Research Article |
Corresponding author: Salinee Khachonpisitsak ( salineek@go.buu.ac.th ) Academic editor: Michael Ohl
© 2017 Ashitapol Pochai, Sutin Kingtong, Woranop Sukparangsi, Salinee Khachonpisitsak.
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:
Pochai A, Kingtong S, Sukparangsi W, Khachonpisitsak S (2017) The diversity of acorn barnacles (Cirripedia, Balanomorpha) across Thailand’s coasts: The Andaman Sea and the Gulf of Thailand. Zoosystematics and Evolution 93(1): 13-34. https://doi.org/10.3897/zse.93.10769
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The acorn barnacle is a sessile crustacean, inhabiting the intertidal areas of tropical and temperate regions worldwide. According to current practices on Cirripedia morphology, shell, opercular valves, and arthropodal characters including cirri and mouthparts are used as a tool for taxonomic classification, and using these characteristics the present study aimed to provide better resolution for the barnacle diversity and geographical distribution within coastlines of Thailand: the Andaman Sea and the Gulf of Thailand. A total of ten species belonging to three families (Chthamalidae, Tetraclitidae, and Balanidae) were identified in this study. Subsequently, five species were newly recorded for the first time from Thailand’s coasts: Newmanella spinosus Chan & Cheang, 2016, Euraphia hembeli Conrad, 1837, Euraphia depressa (Poli, 1795), Tetraclita kuroshioensis Chan, Tsang & Chu, 2007, and Tetraclita singaporensis Chan, Tsang & Chu, 2007. The others, already mentioned in previous records, include: Tetraclita squamosa (Bruguière, 1789), Chthamalus malayensis Pilsbry, 1916, Amphibalanus amphitrite (Darwin, 1854), Amphibalanus reticulatus (Utinomi, 1967), and Megabalanus tintinnabulum (Linnaeus, 1758). Interestingly, acorn barnacles along the Andaman Sea occur abundantly, and are much higher in number of species (up to 8 species) than those found in the Gulf of Thailand’s coast (up to 6 species). This biased trend of species’ preferences is possibly due to the differences in oceanographic nature between two coastlines and the history of barnacle colonization.
acorn barnacle, Cirripedia , Balanomorpha , shell morphology, opercular valve, distribution, Thailand
Acorn barnacles, a member of marine crustaceans, inhabit a diverse array of substrates (e.g. calcareous rock or limestone, mollusk shells, corals, sponges, mangrove roots, turtle shells, and whale skins) along intertidal zones of temperate and tropical coastlines worldwide, as sessile form throughout their adulthood (
Acorn barnacles were collected from the rocky coastal areas of two distinct geographic regions of Thailand: the Andaman Sea and the Gulf of Thailand, during May 2015-July 2016.
The Andaman Sea located in the eastern part of the Indian Ocean is bordered by the coastlines of Myanmar, Thailand, Malaysia, Indonesia and India. In the Andaman Sea, the tide is semidiurnal. Its water temperature and salinity range 25.9–30.4 °C and 29–33 ppt, respectively (
The Gulf of Thailand, a semi-enclosed sea, is bordered by the coastlines of Vietnam, Cambodia, Thailand, and Malaysia with a connection to the South China Sea in the south. In the Gulf of Thailand, the tide is mixed diurnal. Its water temperature and salinity range 29–32 °C and 30–33 ppt, respectively (
A synopsis and illustration of all the sampling locations are given in Table
Map showing all sampling locations (A) and habitat characteristics (B) of acorn barnacles found along the coastlines of the Andaman Sea and the Gulf of Thailand. See Table
Locality | Habitat characteristics | Coordinates | |
---|---|---|---|
Andaman Sea coast | |||
Ao Khoei | AK | Large boulders on sandy shores | 09°16’44.18”N 098°22’07.01”E |
Na Tai | NT | Rocky shores | 08°14’15.39”N 098°16’51.22”E |
Kalim | KL | Small to large rocks on sandy shores | 07°55’25.47”N 098°15’47.68”E |
Ao Yon | AY | Rocky shores | 07°52’09.79”N 098°26’08.29”E |
Panwa | PW | Large boulders on sandy shores | 07°48’05.09”N 098°24’28.80”E |
Gulf of Thailand coast | |||
Khao Sam Muk | KS | Rocky shores | 13°18’38.88”N 100°54’07.81”E |
Si Racha | SR | Large boulders on sandy shores | 13°10’33.92”N 100°55’33.74”E |
Ko Kham Yai | KK | Small rocks on sandy shores | 13°09’59.30”N 100°49’18.00”E |
Ban Krut | BK | Rocky shores | 11°21’26.07”N 099°34’42.86”E |
Hin Ngam | HN | Rocky shores | 09°00’00.68”N 099°55’09.45”E |
The barnacles were collected from each station by surveying along rocky shores of an intertidal zone during both low and high tides. Whole acorn barnacle individuals were removed from the substratum and immediately preserved in ethyl alcohol (95% v/v) for further examination. All work was done under certified supervision of S.K. (Certificate from Institute of Animal for Scientific Purposes Development-IAD, Royal Thai Government: U1-03104-2559).
Samples were primarily identified based on their shell morphology using an Olympus SZ51 stereomicroscope and was photographed with digital camera. For better species identification in some families, arthropodal characters were observed. Soft bodies were removed from the shells and dissected. Cirri and mouthparts were mounted onto slides for light microscopy observation and imaging using digital camera. Taxonomic identification was performed using keys of
Based on shell morphology, total ten species (6 genera) of acorn barnacles along the coastlines of Thailand in both the Andaman Sea and the Gulf of Thailand were identified and are categorized into three families: Chthamalidae (2 subfamilies: Chthamalinae and Euraphiinae), Tetraclitidae (2 subfamilies: Newmanellinae and Tetraclitinae), and Balanidae (2 subfamilies: Amphibalaninae and Megabalaninae). The descriptions of the identified barnacles are as follows:
Chthamalus stellatus (Poli, 1791)
1 genus, 1 species recorded: Chthamalus malayensis Pilsbry, 1916.
Chthamalus
malayensis
Pilsbry, 1916: 310–311;
Chthamalus
stellatus
:
Chthamalus
challenger
:
Chthamalus
antennatus
:
Andaman Sea: 3 specimens, Phang-nga province, Takua Thung district, Na Tai beach, 16.V.2015, A. Pochai (BUU16.CH.CM01-03). 2 specimens, Phuket province, Mueang Phuket district, Ao Yon beach, 15.VII.2015, A. Pochai (BUU16.CH.CM04-05). 1 specimen, Phuket province, Mueang Phuket district, Panwa beach, 16.VII.2015, S. Khachonpisitsak (BUU16.CH.CM06). 3 specimens, Phuket province, Katu district, Kalim beach, 15.VII.2015, A. Pochai (BUU16.CH.CM07-09).
Gulf of Thailand: 2 specimens, Chon Buri province, Ko Si Chang district, Ko Kham Yai beach, 05.VII.2015, S. Khachonpisitsak (BUU16.CH.CM10-11).
Peduncle absent; body length 3–10 mm; base membranous. Shell elongated oval/shield-shaped, shell white to grey with 6 plates (1 carina, 2 carinal latus, 2 latus and 1 rostrum), carina bigger than rostrum, parietes symmetrical, calcareous and solid, radii solid, inner surface of parietes smooth and white-grey to pale-violet; orifice kite-shaped. Operculum plates symmetrical, articulation of opercular valves deep, scutum and tergum separable. Tergum smaller than scutum, tergum higher than wide, tergum with 4 distinct crests for lateral depressor muscles. Scutum elongated and triangular, adductor pit deep. Mandible with 4 teeth, lower margin pectinated, three large setae at the edge; cirri I with conical spines; cirri II with multi-cuspidate setae and basal guard.
Chthamalus malayensis is widely distributed in the Indo-West Pacific region. It has been previously recorded in Taiwan, Thailand, China, Philippines, Vietnam, Malaysia, India and Australia (
Species list and distribution of acorn barnacles found in ten sampling sites along the coastlines of the Andaman Sea and the Gulf of Thailand. Abbreviations: +, presence; abs, absence. See Table
Species | Sampling sites | |||||||||
---|---|---|---|---|---|---|---|---|---|---|
Andaman Sea | Gulf of Thailand | |||||||||
AK | NT | KL | AY | PW | KS | SR | KK | BK | HN | |
Chthamalus malayensis | abs | + | + | + | + | abs | abs | + | abs | abs |
Euraphia depressa | abs | abs | abs | abs | abs | + | abs | abs | abs | abs |
Euraphia hembeli | abs | + | abs | abs | abs | abs | abs | abs | abs | abs |
Newmanella spinosus | abs | + | abs | abs | abs | abs | abs | abs | abs | abs |
Tetraclita kuroshioensis | + | + | + | + | abs | abs | abs | + | + | abs |
Tetraclita singaporensis | abs | + | abs | abs | abs | abs | abs | abs | abs | abs |
Tetraclita squamosa | abs | abs | abs | abs | abs | abs | abs | abs | abs | + |
Amphibalanus amphitrite | + | + | + | + | + | + | + | + | + | + |
Amphibalanus reticulatus | abs | + | abs | abs | abs | + | + | + | abs | abs |
Megabalanus tintinnabulum | abs | + | abs | abs | abs | abs | abs | abs | abs | abs |
Total number of species | 2 | 8 | 3 | 3 | 2 | 3 | 2 | 4 | 2 | 2 |
Chthamalus malayensis has usually 4 crests for lateral depressor muscles while Euraphia hembeli and Euraphia depressa contains distinct 10–12 crests at the tergum and 3 small crests, respectively. The size of C. malayensis ranges from 3–10 mm similar to E. depressa while that of Euraphia hembeli is much bigger (10–33 mm). In addition, C. malayensis differs from E. depressa in two main characters diagnosed in this study: shape of external shell and jointing pattern of tergum and scutum. The shape of the external shell of C. malayensis shows a distinct and rather uniform ribbed surface from the lower region to the apex; on the other hand, E. depressa exhibits smooth surface that is never ribbed. Secondly, marked articulation and sinous jointing of tergum and scutum can be clearly noticed in C. malayensis while E. depressa shows less articulation. However, these shell morphology is not reliable tool for species identification among Chthamalids; hence, we further investigate arthropodal characters. It is clear that Chthamalus has four teeth on the mandible while Euraphia has three teeth on the mandible. In addition, to further identify Chthamalus into the correct species, setae on cirri I and cirri II were observed. Our specimens of Chthamalids have conical spines on cirri I and multi-cuspidate setae with basal guard on cirri II (Figure
Chthamalus malayensis collected from Ka Lim beach, Phuket (BUU16.CH.CM07). A. Dorsal and ventral view of external shell, B. External (left panel) and internal (right panel) view of tergum (upper panel) and scutum (lower panel), C. External (upper panel) and internal (lower panel) view of shell plates, D–G. Light microscopy on mouthparts, D. Close up of cirri I showing conical spines(↑), E. Cirri II, F. Close up on cirri II showing multi-cuspidate setae with basal guard(↓), G. Mandible with four large teeth. D-G. Scale bars in µm. Abbreviations: c, carina; cl, carinal latus; l, latus; r, rostrum.
Moreover, C. malayensis distributes above the vertical zonation of Tetraclita population. The overlapping of habitats can be seen among these species and even C. malayensis were found to attach to Tetraclita at the overlapping regions of high shore and middle shore.
Euraphia hembeli Conrad, 1837
1 genus, 2 species recorded: Euraphia depressa (Poli, 1795) and Euraphia hembeli Conrad, 1837.
Chthamalus depressus Poli, 1791
Chthamalus
stellatus
var.
depressus
:
Euraphia
depressa
:
Gulf of Thailand: 2 specimens, Chon Buri province, Mueang Chon Buri district, Khao Sam Muk beach, 05.VII.2016, W. Sukparangsi (BUU16.CM.ED01-02).
Peduncle absent; body length 3–10 mm; base membranous. Shell light brown-yellowish brown with 6 plates (1 carina, 2 carinal latus, 2 latus and 1 rostrum), shell flatted and thin-walled; parietes symmetrical and solid, external surface of shell without ribbed, inner surface of parietes smooth and light brown and white with small horizontal striations around aperture, parietes separable, suture distinct and easily parted; orifice rhomboidal. Opercular plates symmetrical, tergum smaller than scutum, scutum and tergum separable jointing between tergum and scutum with slightly sinous. Scutum triangular with slightly curved basal margin, external surface with shallow and horizontal striations from occludent margin to tergal margin, occludent margin of scutum without teeth, tergal margin slightly sinous from interior view; tergum with 2–3 lateral depressor crests. Mandible with 3 teeth, lower margin pectinated with 8 setae, three large setae at the edge; labrum with obvious teeth; caudal appendage absent.
In previous records, Euraphia depressa was found to inhabit along Mediteranean localities, including Spain (Punta Carnero, Punta de la Chullera, Malago, Salobrena and Calpe), France (Cap Bear, La Couronne, and Cassis), Italy (Pegli and Lido), Greece (Amnisso), the Black Sea and Suez canal (
Euraphia depressa (Poli, 1795) was the reassigned name from Chthamalus depressus (Poli, 1795). According to
Euraphia depressa collected from Khao Sam Muk beach, Chon Buri (BUU16.CH.ED01). A. Dorsal and ventral view of external shell, B. External (left panel) and internal (right panel) view of tergum (upper panel) and scutum (lower panel), C. External (upper panel) and internal (lower panel) view of shell plates, D-G. Light microscopy on mouthparts, D. Labrum, E. Close up on the teeth of the labrum, F. Mandible with three large teeth, G. Close up on the pectinated lower margin of mandible. D–G. Scale bars in µm. Abbreviations: c, carina; cl, carinal latus; l, latus; r, rostrum.
Euraphia hembeli Conrad, 1837: 261.
Andaman Sea: 2 specimens, Phang-nga province, Takua Thung district, Na Tai beach, 16.V.2015, A. Pochai (BUU16.CH.EH01-02).
Peduncle absent; base membranous; body length larger than Chthamalus and range from 10–30 mm. Shell brownish grey with 6 plates (1 carina, 2 carinal latus, 2 latus and 1 rostrum), carina bigger than rostrum, carinal latus bigger than latus. External surface of shell irregularly ribbed around basal margin, inner surface of parietes smooth and white with dark brown and pale violet horizontal striations around aperture. Parietes symmetrical, calcareous and solid, parietes separable, sutures coarsely serrate or with interlocking toothed structure. Orifice rhomboidal. Operculum plates symmetrical, tergum smaller than scutum, tergum and scutum separable. Scutum triangular, occludent margin of scutum with strong teeth. Tergum strongly marked with 10–12 lateral depressor crests, scutal margin strongly articulated.
Euraphia hembeli collected from Na Tai beach, Phang-nga (BUU16.CH.CH01). A. Dorsal and ventral view of external shell, B. External (left panel) and internal (right panel) view of tergum (upper panel) and scutum (lower panel), C. External (upper panel) and internal (lower panel) view of shell plates. Abbreviations: c, carina; cl, carinal latus; l, latus; r, rostrum.
Barnacles in the genus Euraphia were recorded in several regions including West Africa, the Mediterranean, Hawaii and Southern Japan (
Distribution of acorn barnacles on different habitat types of intertidal zone (vertical zonation): low shores/sublittoral zone (LS), middle shores/littoral zone (MS), and high shores/supralittoral zone (HS).
Scientific name | Habitat type | Settlement pattern on habitats | ||
---|---|---|---|---|
LS | MS | HS | ||
Family Chthamalidae | ||||
Chthamalus malayensis | + | Attached to rock platform, shell of Tetraclita spp. and other substrates | ||
Euraphia depressa | + | Attached to sheltered sites of rock | ||
Euraphia hembeli | + | + | Attached to rocky shore exposed to heavy wave action | |
Family Tetraclitidae | ||||
Newmanella spinosus | + | Attached to rocks on a wave exposed shore | ||
Tetraclita kuroshioensis | + | Attached to rock platform and sheltered sites of rock | ||
Tetraclita singaporensis | + | Attached to rock platform and sheltered sites of rock | ||
Tetraclita squamosa | + | Attached to rock platform and sheltered sites of rock | ||
Family Balanidae | ||||
Amphibalanus amphitrite | + | + | + | Attached to rocks on a wave exposed shore, shell of oyster and Asian green mussel, offshore vessel and various substrates |
Amphibalanus reticulatus | + | + | Attached to shell of Asian green mussel, oyster, ridged Venus clam and other substrates | |
Megabalanus tintinnabulum | + | Attached to rocky shore exposed to heavy wave action |
Based on the shell and opercular valve morphology (
Newmanella radiata (Bruguiere, 1789)
1 genus, 1 species recorded: Newmanella spinosus Chan & Cheang, 2016.
Newmanella spinosus Chan & Cheang, 2016: 212–220, figs 9–15.
Andaman Sea: 4 specimens, Phang-nga province, Takua Thung district, Na Tai beach, 16.V.2015, A. Pochai (BUU16.TC.NS01-04).
Peduncle absent; base calcareous. Shell greyish green, shell with 4 plates (1 carina, 2 latus, 1 rostrum); parietes low conical, 3–4 rows of irregular parietal tubes (parietes multiple tubiferous), radii board with horizontal striation and summit oblique. External surface with deep longitudinal/radiating lines from base to apex, internal surface of parietes smooth and white with greyish green striations close to operculum. Orifice pentagonal, diamond-shaped. External surface of operculum brownish grey, internal surface of operculum white. Scutum triangular, external surface of scutum with horizontal striations; tergum high and narrow, tergum with numerous depressor crests.
Newmanella spinosus collected from Na Tai beach, Phang-nga (BUU16.TC.NS01). A. Dorsal and ventral view of external shell, B. External (left panel) and internal (right panel) view of tergum (upper panel) and scutum (lower panel), C. External (upper panel) and internal (lower panel) view of shell plates. Abbreviations: c, carina; l, latus; r, rostrum.
Newmanella spinosus was previously recorded from low intertidal to subtidal levels on rock shores along the coastlines of Taiwan and the Philippines and they were also collected from the surfaces of buoys used in fishing cages in the open sea (
N. spinosus is morphologically similar to N. radiata, based on shell and scutum. The shell of N. spinosus is green while those of N. radiata is white. In addition, lateral scutal depressor muscle crest is shallow in the scutum of N. radiata, but deep in N. spinosus. The distribution of N. spinosus is around the North Pacific Ocean, from Okinawan Japan to Taiwan and the Philippines (
Tetraclita squamosa (Bruguiére, 1789)
1 genus, 3 species recorded: Tetraclita kuroshioensis Chan, Tsang & Chu, 2007, Tetraclita singaporensis Chan, Tsang & Chu, 2007 and Tetraclita squamosa (Bruguiere, 1789).
Tetraclita
squamosa
viridis
:
Tetraclita
squamosa
squamosal
:
Tetraclita
pacifica
Andaman Sea: 2 specimens, Phang-nga province, Khura Buri district, Ao Khoei beach, 30.VII.2015, A. Pochai (BUU16.TC.TK01-02). 3 specimens, Phang-nga province, Takua Thung district, Na Tai beach, 16.V.2015, A. Pochai (BUU16.TC.TK03-05). 2 specimens, Phuket province, Mueang Phuket district, Ao Yon beach, 15.VII.2015, A. Pochai (BUU16.TC.TK06-07). 3 specimens, Phuket province, Katu district, Kalim beach, 15.VII.2015, A. Pochai (BUU16.TC.TK08-10).
Gulf of Thailand: 3 specimens, Prachuap Khiri Khan province, Bang Saphan district, Ban Krut beach, 06.IX.2015, A. Pochai (BUU16.TC.TK11-13). 3 specimens, Chon Buri province, Ko Si Chang district, Ko Kham Yai beach, 05.VII.2015, S. Khachonpisitsak (BUU16.TC.TK14-16).
Peduncle absent; base membranous; shell greyish black to purplish-grey with 4 plates (1 carina, 2 latus, 1 rostrum), parietes conical, plates inseparable, 7–8 rows of parietal tubes (parietes multiple tubiferous), external surface with mosaic scales pattern radiating randomly from base to apex, internal surface of parietes smooth and white with dark grey striations around aperture. External surface of operculum mixed grey and yellowish-light brown, internal surface of operculum greyish-dusky green. Scutum bigger than tergum, scutum triangular, external surface of scutum with horizontal striations, occludent margin of scutum with obvious shallow and rough teeth, short articular ridge-basal margin, angle between basal margin and tergal margin is quite perpendicular. Tergum higher than wide, basi-scutal angle 158°, tergum with broad spur, spur angle 30°. Mandible with 4 big teeth, 1st tooth smaller; maxillule not notched with 11 setae; labrum with 5 small teeth on each side; cirri I possessing serrulate setae.
Tetraclita kuroshioensis collected from (BUU16.TC.TK01) from Na Tai beach, Phang-nga. A. Dorsal and ventral view of external shell, B. External (left panel) and internal (right panel) view of tergum (upper panel) and scutum (lower panel), C–F. Light microscopy on mouthparts, C. Labrum, D. Close up on the teeth of the labrum, E. Mandible, F. Close up on the lower margin of mandible. C–F. Scale bars in µm.
Tetraclita kuroshioensis is reassigned the name from Tetraclita squamosa which were collected from Taiwan, and Okinawa and Honsu of Japan, and Tetraclita pacifica. The distribution of this species occurs in broad area along north-west Pacific region (
Tetraclita kuroshioensis is quite similar to Tetraclita singaporensis in following characteristics: tergum without beak and with wide spur, scutum with short articular ridge-basal margin. However, angle between tergal margin and basal margin of T. kuroshioensis is more perpendicular (90°) or shaper while that of T. singaporensis is curved.
Tetraclita singaporensis Chan, Tsang & Chu, 2007: 52–53, figs 1–3.
Andaman Sea: 2 specimens, Phang-nga province, Takua Thung district, Na Tai beach, 16.V.2015, A. Pochai (BUU16.TS.TSG01-02).
Peduncle absent; base membranous; shell purplish-dusky green with 4 plates (1 carina, 2 latus, 1 rostrum), parietes conical, plates inseparable, 5–6 rows of parietal tubes (parietes multiple tubiferous), external surface with deep and irregular longitudinal striations from apex to base and small radiating lines, internal surface of parietes smooth and white with greyish-green horizontal striations around aperture. External surface of operculum yellowish brown mixed with dusky green, internal surface of operculum dusky green-purplish and white around spur of the tergum. Scutum bigger than tergum, scutum triangular, short articular ridge-basal margin, external surface of scutum with horizontal striations, occludent margin of scutum with rough teeth. Tergum higher than wide, tergum with broad spur and not beaked, spur angle 30–35°, basi-scutal margin 148–150°. Mandible with 4 big teeth, 2nd and 3rd teeth consisting double teeth, 1st tooth with small spines, lower margin pectinate with 8 small teeth and obvious double bigger teeth at the edge; maxillule notched, two large setae above notch, 13–17 setae below notch; labrum with 4–5 large teeth on each side; cirri I possessing bidenate serrulate setae.
Tetraclita singaporensis collected from (BUU16.TC.TSG02) from Na Tai beach, Phang-nga. A. Dorsal and ventral view of external shell, B. External (left panel) and internal (right panel) view of tergum (upper panel) and scutum (lower panel), C. Lateral side showing external surface of shell, D. Close up on the external surface of shell, E–H. Light microscopy on mouthparts, E. Labrum, E. Close up on the teeth of the labrum, G. Mandible, G. Close up on the pectinated lower margin of mandible. E–H. Scale bars in µm.
Tetracliata singaporensis has been reassigned the name from previously known as Tetraclita squamosa, which were collected from Singapore. Hence, the distribution of this species is firstly marked at Singapore, Indo-West Pacific region (
Tetraclita singaporensis differs from Tetraclita squamosa in that it has tergum without beak and broader spur, and scutum with short articular ridge-basal margin.
Balanus squamosa Bruguiére, 1789: 170.
Lepas porosa Gmelin, 1791: 3212.
Tetraclita
porosa
var.
viridis
:
Tetraclita
squamosa
:
Tetraclita
squamosa
squamosa
:
Tetraclita
squamosa
forma
viridis
:
Tetraclita porosa perfecta Nilsson-Cantell, 1921: 364.
Tetraclita
squamosa
:
Gulf of Thailand: 2 specimens, Nakhon Si Thammarat province, Sichon district, Hin Ngam beach, 04.VII.2015, A. Pochai (BUU16.TC.TSS01-02).
Peduncle absent; base membranous; shell green mixed with brownish grey, shell with 4 plates (1 carina, 2 latus, 1 rostrum); parietes conical, plate fused, inseparable, 8 rows of parietal tubes (parietes multiple tubiferous), external surface with longitudinal lines from base to apex, internal surface of parietes smooth and white with purplish grey striations close to aperture, External surface of operculum brownish grey, internal surface of operculum purplish grey. Scutum larger than tergum, scutum triangular, long articular ridge-basal margin, external surface of scutum with horizontal striations, occludent margin of scutum with very shallow teeth; tergum higher than wide, basi-scutal margin 158–160°, tergum apex obviously beaked, tergum with spur long and sharp, spur angle 25°. Mandible with 4 big teeth, 1st tooth with three small spines, lower margin pectinate; maxillule notched, two large setae above notch, 11 big setae below notch and some smaller setae at the edge; labrum with 4 large teeth on each side; cirri I possessing bidenate serrulate setae.
Tetraclita squamosa collected from Hin Ngam beach, Nakhon Si Thammarat (BUU16.TC.TS01). A. Dorsal and ventral view of external shell, B. External (left panel) and internal (right panel) view of tergum (upper panel) and scutum (lower panel), C. External (upper panel) and internal (lower panel) view of shell plates, D. Close up on external surface of shell, E–H. Light microscopy on mouthparts, E. Labrum, E. Close up on the teeth of the labrum, G. Mandible, G. Close up on the pectinated lower margin of mandible. E–H. Scale bars in µm. Abbreviations: c, carina; l, latus; r, rostrum.
Tetraclita squamosa is widespread in tropical and subtropical waters from West Africa, the Indo-Pacific, the Indian Ocean, Australia, Indonesia and Singapore (
As described in
Amphibalanus amphitrite (Darwin, 1854)
1 genus, 2 species recorded: Amphibalanus amphitrite (Darwin, 1854) and Amphibalanus reticulatus (Utinomi, 1967).
Balanus amphitrite var. communis Darwin, 1854: 240 (in part).
Balanus
amphitrite
Weltner, 1897: 264;
Balanus
amphitrite
communis
:
Balanus
amphitrite
hawaiiensis
:
Amphibalanus
amphitrite
:
Andaman Sea: 2 specimens, Phang-nga province, Khura Buri district, Ao Khoei beach, 30.VII.2015, A. Pochai (BUU16.BN.AA01-02). 4 specimens, Phang-nga province, Takua Thung district, Na Tai beach, 16.V.2015, A. Pochai (BUU16.BN.AA03-06). 4 specimens, Phuket province, Mueang Phuket district, Ao Yon beach, 15.VII.2015, A. Pochai (BUU16.BN.AA07-10). 3 specimens, Phuket province, Mueang Phuket district, Panwa beach, 16.VII.2015, S. Khachonpisitsak (BUU16.BN.AA11-13). 4 specimens, Phuket province, Katu district, Kalim beach, 15.VII.2015, A. Pochai (BUU16.BN.AA14-17).
Gulf of Thailand: 2 specimens, Nakhon Si Thammarat province, Sichon district, Hin Ngam beach, 09.VIII.2015, A. Pochai (BUU16.BN.AA18-19). 4 specimens, Prachuap Khiri Khan province, Bang Saphan district, Ban Krut beach, 06.IX.2015, A. Pochai (BUU16.BN.AA20-23). 2 specimens, Chon Buri province, Ko Si Chang district, Ko Kham Yai beach, 05.VII.2015, S. Khachonpisitsak (BUU16.BN.AA24-25). 4 specimens, Chon Buri province, Si Racha district, Si Racha beach, 04.VII.2015, A. Pochai (BUU16.BN.AA26-29). 3 specimens, Chon Buri province, Mueang Chon Buri district, Khao Sam Muk beach, 05.VII.2015, A. Pochai (BUU16.BN.AA30-32).
Peduncle absent; base calcareous. Shell white-pale pink with 6 plates (1 carina, 2 carinal latus, 2 latus, 1 rostrum); single rows of parietal tubes (parietes single tubiferous) with transverse septa; radii solid. External surface with purple longitudinal striations from apex to base (3–4 lines per plate) without horizontal striation, transverse teeth on suture edges with denticles on lower regions, internal surface of parietes grey with black horizontal striations close to operculum. External surface of operculum brownish grey, internal surface of operculum grey-white. Scutum bigger than tergum, scutum triangular, external surface of scutum with curved striations; tergum spur board with growth lines.
Amphibalanus amphitrite collected from Khao Sam Muk beach, Chon Buri (BUU16.BA.AA30). A. Dorsal and ventral view of external shell, B. External (left panel) and internal (right panel) view of tergum (upper panel) and scutum (lower panel), C. External (upper panel) and internal (lower panel) view of shell plates. Abbreviations: c, carina; cl, carinal latus; l, latus; r, rostrum.
Amphibalanus amphitrite is a common fouling barnacle and cosmopolitan species distributed along intertidal zones of coastlines in both the Gulf of Thailand and the Andaman Sea. It was found in all stations examined. The settlement patterns are various (e.g. rocks, shells of oyster and green mussels, concrete walls of bridges and harbors, offshore vessels, dock pilling, and mooring robes). In previous records, this species distributes worldwide in both tropical and temperate regions including the Indo-West Pacific, and Western Australia (
The morphology of Amphibalanus amphitrite is variable from diverse habitats worldwide. Shells exposed and eroded by heavy wave action showed no purple stripes on the external surface. The molecular analysis has confirmed its genetic differentiation which might be due to local adaptation and geographical isolation (
Balanus amphitrite var. communis Darwin, 1854: 240, pl. 5, figs. 2e, h, l [type locality: Tachitgatani, Tanabe Bay, Japan].
Balanus
amphitrite
communis
:
Balanus
reticulatus
:
Andaman Sea: 2 specimens, Phang-nga province, Takua Thung district, Na Tai beach, 16.V.2015, A. Pochai (BUU16.BN.AR01-02).
Gulf of Thailand: 3 specimens, Chon Buri province, Si Racha district, Si Racha beach, 04.VII.2015, A. Pochai (BUU16.BN.AR03-05). 3 specimens, Chon Buri province, Mueang Chon Buri district, Khao Sam Muk beach, 05.VII.2015, A. Pochai (BUU16.BN.AR06-08). 3 specimens, Chon Buri province, Ko Si Chang district, Ko Kham Yai beach, 05.VII.2015, S. Khachonpisitsak (BUU16.BN.AR09-11).
Peduncle absent; base calcareous. Shell white-pale pink and orange with 6 plates (1 carina, 2 carinal latus, 2 latus, 1 rostrum); single rows of parietal tubes (parietes single tubiferous) with transverse septa; radii solid. External surface with longitudinal and horizontal striations, transverse teeth on suture edges with denticles on lower regions, internal surface of parietes white. External surface of operculum white-pale pink and orange with striations in both tergum and scutum, internal surface of operculum white. Scutum bigger than tergum, scutum triangular; tergum spur sharp with growth lines.
Amphibalanus reticulatus collected from Si Racha beach, Chon Buri (BUU16.BN.AR01, A; BUU16.BN.AR 03, B & C). A. Dorsal and ventral view of external shell, B. External (left panel) and internal (right panel) view of tergum (upper panel) and scutum (lower panel), C. External (upper panel) and internal (lower panel) view of shell plates. Abbreviations: c, carina; cl, carinal latus; l, latus; r, rostrum.
Amphibalanus reticulatus is widely distributed from Japan, the Indo-West Pacific to Australia, of which the latter is considered as an introduced species carried by ship transport (
Amphibalanus reticulatus exhibits clear vertical and horizontal striations while Amphibalanus amphitrite shows only vertical purple striation in all shell plates. In addition, the shapes of shell of A. reticulatus is more columnar than that of A. amphitrite, which might be due to elongation of parietes in response to crowding when growing as colonies. On all examined stations, distinct distribution and settlement between A. amphitrite and A. reticulatus can be noticed, in that A. amphitrite were found in almost all kinds of substrates but A. reticulatus preferred its attachment on shells which obviously did not live along the rocky shores and it might probably inhabit the deeper areas of the sea and were occasionally carried away into the shores by wave action.
Megabalanus tintinnabulum (Linnaeus, 1758)
1 genus, 1 species recorded: Megabalanus tintinnabulum Linnaeus, 1758.
Lepas tintinnabulum Linnaeus, 1758: 668.
Balanus
tintinnabulum
:
Lepas tintinnabulum Wood, 1815: 38, pl. 6, figs. 1, 2.
Balanus
tintinnabulum
tintinnabulum
:
Balanus tintinnabulum var. tintinnabulum : Oliveira 1941: 11, text-fig. 1, pl. 2, figs. 1, 2, pl. 4, fig. 1, pl. 5 fig. 3, pl. 8, fig. 6.
Megabalanus
tintinnabulum
:
Andaman Sea: 3 specimens, Phang-nga province, Takua Thung district, Na Tai beach, 16.V.2015, A. Pochai (BUU16.BN.MT01-03).
Peduncle absent; base calcareous. Shell cylindric or conic with 6 plates (1 carina, 2 carinal latus, 2 latus, 1 rostrum); parietes reddish to brownish red usually with longitudinal striations on external surface, parietes not prominently ribbed and rather smooth, irregular shape of parietal tubes (parietes tubiferous), sutural edges of radii with regular denticles, radii wide with horizontally striated, radii tubiferous; internal surface of parietes pale-purple with horizontal greyish violet striations around aperture. Orifice subcircular to rhombus. External surface of operculum white-pale pink and orange with prominent growth ridges in both tergums and scutums, internal surface of operculum white. Scutum bigger than tergum, scutum triangular, adductor ridge of scutum prominent; tergum with spur, spur furrow of tergum closed, scutal margin denticulate.
Megabalanus tintinnabulum collected from Na Tai beach, Phang-nga (BUU16.BN.MT01). A. Dorsal and ventral view of external shell, B. External (left panel) and internal (right panel) view of tergum (upper panel) and scutum (lower panel), C. External (upper panel) and internal (lower panel) view of shell plates. Abbreviations: c, carina; cl, carinal latus; l, latus; r, rostrum.
Megabalanus tintinnabulum is widely distributed across almost all continents and is a well-known cosmopolitan fouling species. It was previously found in French Guiana, the United States, Australia, Mexico, Ecuador, Kuwait, Saudi Arabia, Sweden, France, Netherlands, Singapore, Indonesia and India (
Megabalanus tintinnabulum has relatively larger shell plates than those of Amphibalanus. All three examined species (M. tintinnabulum, A. amphitrite and A. reticulatus) in family Balanidae have opercular valves with prominent growth ridges horizontally, and tergum with a clear spur. The coloration among these three species is easily distinguishable, in that purplish longitudinal striations presenting A. amphitrite, vertical and longitudinal red-orange striations with orange-pale pink background presenting A. reticulatus and brownish red surface with some irregular and unclear longitudinal stripes presenting M. tintinnabulum.
1a | Shell conical to low conical with 4 plates with distinct parietes or shell with 4 plates with indistinct parietes or fused parietes, parietes multi-tubiferous | 2 |
1b | Shell with 6 plates with distinct parietes | 5 |
2a | Shell low conical, parietes discrete, summit of radii oblique, orifice pentagonal and wide, external surface of shell with deep longitudinal striations | Newmanella spinosus Chan & Cheang, 2016 |
2b | Shell conical, parietes not discrete, summit of radii horizontal, orifice circular or oval and small | 3 |
3a | Shell green, external surface of shell with longitudinal striation, shell plates separable, tergum with obvious beak and tergum with sharp and narrow spur | Tetraclita squamosa (Bruguiere, 1789) |
3b | Shell greyish black, external surface of shell with mosaic scale-like, plates inseparable, tergum without beak and with broad spur | 4 |
4a | Angle between basal margin and tergal margin of scutum is almost perpendicular | Tetraclita kuroshioensis Chan, Tsang & Chu, 2007 |
4b | Angle between basal margin and tergal margin of scutum is curved | Tetraclita singaporensis Chan, Tsang & Chu, 2007 |
5a | Parietes solid | 6 |
5b | Parietes tubiferous | 8 |
6a | Body length 10–30 mm, gigantic appearance | Euraphia hembeli Conrad, 1837 |
6b | Body length 3–10 mm, tergum with 3–4 lateral depressor crests | 7 |
7a | Mandible with four teeth, cirri I with conical spines, cirri II with multi-cuspidate setae and basal guard, articulation of opercular valves deep (shape of articulation similar to jigsaw-shaped) | Chthamalus malayensis Pilsbry, 1916 |
7b | Mandible with three teeth and 11 smaller setae at the lower margin, articulation of opercular valves shallow (shape of articulation from outside view similar to bird beak) | Euraphia depressa (Poli, 1795) |
8a | Parietal tubes single row and irregular shaped, shell with irregular and deep longitudinal striations, shell purplish white | Megabalanus tintinnabulum (Linnaeus, 1758) |
8b | Parietal tubes single row and uniform | 9 |
9a | External surface with purple longitudinal striations from apex to base against white surface | Amphibalanus amphitrite (Darwin, 1854) |
9b | External surface with shall longitudinal and horizontal striations, shell white-pale pink and orange | Amphibalanus reticulatus (Utinomi, 1967) |
In the present study, we examine geographical distribution of sessile acorn barnacles along Thai Peninsular coastal areas including the Gulf of Thailand and the Andaman Sea. So far, there has been a lack of information regarding the diversity of sessilian Thoracican barnacles in Thailand. Hence, we attempt to generate a checklist to understand the species diversification and how they distribute on intertidal rocky shores and sandy shores along the coast of Thailand. At least ten different forms of acorn barnacles were diagnosed so far that are classified into 6 genera and 3 families (Chthamalidae, Tetraclitidae and Balanidae), which can be distinguished based on their external shell morphology, including pattern of parietes, opercular plates, and arthropodal characters as described in previous literatures (
Our study also shows that the numbers of species found in the Andaman Sea (8 species) are more than those found in the Gulf of Thailand (6 species). At Na Tai station located in the Andaman Sea, up to 8 species (6 genera and 3 families) were recorded. Four of these 8 species were found only at this station including Newmanella spinosus, Euraphia hembeli, Megabalanus tintinnabulum and Tetraclita singaporensis. In other examined stations, only 2–3 species could be found, and most of them were of the genus Amphibalanus, Tetraclita, and Chthamalus. The differences in species abundance between two coastlines might probably due to the past history of the barnacle colonization. It has been shown in
In addition, we found five new records identified as Newmanella spinosus, Euraphia depressa and Euraphia hembeli, Tetraclita singaporensis, and Tetraclita kuroshioensis on which the presence of these species in Thailand has not been mentioned in any literatures. N. spinosus, E. hembeli and T. singaporensis can only be seen at Na Tai station, Phang-nga province while E. depressa is specific to Khao Sam Muk, Chon Buri province. However, we cannot rule out the possibility of their presences in other places and more intensive field surveys covering all provinces along Thailand's coasts are required.
Recently, there are 26 species in the genus Chthamalus (
According to a field survey on water quality and metal contamination of both coastal regions of Thailand, the Andaman Sea is still in a good condition compared to the Gulf of Thailand. On the other hand, habitat degradation along the Gulf of Thailand is much more severe and the number of species of these sessile arthropods has been declining dramatically over the last 20 years due to high amount of water pollution. For example, along Chon Buri’s coast around 20 years ago, at least five species were commonly seen along rocky shores of the now developing centrum area. Recently, however, only Amphibalanus amphitrite have been able to tolerate severe human activities and even in some sites there are no more barnacles on rocky shores. This might be because the local communities have been releasing non-treated waste water directly into the sea (personal communication and unpublished report (1996): Department of Biology, Faculty of Science, Burapha University). Hence, the richness of barnacle species can also be used to indirectly monitor the conditions of sea water.
Taken together, we demonstrate a clearer view of diversity for acorn barnacles from various localities in Thailand. This study shows at least 10 species of barnacles, in total, exist along Thai coast regions. Future works with more sampling sites and further in-depth investigations using SEM and molecular approaches with the help of phylogenetic analysis will provide a much better view especially of the history of barnacles and intraspecific variation between sessile crustaceans and that may reveal new barnacle species inhabiting Thailand.
This work was supported by Grant for Graduate Student 2015, Faculty of Science, Burapha University, Thailand. We would like to thank Assistant Professor Dr. Chuta Boonphakdee, Assistant Professor Pongrat Dumrongrojwattana, Mr. Rungwit Chaijirawong, Mr. Santi Suanla and Ms. Salisa Nithikulthananan for imaging assistance and Mr. Robert Luke for reading through a draft of the manuscript.
Arthropodal characters of Tetraclita kuroshioensis
Data type: species data
Explanation note: Tetraclita kuroshioensis collected from (BUU16.TC.TK01) from Na Tai beach, Phang-nga. A.-I. Light microscopy on arthropodal characters. A. Cirri I, B.-C. Close up on cirri I showing serrulate setae, D. Cirri II, E.-F. Close up on cirri II showing serrulate setae, G. Maxillule, H. Mandible, I. Labrum.
Arthropodal characters of Tetraclita singaporensis
Data type: species data
Explanation note: Tetraclita singaporensis collected from (BUU16.TC.TSG02) from Na Tai beach, Phang-nga. A.-I. Light microscopy on arthropodal characters. A. Cirri I, B.-C. Close up on cirri I showing serrulate setae, D. Cirri II, E.-F. Close up on cirri II showing serrulate setae, G. Maxillule, H. Mandible, I. Labrum.
Arthropodal characters of Tetraclita squamosa
Data type: species data
Explanation note: Tetraclita squamosa collected from Hin Ngam beach, Nakhon Si Thammarat (BUU16.TC.TS01). A.-I. Light microscopy on arthropodal characters. A. Cirri I, B.-C. Close up on cirri I showing serrulate setae, D. Cirri II, E.-F. Close up on cirri II showing serrulate setae, G. Maxillule, H. Mandible, I. Labrum.