Download MolJuscan and crustacean hems in the diet of the loggerhead turtle

RESEARCH NOTES
474
/. Moll Stud. (1997), 63,474-476
© The Malacological Society of London 1997
MolJuscan and crustacean hems in the diet of the loggerhead turtle, Caretta
caretta (Linnaeus, 1758) [Testudines: Chelonidae] in the eastern Mediterranean
BJ. Godley1*2, S.M. Smith3, P.F. Clark* and J.D. Taylor4
'Institute of Biomedical and Life Sciences, Graham Ken Building, University of Glasgow, Glasgow G12 8QQ,
U.K. (e-mail [email protected])
2
Department of Veterinary Anatomy, University of Glasgow Veterinary School, Glasgow G611QH, U.K.
3
Woodleigh, Townhead, Hayton, Carlisle CA4 9JH, U.K.
4
Natural History Museum, Cromwell Road, London, SW7 5BD, U.K.
The loggerhead turtle (Caretta caretta) has a circumglobal distribution in temperate and subtropical areas
including the whole of the Mediterranean.1 However,
little dietary information is available for those individuals foraging in this region.
After hatching on the natal beach, marine turtles
undergo a poorly understood pelagic life history
phase, where they are thought to feed upon planktonic items for a number of years.13 Following this,
turtles migrate into a juvenile developmental habitat,
usually demersal and neritic. It is thought that they
remain in these areas until they reach adulthood, at
which time they begin migrations to seasonal breeding grounds, which they may undertake every few
years.3
For both post-pelagic juveniles and adults of this
species, study of prey items in other regions of the
world have found the diet to be dominated by benthic
molluscs, crustaceans and coelenterates.1 Loggerhead
turtles off Australia have recently been observed
'mining' such prey items in soft sediments.4 Individuals sold in markets in Sfax, Tunisia in 1989, were
observed to have previously ingested benthic molluscs and Crustacea.5 Identification of gut contents
from 31 individuals of varying sizes, caught by
trawlers in Tunisian waters, showed the diet to consist
largely of these two groups, but also of echinoderms
and other items in relatively small proportions.6
These data suggest that certainly in this region, the
loggerhead is a fairly non-selective predator upon sessile and slow moving prey.
Necropsy examinations of two loggerhead turtles
were undertaken as part of an ongoing study of mortality patterns in Mediterranean marine turtles
(B.G.). Lesions present strongly suggested that both
individuals had been killed as the result of interactions with local artisanal fisheries in Famagusta Bay,
off the coast of northern Cyprus. Both individuals
showed signs of cranial trauma, were recently dead, in
good general body condition and had digestive tracts
relatively full of prey items when they were washed
ashore. The first turtle, a subadult female (individual
A), with a standard curved carapace length of 49 cm,
was discovered on 6th September, 1994. This individual was likely to have been resident in the region. An
adult male (individual B), with a standard curved
carapace length of 76 cm, was discovered on the 7th
June, 1995. The breeding season, in this region, is
known to occur at the same time of year as the dis-
covery of this individual.7 Although this male may
have been locally resident, it might also have been a
breeding migrant from a distant feeding ground.
Guts were incised and all dietary items expected to
be identifiable were collected and fbted for later
taxonomic identification. Mollusc shell fragments
were identified according to an established guide8
(S.S.) and opercula were identified by comparison
with specimens in the Mollusca collections of the
Natural History Museum, London (J.T.). Crustacea
were identified according to existing publications
for [Anomura: Paguridae] and [Brachyura: Majidae]9"13 and then compared with material in the reference collection of the Natural History Museum
(P.C.).
The dietary items identified, substrate and depth
where the species are normally found, and minimum
numbers of each prey species recorded for each individual are shown in Table 1. Five of these genera
(Cerithium, Hexaplex, Fasciolaria, Pagurus and
Pagunstes) have been previously recorded as prey
items in this turtle species in the Mediterranean.6 Outside this region, at least six of these genera (Astraea,
Cerithium, Conus, Strombus, Pagurus, Paguristes)
have previously been recorded as prey items for the
loggerhead turtle.1
The occurrence of Strombus decorus raybaudi
(identified from opercula) in the diet is noteworthy
since this species has diversified morphologically
since invading the eastern Mediterranean via the Suez
canal from the Indian Ocean-Red Sea.14
It is difficult to generalise from such a limited sample size, however there was considerable overlap in
prey items between both individuals. From general
inspection of fragments, several other facts could be
ascertained. Both individuals crushed, even the most
robust, prey items before swallowing and there was
no apparent difference in size of prey selected by different individuals, in that most mollusc fragments
originated from shells of range 10-30 mm. Distribution data pertaining to the prey species suggest that
loggerhead turtles in the eastern Mediterranean do
indeed feed upon benthic molluscs and Crustacea, at
shallow to moderate depths, from both rocky and
sedimentary habitats. It is strongly recommended that
similar studies are carried out upon incidentally
caught or stranded turtles within this region, to allow
greater understanding of the synecology of this
endangered population.
rock
sand & mud
rock
rock
rock
Buccinulum corneum (Linnaeus, 1758)
Fusinus syracusanus (Linnaeus, 1758)
Fasciolaria lignaria (Linnaeus, 1758)
Conus ventricosus (Gmelin, 1791)
Anomiidae spp.
rock
sand
sandy-mud
rock
sand & seagrass
Hexaplex trunculus (Linnaeus, 1758)
Superclass: Crustacea
Class: Malacostraca
Infradorder: Anomura Pagurus anachoretus (Risso, 1827)
Family: Paguridae
Pagurus cuanensis (Bell, 1845)
Paguristes eremita (Linnaeus, 1767)
Infraorder: Brachyura Maja goltziana (d'Oliviera, 1888)
Family: Majidae
Class: Bivalva
sand
Phalium undulatum (Gmelin, 1791)
6-10 m
occ. 100 m
15-91 m
10-80 m
15-200 m
0-20 m
0-20 m
0-20 m
1-50 m
intertidal-27 m
1-100 m
8-80 m
>25m
sand & mud
Naticarius stercusmuscarum (Gmelin, 1791)
intertidal-20 m
0-20 m
sand & mud
Cerithium vulgatum (Bruguiere, 1792)
8-59 m
Depth
Strombus decorus raybaudi (Nikolay & Manoja, 1983) sand
sand
rock
Astraea rugosa (Linnaeus, 1767)
Class: Gastropoda
Substrate
Species
Phylum: Mollusca
(SH. &O.)
-
(SH. &O.)
4
1
1
2
1
(SH.)
1
-
_
(SH.)
1
(SH.)
(SH.)
20
1
(SH.)
(SH.)
8
(SH.)
20
6
4
(O.)
5
(SH.)
30
39
(SH.)
_
(O.)
100
—
Individual
B
40
(SH.)
1
_
(SH.)
6
(SH.)
6
Individual
A
Table 1. Classification of prey items found, substrate and depths where they are normally found. Minimum numbers in both turtle individuals A and
B are given. (Key: SH.= Identified by shell fragments, O. = Identified by opercula)
a
In
z
o
o
/0
S
3
tn
rn
RESEARCH NOTES
476
We would like to acknowledge the help of Glasgow
University Turtle Conservation Expedition members,
A.C. Broderick, K. Dodd Jr., E.G. Hancock, L.
Laurent, M. Reilly and F. Woodward. B.G. is funded
by a post-graduate scholarship from the University of
Glasgow and would like to acknowledge further
supervision and material support from Dr. R.W.
Furness and Prof. S.E. Solomon, both of University of
Glasgow.
REFERENCES
1. DODD, JR., C.K. 1988. BioL Rep., 88 (14) F.A.O.
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2. PLOTKIN, P.T. 1996. Chelon, Cons. BioL, 2:78-80.
3. MUSICK, J.A. & LIMPUS, CJ. 1997. In: The Biol-
6. LAURENT, L. & LESCURE, J. 1994. Rev. EcoL
(Terre Vie), 49:63-86.
7. BRODERICK, A.C. & GODLEY, BJ. 1996. ZooL
Middle East, 13:27^46.
8. POPPE, G.T. & GOTO, Y. 1991. European Sea
Shells, Volume 1. Verlag Christa Hemmen, Weisbaden.
9. CAPART, A. 1951. Resultats Scientifiques, 3: 11205.
10. INGLE, R.W. 1993. Hermit crabs of the North-eastern Atlantic Ocean and the Mediterranean Sea: An
illustrated key. Natural History Museum Publications & Chapman & Hall: London.
11. LEWINSOHN, C.H. & HOLTHUIS, L.B. 1980. ZooL
Verharu, 230:1-64.
12. MANNING, R.B. & FROGUA, C. 1982. Quaderni
del Laboratorio di Tecnologia della Pesca., 3 (25): 319-334.
ogy of Sea Turtles (P.L. Lutz & J.A. Musick, eds):
184-254. CRC Press, Boca Raton.
4. PREEN, A.R. 19%.7. Herpetol.,30:94-6.
13. ZARIQUIEY ALVAREZ, R. 1968. Investigacion
5. LAURENT, L. & LESCURE, J. 1992. Proc Sixth
14. NICOLAY, K.
Ord. Gen. Meet S.E.H., Budapest, 1991: 293-295.
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La
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© The Malacological Society of London 1997
J. MolL Stud, (1997), 63,476-478
First report of shell boring predation by a member of the Nassariidae (Gastropoda)
Brian Morton and K. Chan
The Swire Institute of Marine Science, The University of Hong Kong, Cape d'Aguilar, Shek O, Hong Kong
Shell boring predation occurs in a range of animal
groups1, but is most well-studied in the prosobranch
gastropods, notably representatives of the Naticidae
and Muricidae2. In both families, a wide range of
species engage in such predation activities and characteristic boreholes in their even more diverse prey
are evidence of this and provide further evidence in
the fossil record for the origins of such activities2.
Muricid boreholes are generally straight-sided and
such borers are characterized by the presence of an
accessory boring organ in the foot3. The naticid borehole is countersunk, or bevelled, at the edges and
there is also an accessory boring organ, but this time
on the ventral surface of the proboscis.4 In representatives of both families, therefore, boring is by chemical dissolution using secretions from an accessory
boring organ. The boring organs, independently
evolved in both groups, are assisted by mechanical
abrasion using the radula. There is also a suggestion
that species of Cominella (Buccinidae) from Western
Australia bore their bivalve prey5. A fourth, less wellstudied, family, some of which, e.g., Austroginella sp.,
are shell borers, is the Marginellidae6. The Cassidae
(Neotaenioglossa) are specialist, hole-making (but
not boring), echinoderm predators7.
Representatives of the Nassariidae are herbiv-
orous, carnivorous or scavenging members of the
Neogastropoda. There is an extensive literature on
scavenging in the numerous species of the Nassariidae much of which has been reviewed and they are
considered to be 'the closest attempt of an obligate
scavenging life style'8, along with the amphipod
Lysianassidae. The spatial and temporal ephemerality of carrion in the sea, however, it is argued8, can
only sustain facultative scavengers. Yet, in the Nassariidae, only Bullia digitalis9 and Ilyanassa obsoleta10
are known to eat live prey, but not by boring. B. digitalis is also known to consume algae".
Three reports mention12"14, in passing, that nassariids are shell borers, but there is no confirmatory evidence of this and, hitherto, to the contrary, it has been
generally assumed that species of this family are incapable of such activity. This study provides the first
evidence of shell boring in a member of the Nassariidae and was obtained in a wholly accidental manner.
Nassarius festivus (Powys, 1835) is the most common and widely distributed nassariid on Hong Kong's
soft shores and is, undoubtedly, a scavenger13. Where
in Hong Kong, for example, either pollution creates a
stressed biota on beaches or where trash fish discarded by fishermen float ashore, numbers of N. festivus are elevated enormously and they readily and