New records of the bobtail squid, Euprymna hyllebergi Nateewathana, 1997 with designation of a neotype

Abstract

A total of 265 specimens, 118 males and 147 females, of the bobtail squid, Euprymna hyllebergi, are registered in the Reference Collection, Phuket Marine Biological Center, Thailand. Nearly all specimens were collected from Thai waters, the Andaman Sea and the Gulf of Thailand. The species is here reported as a new record for Myanmar waters and the distribution in the Indian Ocean has been extended to the west of the Andaman Islands. A male neotype is designated on a specimen collected from the original locality in order to replace the lost male holotype specimen. The neotype is deposited in the Reference Collection of Phuket Marine Biological Center, Thailand, as is the remaining female paratype, whereas selected specimens are deposited in National Science Museum Tokyo, Japan, U.S. National Museum, Washington D.C., USA and the Zoological Museum, SNM, University of Copenhagen, Denmark. Measurements of the neotype, paratype, and selected specimens are presented and discussed.

Full text

Phuket mar. biol. Cent. Res. Bull. 70: 15–27 (2011)
NEW RECORDS OF THE BOBTAIL SQUID, EUPRYMNA HYLLEBERGI
NATEEWATHANA, 1997 WITH DESIGNATION OF A NEOTYPE
Charatsee Aungtonya
1
, Anuwat Nateewathana
2
, Ole Secher Tendal
3
and Jaruwat Nabhitabhata
4
1
Phuket Marine Biological Center, P.O. Box 60, Phuket 83000, Thailand
2
Department of Marine and Coastal Resources, Bangkok, Thailand
3
Zoological Museum, SNM, University of Copenhagen, Universitetsparken 15, DK-2100
Copenhagen, Denmark
4
Centre for Biodiversity of Peninsular Thailand (CBIPT), Faculty of Science,
Prince of Songkla University, Hatyai, Songkhla 90112, Thailand
Corresponding author: Charatsee Aungtonya
Email: charatsee@gmail.com
ABSTRACT: A total of 265 specimens, 118 males and 147 females, of the bobtail squid, Euprymna
hyllebergi, are registered in the Reference Collection, Phuket Marine Biological Center, Thailand.
Nearly all specimens were collected from Thai waters, the Andaman Sea and the Gulf of Thailand.
The species is here reported as a new record for Myanmar waters and the distribution in the
Indian Ocean has been extended to the west of the Andaman Islands. A male neotype is designated
on a specimen collected from the original locality in order to replace the lost male holotype
specimen. The neotype is deposited in the Reference Collection of Phuket Marine Biological
Center, Thailand, as is the remaining female paratype, whereas selected specimens are deposited
in National Science Museum Tokyo, Japan, U.S. National Museum, Washington D.C., USA and
the Zoological Museum, SNM, University of Copenhagen, Denmark. Measurements of the
neotype, paratype, and selected specimens are presented and discussed.
Key word: bobtail squid, Euprymna hyllebergi, Thai waters, neotype
INTRODUCTION
Bobtail squids are small benthic
cephalopods, belonging to the family Sepiolidae
Leach, 1817, which contains about 14 genera and
over 50 species. Sepiolid squids are distributed
worldwide, ranging from tropical to temperate and
sub-polar waters of all oceans (Nateewathana,
1997a).
According to the most recent revision by
Norman & Lu (1997) and a later paper on the genus
by Nateewathana (1997b), 13 species have been
referred to Euprymna Steenstrup, 1887. Six
species, E. berryi Sasaki, 1929, E. hoylei Adam,
1986, E. hyllebergi Nateewathana, 1997, E. morsei
(Verrill, 1881), E. scolopes Berry, 1913, and E.
tasmanica (Peffer, 1884) are currently accepted
in the genus. Two species, E. pusilla (Peffer,
1884) and E. schneehageni (Peffer, 1884), were
placed as invalid while four species, E. albatrossae
Voss, 1963, E. bursa (Pfeffer, 1884), E. phenax
Voss, 1963, and E. stenodactyla (Grant, 1833),
were treated as unresolved species (Norman &
Lu, 1997). E. albatrossae, E. bursa, and E. phenax
were known only from the types. The original type
material of E. stenodactyla is lost, no further
material has been found in Mauritius yet and the
description of the species is poor (Norman & Lu,
1997). Furthermore, a nominal species, E. similis
Sasaki, 1913, was considered a junior synonym
of E. morsei (Norman & Lu, 1997).
The species E. morsei, E. stenodactyla,
E. berryi and E. hyllebergi, have been reported
from Thai waters, the Andaman Sea and the Gulf
of Thailand, by Chotiyaputta et al. (1992),
Chotiyaputta (1993), Supongpan (1995),
Nateewathana (1997b) and Nateewathana et al.
(2001).

Phuket mar. biol. Cent. Res. Bull.
16
According to Nateewathana et al. (2001)
the occurrence of E. morsei, E. stenodactyla, and
E. berryi in Thai waters was still uncertain since
the voucher material could not be located.
However, E. morsei and E. stenodactyla from the
Andaman Sea and Myanmar waters have been
registered at the PMBC Reference Collection in
2007. Future taxonomic study on those specimens
is pending.
All specimens of Euprymna hyllebergi
deposited in the Reference Collection of Phuket
Marine Biological Center, were checked and
measured, but none were in accordance with the
holotype. The first and the fourth authors
contacted the cephalopod taxonomists who had
previously studied the type material, but they all
denied any knowledge about the fate of those types.
We conclude that the holotype is lost.
Euprymna hyllebergi is close to E. hoylei,
but differs in the arrangement of suckers on the
hectocotylized arm, the size and distribution of
enlarged suckers on arms II–IV, and in the length
of the tentacles (Nateewathana, 1997b: Fig. 3).
E. hoylei is known from the tropical
Western Pacific to North-West Australia (Norman
& Lu, 1997). It is characterized by lacking enlarged
suckers on arm II in mature males, having 3–4
enlarged suckers in dorsal and ventral rows of arm
pair IV and ventral row only of arm pair III
(Norman & Lu, 1997, Nesis, 1987). The suckers
on arm II–IV of E. hyllebergi do not have any
significantly or abruptly enlarged suckers
(Nateewathana, 1997b). E. hyllebergi has a high
number of stout papillae with a slitlike aperture in
the distal half of the hectocotylus. The papillae of
E. hyllebergi are crowded in rows of 4–6 suckers
in the middle part, and reduced to two rows at the
tip of the hectocotylus.
The male characters are the most
important features distinguishing the two species,
E. hoylei and E. hyllebergi. Furthermore, the
arrangement of the sessile suckers of the male is
the only diagnostic feature to characterize the
species of the genus, as well as other genera in
the Family Sepiolidae. Hence it is necessary to
select a male neotype of E. hyllebergi.
The present report lists all specimens of
this species in the Reference Collection, designates
the male neotype of Euprymna hyllebergi in order
to replace the lost male holotype and paratypes
previously listed in Aungtonya et al. (2006, 2007),
and describes specimens deposited in other
museums. This study aims to facilitate future
revision and taxonomic work on this genus and to
update the known distribution of the species.
MATERIALS AND METHODS
The bobtail squids were obtained from
fishing boats, research vessels, fish markets, and
fish landings along the Andaman Sea coast of
Thailand and the Gulf of Thailand as described by
Nateewathana (1997b) and Nateewathana et al.
(2001). Additional material for the present study
was primarily obtained from the R.V. Chulaphorn
of the Deep Sea Fishery Technology Research and
Development Institute operating off the Andaman
Sea coast of Thailand, and from fishing boats, fish
markets and fish landings along the Andaman Sea
coast of Thailand and the Gulf of Thailand.
Taxonomic studies are based on Nateewathana
(1997b).
The specimen designated as the neotype
and five lots of specimens were selected from the
samples in the Reference Collection of Phuket
Marine Biological Center. The neotype was, like
the holotype, collected from small scale fishing
areas in Trang Province, at a depth of less than 40
m off the Andaman Sea Coast of Thailand.
Measurements follow those of
Nateewathana (1997b). Definitions of
measurements and indices are summarized in Table
1 and in Figure 1. The difference of the means of
all the measurements and indices is compared with
those listed by Nateewathana (1997b). Differences
were considered significant when
Specimens of the species, the newly
designated neotype, and selected materials are
deposited in the Reference Collection of Phuket
Marine Biological Center, Thailand (PMBC),
National Science Museum Tokyo, Japan (NSMT),
U.S. National Museum, Washington, D.C., USA
(USNM), and the Zoological Museum, SNM,
University of Copenhagen, Denmark (ZMUC).

17
New records of the bobtail squid
ML Mantle Length dorsal mantle length measured from the anterior-most
point of mantle to posterior tip, along dorsal mid-line.
MWI Mantle Width Index greatest straight-line (dorsal) width of mantle as a
percentage of mantle length.
FLI Fin Length Index greatest length of fins as a percentage of mantle length.
FWI Fin Width Index greatest width (dorsally) across both fins as a percentage
of mantle length.
FBI Fin Base Index length of fin base as a percentage of mantle length.
HLI Head Length Index dorsal length of head measured from point of fusion of
dorsal arms to anterior tip of nuchal locking cartilage as a
percentage of mantle length.
HWI Head Width Index width of head across midpoint of eyes as a percentage of
mantle length.
ALI Arm Length Index length of arm measured from first basal (proximal-most)
sucker to tip of arm as a percentage of mantle length.
ASI Arm Sucker Index diameter of largest normal arm sucker on each designated
arm as a percentage of mantle length.
TtLI Tentacle Length Index total length of tentacular stalk and club as a percentage of
mantle length.
ClLI Club Length Index length of club as a percentage of mantle length.
HcLI Hectocotylized Length Index length of modified portion of arm measured from
proximal-most modified sucker to tip of arm as a
percentage of total length of hectocotylized arm
(left arm I).
EDI Eye Diameter Index diameter of eye across bulbus as a percentage of mantle
length.
LnDI Lens Diameter Index diameter of eyelens as a percentage of mantle length.
Table 1. Definition of counts, measurements and indices (modified after Nateewathana, 1997b).
RESULTS
A total of 265 specimens, 118 males and
147 females, were registered in the Reference
Collection (see Table 2). Nearly all of the specimens
were collection from Thai waters, the Andaman
Sea and the Gulf of Thailand, except for PMBC
11781 and PMBC 11775 which were collected
from the Indian Ocean, west of the Andaman
Islands and Myanmar waters, respectively. The
latter specimens are the first records of E.
hyllebergi from the Indian Ocean, west of the
Andaman Islands and Myanmar waters,
respectively.
The neotype was selected from PMBC
11742 and registered as PMBC 21339 (Fig. 2).
Three lots of NSMT-Mo 76424, USNM 1150474,
and ZMUC CEP-25 have been selected from PMBC
11742, PMBC 11748 and PMBC 11747,
respectively. Two females of PMBC 11734 have
been selected and registered as NSMT-Mo 76425
and ZMUC CEP-51. The male neotype, PMBC
accession number 21339, is deposited in the
Reference Collection of Phuket Marine Biological
Center, as is the remaining female paratype, PMBC
11731.
Selected measurements and indices of the
type materials and selected specimens of E.
hyllebergi are presented in Table 3. Mean of indices
(in percent), standard deviation of five males and
four females are presented in Table 4. The t-test
comparing the means of all the measurements and
indices of the present material and those given by
Nateewathana (1997b) are presented in Table 5.

Phuket mar. biol. Cent. Res. Bull.
18
Figure 1. Diagrammatic illustration of measurements in sepiolids (modified after Nateewathana, 1997b).
AL = arm length, C1L = club length, ED = eye diameter, FB = fin base, FL = fin length, FW = fin width,
HL = head length, HW = head width, LD = lens diameter, ML = mantle length, MW = mantle width, TtL
= tentacle length.
Euprymna hyllebergi Nateewathana, 1997
(Figs. 2A–B, 3A–B, 4A–C, Table 2–5)
Euprymna hyllebergi – Nateewathana, 1997b: 466–
474, figs. 2–5, Table 2.
Neotype. PMBC 21339, 1 male, Kantang fish
landing, Trang province, 14 Feb 1996 (Figs. 2–
3).
Paratype. PMBC 11731, 1 female, Tha Lane,
Phangnga Bay, push net, 23 July 1989
Selected specimens. NSMT-Mo 76424, 1 male,
Kantang fish landing, Trang Province, 14 Feb
1996; NSMT-Mo 76425, 1 female, Chong Pra,
Phangnga Bay, push net, 18 June 1988; USNM
1150474, 1 male and 1 female, Phuket fish market,
Phuket Province, 23 Aug 1995; ZMUC CEP-25, 2
males, Krabi fish market, Krabi province, 17 Dec
1994; ZMUC CEP-51, 1 female, Chong Pra,
Phangnga Bay, push net, 18 June 1988.
Material examined. 265 specimens have been
examined and registered (see Table 2).
Description. Colour in alcohol yellowish;
numerous large and conspicuous purplish brown
chromatophores cover mantle, head and arms,
more dense in middle part of dorsal and ventral
sides. Mantle dome-shaped, thick, broad

19
New records of the bobtail squid
anteriorly and rounded posteriorly, slightly longer
than wide (Figs. 2–3, 4A–B); antero-dorsal margin
fused with head (Figs. 2, 4A). Large portion of
the tubular funnel visible, median ventral margin
slightly concave (Figs. 2B, 4B–C). Fins rounded,
almost circular in outline, separate and attached at
middle of mantle; anterior margin to posterior
margin nearly straight. Head broad, dorsoventrally
flattened and compact, width slightly less than
mantle width; eyes large, oval with almost circular
pupil. Funnel long, tubular, free for most of its
length, reaching to gap between ventral arms (Fig.
4B–C). Funnel valve triangular to rounded flaplike.
Funnel organs with a roughly triangular dorsal pad
and two oval ventral pads. Anterior end of dorsal
pad with a low crest projected in midline. Funnel
locking cartilage ovate, rounded at both ends with
deep groove (Fig. 4C); mantle cartilage straight,
ridge-like, two times longer than funnel cartilage.
Arms long, subequal, rounded in cross section,
tapering distally. Web C (between arms II and III)
developed and D distinct (between arms III and
IV). Web D extends up about one-fourth of arm
length. Suckers almost equal-sized, subglobular,
with a small, smooth aperture; pedicel thin. In
females, arm suckers quadriserial but biserial at
base and distally. In male, arm suckers globular
with smooth horny ring, rounded aperture on
normal sucker, but more ovate on enlarged one.
Left arm I of male hectocotylized, stout, shorter
than other arms and curved outwards
(Nateewathana, 1997b: figs. 3a, 4a–b). The size
of arm suckers on different arms varied. Tentacles
round, flattened on oral surface, edges of flat area
angled, dorsal margin elevated into a low keel
towards club. Club short, curled, and rounded with
numerous rows of very small suckers. Gladius
absent. Buccal membrane smooth without suckers.
Type locality. Small scale fishing areas in Trang
Province, in the depth less than 40 m, the Andaman
Sea coast of Thailand.
Distribution. Indian Ocean (Andaman Sea and
Myanmar waters with range extension to the west
of the Andaman Islands) and Gulf of Thailand.
Remarks. The characters of all specimens match
well with those of E. hyllebergi, as described and
figured by Nateewathana (1997b). Description of
beak, radula, ink sac, and spermatophores of the
species are not repeated herein.
The right tentacle in NSMT-Mo 76424 and
the left tentacle in ZMUC CEP-51 are missing.
Figure 2: Euprymna hyllebergi Nateewathana, 1997 (PMBC 21339). Neotype, male: (A) dorsal and
(B) ventral.
A
B

Phuket mar. biol. Cent. Res. Bull.
20
A
B
Figure 3: Euprymna hyllebergi Nateewathana, 1997 (PMBC 11731). Paratype, female: (A) dorsal and
(B) ventral.
Figure 4. Euprymna hyllebergi Nateewathana, 1997 (PMBC 21339). Neotype, male: (A) dorsal view;
(B) ventral view; (C) funnel and funnel locking-cartilages. Scales = 2 cm (A–B) and 0.5 cm (C).
A
B
C

21
New records of the bobtail squid
Table 2. Details of specimens of Euprymna hyllebergi remaining in the Reference Collection of Phuket Marine Biological Center.
No. PMBC No. Type No. of spec. Male Female Locality Province Identifier Remarks
1 1607 5 3 2 – Phuket A. Nateewathana original recorded as
Euprymna stenodactyla
(Grant, 1833) by C.F.E.
Roper in 1979
2 11727 1 1 Krabi fish market Krabi A. Nateewathana
3 11728 HOLOTYPE specimen lost Kantang fish landing Trang A. Nateewathana
4 11729 6 2 4 Kantang fish landing Trang A. Nateewathana
5 11730 11 5 6 Kapur Ranong A. Nateewathana
6 11731 PARATYPE 1 1 Tha Lane, Phangnga Bay Phangnga A. Nateewathana
7 11732 1 1 Rok Island Trang A. Nateewathana
8 11733 6 3 3 Krabi fish market Krabi A. Nateewathana
9 11734 3 1 2 Chong Pra, Phangnga Bay Phangnga A. Nateewathana
10 11735 2 1 1 Raya Ring Island Phangnga A. Nateewathana
11 11736 3 3 Tha Lane, Phangnga Bay Phangnga A. Nateewathana
12 11737 PARATYPE specimen lost Kantang fish landing Trang A. Nateewathana
13 11738 5 5 8°02´N, 98°30´E Andaman Sea A. Nateewathana
14 11739 PARATYPE specimens lost Southwest of Lanta Island Krabi A. Nateewathana
15 11740 9 2 7 Taeng Cape, Phangnga Bay Phangnga A. Nateewathana
16 11741 9 3 6 Phangnga Bay Phangnga A. Nateewathana
17 11742 32 15 17 Kantang fish landing Trang A. Nateewathana
18 11744 12 6 6 Krabi fish market Krabi A. Nateewathana
19 11745 1 1 Krabi fish market Krabi A. Nateewathana
20 11746 1 1 – Ranong A. Nateewathana
21 11747 5 4 1 Krabi fish market Krabi A. Nateewathana
22 11748 12 5 7 Phuket fish market Phuket A. Nateewathana
23 11749 2 1 1 Tukkae Cape Phuket A. Nateewathana
24 11750 1 1 Raya Ring Island, Phangnga Bay Phangnga A. Nateewathana
25 11751 1 1 Mak Island, Phangnga Bay Phangnga A. Nateewathana
26 11752 4 2 2 Phuket fish market Phuket A. Nateewathana
27 11753 3 3 Southwest of Lanta Island Krabi A. Nateewathana
28 11755 13 6 7 Tamalang fish landing Satul A. Nateewathana
29 11756 4 1 3 – Phangnga A. Nateewathana
30 11757 1 1 Jam Island Ranong A. Nateewathana
31 11758 1 1 7°48´N, 98°30´E Andaman Sea A. Nateewathana
32 11759 1 1 Nakae Island Phangnga A. Nateewathana
33 11760 3 2 1 Sapum Bay Phuket A. Nateewathana
34 11761 1 1 Dam Hok Island Krabi A. Nateewathana

Phuket mar. biol. Cent. Res. Bull.
22
Table 2. (continued)
No. PMBC No. Type No. of spec. Male Female Locality Province Identifier Remarks
35 11762 1 1 Trang fish market Trang A. Nateewathana
36 11763 2 2 off Yao Yai Island Phangnga A. Nateewathana
37 11764 2 1 1 East of Lanta Island Krabi A. Nateewathana
38 11765 1 1 – – A. Nateewathana
39 11766 1 1 – Krabi A. Nateewathana
40 11767 1 1 6°58´N, 98°48´E Andaman Sea A. Nateewathana
41 11768 2 2 6°57´N, 98°47´E Andaman Sea A. Nateewathana
42 11770 1 1 Rang Yai Island Phuket A. Nateewathana
43 11772 3 2 1 – Krabi A. Nateewathana
44 11773 1 1 – Ranong A. Nateewathana
45 11774 1 1 Kantang fish landing Trang A. Nateewathana
46 11775 1 1 13°27´N, 97°00´E Myanmar waters A. Nateewathana
47 11776 18 5 13 Pattani fish landing Pattani A. Nateewathana
48 11777 1 1 Kantang fish landing Trang A. Nateewathana
49 11780 1 1 Samut Prakan fish landing Samut Prakan A. Nateewathana
50 11781 1 1 7°17´N, 90°00´E Indian Ocean A. Nateewathana
51 11782 3 2 1 7°04´N, 98°53´E Andaman Sea A. Nateewathana
52 11785 16 10 6 Kantang fish landing Trang A. Nateewathana
53 11787 26 17 9 Kantang fish landing Trang A. Nateewathana
54 14420 1 1 9°34´N, 97°49´E Andaman Sea A. Nateewathana
55 19903 10 6 4 7°51´N, 98°38´E Andaman Sea T. Kubodera
56 19904 1 1 9°00´N, 97°54´E Andaman Sea T. Kubodera
57 21339 NEOTYPE 1 1 Kantang fish landing Trang A. Nateewathana specimen was selected
from PMBC 11742
58 23937 4 3 1 – – A. Nateewathana specimens found in the
bottle of PMBC
11737, but not
identical to original
paratype
59 25004 5 3 2 – – A. Nateewathana specimens found in the
bottle of PMBC
11739, but not
identical to original
paratype specimens
Remarks: the number of specimens in some PMBC accession numbers is changed, compared to that published in Appendix 1 of Nateewathana (1997b), and some
PMBC accession numbers were not included in that appendix.

23
New records of the bobtail squid
Table 3. Measurements (mm) and indices (%) of neotype, paratype, and selected specimens of Euprymna hyllebergi from the Andaman Sea,
Thailand.
Remarks:
1
= tip of the right arm broken;
2
= left tentacle due to the right one lost. The values in bold text are out of the range of the
measurements and indices reported by Nateewathana (1997b).
Neotype Paratype Selected specimens
Registration PMBC PMBC NSMT-Mo NSMT-Mo USNM ZMUC CEP ZMUC CEP
No. 21339 11731 76424 76425 1150474 25 51
Index\Sex Male Female Male Female Male Female Male Female
ML (mm) 30.98 22.27 33.63 35.22 29.02 26.79 27.21 28.65 28.42
MWI 84.83 91.02 77.19 74.82 90.45 88.28 83.83 81.85 76.18
FLI 44.09 58.96 48.41 51.02 54.51 50.09 52.11 48.94 57.74
FWI 129.50 152.09 119.92 135.15 146.76 159.69 132.82 134.90 135.50
FBI 26.44 46.74 28.49 33.19 35.70 39.94 32.97 37.63 34.24
HLI 54.71 46.43 52.81 50.03 53.62 64.05 53.55 58.71 57.35
HWI 63.52 73.15 61.11 59.71 64.13 67.19 68.83 64.96 57.74
AL
I
I 106.75
1
69.33 97.71 59.00 91.94 91.75 88.06 99.34 84.87
AL
II
I 143.54 86.30 114.93 74.76
1
124.91
1
99.22 110.66 124.15 102.39
AL
III
I 120.27 77.19
1
98.33
1
69.96 104.31
1
93.77 101.14 108.34 91.87
AL
IV
I 116.17 73.37 110.70 67.18
1
105.10 96.90 98.46 101.22 88.53
AS
I
I 3.23 2.92 2.97 2.13 3.96 2.24 2.94 4.01 2.53
AS
II
I 4.03 3.37 4.16 2.30 3.79 2.61 2.94 3.66 2.43
AS
III
I 5.23 2.92 4.46 2.98 5.34 2.43 4.41 5.34 3.20
AS
IV
I 6.17 2.25 4.46 2.73 5.00 2.43 4.59 4.54 2.81
TtLI 327.73 119.98 234.67
2
84.44 290.18 246.62 285.34 229.60 169.11
CILI 42.32 34.98 46.65 31.63 31.74
1
62.64 42.08 41.64 39.94
HcLI 65.73 59.99 62.93 58.01 60.94 0.00
EDI 22.60 25.82 19.80 24.11 27.08 24.15 30.10 26.35 25.97
LnDI 12.33 15.67 13.56 12.12 13.20 15.57 15.40 14.52 13.62

Phuket mar. biol. Cent. Res. Bull.
24
Table 4. Mean (X) of indices (%) and standard deviation of type materials and selected specimens
of Euprymna hyllebergi from the Andaman Sea, Thailand.
Table 5. t-test of the mean of all measurements and indices by Nateewathana (1997b) and this study.
Male Female
Index
n Mean SD Range n Mean SD Range
ML (mm) 5 29.90 2.48 27.21–33.63 4 28.18 5.37 22.27–35.22
MWI 5 83.63 4.81 77.19–90.45 4 82.57 8.27 74.82–91.02
FLI 5 49.61 3.96 44.09–54.51 4 54.45 4.54 50.09–58.96
FWI 5 132.78 9.70 119.92–146.76 4 145.61 12.27 135.15–159.69
FBI 5 32.24 4.72 26.44–37.63 4 38.53 6.23 33.19–46.74
HLI 5 54.68 2.35 52.81–58.71 4 54.47 7.84 46.43–64.05
HWI 5 64.51 2.81 61.11–68.83 4 64.45 7.09 57.74–73.15
AL
I
I 5 96.76 7.18 88.06–106.75 4 76.24 14.83 59.00–91.75
AL
II
I 5 123.64 12.67 110.66–143.54 4 90.67 12.68 74.76–102.39
AL
III
I 5 106.48 8.56 98.33–120.27 4 83.20 11.52 69.96–93.77
AL
IV
I 5 106.33 7.17 98.46–116.17 4 81.50 13.64 67.18–96.90
AS
I
I 5 3.42 0.53 2.94–4.01 4 2.46 0.35 2.13–2.92
AS
II
I 5 3.72 0.48 2.94–4.16 4 2.68 0.48 2.30–3.37
AS
III
I 5 4.96 0.48 4.41–5.34 4 2.88 0.33 2.43–3.20
AS
IV
I 5 4.95 0.71 4.46–6.17 4 2.55 0.26 2.25–2.81
TtLI 5 273.50 41.21 229.60–327.73 4 155.04 70.23 84.44–246.62
CILI 5 40.89 5.50 31.74–46.65 4 42.30 13.98 31.63–62.64
HcLI 5 61.52 2.95 58.01–65.73 4
EDI 5 25.19 4.02 19.98–30.10 4 25.01 1.02 24.11–25.97
LnDI 5 13.80 1.19 12.33–15.40 4 14.24 1.70 12.12–15.67
Male Nateewathana (1997b) present study
Index n Mean SD n Mean SD T-test
ML (mm) 20 27.20 4.20 5 29.90 2.48 No diff
MWI 20 81.20 11.30 5 83.63 4.81 No diff
FLI 20 49.10 7.10 5 49.61 3.96 No diff
FWI 20 131.10 13.80 5 132.78 9.70 No diff
FBI 20 31.50 4.00 5 32.24 4.72 No diff
HLI 20 52.80 8.50 5 54.68 2.35 No diff
HWI 20 65.20 7.10 5 64.51 2.81 No diff
AL
I
I 20 103.70 20.00 5 96.76 7.18 No diff
AL
II
I 20 141.00 15.70 5 123.64 12.67 Sig diff
AL
III
I 20 118.20 14.10 5 106.48 8.56 No diff
AL
IV
I 20 118.60 18.00 5 106.33 7.17 No diff
AS
I
I 20 3.50 0.50 5 3.42 0.53 No diff
AS
II
I 20 4.40 0.60 5 3.72 0.48 Sig diff
AS
III
I 20 5.10 0.70 5 4.96 0.48 No diff
AS
IV
I 20 5.30 0.60 5 4.95 0.71 No diff
TtLI 20 282.80 47.10 5 273.50 41.21 No diff
CILI 20 48.40 7.10 5 40.89 5.50 Sig diff
HcLI 20 63.40 8.30 5 61.52 2.95 No diff
EDI 20 23.30 5.60 5 25.19 4.02 No diff
LnDI 20 14.40 2.80 5 13.80 1.19 No diff

25
New records of the bobtail squid
Female Nateewathana (1997b) present study
Index n Mean SD n Mean SD T-test
ML (mm) 20 24.90 5.50 4 28.18 5.37 No diff
MWI 20 80.70 8.90 4 82.57 8.27 No diff
FLI 20 52.50 7.80 4 54.45 4.54 No diff
FWI 20 142.40 12.80 4 145.61 12.27 No diff
FBI 20 35.80 5.00 4 38.53 6.23 No diff
HLI 20 55.30 6.20 4 54.47 7.84 No diff
HWI 20 67.70 7.90 4 64.45 7.09 No diff
AL
I
I 20 85.40 11.40 4 76.24 14.83 No diff
AL
II
I 20 110.60 12.30 4 90.67 12.68 Sig diff
AL
III
I 20 93.20 8.80 4 83.20 11.52 No diff
AL
IV
I 20 89.70 9.20 4 81.50 13.64 No diff
AS
I
I 20 2.70 0.40 4 2.46 0.35 No diff
AS
II
I 20 2.80 0.50 4 2.68 0.48 No diff
AS
III
I 20 3.00 0.40 4 2.88 0.33 No diff
AS
IV
I 20 2.80 0.40 4 2.55 0.26 No diff
TtLI 19 266.60 60.70 4 155.04 70.23 Sig diff
CILI 19 53.30 10.90 4 42.30 13.98 No diff
EDI 20 23.50 3.80 4 25.01 1.02 No diff
LnDI 20 14.90 2.10 4 14.24 1.70 No diff
DISCUSSION
The Euprymna hyllebergi arm length
formula is II > III > IV > I, but occasionally II >
III = IV > I (Nateewathana, 1997b). The arm length
formulas of the present material of males and
females (Table 4, II > III > IV > I), matches those
of Nateewathana (1997b) as well as those in the
neotype and paratype (Table 3). Differences are,
however, found in some of the selected specimens;
four specimens show II > III > IV > I but three
other specimens show II > IV > III > I (Table 3).
These differences occur because the tips of the
right arms were broken.
All measurements and indices of the
neotype are in the ranges reported by
Nateewathana (1997b). Some measurements and
indices in the paratype and selected specimens are,
however, out of these ranges, i.e., Mantle Length
(ML), Arm Length Index (ALI), Arm Sucker Index
(ASI), Tentacle Length Index (TtLI), and Club
Length Index (ClLI) (Tables 3–4). Furthermore,
the t-test of the mean of all measurements and
indices by Nateewathana (1997b) and in this study
were considered significant for AL
I
I in both male
and female, for AS
II
I and ClLI in male only, and
for TtLI in female (Table 5).
These differences may occur because the
suckers on arms easily fall off and are lost in
preserved material and the tip of the first right arm
in male specimen was broken. Therefore some
errors occurred in estimation of the length of the
first right arm, which was measured from the first
basal (proxima-most) sucker to tip of arm as a
percentage of mantle length.
Furthermore, according to C.C. Lu (pers.
comm., in Nateewathana, 1997b), the length of
the tentacles in cephalopods may not be a usable
taxonomic character since it varies greatly
depending on how the specimen is fixed and
preserved. Live fixed animals have short tentacles
because of contraction and, on the other hand,
specimens thawed from frozen condition have long
tentacles. In order for this character to be of some
Table 5. (continued)

Phuket mar. biol. Cent. Res. Bull.
26
use, specimens should be fixed under identical
conditions. Specimens from the same batch may
vary greatly (C.C. Lu, pers. comm., in
Nateewathana, 1977b).
The mantle length, the first arm length
index, the tentacle length index, and club length
index are the main characters/indices used for
distinguishing the species from other members of
the genus. Although the tentacle length is
particularly important in recognizing this species,
it is not necessarily an autopomorphy for the
species. It is the combination of the arrangement
of suckers on the hectocotylized arm, the size and
distribution of enlarged suckers on arms II–IV,
and in the length of the tentacles that distinguishes
Euprymna hyllebergi.
ACKNOWLEDGEMENTS
We express our appreciation to Dr.
Kongkiat Kittiwattanawong, Phuket Marine
Biological Center (PMBC) for his kind assistance
in t-test Analysis, and Dr. Janek von Byern,
University of Vienna, Austria, for providing valuable
comments on the draft of this manuscript. Sincere
thanks are given to Ms. Kanjana Bussabong, the
Reference Collection, Phuket Marine Biological
Center, and Ms. Thitima Boonkaew, training
student, PSU, for their kind assistance. Our sincere
thanks also go to Mr. Rueangrit Promdam, (former
staff of Reference Collection), and Mr. Patirat
Singdum, the PMBC artist, for photographing and
drawings.
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Manuscript received: 17 August 2009
Accepted: 12 June 2011

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