Corresponding author: Nesrine Akkari (
Academic editor: P. Stoev
Morphological characters have been widely used in centipede systematics. Here, we aim to obtain morphological information from the preoral chamber and peristomatic structures of lithobiomorph centipedes, with taxonomic sampling focused on the species-rich genus
Ganske A-S, Edgecombe GD, Akkari N (2018) The peristomatic structures as a source of systematic characters in the genus
The peristomatic structures – the epipharynx and hypopharynx – of
The studied material consists of 61 specimens belonging to 35 species preserved in 70% or 95% EtOH (Table
List of studied material deposited in the
Species | Studied material |
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2 females, |
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1 male, |
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1 female, |
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1 female, |
|
1 female, |
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2 females, |
|
2 females, |
|
1 male, |
|
1 male, |
|
1 female, |
|
2 females, |
|
2 females, |
|
1 male, |
|
2 females, |
|
1 male, |
|
2 females, |
|
1 male, |
|
1 female, |
|
1 male, |
|
1male, |
|
1 male, |
|
2 females, |
|
2 females, |
|
1 female, |
|
2 females, |
|
1 male, |
|
2 males, |
|
2 females, |
|
2 females, |
|
1 female, |
|
2 males, |
|
2 males, |
|
1 female, 1 male, |
|
1 female, |
|
1 male, |
|
1 female, |
|
1 female, |
|
1 male, |
|
1 male, |
The epipharynx and hypopharynx were dissected from the preoral chamber as described in
Terminology follows
The epipharynx is distally and proximally bordered by the inner walls of the labrum and the clypeus, respectively (Fig.
Multifocus light-micrographs and
Details of transverse bulge, ‘bottle-shaped’ epidermal glandular shafts and median spine field of the epipharynx of
Details of transverse bulge, ‘bottle-shaped’ epidermal glandular shafts and median spine field of the epipharynx of
Epipharyngeal structures of
‘Bottle-shaped’ epidermal glandular shafts always occur proximal to the transverse bulge (Fig.
Proximal to the ‘bottle-shaped’ epidermal glandular shafts is a median spine field arranged as a wide or a narrow band with a subequal width, medially or laterally widened and consisting of a variable number of branching spines (Figs
Epipharyngeal structures of
Details of spines from the median spine field on the epipharynx of
Paired labral bristle bands occur on the distal bars on each side of the tooth plate (Fig.
Labral bristle bands on the distal bar of the epipharynx of
Details of branching bristles on the outer row of the labral bristle bands on the distal bar of the epipharynx of
The labral branching bristles on the distal bar expand towards the proximal part in a continuous manner (Fig.
Details of branching bristles on the lateral flap on the distal bar of the epipharynx of
On the lateral borders of the distal bar, ovoid tubercles are observed in nearly all investigated species (Figs
The median sensilla cluster (Fig.
Median sensilla cluster and lateral spine fields on the epipharynx of
Proximal to the clypeal part pairwise lateral spine fields are present bordering the median sensilla cluster except for
The hypopharynx is a subtriangular outgrowth consisting of paired lips forming a median crest (Fig.
‘Nipple-shaped’ sensilla on pharyngeal plate and hypopharyngeal spines of hypopharynx of
Distal to the pharyngeal plate appears a ‘tuft-like’ cluster of branching bristles (Fig.
Lateral to the pharyngeal plate, hypopharyngeal spines are always present (Figs
Shapes of branching bristles forming a tuft distally to the pharyngeal plate of the hypopharynx of
Examples of number and shape of the hypopharyngeal spines and surrounding pores of
‘Button-shaped’ sensilla are arranged in continuous clusters on the lips of the median crest medially up to the ventrolateral bars within the branching bristles and are present in all examined species (Figs
Examples of ‘button-shaped’ sensilla on the lips of hypopharynx of
Examples of spines and bristles flanking the median crest margins of hypopharynx of
The trichomes on the paired lips forming the median crest exhibit an intergrading transition from the tuft area proximal to distal up to the tips of the ventrolateral bars and medially to the proximoventral parts of the hypopharynx (Fig.
Examples of bristles transitioning in shape and length along the median crest margin on hypopharynx of
Bristles and scales on the distal tips of the lips on hypopharynx of
In the following, eight peristomatic characters are proposed for the genus
1. ‘Bottle-shaped’ glandular shafts at the border between labral and clypeal part of epipharynx: (0) one distinct regular row; (1) more than one regular or irregular row.
All the investigated lithobiomorph species possess ‘bottle-shaped’ epidermal glandular shafts at the border between the labral and clypeal parts of the epipharynx. The latter can be in one regular row (Figs
2. Labral bristle bands of epipharynx: (0) bristle bands continuous across transverse bulge; (1) distinct break in bristle bands proximal and distal to transverse bulge. (Character 31 in
The subgenera of
3. Number of transverse bulge(s) at border between labral and clypeal parts of epipharynx: (0) none; (1) one; (2) two.
The presence of one or two transverse bulges is common for the genera
4. Direction of distal and proximal furrowed margins of transverse bulge or transverse bulges on epipharynx: (0) parallel; (1) non-parallel.
Both states occur in all studied genera, state (0) e.g. in
5. Median field of branching spines immediately proximal to the border between labral and clypeal parts of epipharynx: (0) rhomboid, widening medially; (1) widening laterally; (2) subequal width medially and laterally.
State (2) is most common throughout the
6. Shape of branching bristles on labral flap of epipharynx: (0) lateral to medial transition from plumose to ‘fan-shaped’ bristles; (1) ‘fan-shaped’ bristles only; (2) plumose bristles only; (3) simple bristles only.
A transition of branching bristles from plumose laterally to ‘fan-shaped’ medially is the most common state (0) across the genus
7. Lateral expansion of median sensilla cluster of epipharynx: (0) isolated from the lateral spine fields; (1) partly overlapping with the lateral spine fields.
In all
8. Differentiation of spines flanking median crest of hypopharynx: (0) intergrading rows of branching bristles; (1) single outer row of simple flattened spines with abrupt transition to multifurcating inner rows of branching bristles. (Character 39 in
Species of the
Studies on the external morphology and microanatomy of the peristomatic structures of centipedes have hitherto unveiled phylogenetically useful information (
While studying the peristomatic structures of
The same authors (
The examination of additional taxa within
Although differences in shape of the bristles on the labral flap were briefly mentioned by
Generally, the median sensilla cluster borders or overlaps marginally with the lateral field of spines in
As mentioned in the introduction, the hypopharynx as a short outgrowth with a median crest is an apomorphic character for
Besides the well-defined characters listed in the previous paragraph, our investigation also yielded several structures with high variability in appearance and/or intermediate forms between and even within species. For example, the branching bristles of (i) the labral bristle band on the distal bar, (ii) the spines of the median spine field of the epipharynx and (iii) the branching bristles as a tuft on the hypopharynx occur with several non-definable forms.
The paired oblique rows of elongated lateral spines on the clypeal part of the epipharynx were also considered as an apomorphic character for
A correlation between the number of ‘bottle-shaped’ epidermal glandular shafts of
The peristomatic structures of
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 642241. Critical point drying (Leica 300CPD) for some specimens was performed at the Core Facility Cell Imaging and Ultrastructure Research, University of Vienna. Thanks are due to Dan Topa for support with the
Data matrix of 8 peristomatic characters of
Species | Characters |
---|---|
12345678 | |
|
111(0?)1000 |
|
11212000 |
|
10111000 |
|
10102000 |
|
01110101 |
|
11112000 |
|
11112001 |
|
10101000 |
|
10100001 |
|
01112001 |
|
11112001 |
|
11202101 |
|
11111001 |
|
01112001 |
|
00110001 |
|
111110?1 |
|
10100200 |
|
10112200 |
|
11102101 |
|
00100001 |
|
0121200? |
|
101022?0 |
|
10101001 |
|
01112001 |
|
01111001 |
|
01112001 |
|
10111001 |
|
(1?)1110001 |
|
0111?000 |
|
01112100 |
|
11111001 |
|
10102001 |
|
11100011 |
|
100-0311 |
|
10200010 |