Research Article |
Corresponding author: Lihong Tu ( tulh@cnu.edu.cn ) Academic editor: Dimitar Dimitrov
© 2017 Mengdie Bao, Zishang Bai, Lihong Tu.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Bao M, Bai Z, Tu L (2017) On a desmitracheate “micronetine” Nippononeta alpina (Li & Zhu, 1993), comb. n. (Araneae, Linyphiidae). ZooKeys 645: 133-146. https://doi.org/10.3897/zookeys.645.10685
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The phylogenetic analyses based on molecular data demonstrate that all “micronetine” species of a desmitracheate system form a monophyly. Macrargus Dahl, 1886 is a “micronetine” genus, the species of which have a haplotracheate system in general, while Macrargus alpinus Li & Zhu, 1993 was found to have a desmitracheate system; this makes its generic placement problematic. According to the results of phylogenetic analysis, we transfer M. alpinus to another genus as Nippononeta alpina (Li & Zhu, 1993), comb. n., and provide a redescription of its genital characters and somatic features. Comparisons with other “micronetine” species with a desmitracheate system are provided. Putative synapomorphies for Nippononeta, the clade Nippononeta + Agyneta, and for the “desmitracheate micronetines” clade, as well as their relationship with Helophora, are provided and discussed.
Epigynal scape, genital morphology, phylogenetic placement, tracheal system
Linyphiidae Blackwall, 1859 is a species-rich family of spiders which has species-specific genitalia but more conservative somatic features in general. The tracheate system in linyphiids consists of two pairs of trachea; “desmitracheate” and “haplotracheate” are the two terms referring to the two main tracheal conditions having the median pair highly branched and unbranched, respectively (
Macrargus Dahl, 1886 is a typical “micronetine” genus with a haplotracheate system (
To test the phylogenetic placement of Macrargus alpinus and its relationships with other desmitracheate “micronetines”, we added the newly sequenced DNA sequence data of M. alpinus into the dataset of
Two mitochondrial genes, cytochrome c oxidase subunit I (CO1) and 16S rRNA (16S), and two nuclear genes, 18S rRNA (18S), and 28S rRNA (28S) were amplified and sequenced for Macrargus alpinus and added to the dataset of
Molecular protocols for amplification and sequencing follow that of
Specimens were examined and illustrated by using a Leica M205A stereomicroscope and a Leica DM5500B compound microscope. The male palp and female epigynum were examined after they were dissected from the body. The embolic division was excised by breaking the membranous column connecting between the suprategulum and radix. For microscopic examination and illustration, the male palp and epigynum were cleared in methyl salicylate. Illustrations were made using a drawing tube. Scanning Electron Microscopy (SEM) images were taken by using a LEO 1430VP at the Department of Biological Sciences at George Washington University. For SEM examination the specimens were prepared following
With the data on Macrargus alpinus and an additional Nippononeta species added to their dataset, the Maximum Likelihood analysis recovered the general topology of
Linyphiid phylogeny resulting from the Maximum Likelihood analysis based on DNA sequence data. Numbers at nodes indicate bootstrap support above 50%. Branches in color represent seven robustly supported main clades within Linyphiidae. Branches in bold indicate the desmitracheate type. Taxa in blue are currently placed in Micronetinae.
Nippononeta kurilensis Eskov, 1992.
Macrargus alpinus Li & Zhu, in Song et al. 1993: 863, f. 21A–I (D♂♀); Li et al. 1994: 81, f. 31–33 (♀); Li and Zhu 1995: 41, f. 2a–i (♂♀); Song et al. 1999: 186, f. 104D, G, J (♂♀).
♂ holotype (
4♂ and 4♀(
The male of Nippononeta alpina comb. n. can be distinguished from all other Nippononeta species by the proximal tibial process (Fig.
Nippononeta alpina comb. n. (A–F) male palp A retrolateral B ventral C prolateral D embolic division E embolus F distal suprategular apophysis (G–K) epigynum G ventral H lateral I dorsal J dorsal, cleared K lateral, cleared. Abbreviations: AX apex of embolus; CG copulatory groove; CRL cymbial retrolateral lobe; DLW lateral wing on distal part of scape; DTA distal tibial apophysis; E embolus; EC embolus column; EM embolic membrane; EP embolus proper; FiG Fickert’s gland; LC lamella characteristica; P paracymbium; PH pit hook; PHS pit hook sclerite; PTP proximal tibial process; R radix; S1 upper chamber of spermatheca; S2 lower chamber of spermatheca; ST stretcher; TA terminal apophysis; TH thumb of embolus.
Nippononeta alpina comb. n., male palp. A retrolateral B prolateral C prolateral with embolic division removed D detail of A, arrows indicate serrated surface of DTA (upper right), median branch of paracymbium (upper left) and outer margin fold (lower) (E–H) embolic division E dorsal F ventral, arrow indicates embolic spine G anterior H detail of F, shows hided EP. Abbreviations: ARP anterior radical process; AX apex of embolus; CRL cymbial retrolateral lobe; DTA distal tibial apophysis; E embolus; EM embolic membrane; EP embolus proper; LC lamella characteristica; P paracymbium; PF posterior fold; PH pit hook; PHS pit hook sclerite; PTP proximal tibial process; R radix; SPT suprategulum; TA terminal apophysis; TH thumb of embolus.
Nippononeta alpina comb. n. (A–E) epigynum A ventral B dorsal C lateral D ventral, cleared with ventral plate removed E lateral, cleared with ventral plate removed F male abdomen, ventral, shows epiandrous gland spigots absent G tracheal system, cleared H female palp, shows distal claw absent. Abbreviations: CG copulatory groove; DLW lateral wing on distal part of scape; DPS distal part of scape; FG fertilization groove; IL inner lobe; PLW lateral wing on proximal part of scape; S1 upper chamber of spermatheca; S2 lower chamber of spermatheca; SC scape; SG special gland; ST stretcher; TDF transversal dorsal fold; VP ventral plate.
Chelicerae of normal size, with narrower fang base and denser stridulatory ridges in the male than those in the female (Fig.
Nippononeta alpina comb. n. A male prosoma, lateral B female prosoma, lateral C male chelicerae, ectal D female chelicerae, ectal E female ALSF female PLSG female PMSH male PLS. Abbreviations: AC aciniform gland spigots; AG aggregate gland spigots; ALS anterior lateral spinneret; CY cylindrical gland spigot; FL flagelliform gland spigot; MAP major ampullate gland spigot; mAP minor ampullate gland spigot; PI piriform gland spigot; PLS posterior lateral spinneret; PMS posterior median spinneret.
Male palp (Figs
Epigynum (Figs
Nippononeta alpina comb. n. originally was placed in the genus Macrargus Dahl, 1886, whose type species M. rufus Wider, 1834 has a typical haplotracheate system (
In addition, Micrargus is masculine in gender, while Nippononeta is feminine. As M. alpinus is being transferred to Nippononeta, the species name has to be changed to alpina. However,
Our results show that all desmitracheate “micronetines” form a monophyly, and Macrargus alpinus falls into the Nippononeta clade, distantly related to Macrargus rufus (Fig.
According to
The monophyly of the Nippononeta clade is supported by the following four putative synapomorphies: the pointed apophysis on the paracymbial proximal arm (Fig.
The monophyly of Agyneta is not supported and its relationships with other desmitracheate “micronetines” remain unresolved. Nevertheless, morphological studies show that Agyneta species are easily distinguished by some genital characters: e.g. the presence of a conical cymbial elevation and a sickle-shaped embolus with a large thumb, and the scaped epigynum with a pair of well-developed lateral lobes (see the review of
We would like to thank Yuri Marusik, Mike Rix and Dimitar Dimitrov for their comments on an earlier version of this paper. We also thank Lara Lopardo, Dimitar Dimitrov, Fernando Álvarez-Padilla and Gustavo Hormiga for their help on collection for SEM images. This research is supported by National Sciences Foundation, China (NSFC-31572244).
GenBank accession numbers
Data type: molecular data