Corresponding author: Mizuho Munakata (
Academic editor: Kay Van Damme
We describe the cypridoidean ostracod
The genus
To date, six
Streams in the alpine vegetation zone between the treeline and the permanent snow line are cold and nutrient-poor (
The Taisetsu Mountains in Daisetsuzan National Park are located in the center of Hokkaido, Japan, and consist of several gently sloping volcanic peaks in the 2000 m class. Above the treeline at ca. 1400–1500 m elevation (
Here we describe a new species of
Sampling was conducted at seven sites, including four streams (Stns 1–3, 7) fed by springs, a hot spring, and/or snowmelt, two ponds (Stns 5, 6), and one waterfall basin (Stn. 4) (Table
List of sampling sites in Daisetsuzan National Park.
|
|
|
|
|
|
---|---|---|---|---|---|
1. Hokkai-sawa Stream | Stream fed by spring |
|
1853 m | 3.5 (2.2–4.8) °C | 25.viii.2020, 26.vii.2021 |
2. Hokkai-sawa Stream | Stream fed by spring and snowmelt |
|
1837 m | 4.1 (2.4–5.7) °C | 25.viii.2020, 26.vii.2021 |
3. Akaishi Stream | Stream fed by hot spring with high-H2S concentration and snowmelt |
|
1829 m | 13 °C | 26.vii.2021 |
4. Momizi Fall | Fall basin in Akaishi Stream |
|
813 m | 13 °C | 27.vii.2021 |
5. Sugatami Pond | Pond |
|
1665 m | No data | 26.viii.2020 |
6. Unnamed Pond | Pond |
|
1597 m | No data | 26.viii.2020 |
7. Daisetsu Asahidake Spring | Stream fed by spring |
|
445 m | 7.0 °C | 26.viii.2020 |
Sampling sites for
Ostracods were fixed in 80% ethanol. The methods used for dissection, preparation of slides, light microscopy, scanning electron microscopy (
The following abbreviations are used in the text: Ca, carapace; LV, left valve; RV, right valve; H, height; L, length; W, width; An1, antennula; An2, antenna; Md, mandible; Mx, maxillula; L5–7, fifth, sixth, and seventh limbs, respectively; UR, uropodal ramus. The appendage chaetotaxy follows
An attempt was made to extract total DNA from the soft parts of three individuals by using a NucleoSpin Tissue XS Kit (Macherey-Nagel, Germany) following the manufacturer’s protocol, but only one of the three extracts allowed successful PCR amplification. Primers used for the PCR amplification and sequencing of ostracod
To explore the phylogenetic position of this species, a maximum likelihood (
To obtain information on the life cycle, three non-adult individuals collected on 26 July 2021 were maintained singly in wells of a tissue culture plate filled with water collected from sampling site Stn. 1 and placed in a refrigerator at a temperature of 7 °C. Detritus collected from sampling site Stn. 1 was added to each well as a food source. Observations were made twice or more per month.
Among seven sampling sites,
Three captive non-adult individuals have remained alive and active for more than five months. The body length (LV-L) of each individual was 0.47, 0.48, 0.39 mm. No molts have been observed to date (the latest observation was on 7 January 2022).
Family
The epithet
Hokkai-sawa Stream, Daisetsuzan National Park, Hokkaido, Japan (Stn. 1:
Measurements (in millimeters, except for ratios) of carapace and valves: LV-L, 0.59–0.61 (0.60, N=3); LV-H, 0.30–0.31 (0.31, N= 3); LV-H/LV-L, 0.50–0.51 (0.51, N=3); RV-L, 0.58–0.61 (0.60, N=3); RV-H, 0.29–0.31 (0.30, N=3); RV-H/RV-L, 0.50–0.51 (0.51, N=3); Ca-W, 0.25–0.26 (0.26, N=2); Ca-W/LV-L, 0.41–0.42 (0.42, N=2).
Carapace (Fig.
LV (Figs
An1 (Fig.
An2 (Fig.
Md (Fig.
Mx (Fig.
L5 (Fig.
L6 (Fig.
L7 (Fig.
UR (Fig.
Rake organ (Fig.
Genital hooks on female copulatory organ present (not illustrated).
The partial
The sequences in the
Comparison of morphological characteristics between species of
|
|
|
|
|
|
|
|
---|---|---|---|---|---|---|---|
Shape of valves | elongate | elongate | triangular | elongate | elongate | elongate | elongate |
Surface of valves | with numerous shallow pits, most distinct towards anterior and posterior margins, less distinct in central area | with very finely pitted | with elongate shallow pits in central area, and with much smaller rounded pits in posterior region | with small shallow pits | with small shallow pits in a central transverse band; pits may be reduced or even absent | smooth | smooth |
Number of An1 podomeres | 7 | 6 | 7 | 7 | 7 | 7 | 7 |
Number of setae on 1st podomere of Mx-palp | not described | 5 distal and 1 subdistal | 5 distal | 5 distal | 5 distal and 1 subdistal | 4 distal and 1 subdistal | 5 distal and 1 subdistal |
Seta b on L5 | absent | present | absent | absent | present | present | absent |
Seta d on L5 | absent | absent | absent | present | present | present | absent |
Number of rays comprising vibratory plate on L5 | 2 | 4 | 1 | 4 | 2 | 3 | 0 |
Reference |
|
|
|
|
this study |
Our sample comprised only females, indicating that
The results of our field survey suggest that
Our rearing experiment, though we could prepare only three live individuals, provided preliminary data about the life history of
Our field survey and observation of captive individuals may indicate that
1 | An1 with 7 podomeres | 2 |
– | An1 with 6 podomeres | |
2 | 6th swimming seta of An2 longer than the other 5 setae, second podomere of Md-palp with β+4 setae | 3 |
– | 6th swimming seta of An2 shorter than others, second podomere of Md-palp with β+3 setae | |
3 | Seta b present on L5 | 4 |
– | Seta b absent from L5 | 5 |
4 | First palpal podomere of Mx with 5 distal and 1 subdistal setae, vibratory plate of L5 with 2 rays | |
– | First palpal podomere of Mx with 4 distal and 1 subdistal setae, vibratory plate of L5 with 3 rays | |
5 | Carapace triangular in lateral view, with distinctive hump on LV | |
– | Carapace elongate in lateral view, without hump on LV | 6 |
6 | Surface of valves covered with numerous shallow pits, vibratory plate of L5 with 2 rays | |
– | Surface of valves smooth, L5 without vibratory plate |
We thank Akane Saito and Sota Matsuno in the Ministry of the Environment for support in obtaining a sampling permit; Yuki Kita at Hokkaido University (HU) for supporting the field work; Akira Tsukagoshi at Shizuoka University for literature; Yuki Oya at HU for helping with molecular analyses; and Matthew H. Dick at HU for reviewing the manuscript and editing the English. Permit numbers 1910241 and 2104201 allowed field sampling of animals in Daisetsuzan National Park. This study was funded in part by a research grant from the Research Institute of Marine Invertebrates Foundation to MM.
Table S1
table (Excel format)
List of species included in the molecular phylogenetic analysis and respective GenBank accession numbers.
Alignment S1
molecular dataset (fasta format)
Aligned
Alignment S2
molecular dataset (fasta format)
Aligned
File S1
text with one figure (docx format)
Phylogenetic analysis of cypridoidean ostracods based on