Achaeta Vejdovský, 1878

Rota, Emilia, 2015, Five new species of Enchytraeidae (Annelida: Clitellata) from Mediterranean woodlands of Italy and reaffirmed validity of Achaeta etrusca, Fridericia bulbosa and F. miraflores, Journal of Natural History 49 (33), pp. 1987-2020 : 1990

Genus Achaeta Vejdovský, 1878

Anatomical remarks on the genus

The flask-shaped (=pyriform) glands, when occurring, always start in a speciesspecific segmental position (own observation) (e.g. Figures 1B , 3A ), although this diagnostic character is generally omitted in identification keys (e.g. Nielsen and Christensen 1959; Schmelz and Collado 2010). The lateral commissures between dorsal and ventral blood vessels in European Achaeta are always three pairs (two in III, one in IV) (see Vejdovský 1884, plate 7, figure 1; Rota 1995). The shortness of the longitudinal muscle fibres gives the body wall surface a peculiar lozenge pattern; this condition, first noted by Michaelsen (1889) in Achaeta bohemica : ‘The slow, lumbering movement of the animals is related thereto’ (pp. 47–48) ( Figure 2B ), seems to be distinctive for most species in the genus (pers. obs.; Figure 3D ), as compared with the longer muscle strands observed in other genera. In A. bohemica, Michaelsen (1889) also detected intracellular canals ( Figure 2C ) in the gut epithelium of segments behind the origin of the blood vessel: ‘The columnar epithelial cells are run through by a system of exceedingly fine canals, which apart from being much finer, recall the chylus cells of some Fridericia species. The canals lie parallel to the length direction of the cells, so that a cross section thereof has a sieve-like appearance. A more intimate relationship with the blood vascular system could not be proven’ (p. 48). However, these intracellular canals have never been observed since in Achaeta , not even in the very large-sized A. gigantea Dózsa-Farkas, 2000 ; the question should be further investigated by histological methods.

Figures

Figure 1. Achaeta borbonica sp. nov. (A) Anterior body half in a dorsal view. Note the intestinal loop in IX; (B) lateral view of segments IV–V, showing the right spermatheca; asterisks indicate the oesophageal dorsal ridge; (C) ventral view of segment V, revealing the closely spaced spermathecal pores; (D) sperm funnel in segment X; (E) lateral view of nephridium in segment VIII; (F) coelomic cavity of caudal segments (lateral view), showing the coarse granulation of the chloragogenous cells and the small size of coelomocytes as compared with the flask-shaped glands. (G and H) Lateral views of clitellum, in vivo (G) and after fixation (H). All except (H) from live specimens. In (A), (D) and (E) anterior to the top; in all others, anterior to the right.

Figure 2. Achaeta bohemica (Vejdovský, 1879a) as illustrated by Michaelsen (1889). (A) Crosssection through segment XII, showing the conspicuous hyaline gland cells on the dorsolateral sides of the clitellum, the flask-shaped glands (b), and the glands surrounding the male openings (p); (B) arrangement of the longitudinal muscle fibres in the body wall; (C) intestinal epithelial cells of segment IX, showing their fine intracellular canals in cross (q) and longitudinal (l) section.

Figure 3. Achaeta giustii sp. nov. (A) Cephalic region (lateral view); (B) dorsolateral view of segments I–VIII, showing the well-developed pharyngeal glands; (C) dorsal view of clitellum. Note the granular cells bordering the middorsal interruption (dg); (D) shallow lateral view of body wall (segment IX), revealing the lozenge pattern of the longitudinal muscle fibres; (E) lateral view of clitellum, showing the reticulate pattern of the gland cells; (F) lateral view of same clitellum in a deeper optical section, documenting its midventral continuity and middorsal gap; (G) ectal portion of the spermatheca; (H) sperm funnel. All from permanent wholemounted specimens, anterior to the left.