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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Dendrobaena

Dendrobaena Eisen, 1872 emm. Rosa, 1893 (ref. ID; 3692), Eisen, 1873 (ref. ID; 6916) or Eisen, 1874 emmend. Rosa, 1893 (ref. ID; 1257)

Family Lumbricidae (ref. ID; 6033, 7651)

Family Lumbricidae: Subfamily Lumbricinae Michaelsen, 1910 emm. Omodeo, 1956 (ref. ID; 1257)

ref. ID; 6916

The genus Dendrobaena comprises small to medium-sized species with reddish pigmentation, epi- and tanylobous prostomium, distant setae, first dorsal pore located anteriorly, spermathecal pores in 9/10 and 10/11, a variable number of seminal vesicles (2, 3 or 4 pairs) in 9, 10, 11 and 12 and fasciculate or pinnate musculature (Bouche 1972; Sims and Gerard 1999; Csuzdi and Zicsi 2003). From this morphological description it is obvious that this genus is very heterogeneous and after several attempts trying to clarify the diagnosis of this genus (Cognetti 1931; Pop 1941), Omodeo (1956) divided it into two subgenera, Dendrobaena and Dendrodrilus, the latter being defined by the presence of pouches in 10. This finer division was followed by Bouche (1972) in this description of the Frence fauna. Later Gates (1973) raised these two taxa to generic level which was fully adopted in the English literature (Gates 1975; Fender 1985; Sims and Gerard 1999) based on the presence of pouches in 10 in Dendrodrilus, the arrangement of the nephropores (obviously in a single rank in the of former but inconspicuous and alternating irregularly in the latter) and the different shapes do their nephridial bladders (ocarina and forming a U-shaped loop, respectively). However, some of these characters (e.g. the aligned nephropores) are only observed in just a few species (Csuzdi and Zicsi 2003). Csuzdi (1984) carried out a detailed revision of the genus and established four species groups: "octaedra group", "schmidti group", "byblica group" and "veneta group" based on the morphology of the male pores and structure of the circulatory system, the calciferous gland and musculature. Later taxonomic revisions have not attempted to solve this heterogeneity problem, but highlighted the enormous morphological variation of the species included and the need for a more detailed revision (Mrsic 1991; Qiu and Bouche 1998; Csuzdi and Zicsi 2003). Part of the problem is the high degree of homoplasy (Rota and Erseus 1997), which makes it difficult to reconstruct the evolutionary history. More recently, Cech (2005) used molecular techniques to produce a better taxonomic division of the genus; unfortunately the 18S rDNA subunit did not allow the clarification of the Dendrobaena clade and concluded that more sensitive genes should be tested. In relation to this, it has been recently recognised that 18rDNA genes provide limited information in earthworm phylogeny at the genus level (Pop et al. 2008). The three Dendrobaena species present in the British Isles, i.e. D. attemsi Michaelsen, 1901, D. octaedra (Savigny, 1826) and D. pygmaea (Savigny, 1826) have also been recorded in France (Bouche, 1972) and in the Iberian Peninsula (Mato 1986; Mascato 1986; Marino et al. 1986, 1987; Trigo et al. 1988, 1990; Briones et al. 1991, 1992, 1994; Souto 1992; Souto and Mascato 1993; Sanchez et al. 1998, 1999; Monroy 1999; Monroy et al. 2003). In our phylogenetic study we included D. attemsi, D. octaedra and D. madeirensis Michaelsen, 1891; and the results strongly indicate that Dendrobaena does not form a clade as the species assigned to this genus are scattered throughout the phylogeny. Furthermore, D. attemsi does not seem to be related to D. octaedra, in agreement with previous studies (Fender 1982, 1985; Rota and Erseus 1997) due to their distinct arrangement of the nephropores, the unique shape of their nephridial bladders (J-shaped but with an 180 degrees bend at the ventral extremity), the development of the calciferous gland, the shape of the clitellum, the intersetal distances and the morphology of the genital setae. These differences are, according to Fender (1982), so significant as to justify its exclusion from the genus Dendrobaena. D. octaedra is a widely distributed peregrine species with variable chromosome number due to polyploidy (120-130) and parthenogenetic races, which could explain the observed high morphological variation in several of its reproductive organs (e.g. reduction in the number of spermathecae and seminal vesicles) leading to the description of several synonyms (Csuzdi and Zicsi 2003). Furthermore, both trees suggest that D. attemsi is very closely related to Dendrodrilus rubidus (98 and 100% BS for 16S and COI, respectively) and with L. eiseni. Using 18S rDNA sequences, Cech (2005) found a similar arrangement in which Ad. eiseni, Dd. rubidus, Dd. subrubicundus and E. andrei (GeneBank data) were grouped. Full elucidation of these genera will require further investigation using other genes and by including a greater number of these forms in the analyses. Bouche (1972) also include in his species' list D. mammalis (Savigny, 1826) which was placed by Gates (1975) in a new genus Satchellius based on its sausage-shaped nephridial bladders, conspicuous alternation nephropores, prostomium epilobous and calciferous gland with pouches opening posterior and ventrally in segment 10. Interestingly, this species shows the primitive octovesiculate condition and the 16S sequences place this taxon close to the epigeic clade formed by D. attemsi/Dd. rubidus and L. eiseni, although with low confidence. Two species are included in the subgenus Dendrodrilus according to Bouche (1972), Dendrobaena (Dendrodrilus) rubida and Dendrobaena (Dendrodrilus) subrubicunda as a result of their distinct morphology (length of the clitellum and tubercula pubertatis) and ecology (hygrophilous and preferring highly organic soils, respectively). Furthermore, the former species is also considered by this author to comprise two subspecies, Dendrobaena (Dendrodrilus) rubida rubida (Savigny, 1826) and Dendrobaena (Dendrodrilus) rubida tenuis Eisen, 1874, based on the reduction of the tubercula pubertatis, the total disappearance of the spermathecae and atrophy of the seminal vesicles in segment 9. However, according to Gates (1975) they are indeed parthenogenetic morphs and the genus Dendrodrilus contains only one species. In addition, Dd. norvegica (Eisen, 1874) has been described for Norwegian fauna (Stop-Bovitz 1969) and it only differs from Dd. rubidus in having only two pairs of seminal vesicles instead of three pairs and spermathecae reduced in size. These are the diagnostic characters of Dd. r. tenuis given by Bouche (1972) and for this reason, it is now considered as a synonym (Gates 1980). Certain authors regard the three taxa as subspecies (Zicsi 1982; Mrsic 1991; Csuzdi and Zicsi 2003), forms (Perel 1979), morphs (Sims and Gerard 1999) or independent species (Qiu and Bouche 1998). Noteworthy is that Csuzdi and Zicsi (2003) question the validity of the three subspecies as they are widely distributed peregrine worms with different states of polyploidy and parthenogenesis and accordingly, they consider that Dd. r. tenuis is just a parthenogenetic form of the nominal subspecies. Indeed, Sims and Gerard (1999) pointed out the different chromosome number attributed to the different morphs in the British Isles, with Dd. r. rubidus having 34, Dd. r. subrubicundus 68 and Dd. r. tenuis 48 and the contrasting values for the same morphs in other parts of the world (e.g. Dd. r. subrubicundus in Italy has 34 chromosomes and Dd. r. rubidus from Greenland and Dd. r. tenuis from eastern Alps have 102). Finally, the sequence fragments used here did not provide a good phylogenetic discrimination for the endemic species of the north-western area of the Iberian Peninsula (Alvarez 1971), D. madeirensis. Unfortunately, very little is known about the anatomy, biology and ecology of this species and available information refers to its geographical distribution (Trigo et al. 1990; Briones et al. 1992; Souto 1992; Rodriguez et al. 1997; Monroy et al. 2003). (ref. ID; 6916)
  1. Dendrobaena alpina (Rosa) (ref. ID; 7651) reported author and year? (ref. ID; 6033)
  2. Dendrobaena alvaradoi (ref. ID; 6033)
  3. Dendrobaena attemsi (Michaelsen, 1901) (ref. ID; 6916) or 1902 (ref. ID; 6653) reported year? (ref. ID; 7651) reported author and year? (ref. ID; 6033)
  4. Dendrobaena auriculata (Rosa) (ref. ID; 7651)
  5. Dendrobaena byblica (Rosa) (ref. ID; 7651) reported author and year? (ref. ID; 6033)
  6. Dendrobaena calarensis (ref. ID; 6033)
  7. Dendrobaena cognettii (Michaelsen, 1903) (ref. ID; 6036) reported author and year? (ref. ID; 6033)
  8. Dendrobaena cognettii gallurensis Rota, 1992 (ref. ID; 6038 redescribed paper)
    Syn; Helodrilus ribaucourti Cognetti, 1901 (ref. ID; 6038)
  9. Dendrobaena franzi (ref. ID; 6033)
  10. Dendrobaena hortensis (Michaelsen, 1890) (ref. ID; 6036) reported author and year? (ref. ID; 6033)
  11. Dendrobaena kuraschvilii Kvav. (ref. ID; 7651)
  12. Dendrobaena lacustris (Steph.) (ref. ID; 6609) reported author and year? (ref. ID; 6033)
  13. Dendrobaena lusitana (ref. ID; 6033)
  14. Dendrobaena madeirensis Michaelsen, 1891 (ref. ID; 6916) reported author and year? (ref. ID; 6033)
  15. Dendrobaena mammalis (Savigny, 1826) (ref. ID; 1257, 6916) reported author and year? (ref. ID; 6033)
  16. Dendrobaena mariupolienis (Wyssotsky) (ref. ID; 7651)
  17. Dendrobaena montana (Michaelsen) (ref. ID; 7651)
  18. Dendrobaena octaedra (Savigny, 1826) (ref. ID; 1257, 3692, 6916) reported year? (ref. ID; 7651) reported author and year? (ref. ID; 6033)
  19. Dendrobaena osellai (ref. ID; 6033)
  20. Dendrobaena pantaleonis (ref. ID; 6033)
  21. Dendrobaena parabyblica Perel (ref. ID; 7651)
  22. Dendrobaena pentheri (Rosa) (ref. ID; 7651)
  23. Dendrobaena platyura f. depressa (ref. ID; 6913)
  24. Dendrobaena platyura f. montana (Cern.) (ref. ID; 7651) reported author and year? (ref. ID; 6913)
  25. Dendrobaena pseudorrosea (ref. ID; 6033)
  26. Dendrobaena pygmaea (Savigny, 1826) (ref. ID; 6916)
  27. Dendrobaena rhodopensis Cern. (ref. ID; 7651)
  28. Dendrobaena rubida (ref. ID; 6033)
  29. Dendrobaena rubida f. subrubicunda (Eisen, 1874) (ref. ID; 1257) reported year? (ref. ID; 7651)
  30. Dendrobaena rubida f. tenuis (Eisen, 1874) (ref. ID; 1257)
  31. Dendrobaena rubida f. typica (Savigny, 1826) (ref. ID; 1257)
  32. Dendrobaena rubidus (Savigny, 1826) (ref. ID; 6653)
  33. Dendrobaena ruffoi (ref. ID; 6033)
  34. Dendrobaena schmidti (Michaelsen) (ref. ID; 7651)
  35. Dendrobaena veneta Rosa (ref. ID; 6121, 6127, 7651) reported author and year? (ref. ID; 6033)
  36. Dendrobaena veneta f. typica (Rosa, 1886) (ref. ID; 1257)
  37. Dendrobaena veneta var. hibernica f. dendroidea (Friend, 1909) (ref. ID; 1257)
  38. Dendrobaena veneta var. hibernica f. typica (Friend, 1892) (ref. ID; 1257)
  39. Dendrobaena veneta var. hortensis (Michaelsen, 1890) (ref. ID; 1257)
  40. Dendrobaena veneta var. zebra (Michaelsen, 1902) (ref. ID; 1257)

Dendrobaena cognettii gallurensis Rota, 1992 (ref. ID; 6038 redescribed paper)

Synonym

Helodrilus ribaucourti Cognetti, 1901 (ref. ID; 6038)

Descriptions

  • External: Body elongate, cylindrical, narrowing posteriorly. Size: 16-34x1-1.2 mm. Segment number: 70-102. Red pigmentation. Prostomium 1/2 epilobous very large. Dorsal pores absent. Nephridiopores very large, aligned over setal lines b. Setae almost invisible, intersetal ratio at segment 40, aa:ab:bc:cd:dd=1.4:1.3:1.3:1:1.5. Male porophores middle-size, restricted to segment 15. Female pores in 14, over setae b. Spermathecal pores absent. Clitellum saddle-shaped over 31-35 with clear intersegmental furrows. Tubercula pubertatis absent. Genital papillae absent. (ref. ID; 6038)
  • Internal: The internal anatomy fits exactly the descriptions of the nominal subspecies. The typhlosole is ribbon-like and begins in 20. It must be remarked that the seminiferous funnels are covered with sperms. (ref. ID; 6038)

    Taxonomy

    Dendrobaenea cognettii gallurensis differs from all the nominal populations described up to now, mostly in having the clitellum exceptionally displaced forward. The species was originally described under the name of Helodrilus ribaucourti (Cognetti, 1901) from the surroundings of Sassari (northwest Sardinia), ca. 100 km away from the present record. In the type material the clitellum extended over segments 32(or 33)-37. (ref. ID; 6038)

    Habitat

    Leaf litter of cork oak. (ref. ID; 6038)

    Dendrobaena veneta Rosa (ref. ID; 6121, 6127, 7651) reported author and year? (ref. ID; 6033)

    Descriptions

    D. veneta has paired ovaries located ventrally in segment 13. The ovaries were ligament-attached to the disseptimentum at one end and at the other extended freely into the coelom. Germ cells formed distinct zones within the ovary. The vicinity of intersegmental septum was occupied basally by oogonia. Differently sized cells were located in the ovaries medially. Within that, zone oogonia were no longer present but cells became differentiated into oocytes and trophocytes. The apical part of ovary contained large mature oocytes with few trophocytes scattered around. The outer epithelial layer was built by squamose somatic cells. The ovarian strom was also composed of somatic cells whose processes wound tightly around germ cells at different stages of development and trophic cells (trophocytes) inside the ovary. The processes of adjacent somatic cells were all connected by numerous desmosomes. Initially, young oocytes were spherical in shape and contained poorly differentiated ooplasm with large spherical nuclei. Nuclear chromatin formed synaptonemal complexes accompanied by perichromatin granules. Cell nuclei contained nucleoli. Oocytes increased in volume while migrating towards the apical part and their ooplasm became more and more differentiated; it contained numerous elongated electron-dense mitochondria and numerous dictyosomes of Golgi complexes. Within that zone oocytes were accompanied by quite numerous trophocytes which were initially hardly distinguishable from the former, but while maturing the trophocytes increased in volume and elongated in shape. Cell nuclei in trophocytes were large, elongated and bound by an undulated membrane. While maturing, trophocytes became rich in cell organelles and storage materials in the cytoplasm. (ref. ID; 6121)

    The suprapharyngeal (cerebral) ganglion was located over the pharynx in body segment 3 and connected by peripharyngeal connectives with the ventrally located subpharyngeal one. The latter was larger than the former extending along body segments 3 and 4 and forming the initial part of the ventral chain. In the cerebral ganglion neurosecretory cells lay cortically and exhibited different sizes, shapes and the content of neurosecretion. Medium and large cells were oval or pear-like in shape. Most of them contained moderate amounts of neurosecretion. Neurosecretion was granular in nature and stained dark violet with paraldehyde fuchsin. Granules of neurosecretion were present also in the axons of neurosecretory cells in neuropile, intercellular spaces and in the sheath enveloping the ganglion. The subpharyngeal ganglion was structured similarly. Neurosecretory cells there did not differ so much in their sizes and shapes. They were large, oval and contained moderate or large amounts of granular neurosecretion which was distributed throughout the cytoplasm. There were numerous granules of neurosecretion in axons of these cells, between the cells and in the neuropile and in the sheath enveloping the ganglion. Blood vessels were also located there. The area between the neurons and in the neuropile containing neurosecretory granules is called "storage zone". Ribonucleic acid (RNA) was present in all neurosecretory cells in both tested ganglia. It occurred in nucleoli and in the cytoplasm in form of the fine granules. In most cells RNA was evenly distributed throughout the cytoplasm. In some cells aggregations of RNA granules occurred peripherally. The reaction was stronger in cells of the subpharyngeal ganglion that in the suprapharyngeal one. (ref. ID; 6127)