Types Of Chaetae Research Articles

Formation and degeneration of scaled capillary notochaetae in Owenia fusiformis Delle Chiaje, 1844 (Oweniidae, Annelida)

Phylotranscriptomic studies of the past decade have repeatedly placed Oweniidae together with Magelonidae, as the sister group to remaining annelids. This newly established placement clearly makes them a key-lineage for understanding annelid evolution and morphology. One of the most prominent morphological features of all annelids are their chaetae. The arrangement and formation process (chaetogenesis) of these chitinous bristles have been studied extensively in hooked chaetae that are arranged in rows. However, the information on other types of chaetae is still scarce. In this study, we investigated the scaled capillary notochaetae of Owenia fusiformis, looking both into the formation process that causes the scaly surface ornamentation and into their arrangement within tight bundles. Our results demonstrate the incredible plasticity of chaetogenesis that allows forming a vast array of three-dimensional structures. The capillary chaetae of Owenia fusiformis are unique in lacking an enamel coating and the scales covering the apical surface of each chaeta are formed by a single microvillus of the chaetoblast. Furthermore, the bundle of chaetae has a peripherally located formative site and a central degenerative site and it appears to result from a secondary curling of the chaetal sac.

The multiformity of antennal chaetae in Troglopedetes Joseph, 1872 (Collembola, Paronellidae, Troglopedetinae), with descriptions of two new species from Thailand.

Two new species of the genus Troglopedetes Joseph, 1872 (T. meridionalissp. nov. and T. kaesp. nov.) are described from caves of the Thai peninsula. This is the first report of the genus south of the Kra Isthmus. The two new species have two rows of dental spines shared by all Thai Troglopedetes. They differ from other members of the genus mainly in the arrangement of dorsal chaetotaxy on head. The antennal chaetotaxy of the two species is analysed in detail in the second part of the paper. All types of antennal chaetae of both new species and their distribution patterns are described for each antennal segment: scales, ordinary chaetae, S-chaetae and subapical organite of Ant. IV. Twenty different types of chaetae are recognised and all except one are present in both species. The total numbers of ordinary chaetae and S-chaetae and their patterns of distribution on antenna are very similar between the two species (483 vs. 518 ordinary chaetae; 207 vs. 208 S-chaetae). Each type of chaetae has its own distribution pattern, markedly contrasted between dorsal and ventral side of antennae, and between antennal segments. This diversity of morphologies and distribution patterns and their similarity between the two species, as well as differences with other species of the same family, suggest that antennal chaetotaxy could provide powerful new characters for the taxonomy of Troglopedetes and related genera.

Revision of Fauveliopsidae Hartman, 1971 (Annelida, Sedentaria).

Revision of Fauveliopsidae Hartman, 1971 (Annelida, Sedentaria).

Two new Isotomidae species (Collembola: Entomobryomorpha) from Rio de Janeiro State, Brazil.

In the present paper, two new species of Isotomidae belonging to the genera Isotomiella Bagnall, 1939 and Paracerura Deharveng & Oliveira, 1994 are described and illustrated. Isotomiella denticulata sp. nov. is distinguished from all known species specially by a single tooth in the inner edge of the unguis, a unique feature among the members of the genus. Paracerura bella sp. nov., differs from other congeners with respect to overall coloration, the sensillary pattern on tergite abd. IV-V and type of chaetae on both lateral margins of dens. Both species are described from Rio de Janeiro, Brazil.

Marphysa (Eunicidae, polychaete, Annelida) species of the Sanguinea group from Australia, with comments on pseudo‐cryptic species

AbstractThe genus Marphysa is widely collected for bait by recreational fishermen in Australia, and yet the number of species remains unresolved. A new species is described together with additional information on a previously described species. This study reveals that while species of Marphysa superficially resemble one another, detailed studies on the distribution of different types of chaetae along the body, together with molecular studies, uncover species which may co‐occur. Correct identification is critical for management of these largely intertidal species. This study also highlights the increasing awareness of the presence of pseudo‐cryptic species in polychaetes.

Re-description of Cirratulus dollfusi (Polychaeta: Cirratulidae), and Fauvelicirratulus as a new genus

Cirratulus dollfusi Fauvel, 1928 is re-described from the material from the Sea of Marmara. The specimens collected from the Sea of Marmara were compared to the holotype of the species. The species is a multitentaculate and multibranchiate cirratulid; it differs from all other known cirratulid genera in its type of chaetae and the way the multiple branchial filaments arise from the notopodia. Chaetae are of two types: numerous long, fine capillaries in both rami throughout, also 2–4 shorter, wider, finely tapering spines in noto- and neuropodia. There are no slightly flattened sigmoid spines, typical of most Cirratulus species. Very short, slender grooved tentacles arise in a small circular group on either side of chaetiger 1. Branchial filaments are multiple; they arise as 1–2 filaments from each of 4–8 raised notopodial lobes on parapodia of anterior and middle segments, with lobes fading out and fewer (holotype) or no branchiae posteriorly (our material). No other cirratulid genera appear to have straight, tapering spines plus so many fine capillaries. We propose Fauvelicirratulus gen. nov. for this species. The species seems most closely related to Cirratulus hedgpethi Hartman, 1951, from the northern Gulf of Mexico, still only known from the incomplete original description. Features of some cirratulid genera are compared and the use of multiple branchiae as a generic character is discussed.