Research Article |
Corresponding author: Min Wu ( minwu1969@aliyun.com ) Academic editor: Frank Köhler
© 2021 Zhe-Yu Chen, Zhi-Tong Lyu, Min Wu.
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:
Chen Z-Y, Lyu Z-T, Wu M (2021) Systematic revision of Stegodera Martens, 1876 (Gastropoda, Stylommatophora, Camaenidae), with description of a new genus. ZooKeys 1059: 1-21. https://doi.org/10.3897/zookeys.1059.68385
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The monotypic genus Stegodera Martens, 1876 is systematically revised based on anatomical and morphological examination of freshly collected specimens. A new species from southern Hunan, which resembles Stegodera angusticollis, is confirmed to represent a new genus evidenced by comparative shell morphology and anatomy as well as by molecular phylogenetic analyses. The new genus might be more closely related to Stegodera and Nesiohelix Kuroda & Emura, but differs anatomically from the latter two genera by the absence of a dart apparatus.
16S rRNA, Bradybaeninae, Camaeninae, China, CO1, new genus, new species
Stegodera Martens, 1876 is a monotypic camaenid genus endemic to southern Hubei and northern Jiangxi, China (
A piece of foot tissue was cut from the living animal and preserved in 99.7% ethanol for molecular analysis. Then the animal was relaxed by drowning in water before being transferred to 70% ethanol for fixation, which was replaced with ethanol of the same concentration after three days. Photographs of the shell and reproductive system were taken using a Canon camera with Macro lens, and then modified in Adobe Photoshop CC 2018. The shells were measured with digital vernier calipers to the nearest 0.1 mm. Measurement abbreviations:
SDma j shell major diameter;
SDmin shell minor diameter;
SH Shell height.
Whorls were counted as described by
Muscle tissue was obtained from eleven species in this study (Table
Vouchers and the GenBank accession numbers of the species for phylogenetic study (*, from NCBI).
Species | Subfamily | 16S/CO1 | Museum voucher | Voucher inf. |
---|---|---|---|---|
Pseudostegodera qiului gen. et sp. nov. | Camaeninae | MW810083/ MW810790 | SYS m001017 | Paratype of the species; see text |
Stegodera angusticollis | Camaeninae | MW810079/ MW810793 | SYS m001016 | See text |
Amphidromus inversus | Camaeninae | AB112400*/ FJ472655* | / | / |
Camaena cicatricosa | Camaeninae | KU586474*/ KU061276* | / | / |
Camaena poyuensis | Camaeninae | KU586468*/ KU061273* | / | / |
Satsuma guandi | Camaeninae | MW804648/ MW810791 | HBUMM08239a1 | Guangdong, Shaoguan, coll. Di Yu |
MW804647/ MW810792 | HBUMM08239a2 | |||
Exiligada gregoriana | Camaeninae | JX393672*/ JX393761* | / | / |
Falspleuroxia overlanderensis | Camaeninae | KU519178*/ KU519261* | / | / |
Tatemelon musgum | Camaeninae | KU519194*/ KU519277* | / | / |
Sinumelon vagente | Camaeninae | KP965282*/ KP965358* | / | / |
Acusta ravida | Bradybaeninae | MW800197/ MW810782 | HBUMM06616a | Sichuan, Jiuzhaigou, coll. Min Wu |
Bradybaena qixiaensis | Bradybaeninae | MW810081/ MW810783 | HBUMM06900–1/HBUMM06900–2 | Jiangsu, Nanjing, coll. Min Wu |
Cathaica fasciola | Bradybaeninae | MW800200/ MW810784 | HBUMM06477–1/HBUMM06477–2 | Jiangsu, Zhenjiang, coll. Min Wu |
Coccoglypta liui | Bradybaeninae | MK680922*/ MK680001* | / | / |
Coccoglypta pinchoniana | Bradybaeninae | MK680923*/ MK680002* | / | / |
Dolicheulota formosensis | Bradybaeninae | KR338956*/ KR338956* | / | / |
Euhadra dixoni | Bradybaeninae | AF098711*/ AB916773* | / | / |
Laeocathaica polytyla | Bradybaeninae | MW810082/ MW810787 | HBUMM06726a1 | Sichuan, Jiuzhaigou, coll. Min Wu |
Laeocathaica distinguenda | Bradybaeninae | MW810084/ MW810785 | HBUMM06491a1 | Gansu, Wenxian, coll. Min Wu |
MW810085/ MW810786 | HBUMM06491a2 | |||
Nesiohelix moreletiana | Bradybaeninae | MW810080/ MW810788 | HBUMM06796 | Zhejiang, Hangzhou, coll. Min Wu |
Pseudobuliminus piligerus | Bradybaeninae | MW800362/ MW810789 | HBUMM06527a1 | Gansu, Wenxian, Coll. Min Wu |
Cornu aspersum (out-group) | Helicidae | KU586459*/ KU586502* | / | / |
For phylogenetic analysis, sequences from seven camaenid species and one out-group species were obtained from GenBank and incorporated into our dataset (Table
Bayesian Inferences of camaenids (representatives of genera in Table
We used Mesquite v. 3.61 (
HBUMM Mollusk collection of Museum of Hebei University, Baoding, China;
MYNU Mianyang Normal University (Mianyang, China);
OYKC Private collection of Kai-Chen Ouyang (Kunming, China);
QL Private collection of Lu Qiu (Luzhou, China);
AS accessory sac;
At atrium;
BC bursa copulatrix;
BCD bursa copulatrix duct;
DS dart sac;
DSC dart sac chamber;
Ep epiphallus;
Fl flagellum;
FO free oviduct;
MG mucous glands;
MGP papilla distally leading to mucous glands on inner wall of accessory sac;
P penis;
PC penial caecum;
PR penial retractor muscle;
PS penis sheath;
Va vagina; V
VD vas deferens.
The substitution saturation assessment for CO1 sequences suggested that the first and second codon positions were relatively conserved but that the third codon positions revealed sequence saturation and are therefore not suitable for phylogenetic inference (for both symmetrical and asymmetrical trees, Iss > Iss.c, ps < 0.001). Our final molecular dataset contained nineteen sequences of partial 16S and CO1 genes. After eliminating poorly aligned positions and divergent regions of the alignment of 16S using Gblocks 0.91b (
The phylograms produced by both Maximum Likelihood Inference and Bayesian Inference based on partial 16S + partial CO1 sequences are topologically identical in major branches (Fig.
As suggested by the analyses of character evolution, the ancestral character states among most studied camaenids, except Satsuma, Pseudostegodera gen. nov., Stegodera, and Nesiohelix, are: penial sheath, epiphallic papilla, flagellum and dart sac apparatus present, penial caecum absent (Fig.
Helix (Stegodera)
Martens in Pfeiffer 1876: 150;
Stegodera. –
Steganodera
Kobelt, 1879: 236 (incorrect subsequent spelling or unjustified emendation);
Plectopylis (Stegodera). – Pilsbry 1894: 147.
Planispira (Stegodera). –
Helix angusticollis Martens, 1875, by original designation.
Shell sinistral. Apical whorls with dense fine ribs that gradually becoming granules. The last 1/4 body whorl compressed, apically covering the contacted penultimate whorl. Peristome expanded and slightly reflexed. Head wart absent. Each side of mantle edge with a leaf-shaped appendage. Penis sheath weakly present. Penis externally simple. Epiphallic papilla absent. Flagellum present. Dart sac apparatus present. Accessory sac well developed. Mucous glands with numerous gland tubes. Membranous sac surrounding terminal genitalia absent. Poly-layered structure in dart sac and/or accessory sac absent.
This genus was considered as a subgenus of Helix Linnaeus, 1758 or Plectopylis Benson, 1860 for some time (Martens 1876;
In light of the genital system, Stegodera shares with Nesiohelix the most important character states like the presences of flagellum, numerous tubes of mucous glands and the papilla distally leading to mucous glands on the inner wall of the accessory sac, and the absences of the epiphallic papilla, poly-layered structure in dart sac apparatus and membranous sac surrounding terminal genitalia (
Helix angusticollis
Martens, 1875a: 2.
Helix (Stegodera) angusticollis. – Martens, 1876 (in
Plectopylis (Stegodera) angusticollis. – Pilsbry 1894: 147.
Planispira (Stegodera) angusticollis. –
Stegodera angusticollis. –
•
•One shell of HBUMM08435 (dissected), Guanyin Cave [观音洞], Taizi Town [太子镇], Yangxin County [阳新县], Huangshi City [黄石市], Hubei Province, China, 30°0'3.816"N, 115°11'24.428"E, 140 m a.s.l., 2020-X-15, leg. Xiao-Long Wang & Zi-Hao Shen (SDmaj = 26.7 mm, SDmin = 21.3 mm, SH = 11.3 mm). •Three shells of OYKC, one shell of QL, Lushui Lake [陆水湖], Chibi City [赤壁市], Xianning City [咸宁市], Hubei Province, China, 29°40'12"N, 113°58'35"E, 2020-X-03, leg. Di Yu & Kai-Chen Ouyang.
Poyang-See (= Poyang Lake [鄱阳湖], Jiangxi).
SDmaj = 26.7–30.6 mm, SDmin = 21.3–23.7 mm, SH = 11.3–12.2 mm (n = 6).
Body whorl completely covering partial penultimate whorl. Penial sheath weakly present. Epiphallic papilla absent. Dart sac apparatus and flagellum present. Mucous glands with numerous tubes.
Shell (Fig.
General anatomy (Fig.
Genitalia (Figs
This species was observed under litter layer, on nearby rocks and crevices.
The peristome of Stegodera angusticollis is in chestnut in fresh specimens, but in most museum specimens this color gets faint to white. In Stegodera angusticollis, the compressed part of body whorl usually completely cover the penultimate whorl, while in Pseudostegodera qiului gen. et sp. nov. the corresponding part is not so compressed and the compressed part of body whorl can hardly cover the penultimate whorl.
General anatomy A–D Stegodera angusticollis (Martens, 1875), HBUMM08435 A lobe (arrowed) on the left side of mantle edge B lobe (arrowed) on the right side of mantle edge C internal surface of head region D jaw E–H Pseudostegodera qiului gen. et sp. nov., holotype
Some authors (
Pseudostegodera qiului gen. et sp. nov.
Shell sinistral. Apical whorls with dense fine ribs gradually becoming granules. The last 1/8 to 1/4 body whorl compressed, only partly covering penultimate whorl. Umbilicus broad. Head wart absent. Each side of mantle edge with a leaf-shaped appendage. Penis sheath present. Penis externally simple. Epiphallic papilla absent. Flagellum present. Dart sac apparatus absent.
Conchologically the new genus can be distinguished from Stegodera by the detached body whorl and penultimate whorl. The new genus is supported to be the closest relative of a clade containing Stegodera + Nesiohelix as based on the Maximum Likelihood/Baysian Inference phylogeny shown in Fig.
•Holotype,
SDmaj = 31.0 – 34.0 mm, SDmin = 25.0 – 26.4 mm, SH = 12.0 – 13.7 mm (n = 2).
Body whorl incompletely covering partial penultimate whorl. Dart sac apparatus absent. Flagellum present.
Shell (Fig.
General anatomy (Fig.
Genitalia (Fig.
This new species is named after Dr Lu Qiu [邱鹭], who provided the specimens and field data.
Only known from the type locality (Fig.
See under the genus.
The comparison of the phylograms (Fig.
The current work also corfirms that so-called important characters of genital system, including penial sheath, epiphallic papilla, penial caecum, flagellum, and dart sac apparatus, have homoplasiously evolved more than once in the studied terminal taxa and their ancestral nodes (Fig.
We are grateful to Sigrid Hof (
This work is supported by the National Natural Science Foundation of China (NSFC 31872196) and Guangdong Academy of Science (GDAS) Special Project of Science and Technology Development (No. 2020GDASYL-20200102021).