Taking eDNA underground: Factors affecting eDNA detection of subterranean fauna in groundwater

Stygofauna are aquatic fauna that have evolved to live underground. The impacts of anthropogenic climate change, extraction and pollution on groundwater pose major threats to groundwater health, prompting the need for efficient and reliable means to detect and monitor stygofaunal communities. Conventional survey techniques for these species rely on morphological identification and can be biased, labour-intensive and often indeterminate to lower taxonomic levels. By contrast, environmental DNA (eDNA)-based methods have the potential to dramatically improve on existing stygofaunal survey methods in a large range of habitats and for all life stages, reducing the need for the destructive manual collection of often critically endangered species or for specialized taxonomic expertise. We compared eDNA and haul-net samples collected in 2020 and 2021 from 19 groundwater bores and a cave on Barrow Island, northwest Western Australia, and assessed how sampling factors influenced the quality of eDNA detection of stygofauna. The two detection methods were complementary; eDNA metabarcoding was able to detect soft-bodied taxa and fish often missed by nets, but only detected seven of the nine stygofaunal crustacean orders identified from haul-net specimens. Our results also indicated that eDNA metabarcoding could detect 54%–100% of stygofauna from shallow-water samples and 82%–90% from sediment samples. However, there was significant variation in stygofaunal diversity between sample years and sampling types. The findings of this study demonstrate that haul-net sampling has a tendency to underestimate stygofaunal diversity and that eDNA metabarcoding of groundwater can substantially improve the efficiency of stygofaunal surveys.     

Suppression of termite feeding and symbiotic protozoans by the dye, Sudan Red 7 B

Laboratory groups of the Formosan subterranean termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), were fed for 14 days on wood shavings soaked in acetone solutions of 0%, 0.5% or 1% concentrations of the dye, Sudan Red 7B or on shavings not soaked in acetone (0% non-acetone, NA). Termites feeding on dyed wood became visibly stained red. Groups of dyed or non-dyed termites were then placed in containers and allowed to feed on non-dyed wood for 21 days. Dyed termites had lower numbers of symbiotic protozoans, lower feeding rates, and lower survivorship than did non-dyed termites. Survivorship was significantly lower in the 1% concentration than in the 0.5% concentration. Covariate analyses suggested that Sudan Red acts both directly and indirectly (via suppression of gut fauna) to reduce vigor in termites. Because there is variable survival response to this dye by different populations of C. formosanus, we recommend preliminary tests of dye toxicity before using it extensively in experiments.

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Résumé Le colorant rouge Soudan 7B (BASF, Wyandotte Corp.) soluble dans l'huile, est un marqueur efficace des termites pour les études dans la nature. Quand les termites consomment des matériaux marqués par ce colorant, ils deviennent nettement colorés en rouge. Bien que certains travaux indiquent que le rouge Soudan n'augmente pas considérablement la mortalité, il n'y a aucune donnée concernant l'effet du colorant sur l'alimentation des termites.Un groupe de Coptotermes formosanus récolté au lac Charles en Louisiane, a été alimenté pendant 14 jours sur copeaux de Pinus sp. colorés avec des solutions 0, 0.5% et 1% (en poids) de rouge Soudan 7B dans l'acétone, ou sur copeaux non colorés et sans acétone (NA). Les groupes de termites colorés ou non sont alors placés dans des récipients pour s'alimenter sur bois non coloré pendant 21 jours. Des différences significatives ont été observées (t. 1): les termites colorés avaient moins de protozoaires symbiontes, consommaient moins de bois et vivaient moins long-temps que les termites sans colorant (t. 2). La survie a été plus faible avec la concentration 1% qu'avec 0.5%. Le nombre de protozoaires était plus faible avec une solution acétonique sans rouge Soudan qu'avec du bois sans acétone, ce qui suggère que l'effet négatif du rouge Soudan sur les protozoaires a pu être augmenté par l'extraction d'une substance favorisant les protozoaires contenue dans les copeaux de pin.La chute de la prise de nourriture a été accompagnée d'une chute parallèle de l'effectif de protozoaires. En réexaminant les résultats de Lai et al. (1983), nous constatons qu'eux aussi avaient observé une réduction de l'effectif de protozoaires de C. formosanus sous l'effet du rouge Soudan. Dans notre étude, nous trouvons que 49,6% de l'effet réducteur du colorant sur la nutrition est expliqué par l'effet simultané sur les protozoaires. Nos résultats sur la survie confirment dans l'ensemble ceux de Su et al. (1983 a) sur C. formosanus de Louisiane. Cependant, C. formosanus de Hawaï (Lai et al., 1983) et de Floride (Su et al., 1988) avaient des taux de survie bien plus élevés. C. formosanus présente nettement des réactions variables au rouge Soudan. Dans notre travail, 64,1% de l'effet du colorant sur la survie a été expliqué par des modifications chez les protozoaires. Ainsi, il semble que le rouge Soudan agisse directement sur l'alimentation et la survie de C. formosanus, et indirectement par la suppression de sa faune intestinale.Bien que nos résultats montrent les effets délétères du rouge Soudan 7B sur C. formosanus, il reste le meilleur colorant pour les termitologistes. par suite de la variabilité de son effet sur la survie, nous conseillons des tests de toxicité avant son utilisation intensive dans des expériences.

     

Juvenile Hormone titre and vitellogenin gene expression related to ovarian development in primary reproductives compared with nymphs and nymphoid reproductives of the termite Reticulitermes speratus

To elucidate the reproductive cycle of termite queens, incipient colonies of Reticulitemes speratus (Isoptera: Rhinotermitidae) are established under laboratory conditions, and the transition of colony development is observed at 0.5, 1.5, 2.5, 3.5, and 7.5 months (stages I–V, respectively) after colony foundation. Ovarian development, vitellogenin gene expression and Juvenile Hormone (JH) titres are examined in the queens and in nonphysogastric nymphoids collected from natural colonies. A reproductive cycle in queens is observed, in which the oviposition rate is relatively higher during stages I and II, and then decreases during stages III and IV. Vitellogenic oocytes are not observed in the ovaries during stages III and IV, and the expression level of the vitellogenin gene is low, suggesting that egg production in queens is repressed during these stages. However, vitellogenin gene expression and egg deposition in queens resumes during stage V. Juvenile Hormone levels rise during the transition from nymphs to stage I queens, and elevated JH titres are observed also during stages III and IV. The decrease in JH titre in queens at stage II precedes the decline in vitellogenesis at stages III and IV. Thus, JH titre and vitellogenesis are correlated in an offset pattern. However, nonphysogastric nymphoid reproductives do not have vitellogenic oocytes in their ovaries, and their JH titre is two‐fold higher than that of queens, suggesting that elevated JH titre precedes vitellogenesis, as in queens.     

Species richness patterns of obligate subterranean beetles (Insecta: Coleoptera) in a global biodiversity hotspot – effect of scale and sampling intensity

We studied species richness patterns of obligate subterranean (troglobiotic) beetles in the Dinaric karst of the western Balkans, using five grid sizes with cells of 80 × 80, 40 × 40, 20 × 20, 10 × 10, and 5 × 5 km. The same two hotspots could be recognized at all scales, although details differed. Differences in sampling intensity were not sufficient to explain these patterns. Correlations between number of species and number of sampled localities increased with increasing cell size. Additional species are expected to be found in the region, as indicated by jackknife 1, jackknife 2, Chao2, bootstrap, and incidence‐based coverage (ICE) species richness estimators. All estimates increased with increasing cell size, except Chao2, with the lowest prediction at the intermediate 20 × 20 km cell size. Jackknife 2 and ICE gave highest estimates and jackknife 1 and bootstrap the lowest. Jackknife 1 and bootstrap estimates changed least with cell size, while the number of single cell species increased. In the highly endemic subterranean fauna with many rare species, bootstrap may be most appropriate to consider. Positive autocorrelation of species numbers was highest at 20 × 20 km scale, so we used this cell size for further analyses. At this scale we added 137 localities with less positional accuracy to 1572 previously considered, and increased 254 troglobiotic species considered to 276. Previously discovered hotspots and their positions did not change, except for a new species‐rich cell which appeared in the south‐eastern region. There are two centres of troglobiotic species richness in the Dinaric karst. The one in the north‐west exhibited high species richness of Trechinae (Carabidae), while in the south‐east, the Leptodirinae (Cholevidae) were much more diverse. These centres of species richness should serve as the starting point for establishing a conservation network of important subterranean areas in Dinaric karst.     

白蚁肠道微生物

对近年来白蚁肠道微生物方面的研究成果作一综述,主要强调白蚁肠道中存在的原生动物、发酵性细菌、固氮菌、螺旋体、同型产乙酸细菌、产甲烷细菌和硫酸盐还原菌对白蚁消化木质纤维素类食物有着重要的作用。     

Comparison of colony foundation success between sexual pairs and female asexual units in the termite Reticulitermes speratus (Isoptera: Rhinotermitidae)

In termites, a male and a female usually found a colony cooperatively. However, pairing efficiency tends to be low in Reticulitermes speratus because of a limited mate-searching range, the female-biased sex ratio, and a relatively low calling ability. Females that fail to pair with males found colonies either in female–female pairs or even alone. In the laboratory, we examined colony foundation by single females (F), female–female pairs (FF), and normal male–female pairs (FM). The time until colony foundation (when termites began excavating wood baits) differed significantly among the unit types. Time until excavation was much longer for single females than for FF and FM units, which reflects the relative success of colony foundation. The survival rate of single females was also significantly lower than that of FF- and FM-unit females, although there was no difference between FF and FM units. This result demonstrates that cooperation, even female–female, promotes female survivorship. Nevertheless, the number of progeny per female was significantly lower in FF units than in FM units, possibly because females of FF units must share reproductive output. These results lead us to the conclusion that a normal monogamous pair is the best unit for colony foundation. Nevertheless, females alone can establish colonies by parthenogenesis, and even female–female cooperation promotes colony foundation success if pairing with males is not possible. Considering the functional decision for females in F and FF units of how much time to spend searching for a male mate, we believe that these facultative pathways of colony foundation by parthenogenesis have adaptive significance. Received: November 30, 2000 / Accepted: March 6, 2001     

The imprint of Quaternary glaciers on the present-day distribution of the obligate groundwater amphipod Niphargus virei (Niphargidae)

Aim A plausible yet untested biogeographical scenario suggests that Quaternary glaciers shaped the present‐day distribution of the groundwater amphipod Niphargus virei. This study was designed to test two hypotheses pertaining to this scenario: (1) the probability of occurrence of N. virei in ice‐free areas decreases in the vicinity of the Würm glacier; and (2) dispersal is sufficiently low for the historical record of glacial effects to persist over time. Location The study area was located in the southern Jura Mountains, France. Methods A total of 497 sites were sampled to ascertain the distribution of N. virei in the southern Jura. Amplified fragment length polymorphism was analysed from a subset of 24 sites. The relationships between the probability of occurrence of N. virei and distance to the Würm glacier or elevation were investigated using a logistic regression. Spatial autocorrelation analyses were performed on both the residuals of the logistic regression and genetic distance to test the significance of dispersal and barriers to post‐glacial recolonization. The influence of catchment boundaries as barriers to dispersal was examined using different neighbouring relationships between sites. We tested the statistical significance of the reduction in deviance and gain in precision of an autologistic regression that took into consideration the influence of dispersal constraints on the distribution of N. virei. Results Niphargus virei rarely occurred in formerly glaciated areas, and its probability of occurrence in ice‐free areas decreased in the vicinity of the Würm glacier. Combined autocorrelation analyses of spatial distribution and spatial genetic structure showed that: (1) the distance at which spatial autocorrelation was no longer significantly positive did not exceed 16 km; (2) genetic differentiation fitted a model of isolation by distance; and (3) catchment boundaries acted as barriers to dispersal. The autologistic regression with dispersal constraints significantly increased our capacity to predict the distribution of N. virei. Maps of probabilities of occurrence suggested that post‐glacial recolonization was impeded by the extension of glacial outwash. Main conclusions The present distribution of N. virei in southern Jura is probably the result of a historical range reduction driven by glaciation coupled with restricted dispersal and isolation by distance.     

Amino acid concentration and distribution of lysozyme and protease activities in the guts of higher termites

Abstract The distributions of lysozyme and protease activities and of amino acids was measured in the guts of five species of higher termites, Macrotermes annandalei, Odontotermes formosanus, Pericaproitermes nitobei , Termes comis and Nasutitermes takasagoensis . Lysozyme activity was found only in M. annandalei, P. nitobei and N. takasagoensis. Protease activity was high in the midgut of all species but negligible elsewhere in the gut. Amino acid concentration was highest in the midgut of all species of workers.     

A new Palliduphantes Saaristo & Tanasevitch, 1996 from the Elburz Mountains,Iran (Araneae: Linyphiidae)

A new linyphiid spider, Palliduphantes elburz, sp. n., is described, based on material of both sexes taken from high altitudes in the Elburz Mts, northern Iran. The male of the new species is easily distinguished not only from the single Iranian congener, P. sbordonii (Brignoli, 1970), but also from other species of the genus by the strongly modified palpal tibia, the peculiar shape of the lamella characteristica, as well as the form and armature of the embolus. The epigyne of P. elburz, sp. n. seems to be most similar to P. stygius (Simon, 1884) from the western Mediterranean, but differs well by the much longer stretcher.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:E10F35CE-47D2-4FF8-9386-A00F3E61659B