This page presents new as well as continuing perspectives associated with historical and present day Oligochaetology, including (but not limited to) publications focusing on phylogeny, taxonomy, systematics, and nomenclature of oligochaetes and other annelids. When possible, abstracts from or summaries of these publications follow the citations. We provide a link {in blue} for papers referenced below that are accessible via open access journals and other literature websites. Full citations for publications referenced in text, below, will be included in the References page (accessible via the left navigator bar). We take no position here on the scope or content of these publications, but do encourage constructive dialog between oligochaetologists on the perspectives, concepts, recommendations, and suggestions presented therein. – J.W.R. and M.J.W.
Historical Oligochaetology
Rota, E. 2011. Early oligochaete science, from Aristotle to Francesco Redi. Archives of Natural History 38.1 (2011): 136-163.
Summary: This paper reviews knowledge on earthworms from early classical times to the end of the seventeenth century. The Aristotelian view that these “imperfect” animals developed spontaneously from mud and lacked internal organs except the gut was not challenged until the late Renaissance but, by the end of the 1600s, it was overthrown. Aldrovandi and Mouffet presented field observations of sexual reproduction and specific habitat requirements. Willis demonstrated the complex internal anatomy of an earthworm. Finally Redi, based on numberless dissections, showed the existence of variations on that basic anatomical plan, which anyway remained distinct from that of parasitic worms. Through a series of controlled laboratory tests, Redi also proved that earthworms have a physiology of their own and are most sensible to water loss. In those same years, Swammerdam investigated earthworm cocoons nursing them in his room, and Tyson discovered earthworms’ hermaphroditism. Two significant interpretations of earthworm’s locomotion, by Fabrici ab Aquapendente and Borelli, also belong to this period, but were both short-lived in their influence. An awareness of the ecological role of earthworms in pedogenesis and soil fertility did not emerge until the late eighteenth century.
Rota, E. 2022a. How the discovery of oligochaete regeneration during the Enlightenment was pivotal to the advancement of annelid research. Zoological Journal of the Linnean Society XX: 1–24.
Summary: Within a few months of the year 1741, Lyonet and Trembley in Holland, Bonnet in Geneva and Réaumur in Paris all experimented industriously with the regeneration of various invertebrates, including the still unknown microdrile oligochaetes. Some of these worms were prone to spontaneous fragmentation as a natural mode of asexual multiplication, preceded (paratomy) or followed (architomy) by regenerative processes. Bonnet and Réaumur raised the stakes and began to study regeneration in earthworms, a challenge that, especially in Italy, inspired scholars and educated people among the clergy and aristocracy. Spallanzani conducted the most rigorous experiments and was the first to obtain consecutive regenerations of the head in one and the same megadrile. He saw detached mid-body sections becoming complete with a new head and a new tail, and he determined the points of the body where regeneration does not take place and how much length to leave for each section so that it could reintegrate. Above all, Spallanzani obtained regeneration of the gonadic segments, both in terrestrial and in freshwater megadriles, the latter today identified as Criodrilus lacuum. This and other important anatomical and physiological findings by Spallanzani, largely unpublished during his lifetime and for a long time after, preceded the discoveries of later authors by almost 50 years.
Dr. Rota encourages contact from readers regarding the content of her publications.
Rota, E. 2022b. Exploring annelids in the age of Enlightenment and beyond: classification and bioluminescence. Zoological Journal of the Linnean Society XX: 1–27.
Summary: The diversity of segmented worms was gradually recognized during the 18th century and referred to a special type of animal, distinct from insects and other groups. The relationship of microdriles with earthworms was suspected, thanks to the pioneering work of Rösel, Schäffer and Müller. However, annelids could not be diagnosed correctly, nor could any reliable classification be elaborated, as long as life forms were grouped by body shape, ‘degree of perfection’ (morphoanatomical or behavioural complexity), type of reproduction (sexual/asexual) or other aspects considered in isolation, as practised by Bonnet, Linnaeus and, later, Lamarck and Ehrenberg. The different attitude of Pallas and Cuvier, based on a rigorous anatomical/physiological evaluation, led to the unveiling of the interrelationships between the most varied forms and the specificities of the annelid body plan. In particular, Cuvier’s deep understanding of the internal structures of animals allowed him to recognize, at the close of the 18th century, the kinship between microdriles, megadriles and leeches. The reinterpretation of two episodes of oligochaete bioluminescence, one in France, the other, hitherto neglected, in Siberia, provides a good illustration of the state of knowledge of clitellates in the early 1770s. Neither species was named at the time, yet both were characterized sufficiently to be identified unequivocally today.
Dr. Rota encourages contact from readers regarding the content of her publications.
Classification
Over the years, many proposed classifications for annelids have been presented in the literature; one such classification divided the phylum Annelida into two subphyla: the Aclitellata (with the two classes Aphanoneura and Polychaeta) and the Clitellata (including the Acanthobdellida, Branchiobdellida, ‘Oligochaeta’, and Hirudinea). Yet, because the Aclitellata is a general term — established only as an equivalent ranking to the Clitellata rather than being based on phylogenetic studies — we think it is better to refer to the two groupings as clitellates and non-clitellates. Regardless, this checklist is not the place to discuss or resolve the most appropriate or accurate classification for the ‘Oligochaeta’, let alone for the entire Phylum Annelida.
Indeed, the nominal taxon ‘Oligochaeta’ is paraphyletic, and thus – in a strict cladistic approach – invalid if using in exclusion of leeches. The corresponding monophylon, Clitellata, includes the leeches and leech-like successors of the ‘Oligochaeta’. Thus, Oligochaeta (with a new meaning) and Clitellata are synonyms; however, because the Code (ICZN 1999) does not use priority rules for taxa above the family-group level, either name is acceptable for use. Clitellata may be preferred as it retains its original meaning. Based upon the extensive discussions presented by Martin et al. (2000), Martin (2001), Timm (2005), Erséus (2005), and the recent phylogenetic work of Erséus et al. (2000), Erséus and Gustavsson (2002), Erséus et al. (2002), Erséus and Källersjö (2004), and Envall et al. (2006), the term ‘oligochaetous Clitellata’ (oligochaetoid Clitellata) also could be used for the oligochaetes instead of the name ‘Oligochaeta’ (albeit these two terms seem awkward) — at least until this issue is more formally addressed. Timm (2005, p. 57) does temper us with this observation: “However, any good idea can be discredited when developed into [the] absurd, and so does the principle of monophyly in systematics.” If you are intrigued by this quandary, you are directed to read the above papers (as well as those cited therein, including Ashlock, 1971 and Valentine, 2004).
There are many more recently published papers that need to be highlighted here – several that provide additional insight to the information presented in the cited publications above; we hope do add these sometime in the near future. Please also visit the ‘Classification’ page accessed from the left navigation bar on each page of this NO2 site.
Family Naididae and Family Tubificidae
Summary: Morphological and molecular characters support the premise that all members in the clitellate family Naididae (sensu stricto) are phylogenetically nested within the family Tubificidae (sensu stricto). Erséus and Gustavsson (2002) proposed that these taxa, together, should be regarded as a single family to avoid this paraphyly of Tubificidae, also suggesting that all naidids be classified as members of Tubificidae – thus lowering their rank to the subfamily, Naidinae, within this taxon. In that same paper, Erséus and Gustavsson also re-confirmed that Naididae is the older of the two (family-group) names, with the realization that the suggested action would violate the principle of priority stipulated by the International Code of Zoological Nomenclature [Code] (International Commission on Zoological Nomenclature [Commission] (ICZN 1999).
Erséus et al. (2005) subsequently submitted an application to the Commission, requesting their ruling to establish precedence of Tubificidae Vejdovský, 1876 over Naididae Ehrenberg, 1828 – which would result in Tubificidae (the most inclusive of the two former families) retaining its name, and with the former naidids thus being included within the Tubificidae. However, members of the Commission voted against this request, stating that the use of Tubificidae (sensu stricto) was not so great as to justify reversal of procedure and that no confusion would result from adherence to priority (ICZN 2007: opinion 2167 [case 3305]).
It is important to emphasize that, in its decision, the ICZN dealt specifically with the use of names, but expressed no opinion whether or not the names Tubificidae and Naididae are synonyms. Furthermore, the ICZN decision neither affirmed nor rejected any hypothesis of phylogenetic relationships among the taxa involved, and was neither in favor nor against the principle of monophyly in classification. Regardless, the application of this decision was that – whenever the former naidids and tubificids together are treated as a single family (as recommended in Erséus et al. 2008), the name of this family is Naididae Ehrenberg, 1828, with Tubificidae Vejdovský, 1876 as its junior synonym, with both names are included on the Official List of Family-Group Names in Zoology (ICZN 2007). Please refer to Erséus et al. (2008 – accessible via the link via the full citation, above this summary) for a more extensive history of and supportive literature for this change.
Please note that several of our esteemed colleagues disagree with the above recommendation, supporting the two familes sensu stricto.
Family Pristinidae / Subfamily Pristininae
Envall et al. (2006) showed that Naididae in its former, restricted, sense (sensu stricto) is likely to be polyphyletic, leading Erséus et al. (2008) to advocate that Pristina Ehrenberg, 1828, should be referred to a separate subfamily, Pristininae Lastočkin, 1921 – well separated from Naidinae Ehrenberg, 1828; the latter containing all other former naidid genera.
Timm (2009) stated that all Pristina species should be placed in their own family, Pristinidae, rather than be placed in the subfamily Pristininae within the Naididae.
Family Opistocystidae
Abstract: Opistocystidae Černosvitov, 1936 is a largely Neotropical oligochaete taxon containing seven species. Its familial status has never been formally challenged, although possible close relationships with Naididae and Phreodrilidae have been noted. Mitochondrial 12S and 16S rDNA, and nuclear 18S rDNA, of a range of aquatic oligochaete taxa, including Trieminentia corderoi (Opistocystidae), were analysed by Bayesian inference. This showed that T. corderoi is a derived lineage within Naididae, closely related to Pristina and its monotypic subfamily Pristininae. Opistocystidae as a whole (with its three genera, Opistocysta, Trieminentia, and Crustipellis) is thus likely to be a group within Naididae.
Updated Species List of World Oligochaeta and Lumbricidae
In late April 2015, our esteemed colleague, Dr. Tarmo Timm, informed us that he has compiled an updated species list of world aquatic Oligochaeta and Lumbricidae, with synonyms. This project, part of the Estonian Species Registry (a database of species and other taxa found in Estonia and elsewhere) was prepared with support from the Estonian Biodiversity project at the Nature Museum of Tartu University in Tartu, Estonia. Records of taxa included in this registry are based on specimens deposited in collections, environmental DNA, human observations, and references. Dr. Timm notes that the exotic terrestrial earthworm families have generally been ignored in this list.
Please visit this website via the URL addresses, below:
http://elurikkus.ut.ee/elr.php?lang=est (in Estonian), and http://elurikkus.ut.ee/elr.php?lang=eng (in English)
The Importance of Correct Scientific Names in the Biological Sciences
Abstract: Researchers are continuing to identify polychaetes using inappropriate references and failing to appreciate that many if not most species have restricted distributions. Using Marphysa sanguinea (Montagu, 1813) as a case example, we discuss the loss of valuable data by misidentifying a species. We suggest ways in which this problem can be addressed by both taxonomists, ecologists and other researchers. Furthermore, this situation is not unique to polychaetes but applies to many other groups of marine invertebrates.
[ page update: 2017-I-11; 2022-II-08; III-27; 2023-I-16 mjw; 2023-X-24 jld; ]