TETRAODONTIDAETETRAODONTIFORMES – puffers and allies
Fishes of Tetraodontiformes comprises 9 families, and, of these,
only 2 families, viz., Triacanthidae and Tetraodontidae, arehitherto recorded from the Mekong. During our field surveys in
2007–2013, we were able to collect fishes of the latter (Tetraodontidae) from the region. Rainboth et al. (2012: 111, pl. 117,
fig. 2452) showed a photograph of a triacanthid fish Tripodichthys oxycehalus from the Hà Tiên River (a distributary of
the Mekong) at Kiên Giang, Vietnam; some additonal speciesof the Triacanthidae are also expected in the brackish estuariesof the Mekong.
The tetraodontid fishes, commonly known as puffers, usually
have a soft, inflatable body, with numerous minute spinules(entirely naked in some). Pelvic fins, as well as fin spines, areabsent. Teeth in jaws are fused and modified into 4 beak-likeplates (Tetraodon means "four teeth" in Greek).
Many of the tetraodontid fishes are well known to havea strong poison "tetraodotoxin" in the body. Although theposition of the poisonous parts varies depending on the species,
hitherto it is not well studied in many of the species found in
fresh- and brackish water areas of Southeast Asia. Nevertheless,the freshly-collected fish are sometimes seen at the markets
in the Indochinese Mekong region [see photographs in Pao
suvattii (p. 503) and P. cochinchinensis (p. 505)].
Many of the tetraodontid fishes are confined to marine
waters, but some enter into, or spend their whole life in, thebrackish- and/or fresh-water areas. About 15 species of thisfamily were recorded from the Mekong; of these, more than

Arothron immaculatus, Bến Tre, Vietnam (aquarium photo: KS)

one-third (6 species) belong to a single genus Pao [previously
misassigned to Monotrete, a junior synonym of Leiodon (seeKottelat, 2013c: 478–479)].

Carinotetraodon lorteti (Tirant, 1885)
Family: Tetraodontidae (FC: 509)
Size: 5.4 cm SL (Kottelat et al., 1993: 173).
Distribution: Mekong Basin in Cambodia and Vietnam; Chao
Phraya Basin.

498

A

female and/or immature fish with adistinct reticulated pattern on bodyadult male (not shown here) has a reddish dorsal andanal fins, grayish caudal fin with black distal half andwhite edge, and more uniformely colored and patternedbody with a reddish midventral stripe on belly

IFREDI-P 5054 (photo: PT)

Notes: A small-sized species of puffers, found in brackish estuaries and adjacent freshwater areas. The photographed specimens
shown here were collected from the Tonle Sap River (a tributaryof the Mekong) in Phnom Penh, Cambodia.
Fishes of Carinotetraodon are small-sized freshwater puffers[largest size known is 55.4 mm SL in C. salivator (Tan, 1999:354)], having mid-dorsal and mid-ventral cutaneous ridges inadult male, and distinct sexual dimorphism in adult coloration(Tan, 1999). The genus comprises 6 species from South andSoutheast Asia (Britz & Kottelat, 1999a; Tan, 1999): C. borneensis, C. imitator, C. irrubesco, C. lorteti, C. salivator, andC. travancoricus. Of these, only a single species C. lorteti is
known from the Indochinese Mekong (Tan, 1999: 350, fig.
5). The specimens shown here, as well as all other specimensof C. lorteti collected during our field surveys in 2007–2013
in the Mekong, appear to be immature fish or females (< 2.5
cm SL), having a distinct reticulated pattern on the body (seephotos); adult males of C. lorteti have reddish dorsal and anal
fins, a grayish caudal fin with black distal half and white edge,
and a more uniformely colored/patterned body with a reddish
midventral stripe on the belly (Kotellat et al., 1993, pl. 82;
Rainboth, 1996b: 225; Tan, 1999: 348, tab. 2). Its small size andcompressed body with characteristic coloration readily distinguishes C. lorteti from the other Mekong puffers.

TETRAODONTIDAE
Lagocephalus lunaris (Bloch, 1801)
Family: Tetraodontidae (FC: 509)

A

Size: 50.0 cm SL (Yamada & Yagishita in Nakabo, 2013:1741).
Distribution: Mekong Basin in Vietnam; Indo-West Pacific.
Notes: A large-sized species of puffers, found in coastal marine
waters; it is also known to enter brackish estuaries. The photographed specimen shown here is a young, collected from a brackish estuary in an extensive mudflat at the Mekong Delta in BạcLiêu, Vietnam.
Lagocephalus is readily distinguished from the other generaof the Mekong puffers by having sharply-contrasted bicolorationof the head and body, formed by a dark dorsal surface and asilvery white side and venter, a distinctive longitudinal skin foldon the lower side of the head and body, and an emarginate caudal
fin (rather than truncate or rounded as in the other genera). The
silvery white coloration of the venter is also found in Auriglobus(below), but Auriglobus, a genus of small-sized freshwater puffers
reaching up to 10.6 cm SL (Roberts, 1982: 2, as Chonerhinos),has many more dorsal- and anal-fin rays, no raised skin fold on
the ventral side of the head and body, and a truncate caudal fin.
Matsuura (2001) recorded 7 species of Lagocephalus from theWestern-Central Pacific region, and, of these, Kottelat (2013c)
recognized only a single species, L. lunaris, in his checklist ofinland water fishes of Southeast Asia.

numerous minute spines on dorsal surface of body,extending posteriorly to origin of dorsal fin

Auriglobus nefastus (Roberts, 1982)

caudal fin emarginate

CTU-P 4631 (photo: LXT)

dorsum of head and body dusky, turning to silvery or
whitish on lateral and ventral areas

Family: Tetraodontidae (FC: 509)
Distribution: Mekong Basin in Laos, Thailand, Cambodia, andVietnam; Malay Peninsula, Sumatra, and Borneo.
Notes: A small-sized species of freshwater puffers, found in
slow-flowing rivers.
Puffers of Auriglobus are peculiar amongst the tetraodontids
by having long-based dorsal and anal fins with 22–28 and 18–22
rays, respectively [Roberts, 1982 (as Chonerhinos)]; Chonerhinos, a similar looking genus with the long-based dorsal andanal fins, with 32–38 and 28–29 rays, respectively [Roberts,
1982 (as Xenopterus)]. Auriglobus nefastus appears to be onlya single species of the genus found in the Mekong (see below),
and is unique within the genus in having a projecting upper
lip beyond the lower lip and an exposed portion of eyeballusually horizontally oval rather than rounded [Roberts, 1982
(as Chonerhinos nefastus)]. Its characteristic yellowish, lightgreenish, or golden coloration when alive readily distinguishes
this species from the other Mekong puffers. The generic assignment follows Kottelat (1999, 2013c).
Vidthayanon (2008: 288) listed an additional species of thegenus, Auriglobus modestus, in his checklist of fishes in the
Mekong Delta, but it was an error (C. Vidthayanon, pers. comm.).
Vidthayanon (2008: 288) also listed Chonerhinos naritus (asXenopterus naritus) as a fish found in the Mekong Delta, but he
did not confirm the voucher specimen from there actually (C.
Vidthayanon, pers. comm.). Similarly, Rainboth et al. (2012)listed C. naritus (as Xenopterus naritus) in their book of fishes ofthe "Greater Mekong Ecosystem" (a term mmeaning the entire
region directly affected by the Mekong), but they noted that thesource of their record of it is "Bangkok in Smith, 1945"; Smith's(1945: 574) record of this fish was based on Bleeker's (1865)
old record from "Siam" (Smith presumed that the locality wasprobably "Meanam Chao Phraya at Bangkok or Ayuthia"). Thus,

A

B

yellowish, greenish or golden
sheen on dorsum of body

23–27 dorsalfin rays

C

19–22 dorsalfin rays

we were not able to locate any certain records of both A. modestus
and C. naritus from the Mekong.

499

A and C) NUOL-P 739 (VP); B) IFREDI-P 1463 (photo: PT)

Size: 7.07 cm SL (Roberts, 1982: 11, as Chonerhinos nefastus).

TETRAODONTIDAE
Takifugu oblongus (Bloch, 1786)
Family: Tetraodontidae (FC: 509)

A

Size: 26.3 cm SL (Kottelat et al., 1993: 174).
Distribution: Mekong Basin in Vietnam; Indo-West Pacific.

dorsum dark brown, with many
irregular pale vertical bars

B

C young

Chelonodontops patoca (Hamilton, 1822)

A and B) CTU-P 4874 (photo: HVM); C) CTU-P 1707 (photo: LXT)

Notes: A medium-sized species of puffers, found in coastal
marine waters; it is also known to enter brackish estuaries.
Many fishes of Takifugu are confined to East Asian waters,
and T. oblongus appears to be the only species widely distributedin the Indo-West Pacific, including the estuarine areas of the
Mekong. Its characteristic pale-barred pattern on the dorsum
readily distinguishes T. oblongus from the other Mekong puffers.
Although Rainboth et al., (2012) and Kottelat (2013c) recorded 4
additional congeners from South East Asia, viz., T. alboplumbeus,
T. niphobles [a junior synonym of T. alboplumbeus, see Matsuura(2017a)], T. obscurus, and T. ocellatus, all of these species areapparently not distributed southward beyond the South China
Sea coasts of China and northern Vietnam.
Kottelat (2013c) pointed out that Gastrophysus (rather thanTakifugu) is an available generic name for this group, describedearlier than Takifugu; he stated, "The only way to continue
to use Takifugu as a valid name would be to ask the ICZN toreverse precedence or to suppress Gastrophysus" (Kottelat,
2013c: 476). We here follow Jelks (2018), who used Takifugu
as valid over Gastrophysus.

Family: Tetraodontiformes (FC: 509)
Size: 33 cm TL (Kottelat et al., 1993: 173, as Chelonodon
patoca).

young

Distribution: Mekong Basin in Vietnam; Indo-West Pacific.

500

many close-set pale spots on bodyyoungyellow band at ventral part oflateral side of bodynasal organ
forming a pair ofelongate flaps

Non-Mekong specimen, CTU-P 4331 (Phú Quốc Island, Vietnam, photo: LXT)

Notes: A medium-sized species of puffers, found in shallow
coastal marine waters, brackish estuaries, and adjacent freshwater areas. Rainboth et al. (2012: 113, as Chelonodon patoca)
recorded this species from the Mekong Delta, although we
could not confirm it from the region during our field surveys in
2007–2013. The photographed specimen shown here is a young
fish, collected from Phú Quốc Island, off southwestern coast of
the Mekong Delta in Vietnam, where this species appears to becommon in the mangrove areas.
This species had long been placed in Chelonodon by manyfish researchers (e.g., Kottelat, 1989, 1993; Rainboth et al.,2012; Matsuura, 2002). Kottelat (2013c), however, indicatedthat Chelonodon is a junior synonym of Leiodon, a distinct
genus comprising a single species L. cutcutia; thus Kottelat(2013c) assigned C. patoca to Chelonodontops, the oldest
available name for the genus including this species.
Chelonodontops comprises 3 species, although only a single
species C. patoca is known from Indo-West Pacifc from India
eastward to Indonesia (Matsuura, 2002, as species of Chelonodon); the other 2 similar-looking congeners (C. laticeps and C.
pleurospilus) are confined to Madagascar and/or the east coastof South Africa. Chelonodontops patoca can be distinguishedfrom the other Mekong puffers by having typically 8 anal-fin
rays (vs. 9 or more in the other Mekong puffers), in addition toits characteristic color pattern, including a brownish dorsum
and side of the body (usually tinged with yellow ventrally) withnumerous close-set rounded pale spots, whitish venter, and 3
vague dusky bars on the body (at just behind the pectoral-finbase, below the dorsal fin, and the posterior end of the caudal
peduncle).

TETRAODONTIDAE
1822)

A

Family: Tetraodontidae (FC: 509)
Size: 14.3 cm SL (Kottelat et al., 1993: 174, as Tetraodon
nigroviridis).
Distribution: Mekong Basin in Vietnam (and ?Thailand);coastal basins of Gulf of Thailand, Sundaland, Myanmar, andSri Lanka.
Notes: A medium-sized species of puffers, found in brackish
estuaries and adjacent freshwater areas of coastal basins; it isalso commonly seen in aquarium fish trade. One of us (CG)recently got a specimen of this puffer from a local fisherman,
who collected it from Mun River (a tributary of the Mekong) in
Ubon Ratchathani, Thailand; the fisherman informed CG thatthe species was rarely collected there, although its origin needs
to be confirmed (possibly an accidentally-introduced aquariumfish). Generic assignment follows Kottelat (2013c).
Five species of Dichotomyctere are known from the inland
waters of Southeast Asia (Kottelat, 2013c), and, of these, at least
2 species (D. nigroviridis and D. ocellatus) have been reliably
recorded from the Mekong. Some researchers have also recorded
D. fluviatilis (as Tetraodon fluviatilis) from the Mekong (Kottelat,
1989a; Rainboth, 1996b; Vidthayanon, 2008), but it is presumed
to be in error; Rainboth et al. (2012) did not list the species intheir book of fishes of the "Greater Mekong Ecosystem."Dichotomyctere nigroviridis somewhat resembles the other
Mekong congener D. ocellatus (below), but has many rounded
black spots on the dorsal half of the head and body, and somedusky irregular bars on the caudal fin.

Dichotomyctere ocellatus (Steindachner, 1870)

some dusky irregularbars on caudal fin

Bmany rounded blackspots on dorsal half ofhead and bodyCA) Non-Mekong specimen (Koh Kong, Cambodia, IFREDI-P 6611, photo: PT); B and C) CTU-P 2589 (photo: LXT)

Dichotomyctere nigroviridis (Marion de Procé,A

Family: Tetraodontidae (FC: 509)
Size: 5.9 cm SL (Kottelat et al., 1993: 174, as Tetraodon biocellatus).

Notes: A small-sized species of puffers, found in brackish estuaries and adjacent freshwater areas. During our field surveys in
2007–2013, we were not able to find any specimens from the
Mekong; the photographed specimens shown here were collectedfrom coastal basins in Sihanoukville, western Cambodia, where
this species is common. Kottelat (1989a: 21, as Tetraodon biocellatus) and Rainboth (1996b: 225, as Chelonodon biocellatus)
recorded this species from the Mekong. Tetraodon biocellatus,
described from "Cochinchine" (more specified as "Vietnam:
Thu-dau-mot" by Kotellat, 2013c: 476) by Tirant (1885), isa synonym of D. ocellatus (see Kottelat, 2013c). The genericassignment follows Kottelat (2013c).
Dichotomyctere ocellatus somewhat resembles D. nigroviridis(above) in body shape and coloration, but has more conspicuous
ocelli below the dorsal-fin base and at the caudal-fin base, many
irregular dashed yellowish lines and spots on the side of thehead and body, and no distinct dusky markings on the caudal fin.
Typically D. ocellatus has 8-shaped yellowish marking on thedorsal surface of the predorsal area (see photo B).

many yellow short lines
or dots on lateral side ofhead and bodyno dusky bars
on caudal fin

BC

typically "8"-shaped
yellow marking on dorsum(may be corrupted)

conspicuous black spots
edged with yellow ay basesof dorsal and caudal fins

501A) IFREDI-P 5992 (photo: PT); B) IFREDI-P 5997 (photo: PT); C) IFREDI-P 5999 (photo: PT)

Distribution: Mekong Basin in Vietnam; coastal basins ofGulf of Thailand, Malaya, and Borneo.

TETRAODONTIDAE
Arothron immaculatus (Bloch & Schneider, 1801)
Family: Tetraodontidae (FC: 509)

young

Size: 20.0 cm SL (Yamada & Yagishita in Nakabo, 2013:1740).
Distribution: Mekong Basin in Vietnam; Indo-West Pacific.

Pao baileyi (Sontirat, 1985)
Family: Tetraodontidae (FC: 509)

nasal organ
forming a pair ofelongate flaps

no markings (lines
and/or spots) on bodyyoung
CTU-P 5249 (photo: HVM)

Notes: A medium-sized species of puffers, found in shallow
coastal marine waters; it commonly enters brackish estuaries in
the juvenile stage. The photographed specimen shown here isa small young, collected from a small mangrove creek in BếnTre, Vietnam.
Arothron comprises 14 species (Matsuura, 2016, 2017b) fromIndo-Pacific. Some species are known to enter brackish estuaries
at least in early life stages, but the Arothron fauna in the Mekong is
not yet well resolved. Although Rainboth et al. (2012: 113) listed 9
species of Arothron in their book of fishes of the "Greater Mekong
Ecosystem" (a term meaning the entire region directly affected by
the Mekong), they did not include any species with certain records
from the Mekong; note that at least 5 of 9 species they listed (A.
firmamentum, A. leopardus, A. meleagris, A. nigropunctatus, andA. stellatus) are the typical marine species, probably not expected
to be in brackish estuaries, whereas the other 4 (A. hispidus,
A. immaculatus, A. mappa, and A. reticularis), as well as A.
manilensis, may occur. During our field surveys in 2007–2013, we
confirmed only a single specimen of A. immaculatus (noted above)from the Mekong Delta.
Puffers of Arothron look similar to one another in generalbody shape, but many of them have species-specific coloration(Matsuura, 1994). Arothron immaculatus is similar to A. manilensis that is also expected to be found in the Mekong, but can be
distinguished by having its immaculated coloration (vs. several
dusky lines are on the head and body in A. manilensis).

A

Size: 12.0 cm SL (Kottelat, 2001a: 164, as Monotrete baileyi).
Distribution: Mekong Basin in Laos, Thailand and Cambodia.

502

B young

C young

numerous short
cutaneous outgrowths
on head and bodyA) UNMF uncatalogued (photo: CG); B and C) IFREDI-P 5307 (photo: PT)

Notes: A medium-sized species of freshwater puffers, found in
rapids with rocky bottoms; it is frequently seen in aquarium fish
trade. This species has been considered as rare since its originaldescription (Sontirat, 1985), but one of us (CG) recently foundthat it can be fairly common locally in a particular habitat of
the Thai Mekong; further field investigation of its habitat andecological characteristics is being undertaken by CG. The genericassignment follows Kottelat (2013c).
Puffers of the genus Pao were assigned to the catch-all genus
Tetraodon or Monotrete (e.g., Rainboth, 1996b, as Monotreta;
Kottelat, 2001a), until Kottelat (2013c) described the new genus
Pao for this group. Although Kottelat (2013c) provisionallyrecognized 13 species from Southeast Asia in Pao, the genus
clearly needs revision (see "Notes" of Pao abei, pp. 506–507). Of
these, at least 6 species were confirmed to be from the Mekong,during our field surveys in 2007–2013.
Pao baileyi is peculiar within the genus by having numerous
finger-like cutaneous outgrowths on head and body (Sontirat,
1989: 104, as Tetraodon baileyi; Kottelat, 2001a: 164, as Monotrete baileyi). These outgrowths on the head may be branchedirregularly in large specimens (see, photo A).
This species was described at least 2 times as new with thesame scientific name by Sontirat (1985, 1989); see also Kottelat(2013c: 479).

TETRAODONTIDAE

Pao suvattii (Sontirat & Soonthornsatit, 1985)

A) Marketed fish, not preserved (Savannakhet, Laos, photo: KS); B) NUOL-P 2815 (photo: TP); C) NUOL-P 536 (photo: KS); D and F) NUOL-P 1783 (photo: KS); E) NUOL-P 172 (photo: KS); G) NUOL-P 151 (photo: KS); H) NUOL-P 19 (photo: KS); I) NUOL-P 57 (photo: KS)A

B

Family: Tetraodontidae (FC: 509)
Size: 12.9 cm SL (NUOL-P 5154).
Distribution: Mekong Basin in Laos and Thailand.
Notes: A medium-sized species of freshwater puffers, found inlarge rivers with muddy bottoms. The generic assignment follows
Kottelat (2013c).
Its peculiar appearance, including the upturned mouth, longand narrowly triangular snout, depressed head and body, and anarrowhead-shaped dusky marking behind the interorbital area,
readily distinguishes Pao suvattii from the other Mekong puffers.
As pointed out by Roberts (1998b: 228, as Tetraodon suvattii),
P. suvattii is superficially similar to the African freshwater puffer
Tetraodon miurus rather than the other puffers from Asia.
This characteristic species was named for Chote Suvatti, oneof the pioneer ichthyologists in Thailand who worked with H.M.
Smith, in honor of his contribution to the taxonomy of fishes ofThailand (Sontirat, 1989).

C

D

G
E
H
mouth upturned
snout long, narrowly triangularF
I

arrowhead-shaped dusky marking
behind interorbital space503

Pao fangi (Pellegrin & Chevey, 1940)
Family: Tetraodontidae (FC: 509)

A

Size: 9.2 cm SL (Saenjundaeng et al., 2013a: 78, as Tetraodon
palustris).
Distribution: Mekong Basin in Loas, Thailand, Cambodia, andVietnam; Chao Phraya Basin and ?peninsular Thailand.
Notes: A relatively small-sized species of freshwater puffers,
found in marshes, swamps, and reservoirs with dense aquaticvegetation. The generic assignment follows Kottelat (2013c: 480).
Taxonomy of spotted puffers of the genus Pao in the Mekong
is in a state of flux. For example, Pao fangi was treated by someprevious researchers as a synonym of P. leiurus (e.g., Roberts,
1998b, as Tetraodon leiurus) or P. cochinchinensis (e.g., Kottelat,
2001a, as Monotrete cochinchinensis), but Saenjundaeng et al.
(2013a) resurrected it as valid (as Tetraodon fangi). Subsequently
Kottelat (2013c: 480) also treated P. fangi as valid following
Saenjundaeng et al. (2013a), and, furthermore, considered that acongener from peninsular Thailand, P. ocellatus, is also a possiblesynonym of P. fangi. Saejundaeng et al. (2013a) pointed out thatP. fangi can be distinguished from P. cochinchinensis by having
a shorter snout, although their P. cochinchinensis is possibly conspecific with P. barbatus (see "Notes" of P. abei, pp. 506–507).
Saenjundaeng et al. (2013a) described a new species Tetraodon
palustris from the Mekong Basin in northern Thailand; the species was subsequently regarded as a junior synonym of Pao
brevirostris by Kottelat (2013c: 479); we agree with his decisionthat these 2 are conspecific. According to Saenjundaeng et al.
(2013a), their T. palustris is similar to Pao fangi (as Tetraodon
fangi) in having no spinules on the dorsal surface of the snout,
but has no ocellus on the body (vs. a distinct reddish-centeredocellus present in P. fangi). The condition of the ocellus in P.
fangi, however, varies depending on the specimen; some have a
distinct large ocellus (photos A and C), whereas the others havea smaller and sometimes poorly contrasted ocellus; note that the
specimens in photo E (with a distinct ocellus = fangi-type) andF (with no ocellus = palustris-type), as well as some specimens
with an intermediate condition, were collected together from asingle resourvoir in Battambong, Cambodia. The spinulate patternon the head may be slightly different between these species intheir figures (Saenjundaeng et al., 2013, fig. 5), but the variationof this character actually overlaps between these 2 colormorphs.
We thus conclude here that T. palustris is conspecific with (anda junior synonym of) P. fangi; this means that P. brevirostris,
originally described by Benl (1957), is also a junior synonym of P.
fangi, following Kottelat's (2013c) decision about synonymy of P.
brevirostris and P. palustris. See also "Notes" of P. abei.

I

B

C

D

E

F

G
ground color of head and body yellowish green
dorsally, with numerous close-set dusky spots

Hsnout relatively short(see also Pao abei,
pp. 506–507)

504

distinct ocelled spot (centered withred) usually present (see text)A) IFREDI-P 4222 (photo: PT); B) IFREDI-P 1008 (photo: PT); C) IFREDI-P 1786 (photo: PT); D) IFREDI-P 3535 (photo: PT); E) IFREDI-P 2228 (photo: PT); F) IFREDI-P 2227 (photo: PT); G) NUOL-P 1126 (photo: KS); H) NUOL-P 528 (photo: VV); I) CTU-P 998 (photo: LXT)TETRAODONTIDAETETRAODONTIDAE
Pao barbatus (Roberts, 1998)

A

Family: Tetraodontidae (FC: 509)
Size: 13.6 cm SL (Saejundaeng et al., 2013b: 78, as Tetraodon
barbatus).
Distribution: Mekong Basin in Laos and Thailand.

minute spines on body notextending posteriorly beyond
end of dorsal-fin baseA) NUOL-P 4370 (photo: TP); B) NUOL-P 1413 (photo: KS)

snout relatively
longBventral surface ofhead and body paleA

Pao cochinchinensis (Steindachner, 1866)
Family: Tetraodontidae (FC: 509)
Size: 14.1 cm SL (Saejundaeng et al., 2013b: 81, as Tetraodon
cambodgiensis).
Distribution: Mekong Basin in Cambodia and Vietnam.
Notes: A medium-sized species of freshwater puffers, found inrivers and lakes. The generic assignment follows Kottelat (2013).
Pao cochinchinensis, described from "Cochinchina" (anold name for southern Vietnam), has been seriously confusedwith several nominal species of the genus, e.g., P. abei (and its
possible synonym P. turgidus), P. barbatus, P. fangi (and its
possible synonyms P. brevirostris and P. palustris), and/or P.
leiurus (e.g., Roberts, 1998b; Kottelat, 2001a, 2013; Saenjundaeng et al., 2003a, b). Tetaodon cambodgiensis (= Pao cambodgiensis) is regarded here as a synonym of this species; seedetails in "Notes" of P. abei, next page.
Pao cochinchinens greatly resembles the Mekong congener
P. barbatus (above) in general appearance, but differs in having
spinules on the caudal peduncle behind dorsal-fin base (Saenjundaeng et al., 2013b, as Tetraodon cambodgiensis). As far
as we know, these 2 similar-looking species are distributed
allopatrically in the Mekong.

B
snout relatively
longminute spines on bodyextending posteriorly beyond
end of dorsal-fin baseC
ventral surface ofhead and body pale

black spot encircled by narrow
pale or pale blue line

D young
Original figure of Crayacion cochinchinensis (=Pao cochinchinensis)(from Steindachner, 1866).
Note that the lips appear
to be turned up.

505A) Marketed fish, not preserved (Siem Reap, Cambodia, photo: KS); B) IFREDI-P 927 (photo: PT); C) IFREDI-P 1814 (photo: PT); D) IFREDI-P 1491 (photo: PT)

Notes: A medium-sized species of freshwater puffers, found inrivers and lakes. The generic assignment follows Kottelat (2013c).
Pao barbatus, described by Roberts (1998b) from the middle and lower reaches of the Mekong, was considered as a
junior synonym of P. cambodgiensis by subsequent researchers(e.g., Kottelat, 2001a, 2013c), but Saenjundaeng et al. (2013b)
resurrected it as valid. According to Saenjundaeng et al. (2013b),
P. barbatus can be distinguished from P. cambodgiensis byhaving no spinules on the caudal peduncle (vs. spinules arepresent on the upper part of the caudal peduncle in P. cambodgiensis) and a broader head (e.g., head width at preorbital
54.1–59.8% of the head length in P. barbatus vs. 48.7–52.9%
in P. cambodgiensis). Although all our Lao (Luang Prabang
and Savannakhet) and Thai (Ubon Ratchathani) specimens lackspinules on the caudal peduncle, the ratio of head width of somespecimens falls into the range of P. cambodgiensis shown by
Saenjundaeng et al. (2013b). We provisionally identify all of
our Lao and Thai specimens as P. barbatus based only on its
distribution pattern of spinules on the body. Further extensive
research, including molecular analysis, is needed to clarify thetaxonomic status of these 2 similar-looking, apparently allopatricspecies in the Mekong. Note that Tetaodon cambodgiensis Chabanaud, 1923 (= Pao cambodgiensis) is regarded here as asynonym of P. cochinchinensis, below.

Pao abei (Roberts, 1998)
Family: Tetraodontidae (FC: 509)

A

Size: 18.5 cm SL (Kottelat, 2001a: 166, as Monotrete turgidus).
Distribution: Mekong Basin in Laos, Thailand, and Cambodia;
Chao Phraya and Meklong basins.

Freshly-collected fish of Pao abei (Ubon Ratchathani, Thailand, photo: KS)

Notes: A medium-sized species of freshwater puffers, foundin rivers and swift streams; it is common in upland areas. The
generic assignment follows Kottelat (2013c).
Pao abei was originally described by Roberts (1998b, as
Tetraodon abei) from the Mekong, Chao Phraya, and Meklong
basins of Thailand and Laos (type locality: Xe Bangfai, Laos). In
the description, Roberts (1998b: 228) stated that the species was
immediately distinguished from "closely related" his T. leiurus(presumed to comprise P. barbatus and P. cochinchinensis recognized here) by having "entire dorsolateral surface of bodywith numerous pale spots uniformly distributed over a dark
background." Subsequently Kottelat (2000) describe a new darkspotted puffer Monotrete turgidus (= Pao turgidus) from Savannakhet Province of Laos; Kottelat (2001a: 165) stated that the
species can be distinguished from the other Mekong congeners
by having "adult without ocellus or larger black blotch under
dorsal origin, but with several black spots on body with a paler(orange to red in life) central area."
During our field surveys in 2007–2013, we collected numerous specimens that can be identified as P. abei and/or P. turgidus
from rivers and upland streams of the Mekong Basin in Laos andThailand, as well as some from northern Cambodia. We were
surprised by the fact that these puffers represent great variationin coloration of the head and body. Even in a single individual,
they can change their coloration rapidly from paler backgroundwith dark spots (= P. turgidus-type) to a dark background withpale orange or yellow spots (= P. abei-type); such color variants
are frequently found together in a single-netting collection (seephotograph below). Since no other definitive characters differentiating these 2 species have been known, we here provisionallyconclude that these 2 are conspecific; namely, P. turgidus isregarded here as a junior synonym of P. abei.
Within the Mekong puffers, Pao abei recognized here issimilar to P. fangi (p. 504) in general appearance in particular
its dusky spotted pattern (in the P. turgidus-type specimens) andspinulate area on the dorsal surface of the head, wihch does notextending anteriorly beyond a vertical line through the middle
or anterior margin of the eye, but has a slightly longer snout (see

B

C

D

E

F

G

H

506

A) One of UNMF specimen (Ubon Ratchathani, Thailand, photo: KS); B) NUOL-P 1899 (photo: KS); C) NUOL-P 2029 (photo: KS); D) NUOL-P 3001 (photo: TP); E) NUOL-P 4522 (photo: TP); F) NUOL-P 1943 (photo: KS); G) NUOL-P 2572 (photo: TP); H) IFREDI-P 456(photo: PT)

TETRAODONTIDAETETRAODONTIDAEIJI) NUOL-P 4507 (photo: TP); J) NUOL-P 4509 (photo: TP); K) NUOL-P 4021 (photo: TP); L) NUOL-P 2029 (photo: KS); M) IFREDI-P 1546 (photo: KS); N) NUOL-P 3843 (photo: TP)also photographs of P. fangi, p. 504) and more or less paler bodyspots (usually dark brown, grayish brown, orange or yellowish,vs. black or gray in P. fangi). In the Mekong Basin, Pao abei
is usually found in rivers and streams, whereas P. fangi mostfrequently inhabits marshes, swamps or reservoirs. We tentatively
follow Tan & Kottelat (2009) that these Indochinese puffers of
Pao are non-conspecific with similar-looking Pao leiurus, known
from Java, Sumatra, and the Malay Peninsula. According to Tan& Kottelat (2009: 62–63, fig. 44, as Monotrete leiurus), their P.
leiurus has "usually a pale brown unspotted patch in the upper
part of the caudal peduncle and a broad pale brown band along theupper edge of the caudal fin"; these color patterns are not foundin P. abei shown here. Note that we examined 3 specimens fromthe Bangpakong River in western Thailand (UNMF 8619, 8620,
and 8621), that represent a similar color pattern with P. leiurus ofTan & Kottelat (2009) (i.e., a pale brown patch in the upper partof the caudal peduncle, and a broad pale brown band along theupper edge of the caudal fin, as well as an ocellus with/without
dull orange center below the dorsal-fin origin); spinulate patternon the head and body of the Bangpakong specimens resemble thatof P. barbatus redescribed by Saenjundaeng et al. (2013b).
Great variation in spotted pattern (not of a color tone) on the
body of Pao abei is found in the population from the Nam Ou
River (a tributary of the Mekong) in Luang Prabang, northern
Laos (photos D, E, I–K, and N). For example, the specimen in
photo K has close-set large dusky spots without a paler center on
the body; it looks similar to the photographed specimen shownby Saenjundaeng et al. (2013a, fig. 4) as "Tetraodon cochinchinensis" rather than the typical P. abei. However, we identify
this specimen as P. abei (rather than P. cochinchinensis), since it
has no spiniles on the dorsal surface of the head before a verticalline through the middle of the eye (see also comment on T.
cochinchinensis of Saenjundaeng et al., 2013a, below).
Note that the identification of Pao cochinchinensis has been
seriously confused. The species was originally described by
Steindachner (1866: 480, as Crayacion cochinchinensis) basedon 2 specimens from "Cochinchina" (an old name for southern
Vietnam). As far as we know, in southern Vietnam, only 2 speciesof Pao are known from the Mekong and Dong Nai basins: P.
cambodgiensis of Saenjundaeng et al. (2013b, as Tetraodon
cambodgiensis) and P. fangi. Although we did not examine thesyntypes [that Kottelat (1998: 120) stated, "cannot be located in
NMW"], Steindachner (1866) provided a good illustration in his
original description of C. cochinchinensis; it is reproduced inp. 505. The fish in this original illustration looks similar to our
specimen of P. cochinchinensis (= T. cambodgiensis of Saenjundaeng et al., 2013b) (p. 505) in having relatively long snout(though the lips are turned up), a distinctive eye-sized black spotsurrounding narrow pale ring, many close-set, irregularly-shaped
dusky markings on the side of the head and body (sometimes
faded in the Mekong specimens), and whitish abdomen. The othercandidate, P. fangi, differs obviously from C. cochinchinensis of
Steindacher (1866) in having a shorter snout and black spotted
pattern entirely on the body (see photographs of P. fangi, p. 504).
We thus identify our fish in p. 505 as Pao cochinchinensis. Tetraodon cambodgiensis, redescribed by Saenjundaeng et al. (2013b),
is regarded here as a synonym of P. cochinchinensis.
The taxonomic status of "Tetraodon cochinchinensis" of
Saenjundaeng et al. (2013a, figs 4 and 5A–B) is not clear; they
did not state anything about the reason why they identified
their specimens examined as T. cochinchinensis. Although their
species resembles P. barbatus by having spinules on the dorsal
surface of the snout (before a vertical line through the anterior
margin of the eye) and no spinules on the caudal peduncle, it

K variant?
L paler-coloredindividual

snout slightly long(see similar-looking
Pao fangi, p. 504)

center of dusky spot
may be orange

M intermediatecolored individual

N darkercolored individual
appears to have a more robust body and a slightly shorter snout
than the typical specimens of P. barbatus shown in p. 505; thecoloration is more darkened and brownish than the latter. We
also examined similar specimens from tributaries of the Mun
River (itself a tributary of the Mekong), but could not reasonably
differentiate those from typical P. barbatus due to their variationin body shape and coloration; actually, the ranges of % of
snout length in head length of their T. cochinchinensis and T.
barbatus shown by their papers (Saenjundaeng et al., 2013a, b)
are broadly overlapped. Further extensive research, including
molecular analysis, is needed to clarify their taxonomic statuses.

507