Description of a new species of Sabellidae (Polychaeta, Annelida) from fresh and brackish waters in Europe, with some remarks on the branchial crown of Laonome

In 2009, a hitherto unknown Laonome species was found in the Canal Ghent-Terneuzen in the Netherlands and subsequently in other Dutch rivers, canals and estuaries. A few years later, more unknown Laonome specimens were found in the eastern part of the Baltic Sea and in the Don River estuary, Sea of Azov. Initially, it was assumed that these specimens could represent Laonome calida Capa, 2007, originally described from Australia. In the present study we examine all these unknown European Laonome specimens and compare these specimens with the type material of L. calida from Australia. This lead to two main results: First, all specimens from Europe have the same diagnostic characters and therefore belong to one species. This finding was also supported by the results of a correspondence analysis, and genetic analyses using four different DNA sequences (COI, 16S, 28S). Second, it turned out that the type material of L. calida contains two morphologically distinct groups of specimens. The holotype and 7 paratypes are similar to each other but differ significantly from the other also similar 16 paratypes, and from all European specimens. On the basis of these observations, the Laonome specimens from European waters are described here as L. xeprovala sp. nov. We also provide the characters of the branchial crown of three Laonome species for a prospective revision of this genus.

Anaesthetization and fixation effects on the morphology of sabellid polychaetes (Annelida: Polychaeta: Sabellidae)

One hundred and four specimens of Branchiomma luctuosum (Grube, 1870), a sabellid polychaete, were submitted to different anaesthetization and fixation procedures: a control group with living animals, immediate fixation with formaldehyde 4% (FO), ethanol 100% (AE) or ethanol 70% (ET), and anaesthetization with magnesium chloride (MC), refrigeration (RE), menthol crystals (ME) or freshwater (FW). Twenty-three morphometric variables of the body were measured and analysed with size-free multivariate statistics. The first three canonical variables explained 80% of the variation, being significantly correlated with 19 measured variables, mainly those related to the shape of the body setigers. Besides morphometric variables, some morphological characters commonly used in polychaete taxonomy also presented variation among fixation procedures, such as the release of parapodial elements and the integument. Among the procedures tested, AE, ET and FW were the best in approximating the shape of living specimens. Specimens submitted to FO and RE had shorter, wider, and thicker bodies, whereas those submitted to MC and ME were more elongated, narrower, flatter, and had wider pygidia than living specimens. Lengths of branchial crown, setiger 1 and pygidium seem to be the most informative morphometric characters for taxonomic purposes since they did not present deformation due to fixation procedures.

Redescription of Chone infundibuliformis Krøyer, 1856 (Polychaeta: Sabellidae) and histology of the branchial crown appendages, collar and glandular ridge

Fifty-three species have been formally described in Chone Krøyer, 1856, showing wide variation in the shapes of dorsal lips, peristomium, and posterior abdominal uncini. Previous studies indicate that such variation could result in splitting of the genus; however, the original description of the type species, C. infundibuliformis did not include critical details and illustrations, and for other species, incomplete or misleading information has been provided. In order to redescribe the species C. infundibuliformis and delineate the genus, type and topotype materials were reviewed, and histological sections of the appendages of the branchial crown, collar and glandular ridge are described. The redescription points out that in C. infundibuliformis: 1) insertion of the branchial lobes is not exposed beyond the collar; 2) radioles have a paired series of pinnules of different sizes; 3) radiolar flanges are broad; 4) dorsal lips are broadly rounded, as long as wide, without mid-rib; they have hyaline cartilage, but there is no extension of the branchial skeleton; 5) dorsal lips are vascularized by a plexus of small blood vessels derived from the basal branchial blood vessels, which further back communicate with the dorsal vessel; 6) thoracic uncini have teeth above the main fang of unequal size, median tooth of basal row larger than teeth in subsequent rows; 7) uncinus shape shows variation within each torus, but no intersegmental gradation is appreciable; 8) females with oocytes distributed in all thoracic and abdominal segments; males with sperm in abdomen, with barrel-shaped nucleus and mushroom-shaped acrosome. The collar is supported by a dense mass of hyaline cartilage and covered by glandular epithelium composed of basophile glands. Acidophil glands, tubular-shaped with granulose secretions, constitute the glandular ridge. Size of teeth in thoracic uncini, presence or absence of abdominal uncini variation, latero-ventral posterior abdominal depression, dorsal lips internal construction and glandular ridge are compared among some species of Chone and close genera.

Redescription of Chone americana Day, 1973 (Polychaeta: Sabellidae) and description of five new species from the Grand Caribbean Region

In this study Chone americana Day, 1973 from off the coast of North Carolina is redescribed and five new species are described from the Grand Caribbean region, as part of a revision of the genus. Chone americana is easily distinguishable from the other species by the presence of a pygidial cirrus, a radiolar membrane extending beyond half of the branchial crown length and long-sized radiolar tips. The unique distinguishing features for each new species are as follows: Chone diazi sp. nov. has completely exposed branchial lobes beyond the collar segment. In Chone farringtonae sp. nov. the main fang of posterior abdominal uncini extends beyond breast, and posterior peristomial ring collar length is twice as long as chaetiger 1. In Chone johnstonae sp. nov. the middorsal collar margin forms a broad gap. Chone perkinsi sp. nov. has a glandular ridge on chaetiger 2 broadest dorsally. Chone uebelackerae sp. nov. has a triangular pygidium and long radiolar tips. A taxonomic key for Chone species from the Grand Caribbean is included.

Kirkia heterobranchiata, a new genus and species of extratubular brooding sabellid (Polychaeta: Sabellidae) from São Paulo, Brazil

A new genus and species of sabellid polychaete from an organically enriched beach in São Sebastião, State of São Paulo, is described. Kirkia heterobranchiata is unique among sabellids for brooding the embryos on the dorsalmost pair of radioles, which exhibits several modifications for this purpose, rather than on ventral radioles. Morphologically, K. heterobranchiata is most closely related to Perkinsiana riwo, here referred to as the new genus, as suggested by phylogenetic analysis. The new genus is characterized by the shape of the lips (dorsal lips roughly triangular, broader than long; ventral lips lower, ventrally fused and distally rounded), by the absence of both radiolar and pinnular appendages, by having uncini with very short handles in both the thorax and abdomen, and by the ability to brood embryos in cocoons attached to the branchial crown.

Aspects of the feeding biology of the fanworm Bispira volutacornis (Polychaeta: Sabellidae)

The detail of the characteristic double whorled branchial crown of the tubiculous polychaete Bispira volutacornis, with its internal skeleton of large vacuolated cells and ciliated radioles, is consistent with the feeding apparatus of sabellids at large. Studies show that ingested particulate matter has at least one dimension less than 15 μm. Feeding seems to be most readily accommodated at current speeds from 1 cm s−1 to 3 cm s−1 with the crown apex angled downstream. Particulate matter passes through the alimentary canal in 7·7 h at 14°C, for an average sized specimen of 97 segments. Whilst the tube provides protection against predatory fish and crustaceans (with ample evidence of sub-lethal cropping of the branchial crown), it also has a role in irrigation and respiration. The worm will retreat within the tube when current flow exceeds 8·7 cm s−1.

Développement morphologique et croissance des juvéniles de l'Owenia fusiformis Delle Chiaje (Polychaeta, Oweniidae)

The morphological development of the branchial crown and uncinigerous tori, growth, and demographic structure were observed in juveniles of Owenia fusiformis Delle Chiaje, 1841 from the Bay of Seine (eastern English Channel). Growth becomes significant only after one and a half months of benthic life; individual growth is highly variable and results in a progressive widening of the size distribution of the population over time. From six initial branches present at the post-larval stage, seven stages of branchial development can be distinguished. The branchial crown develops by successive dichotomous divisions and growth of the new branches. The number of dichotomous divisions (D) increases with total length (LT) and age (A): D = 1.718 ln(LT) − 0.291; D = 0.987 ln(A) − 1.471. The number of uncinigerous tori (T) increases with total length (LT) and age (A): T = 4.272 ln(LT) + 7.272; T = 4.477 ln(A) − 2.479. The acquisition of fully grown characters after metamorphosis was progressive and depended more on total length of the juvenile than on age. At any given age, there was an important variability in investigated characters because of differential growth of juveniles. Ecological consequences resulting from interactions between morphological development and growth with respect to recruitment are discussed.