The beagle : occasional papers of the Northern Territory Museum of Arts and Sciences

The BEAGLE

Occasional Papers of

The Northern Territory Museum

of Arts and Sciences

Vol. 1 No. 1

Editorial Address: G.P.O. Box 4646, Darwin, N.T., Australia 5794

10 February 1983

THOR SPINIPES SP. NOV., A NEW HIPPOLYTID
SHRIMP FROM THE COBOURG PENINSULA,
NORTHERN AUSTRALIA

A. J. BRUCE

Division of Natural Sciences, Northern Territory Museum,
G.P.O. Box 4646, Darwin, Australia5794

ABSTRACT

A new species of hippolytid shrimp, Thor spinipes sp. nov., from the Cobourg
Peninsula, Northern Australia, is described and illustrated. The species is most
closely related to T. paschalis Heller and is a cryptically coloured, free-living
species. A key for the identification of the species of Thor known from
Australian waters is presented.

INTRODUCTION

Six species of the hippolytid genus Thor
Kingsley, 1878, have been described from
the Indo-West Pacific region, with a further
three species known from the western
Atlantic region. One species, T.
amboinenis, occurs in both regions. The
discovery of an undescribed species on the
Cobourg Peninsula of the Northern
Territory raises to four the number of
species known from Australian waters. Of
the six previously described Indo-West
Pacific species, three are known to be
associated with other marine invertebrates
and three are apparently free-living. All
occur in shallow or intertidal waters. The

present new species possesses a well
developed supraorbital spine which
distinguishes it immediately from all
Indo-West Pacific species except T. spinosus
Boone and T. maldivensis Borradaile, which
have not yet been recorded from Australian
waters but could well occur, as well as from
the West Atlantic species. Keys for the
identifications of most of the Indo-West
Pacific species of Thor have been provided
by Holthuis (1945) and Bruce (1976).
Miyake and Hayashi (1966) and Hayashi
and Miyake (1968) discuss the species
occurring in Japanese and western Pacific
waters.

2

A. J. Bruce,

10 February 1983

Fig. 1. Thor spinipes sp. nov., ovigerous female. Scale in millimetres.

Thor spinipes sp. nov.

(figs. 1-6)

Material examined — 3cf. 7 ovig. 9,1$,
2 juv.; Burford Island, Cobourg Peninsula,
Northern Territory, Australia; Stn. CP/14,
11°29.3'S, 131°57.5'E; muddy reef flat pools
at LWS tide, 13 October 1981, coll. A. J.
Bruce.

Description — Small sized, rather stout
bodied hippolytid shrimp, with body
subcylindrical, glabrous, without plumose
setae. Carapace smooth with short slender
compressed rostrum equal to about half
postorbital carapace length, horizontal,
reaching to about level of distal border of
proximal segment of antennular peduncle,
bearing three acute dorsal teeth and one
distal ventral tooth, (one specimen has a
rostral dentition of 4/1), lateral carina feebly
developed. Acute supraorbital spines
present, epigastric and hepatic spines
absent; inferior orbital angle slightly
produced, subacute; antennal spine acute,
slender, submarginal, close below and

exceeding inferior orbital angle,
anterolateral angle of carapace broadly
rounded, unarmed orbital angle.

Abdomen smooth, with third segment
slightly produced posterodorsally; pleura of
first three segments broadly rounded, fourth
and fifth with posteroventral angles acutely
produced; sixth segment about 1.4 times
longer than deep and about 1.8 times length
of fifth segment, posterolateral and
posteroventral angles acute. Telson about
1.3 times length of sixth segment, sides
straight or slightly concave, posteriorly
convergent, about 2.! times longer than
wide with narrow rounded posterior margin,
without median point, equal to 0.25 of the
anterior width; three pairs of small subequal
dorsal spines at about 0.55, 0.70, and 0.85 of
telson length; three pairs of posterior
marginal spines, with lateral spines subequal
to dorsal spines, intermediate spines about
four times as long and submedian spines
three times longer and plumose.

Eyes with large globular cornea, wider
than eyestalk.

Thor spinipes sp. nov., [Crustacea, Decapoda, Hippolytidae]

3

Fig. 2. Thor spinipes sp. nov., ovigerous female. A, anterior carapace and antennal peduncles, lateral. B, anterior
carapace and antennal peduncles, dorsal. D, antennule. e. antenna. Male: C anterior carapace, lateral.

Antennular peduncle with long slender
acute stylocerite reaching beyond
intermediate peduncular segment, with
small acute tooth at proximal end of lateral
margin: small acute tooth present at 0.75 of
ventral medial margin; statocyst obsolete;
intermediate segment with acute distolateral
tooth; distal segment with triangular mobile

scale distodorsally: upper flagellum
biramous with rami fused, proximal portion
stout, 10-12 segments, with dense masses of
aesthetascs, distal portion slender: lower
flagellum filiform.

Antenna with basicerite bearing acute
ventrolateral tooth; scaphocerite far
outreaching antennular peduncle, about 2.5

4

A. J. Bruce,

10 February 1983

Fig. 3. Thorspinipes sp. nov., ovigerous female. A, mandible. B. molar process. C, incisor process. D, maxillula.
E, idem , palp. F. maxilla. G. idem, palp. H. first maxilliped. I. second macilliped. J. third maxilliped. K.
idem, tip of distal segment. L, idem, distal ischiomeral spine.

times longer than wide, lateral border
straight with strong distolateral tooth, not
exceeding rounded anterior margin of
lamella; carpocerite robust, reaching middle
of scaphocerite, with well developed slender
flagellum.

Mouthparts normal. Mandible with
corpus robust, without palp; molar process
stout with complex masticatory surface (fig.
3b); incisor process slender, distally oblique
with five small acute teeth. Maxillula with
bilobed palp, lower lobe with long serrulate

Thor spinipes sp. nov., [Crustacea, Decapoda, Hippolytidae]

5

setae and upper lobe with short plumose
seta; upper lacinia broad, obliquely truncate
distally with about 15 short stout spines,
ventrally setose; lower lacinia slender
tapering with numerous long spiniform
setae. Maxilla with short stout palp, bearing
a pair short simple terminal setae, a longer
preterminal seta with one plumose seta on
medial border and three on lateral border;
distal endite deeply bilobed, finely setose;
proximal endite reduced, coarsely setose;
scaphognathite three times longer than
broad, anterior lobe large and rounded,
posterior lobe small. First maxilliped with
palp robust, two segmented with two long
setae and numerous short setae along
medial and ventral borders; basal endite
broad, medially setose; coxal endite also
broad, sparsely setose; exopod with
flagellum well developed with numerous
plumose distal setae; caridean lobe small
with six short marginal plumose setae;

epipod large, bilobed. Second maxilliped
normal; distal segment small and narrow,
densely spinose; propod broad, about 2.2
times longer than broad, twice as long as
width of dactylar segment, with slender
spines on the distomedial angle; flagellum
well developed; epipod triangular with small
podobranch. Third maxilliped with slender
endopod extending beyond antennular
peduncle by one third of length of distal
segment; distal segment, slender, tapering,
about 7.5 times longer than wide with
cornified spines distally and numerous
groups of short spines ventromedially,
penultimate segment robust, about 0.3 of
length of distal segment; antepenultimate
segment robust, bowed, with two small
distodorsal teeth, a dentate spine laterally
and a distoventral spine; flagellum well
developed; epipod rounded, small, without
arthrobranch.

Table 1

Pereiopodal spinulation in Thor

spinipes

sp. nov.

C.L.,

Merus, L/R

Carpus,

L/R

Spm.

mms

P3

P4

P5

P3

P4

P5

Ovig. $

2.7

5/5

2/1

1/1

1/1

1/1

0/1

Ovig. 9

2.4

4/4

1/1

1/1

1/1

1/1

0/0

Ovig. 9

2.0

4/4

1/1

0/0

1/1

1/1

0/1

Ovig. 9

2.6

3/3

1/1

1/1

1/1

1/1

1/1

Ovig. 9

2.2

1/2

1/1

1/1

1/1

1/1

0/0

Ovig. 9

2.0

2/3

1/1

1/1

1/1

1/1

0 /-

Ovig. 9

1.9

31-

1 /-

1/1

1 /-

1 /-

1/1

9

1.9

2/3

1/1

0/0

1/1

1/1

0/0

cf

—

2/3

-/I

0/0

1/1

-/I

0/0

cf

1.6

2/2

1/1

0/0

1/1

1/1

0/0

cf

1.6

-/-

1 /-

01-

-/-

1 /-

0 /-

juv. 9

1.6

2/3

1/1

1/1

1/1

1/1

0/1

juv.

1.5

3/4

1/1

0/0

1/1

1/1

0/0

First pereiopods, equal, similar, short and
robust, extending anteriorly to level of distal
carpocerite; chela with palm subcylindrical,
slightly compressed, twice as long as deep;
fingers feebly subspatulate, half length of

palm, slender, tapering with strongly
cornified distal spines, carpus robust,
unarmed, feebly expanded distally, slightly
longer than palm; merus slightly longer than
carpus, 2.2 times longer than wide with

6

A. J. Bruce,

10 February 1983

Fig. 4. Thorspinipes sp. nov., ovigerous female. A. first pereiopod. B, idem chela, C, idem fingers of chela, setae
omitted. D, idem, literal and ischial spines. E. second pereiopod. F. idem, ischiuum. G. third pereiopod.
H. distoventral spines of propod of fourth pereiopod. I. fourth pereiopod. J, fifth pereiopod. Male: K,
chela of second pereiopod. L, third pereiopod. M. fourth pereiopod. N, fifth pereiopod.

three short spines on proximal ventral
border; ischium short, half length of merus,
with a row of short spines at distoventral
angle; basis and coxa normal. Second

pereiopods slender, extending beyond tip of
antennal scale; chela with palm about twice
as long as deep. 1.3 times length of fingers,
slender, tapering, acute; carpus

Thor spinipes sp. nov., [Crustacea, Decapoda, Hippolytidae]

7

Fig. 5. Thor spinipes sp. nov., ovigerous female. A, third pereiopod, dactyl. B, idem, carpo-meral joint. C, fourth
pereiopod dactyl. D. fifth pereiopod. dactyl. Male: E. third pereiopod, dactyl. F, idem, spines on cutting
edge of propod.

six-segmented, decreasing in segment order
3, 6, 4, 1, 5, 2, about 2.7 times length of
chela; merus eight times longer than wide,
equal to length of first four carpal segments;
ischium more robust, six times longer than
wide, slightly shorter than merus, with a
pair of slender ventral spines proximally;
basis and coxa normal. Third pereiopods,
female, moderately slender, exceeding
antennal scale by distal fourth of propod;
dactyl biunguiculate with unguis longer and
more slender than accessory spine, equal to
half corpus length, ventral border with three
slender spines of decreasing size proximally,
propod about 3.5 times length of dactyl,
10.0 times longer than wide, with a pair of

serrulate distoventral spines and eight
spines along ventral border; carpus more
robust, 0.4 of propod length, with a single
spine on proximal lateral aspect; merus
slightly shorter than propod, 6.0 times
longer than wide, with 1-5 mobile spines
(usually 2-3) (see Table 1) along distal half
of lateral aspect, longer spines distally;
ischium, basis and coxa normal, unarmed.
Fourth and fifth pereiopods similar, less
robust, propod of fourth pereiopod with
small distoventral pectinate spine; carpus
with single proximal lateral spine, merus
with single lateral spine distally, (one
specimen with two); fifth pereiopod with
cleaning setae distally on propod, with or

8

A. J. Bruce,

10 February 1983

Fig. 6. Thor spinipes sp. nov., ovigerous female. A, telson. B. idem, posterior spines. C, uropod. D, idem
distolateral spine of exopod. Male: E, endopod of first pleopod. F, endopod of second pleopod.

without lateral spines on carpus and rnerus.
Third pereiopod of male prehensile,
subchelate, with dactyl slender, palm 2.3
times length of unguis, 4.5 times longer than
wide, with about 16 closely adpressed
similar ventral spines, of increasing size
distally; propod expanded at 0.6 of length

with ventral border distally tapering,
bearing about 25 erect spines: in other
features male pereiopods generally similar
to female but both carpus and merus may be
unarmed.

Endopod of male first pereiopod three
times longer than wide, tapering to point,

Thor spinipes sp. nov., [Crustacea, Decapoda, Hippolytidae]

9

medial border with short feebly plumose
setae proximally and simple setae distally,
lateral border with longer plumose setae.
Appendix masculina exceeding appendix
interna, carpus about 5.0 times longer than
wide with numerous, about 15. finely
serrulate setae distally and ventrally.
Exopod of uropod extending beyond telson
tip; protopod posterolaterally acutely
produced; exopod 2.9 limes longer than
wide, lateral border straight, ending with
small distolateral tooth, larger mobile spine
medially; endopod 3.4 times longer than
wide, slightly shorter than exopod.

Types —An ovigerous female, postorbital
carapace 2.9 mm is selected as holotype,
NTM Cr. 00083/a; male allotype NTM Cr.
00083/b. Paratypes are deposited in the
collections of the Australian Museum and
the Rijksmuseum van Natuurlijke Historie,
Leiden.

Measurements —Post-orbital carapace
lengths, O' 1.6 mm, 9 1-9 mm, ovigerous 9
1.9-2.7 mm, juveniles 1.5-1.6 mm.

Colouration —Semitransparent but heavily
mottled with superficial and deep patches of
dull yellow-brown on body and appendages,
with reddish markings on the third

maxillipeds and pereiopods.

Systematic Position —The only Indo-west
Pacific species of the genus Thor with acute
supraorbital spines are T. maldivensis
Borradaile and T. spinosus Boone (Bruce
1976). T. spinipes may be readily
distinguished from both these species by the
presence of a small spine on the proximal
lateral aspect of the carpus of the third and
fourth, and often also fifth, pereiopods. The
merus of these appendages is also much
more strongly spinulate in T. spinipes. In
the form of the rostrum T. spinipes is more
similar to T. spinosus , but that species lacks
a distinct ventral rostral tooth. In T.
maldivensis the rostrum is typically very
short, almost styliform and with only a
single dorsal rostral tooth. The rostrum in
T. spinipes is most similar to that of T.
paschalis , which lacks supraorbital spines,
and these two species have similar cryptic
colour patterns and are not known to be
associated with any specific host animals,
unlike T. spinosus, which has an ornate
colour pattern and is associated with
Millepora hydroids. T. spinipes in general
appears to be most closely related in both
morphology and biology to T. paschalis.

DISCUSSION

The discovery of T. spinipes in the Northern Territory, raises to four the number of species of
the genus Thor known to occur in Australian waters. In addition four other forms are known
to occur in the Indo-West Pacific region but are yet to be recorded from Australia. The
Australian species may be distinguished by the following key:—

Key to the Australian species of the Genus Thor Kingsley, 1878

1. Supraorbital spines present. T. spinipes sp.nov.

— Supraorbital spines absent.2

2. Stylocerite u'ith a small acute proximal lateral tooth.3

— Stylocerite without proximal lateral tooth. T. paschalis Heller

3. Rostral lamina typically slender, with simple acute tip; meral spinulation of third to fifth

pereiopods usually 1:1:0. T. amboinensis De Man

— Rostral lamina typically deep, with truncated trifid tip; meral spinulation of third to fifth

pereiopods usually 3-4:2:0. T. marguitae Bruce

10

A. J. Bruce,

10 February 1983

The species T. amboinensis and T. marguitae are commensal associated of coelenterates, the
former with a wide variety including actiniarians, alcyonarians and scleractinians, but the
latter has only been found in association with the coral Porites andrewsi at Heron Island,
Queensland, (Bruce, 1978), T. amboinensis is widely distributed throughout the Indo-West
Pacific region. T. paschalis is a cryptically colour species, apparently free-living, like T.
spinipes, and found among algae in intertidal pools.

RESUME

Une nouvelle espece de crevette du genre Thor Kingsley, 1878, [Hippolytidae] est decrite et
illustree. Des specimens nombreux ont ete trouves dans les flaques du recif intercotidale a
Coral Bay, Port Essington, Cobourg Peninsula, Northern Territory, Australie. Cette nouvelle
espece porte a quatre le nombre des especes de Thor connues dans les eaux australiennes. Une
cle pour leur determination est pourvue.

LITERATURE CITED

Bruce, A. J. 1976. A report on a small Collection of Shrimps from the Kenya National Marine
Parks at Malindi, with notes on selected species. Zool. Verhand., Leiden, 145: 1-72,
figs. 1-23.

- 1978. Thor marguitae sp. nov. a new hippolytid shrimp from Heron Island,

Queensland. Crustaceana, 35 (2): 159-169, figs. 1-6.

Hayashi, K. I. and Miyake, S. 1968. Studies in the hippolytid shrimps from Japan, V.
Hippolytid fauna of the sea around the Amakusa Marine biological Laboratory. Ohmu,
/ (6): 121-163, figs. 1-17.

Holthuis, L. B. 1947. The decapoda of the Siboga Expedition, IX. The Hippolytidae
and- Rhynchocinetidae collected by the Siboga and Snellius Expeditions with remarks on
other species. Siboga Exped. Mon., 39a*: 1-100, figs. 1-15.

Miyake, S. and Hayashi, K. I. 1966. Some hippolytid shrimps living in coral reefs of the West
Pacific. J. Fac. Agric., Kyushu Univ., 14 (1): 143-160, figs. 1-10.