Corresponding author: Hayato Tanaka (
Academic editor: R. F. Maddocks
This study is a first report of an interstitial ostracod from Southeast Asia. The ostracod species,
Tanaka H, Dung LD, Higashi R, Tsukagoshi A (2016) A new interstitial ostracod species of the genus
Ostracods are small bivalve crustaceans that inhabit various aquatic environments. They are one of the major constituents of the meiobenthos, especially interstitial animals inhabiting the pore space in sediment (
This study is the first description of an interstitial ostracod species from Southeast Asia. The new species belongs to the genus
Very coarse sand was collected from the Dăm Ngoài Island, in the Phu Quoc Marine Protected Area of Phu Quoc Island, from southwest Vietnam,
Map showing sampling locality of
The type series was deposited in the collection of the National Museum of Nature and Science, Tokyo
The specimens of both
List of
Species | Specimen catalog number | GenBank number |
---|---|---|
|
||
|
||
|
||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Partial sequences of the mitochondrial National Center for Biotechnology Information
The
Holotype: adult male (
The holotype specimen was collected from Dăm Ngoài Island, Phu Quoc Marine Protected Area in Phu Quoc Island, the southwest Vietnam,
Carapace elongate in lateral view and depressed dorsoventrally. Anterior and posterior margins rounded. Carapace surface smooth but with small granular texture visible at high magnification. Sieve-type normal pores with recessed sieve plates and thick rims on carapace surface. Left hemipenis bearing one additional pincer-like structure and one hooked process.
Carapace (Figs
SEM images of valves and carapace of
Valves of
SEM images of the detailed structure of
Dimensions of valves of
Length (µm) | Height (µm) | ||||||
---|---|---|---|---|---|---|---|
Mean | Observed range | N | Mean | Observed range | N | ||
Male | Right valve | 332 | 322–338 | 7 | 107 | 100–111 | 7 |
Left valve | 337 | 325–347 | 7 | 111 | 105–117 | 7 | |
Female | Right valve | 349 | 342–359 | 5 | 115 | 113–119 | 5 |
Left valve | 354 | 346–361 | 5 | 119 | 115–120 | 5 |
Antennula (Fig.
Appendages of
Antenna (Fig.
Mandibula (Fig.
Maxillula (Fig.
Male brush-shaped organ (Fig.
Fifth limb (Fig.
Appendages of
Sixth limb (Fig.
Seventh limb (Fig.
Male copulatory organ (Fig.
Copulatory organ of distal lobe hooked process pincer-like structure tip of capsule
Eye. Present.
Carapace (Fig.
Sixth limb (Fig.
Posterior part of body and female genitalia (Fig.
Posterior body and genitalia of
See Table
Scatter plots of valves of
So far known only from type locality.
Named in recognition of this being the first record of
Morphological difference among four species of
Character |
|
|
|
|
---|---|---|---|---|
Male | ||||
Carapace, length (left; right) [µm] | 256–290 | 497–519; 481–503 | 325–347; 322–338 | 240–254; 236–250 |
height (left; right) [µm] | 84–97 | 166–175; 157–165 | 105–117; 100–111 | 67–82; 72–80 |
granular texture on surface | – | – | present | – |
Antennula, one seta on middle of anterior margin of fourth podomere | present | present | absent | absent |
Mandibula, one seta on antero-distal end of basis | absent | present | present | present |
Maxillula, seta number on endites (anterior; middle; posterior) | 5 to 6 | (6; 5; 4) | (5; 5; 4) | (5; 5; 4) |
Sixth limb, one short seta on antero-distal end of 1st podomere | present | present | absent | present |
third podomere | weakly developed | clearly segmented | weakly developed | clearly segmented |
Seventh limb, proximal spines and hook-shaped structure on distal claw | absent | presnt | absent | absent |
Brush-shaped organ, seta number | 12 | 16 | 16 | 16 |
Copulatory organ, pincer-like structure and hooked process on left hemipenis | absent | absent | present | absent |
Female | ||||
Carapace, length (left; right) [µm] | 260–344 | 466–486; 457–471 | 346–361; 342–359 | 252–266; 246–259 |
height (left; right) [µm] | 92–117 | 162–171; 151–158 | 115–120; 113–119 | 81–89; 81–86 |
length and height larger than male | no | yes | no | no |
The
Evolutionary distances of
A | 1 | 2 | 3 | |
---|---|---|---|---|
1 |
0,03 | 0,03 | ||
2 |
0,31 | 0,03 | ||
3 |
0,41 | 0,37 | ||
B | 1 | 2 | 3 | |
1 |
0,02 | 0,04 | ||
2 |
0,12 | 0,03 | ||
3 |
0,26 | 0,21 |
We discovered that the evolutionary distances among three Asian species of
This new species is the first marine interstitial ostracods described from Southeast Asia. Since there have been no taxonomic studies of interstitial ostracods in this region, their biodiversity has largely remained unknown. The Southeast Asian region (the Oriental realm) is known as a marine biodiversity hotspot (see
We would like to thank the Research Institute for Marine Fisheries (RIMF) and the Provincial People’s Committee of Kien Giang for their help during our field trip in Vietnam. The authors thank Prof. Susumu Ohtsuka (Hiroshima University, Japan) for providing research facilities and the Editage (