Discovery of a glowing millipede in California and the gradual evolution of bioluminescence in Diplopoda

Firefly toxin lucibufagins evolved after the origin of bioluminescence

Fireflies were believed to originally evolve their novel bioluminescence as warning signals to advertise their toxicity to predators, which was later adopted in adult mating. Although the evolution of bioluminescence has been investigated extensively, the warning signal hypothesis of its origin has not been tested. In this study, we test this hypothesis by systematically determining the presence or absence of firefly toxin lucibufagins (LBGs) across firefly species and inferring the time of origin of LBGs. We confirm the presence of LBGs in the subfamily Lampyrinae, but more importantly, we reveal the absence of LBGs in other lineages, including the subfamilies of Luciolinae, Ototretinae, and Psilocladinae, two incertae sedis lineages, and the Rhagophthalmidae family. Ancestral state reconstructions for LBGs based on firefly phylogeny constructed using genomic data suggest that the presence of LBGs in the common ancestor of the Lampyrinae subfamily is highly supported but unsupported in more ancient nodes, including firefly common ancestors. Our results suggest that firefly LBGs probably evolved much later than the evolution of bioluminescence. We thus conclude that firefly bioluminescence did not originally evolve as direct warning signals for toxic LBGs and advise that future studies should focus on other hypotheses. Moreover, LBG toxins are known to directly target and inhibit the α subunit of Na+, K+-ATPase (ATPα). We further examine the effects of amino acid substitutions in firefly ATPα on its interactions with LBGs. We find that ATPα in LBG-containing fireflies is relatively insensitive to LBGs, which suggests that target-site insensitivity contributes to LBG-containing fireflies' ability to deal with their own toxins.

Biophosphorescence in fluorescent millipedes (Diplopoda: Xystodesmidae) and its relationships with bioluminescence

Three types of luminescence have been reported in living organisms: bioluminescence (BL), ultraweak chemiluminescence and biofluorescence (FL). In millipedes, both BL and FL have been reported in Motyxia sequoiae and related Xystodesmidae species. Noteworthy, when walking at night with a UV lantern at the Biological Station of Highlands, I found three blue-fluorescent millipedes (Deltotaria brimleii, Deltotoria sp and Euryus orestes) that also displayed phosphorescence after turning off the UV source. The phosphorescence of the cuticle was in the green region (λmax = 525 nm). The phosphorescence remained associated with cuticle and pellets, but frozen fluorescent supernatants, also displayed phosphorescence. The fluorescent compounds extracted from the cuticles in water and methanol and separated by TLC, displayed fluorescence spectra similar to that of 6-pteridine carboxylic acid. In contrast to Motyxia sequoiae cuticle extracts, no bioluminescence was found in Deltatoria and Euryus extracts  in the presence of MgATP, but weak green chemiluminescence was detected with H2O2 and superoxide. The spectral overlapping of phosphorescence of these millipedes with the bioluminescence of Motyxia (~ 507 nm) and the intimate association of both types of luminescence with the cuticles, raises the possibility that bioluminescence in Motyxia may arise from chemiluminescence reactions preferentially generating triplet excited states instead of singlet states.

An anatomical and ultrastructural study of the eye of the luminescent millipede Paraspirobolus lucifugus (Gervais 1836) (Diplopoda, Spirobolida, Spiroboleliidae)

The two forward-looking eyes and their ultrastructural organization of an 18 mm long adult bioluminescent female millipede (Paraspirobolus lucifugus) were investigated by transmission electron microscopy and energy-dispersive X-ray spectroscopy. Each eye contained approximately 23 ommatidia with 50-60 μm wide and 80 um thick corneal lenses that contained calcium and silicon and proximally ended in truncated flat surfaces of around 20 μm in diameter. A maximally 28 μm thick and 25 μm long rhabdom, made up of at least 12-14 retinula cells and a 4 μm thick sleeve of screening pigment granules in a light-adapted position was present. Compared with the eyes of non-luminescent julid millipede species, those of P. lucifugus share their basic anatomy, but also exhibit features like the wide possible binocular frontal visual overlap, somewhat narrower interommatidial angles combined with relatively larger rhabdoms, which suggests that P. lucifugus has more efficient eyes and makes greater use of its photoreceptors. P. lucifugus is negatively phototactic and strictly nocturnal and its activity rhythm is apparently governed by a circadian clock.

A revision of the wilsoni species group in the millipede genus Nannaria Chamberlin, 1918 (Diplopoda, Polydesmida, Xystodesmidae)

Although many new species of the millipede genus Nannaria Chamberlin, 1918 have been known from museum collections for over half a century, a systematic revision has not been undertaken until recently. There are two species groups in the genus: the minor species group and the wilsoni species group. In this study, the wilsoni species group was investigated. Specimens were collected from throughout its distribution in the Appalachian Mountains of the eastern United States and used for a multi-gene molecular phylogeny. The phylogenetic tree recovered Nannaria and the two species groups as monophyletic, with Oenomaeapulchella as its sister group. Seventeen new species were described, bringing the composition of the wilsoni species group to 24 species, more than tripling its known diversity, and increasing the total number of described Nannaria species to 78. The genus now has the greatest number of species in the family Xystodesmidae. Museum holdings of Nannaria were catalogued, and a total of 1,835 records used to produce a distribution map of the species group. Live photographs, illustrations of diagnostic characters, ecological notes, and conservation statuses are given. The wilsoni species group is restricted to the Appalachian region, unlike the widely-distributed minor species group (known throughout eastern North America), and has a distinct gap in its distribution in northeastern Tennessee and adjacent northwestern North Carolina. The wilsoni species group seems to be adapted to mesic microhabitats in middle to high elevation forests in eastern North America. New species are expected to be discovered in the southern Appalachian Mountains.

Multi-level convergence of complex traits and the evolution of bioluminescence

Evolutionary convergence provides natural opportunities to investigate how, when, and why novel traits evolve. Many convergent traits are complex, highlighting the importance of explicitly considering convergence at different levels of biological organization, or 'multi-level convergent evolution'. To investigate multi-level convergent evolution, we propose a holistic and hierarchical framework that emphasizes breaking down traits into several functional modules. We begin by identifying long-standing questions on the origins of complexity and the diverse evolutionary processes underlying phenotypic convergence to discuss how they can be addressed by examining convergent systems. We argue that bioluminescence, a complex trait that evolved dozens of times through either novel mechanisms or conserved toolkits, is particularly well suited for these studies. We present an updated estimate of at least 94 independent origins of bioluminescence across the tree of life, which we calculated by reviewing and summarizing all estimates of independent origins. Then, we use our framework to review the biology, chemistry, and evolution of bioluminescence, and for each biological level identify questions that arise from our systematic review. We focus on luminous organisms that use the shared luciferin substrates coelenterazine or vargulin to produce light because these organisms convergently evolved bioluminescent proteins that use the same luciferins to produce bioluminescence. Evolutionary convergence does not necessarily extend across biological levels, as exemplified by cases of conservation and disparity in biological functions, organs, cells, and molecules associated with bioluminescence systems. Investigating differences across bioluminescent organisms will address fundamental questions on predictability and contingency in convergent evolution. Lastly, we highlight unexplored areas of bioluminescence research and advances in sequencing and chemical techniques useful for developing bioluminescence as a model system for studying multi-level convergent evolution.

Continued Adaptation of C4 Photosynthesis After an Initial Burst of Changes in the Andropogoneae Grasses

C\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}$_{4}$\end{document} photosynthesis is a complex trait that sustains fast growth and high productivity in tropical and subtropical conditions and evolved repeatedly in flowering plants. One of the major C\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}$_{4}$\end{document} lineages is Andropogoneae, a group of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}$\sim $\end{document}1200 grass species that includes some of the world’s most important crops and species dominating tropical and some temperate grasslands. Previous efforts to understand C\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}$_{4}$\end{document} evolution in the group have compared a few model C\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}$_{4}$\end{document} plants to distantly related C\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}$_{3}$\end{document} species so that changes directly responsible for the transition to C\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}$_{4}$\end{document} could not be distinguished from those that preceded or followed it. In this study, we analyze the genomes of 66 grass species, capturing the earliest diversification within Andropogoneae as well as their C\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}$_{3}$\end{document} relatives. Phylogenomics combined with molecular dating and analyses of protein evolution show that many changes linked to the evolution of C\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}$_{4}$\end{document} photosynthesis in Andropogoneae happened in the Early Miocene, between 21 and 18 Ma, after the split from its C\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}$_{3}$\end{document} sister lineage, and before the diversification of the group. This initial burst of changes was followed by an extended period of modifications to leaf anatomy and biochemistry during the diversification of Andropogoneae, so that a single C\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}$_{4}$\end{document} origin gave birth to a diversity of C\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}$_{4}$\end{document} phenotypes during 18 million years of speciation events and migration across geographic and ecological spaces. Our comprehensive approach and broad sampling of the diversity in the group reveals that one key transition can lead to a plethora of phenotypes following sustained adaptation of the ancestral state. [Adaptive evolution; complex traits; herbarium genomics; Jansenelleae; leaf anatomy; Poaceae; phylogenomics.]

A revision of dragon millipedes I: genus Desmoxytes Chamberlin, 1923, with the description of eight new species (Diplopoda, Polydesmida, Paradoxosomatidae)

The dragon millipede genus Desmoxytes s.l. is split into five genera, based on morphological characters and preliminary molecular phylogenetic analyses. The present article includes a review of Desmoxytes s.s., while future articles will deal with Hylomus Cook and Loomis, 1924 and three new genera which preliminarily are referred to as the ‘acantherpestes’, ‘gigas’, and ‘spiny’ groups. Diagnostic morphological characters of each group are discussed. Hylomus is resurrected as a valid genus and the following 33 species are assigned to it: H.asper (Attems, 1937), comb. n., H.cattienensis (Nguyen, Golovatch & Anichkin, 2005), comb. n., H.cervarius (Attems, 1953), comb. n., H.cornutus (Zhang & Li, 1982), comb. n., H.draco Cook & Loomis, 1924, stat. rev., H.enghoffi (Nguyen, Golovatch & Anichkin, 2005), comb. n., H.eupterygotus (Golovatch, Li, Liu & Geoffroy, 2012), comb. n., H.getuhensis (Liu, Golovatch & Tian, 2014), comb. n., H.grandis (Golovatch, VandenSpiegel & Semenyuk, 2016), comb. n., H.hostilis (Golovatch & Enghoff, 1994), comb. n., H.jeekeli (Golovatch & Enghoff, 1994), comb. n., H.lingulatus (Liu, Golovatch & Tian, 2014), comb. n., H.laticollis (Liu, Golovatch & Tian, 2016), comb. n., H.longispinus (Loksa, 1960), comb. n., H.lui (Golovatch, Li, Liu & Geoffroy, 2012), comb. n., H.minutuberculus (Zhang, 1986), comb. n., H.nodulosus (Liu, Golovatch & Tian, 2014), comb. n., H.parvulus (Liu, Golovatch & Tian, 2014), comb. n., H.phasmoides (Liu, Golovatch & Tian, 2016), comb. n., H.pilosus (Attems, 1937), comb. n., H.proximus (Nguyen, Golovatch & Anichkin, 2005), comb. n., H.rhinoceros (Likhitrakarn, Golovatch & Panha, 2015), comb. n., H.rhinoparvus (Likhitrakarn, Golovatch & Panha, 2015), comb. n., H.scolopendroides (Golovatch, Geoffroy & Mauriès, 2010), comb. n., H.scutigeroides (Golovatch, Geoffroy & Mauriès, 2010), comb. n., H.similis (Liu, Golovatch & Tian, 2016), comb. n., H.simplex (Golovatch, VandenSpiegel & Semenyuk, 2016), comb. n., H.simplipodus (Liu, Golovatch & Tian, 2016), comb. n., H.specialis (Nguyen, Golovatch & Anichkin, 2005), comb. n., H.spectabilis (Attems, 1937), comb. n., H.spinitergus (Liu, Golovatch & Tian, 2016), comb. n., H.spinissimus (Golovatch, Li, Liu & Geoffroy, 2012), comb. n. and H.variabilis (Liu, Golovatch & Tian, 2016), comb. n.Desmoxytes s.s. includes the following species: D.breviverpa Srisonchai, Enghoff & Panha, 2016; D.cervina (Pocock,1895); D.delfae (Jeekel, 1964); D.des Srisonchai, Enghoff & Panha, 2016; D.pinnasquali Srisonchai, Enghoff & Panha, 2016; D.planata (Pocock, 1895); D.purpurosea Enghoff, Sutcharit & Panha, 2007; D.takensis Srisonchai, Enghoff & Panha, 2016; D.taurina (Pocock, 1895); D.terae (Jeekel, 1964), all of which are re-described based mainly on type material. Two new synonyms are proposed: Desmoxytespterygota Golovatch & Enghoff, 1994, syn. n. (= Desmoxytescervina (Pocock, 1895)), Desmoxytesrubra Golovatch & Enghoff, 1994, syn. n. (= Desmoxytesdelfae (Jeekel, 1964)). Six new species are described from Thailand: D.aurata Srisonchai, Enghoff & Panha, sp. n., D.corythosaurus Srisonchai, Enghoff & Panha, sp. n., D.euros Srisonchai, Enghoff & Panha, sp. n., D.flabella Srisonchai, Enghoff & Panha, sp. n., D.golovatchi Srisonchai, Enghoff & Panha, sp. n., D.octoconigera Srisonchai, Enghoff & Panha, sp. n., as well as one from Malaysia: D.perakensis Srisonchai, Enghoff & Panha, sp. n., and one from Myanmar: D.waepyanensis Srisonchai, Enghoff & Panha, sp. n. The species can mostly be easily distinguished by gonopod structure in combination with other external characters; some cases of particularly similar congeners are discussed. All species of Desmoxytes s.s. seem to be endemic to continental Southeast Asia (except the ‘tramp’ species D.planata). Some biological observations (relationship with mites, moulting) are recorded for the first time. Complete illustrations of external morphological characters, an identification key, and distribution maps of all species are provided.

Oculogryphus chenghoiyanae sp. n. (Coleoptera, Lampyridae): a new ototretine firefly from Hong Kong with descriptions of its bioluminescent behavior and ultraviolet-induced fluorescence in females

The first Oculogryphus species with associated males and female was found in Hong Kong and is described as new: O. chenghoiyanaesp. n. Adults of both sexes were collected live in the field and their bioluminescent behavior is reported for the first time in the genus. The captive males emit weak and continuous light from a pair of light spots on abdominal ventrite 6 or do so when disturbed. The larviform (highly paedomorphic) females can glow brightly from a pair of light-emitting organs on the abdomen. The females of Oculogryphus and Stenocladius are to date the only documented representatives of paedomorphism in ototretine fireflies. The finding is consistent with the evidence from male morphology and bioluminescent behavior, supporting the close relationship between the two genera. A key to the Oculogryphus species is provided. The Oculogryphus females can fluoresce with a blue-green light through the whole body under ultraviolet illumination, a phenomenon reported in the Lampyridae for the first time. The co-occurrence of bioluminescence and fluorescence is rare in terrestrial ecosystems, previously known only in some millipedes (Diplopoda). The fluorescence and bioluminescence abilities of Oculogryphus females are functionally independent: abdominal light-emitting organs producing bright yellowish green light while the body wall fluoresces with blue-green light. In contrast, fluorescence and bioluminescence in millipedes are biochemically linked, like in some jellyfish (Cnidaria: Medusozoa).

Step-wise evolution of complex chemical defenses in millipedes: a phylogenomic approach

With fossil representatives from the Silurian capable of respiring atmospheric oxygen, millipedes are among the oldest terrestrial animals, and likely the first to acquire diverse and complex chemical defenses against predators. Exploring the origin of complex adaptive traits is critical for understanding the evolution of Earth's biological complexity, and chemical defense evolution serves as an ideal study system. The classic explanation for the evolution of complexity is by gradual increase from simple to complex, passing through intermediate "stepping stone" states. Here we present the first phylogenetic-based study of the evolution of complex chemical defenses in millipedes by generating the largest genomic-based phylogenetic dataset ever assembled for the group. Our phylogenomic results demonstrate that chemical complexity shows a clear pattern of escalation through time. New pathways are added in a stepwise pattern, leading to greater chemical complexity, independently in a number of derived lineages. This complexity gradually increased through time, leading to the advent of three distantly related chemically complex evolutionary lineages, each uniquely characteristic of each of the respective millipede groups.

Is geography an accurate predictor of evolutionary history in the millipede family Xystodesmidae?

For the past several centuries, millipede taxonomists have used the morphology of male copulatory structures (modified legs called gonopods), which are strongly variable and suggestive of species-level differences, as a source to understand taxon relationships. Millipedes in the family Xystodesmidae are blind, dispersal-limited and have narrow habitat requirements. Therefore, geographical proximity may instead be a better predictor of evolutionary relationship than morphology, especially since gonopodal anatomy is extremely divergent and similarities may be masked by evolutionary convergence. Here we provide a phylogenetics-based test of the power of morphological versus geographical character sets for resolving phylogenetic relationships in xystodesmid millipedes. Molecular data from 90 species-group taxa in the family were included in a six-gene phylogenetic analysis to provide the basis for comparing trees generated from these alternative character sets. The molecular phylogeny was compared to topologies representing three hypotheses: (1) a prior classification formulated using morphological and geographical data, (2) hierarchical groupings derived from Euclidean geographical distance, and (3) one based solely on morphological data. Euclidean geographical distance was not found to be a better predictor of evolutionary relationship than the prior classification, the latter of which was the most similar to the molecular topology. However, all three of the alternative topologies were highly divergent (Bayes factor >10) from the molecular topology, with the tree inferred exclusively from morphology being the most divergent. The results of this analysis show that a high degree of morphological convergence from substantial gonopod shape divergence generated spurious phylogenetic relationships. These results indicate the impact that a high degree of morphological homoplasy may have had on prior treatments of the family. Using the results of our phylogenetic analysis, we make several changes to the classification of the family, including transferring the rare state-threatened species Sigmoria whiteheadi Shelley, 1986 to the genus Apheloria Chamberlin, 1921-a relationship not readily apparent based on morphology alone. We show that while gonopod differences are a premier source of taxonomic characters to diagnose species pairwise, the traits should be viewed critically as taxonomic features uniting higher levels.

The cyanide gland of the greenhouse millipede, Oxidus gracilis (Polydesmida: Paradoxosomatidae)

Although the greenhouse millipede, Oxidus gracilis, is distributed worldwide, there is little work using modern tools to explore its morphology. We used confocal laser scanning microscopy (CLSM) to image the cyanide glands of Oxidus gracilis. Glands from adult millipedes were dissected out before imaging, and we were able to image glands of juveniles through the cuticle due to the strong autofluorescence of the gland extract. We can report that CLSM is a promising technique to non-invasively investigate the development and mechanisms of polydesmid cyanide glands.

Porphyrins produce uniquely ephemeral animal colouration: a possible signal of virginity

Colours that underlie animal pigmentation can either be permanent or renewable in the short term. Here we describe the discovery of a conspicuous salmon-pink colouration in the base of bustard feathers and down that has never been reported because of its extraordinarily brief expression. HPLC analyses indicated that its constituent pigments are coproporphyrin III and protoporphyrin IX, which are prone to photodegradation. Accordingly, an experimental exposure of feathers of three bustard species to sunlight produced a rapid disappearance of the salmon-pink colouration, together with a marked decrease in reflectance around 670 nm coinciding with the absorption of porphyrin photoproducts. The disappearance of the salmon-pink colouration can occur in a period as short as 12 min, likely making it the most ephemeral colour phenotype in any extant bird. The presence of this colour trait in males performing sexual displays may thus indicate to females a high probability that the males were performing their first displays and would engage in their first copulations in the breeding season. In dominant males, sperm quality decreases over successive copulations, thus porphyrin-based colouration may evolve as a signal of virginity that allows females to maximize their fitness in lek mating systems.

A new species of Illacme Cook & Loomis, 1928 from Sequoia National Park, California, with a world catalog of the Siphonorhinidae (Diplopoda, Siphonophorida)

Members of the family Siphonorhinidae Cook, 1895 are thread-like eyeless millipedes that possess an astounding number of legs, including one individual with 750. Due to their cryptic lifestyle, rarity in natural history collections, and sporadic study over the last century, the family has an unclear phylogenetic placement, and intrafamilial relationships remain unknown. Here we report the discovery of a second species of Illacme, a millipede genus notable for possessing the greatest number of legs of any known animal on the planet. Illacme tobinisp. n. is described from a single male collected in a cave in Sequoia National Park, California, USA. After 90 years since the description of Illacme, the species represents a second of the genus in California. Siphonorhinidae now includes Illacme Cook & Loomis, 1928 (two species, USA), Kleruchus Attems, 1938 (one species, Vietnam), Nematozonium Verhoeff, 1939 (one species, South Africa) and Siphonorhinus Pocock, 1894 (eight species, India, Indonesia, Madagascar, Vietnam).

Integrative taxonomic revision of the polymorphic flat-millipede genera Oncocladosoma and Somethus in South Australia (Diplopoda : Polydesmida : Paradoxosomatidae)

The South Australian members of the flat-millipede genera Oncocladosoma Jeekel, 1985 and Somethus Chamberlin, 1920 are revised using an integrative approach incorporating sequence data and morphology. The partial mitochondrial cytochrome c oxidase subunit I (COI) barcoding gene and partial nuclear ribosomal 28S rRNA were amplified and sequenced for 15 Oncocladosoma specimens and 10 Somethus specimens and the datasets were used for molecular phylogenetic analysis and genetic distance determination. Both morphology and molecular data indicate that all species of Oncocladosoma fall within Somethus, and therefore, Oncocladosoma is synonymised with Somethus. Within those species supported by molecular data, features of the solenomere tip are relatively stable and useful for species identification. 28S rRNA has proven to provide sufficient nucleotide variation to provisionally discriminate species. Oncocladosoma castaneum ingens Jeekel, 1985, O. clavigerum Jeekel, 1985 and O. conigerum Jeekel, 1985 are junior synonyms of Somethus castaneus, comb. nov., and Somethus modicus Jeekel, 2002 is a synonym of S. scopiferus Jeekel, 2002. New records and electron scanning micrographs of gonopods are provided for S. castaneus, comb. nov., S. inflatus (Jeekel, 2002), comb. nov., S. lancearius Jeekel, 2002, S. scopiferus Jeekel, 2002, and Somethus grossi Jeekel, 1985, together with a key to the South Australian species of Somethus.