratory fertilizations or field-collected egg masses or capsules. Larvae of other species were obtained from meroplankton and some of these were cultured through metamorphosis. A summary table is presented documenting seasonal occurrence of 60 polychaete taxa in the meroplankton.

Eggs of Marphysa gravelyi are spawned in gelatinous masses and the developing larvae are harboured in them until they are ready to undergo settlement. In order to understand the function of the jelly mass, morphometric, histochemical, biochemical and antimicrobial analyses were performed. The observations indicate the fibrous jelly mass is composed of carbohydrate, protein and lipid, and size is correlated to number of eggs present within. Extracts from the jelly mass of Marphysa gravelyi exhibit inhibitory activity against Escherichia coli, Vibrio vulnificus and Candida albicans but no activity was seen against seven other microorganisms tested. The results show that the function of the jelly mass is to nourish the developing embryos, protect against desiccation and predation from macrofauna, and most importantly prevent the dispersal of the juveniles from the desirable habitat.

Caobangiids are an aberrant group of annelids with an unusual phoronid-like body plan. The most perceptible anatomical characteristic of caobangiids is the anal trunk, which is recurved outside the body and ends with an anal opening located near the head. So far neither the larval development nor the metamorphosis of these worms have been investigated thoroughly. This study describes the larval development and metamorphosis of Caobangia billeti, and focuses mainly on the formation of the alimentary tract. The trochophore has eight chaetigers. Embryogenesis includes the development of segmentally arranged bands of cilia and ventral ciliary fields, the development of chaetae and the early formation of anterior radioles. Upon exiting the larval duct, larvae have eyes with lenses, two pairs of rudimentary radioles on the prostomium, a pair of nephridia on the peristomium, and two capillary chaetae in each parapodium of segments 3–9; parapodia of the 10th segment also bear a row of palmate hooks. Metamorphosis takes about 20 h and involves dorso-ventral folding of the body and enlargement of the pygidium along the dorsal side of segments 5–8. Thus, the anus develops on the dorsal side of the 5th segment, the anal trunk forms from the projection of pygidium whereas the prepygidial growth zone appears posterior to the 8th body segment. After the completion of metamorphosis, the prostomial and peristomial segments are fused and reduced, eight full thoracic chaetigers derive from the larva's body. Abdominal chaetigers grow posteriorly from the prepygidial growth zone.

Anterior regeneration of the annelid polychaete, Myxicola infundibulum (Montagu, 1808) is described from histological and SEM perspectives. This article provides additional evidence that anterior and posterior regeneration of isolated worm pieces does occur in this species, but that regenerative ability is restricted to abdominal pieces obtained from small individuals (less than 5 mm in thorax diameter and 10–20 mm in length). New cartilage tissue forms within the regenerating crown, but thoracic regeneration is limited to three segments. Anterior and posterior regeneration occurred within isolated pieces excised from the abdomen, resulting in the formation of 13 clones, with up to five individuals per clone.

Reproduction in the shallow-water, sponge-dwelling, branching syllid Ramisyllis multicaudata exhibits several features unique among syllids and among annelids in general. We describe and illustrate the segmental asymmetry which intervenes between regions of symmetry, only found in branching annelids. We describe the morphology of the stolons and of the stolon stalks, which are unique to branching syllids but differ in detail from those of the other known branching syllid, Syllis ramosa. We also illustrate newly found paddle-shaped chaetae, which might indicate that these stolons do swim. We list the number of branch points and termini in an effort to gauge the extent of branching in a worm contained in a small sponge. The species appears to have separate sexes, but this cannot be proven. We compare R. multicaudata and S. ramosa as originally described and find new morphological differences between the branching syllid from Japan described as S. ramosa and R. multicaudata. We also compare the known stolons of branching syllids to those of other genera of the ‘ribbon clade’, a group including Trypanobia and Trypanosyllis, now known to be close relatives of R. multicaudata. Ramisyllis multicaudata is the first member of the ribbon clade, and one of few Syllinae, known to have sexually dimorphic stolons.

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.