The Functional Morphology,/Systematics and Behavioural Ecology of Parrot fishes (Family scaridae). Volume 1 Morphology and systematics Thesis submitted by David Roy BELLWOOD BSc (Hons.) (Bath, U.K.) in December, 1985 for the degree of Doctor of Philosophy in the Department of Zoology at James Cook University of North Queensland, Australia.
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The Functional Morphology,/Systematics and
Behavioural Ecology of Parrotfishes (Family scaridae).
Volume 1
Morphology and systematics
Thesis submitted by
David Roy BELLWOOD BSc (Hons.) (Bath, U.K.)
in December, 1985
for the degree of Doctor of Philosophy in
the Department of Zoology at
James Cook University of North Queensland,
Australia.
I, the undersigned, the author of this thesis, understand that the
following restriction placed by me on access to this thesis will not
extend beyond three years from the date on which the thesis is
submitted to the University..
I wish to place restriction on access to this thesis as follows:
Access not to be permitted for a period of 3 years.
After this period has elapsed I understand that James Cook
University of North Queensland will make it available for use within
the University Library and, by microfilm or other photographic
means, allow access to users in other approved libraries. All users
consulting this thesis will have to sign the following statement:
"In consultingparaphrase itof the author;any assistance
this thesis I agree not to copy or closelyin whole or in part without the written consent
and to make proper written acknowledgement forwhich I have obtained from it."
.~ ...~.....
iiiABSTRACT
The functional morphology and behavioural ecology of the
parrotfishes (family scaridae) were investigated to assess the
degree of correlation between them.
Twenty-two species of parrotfishes from the subfamily Scarinae
were examined mainly from reefs around Lizard Island, Great Barrier
Reef, Australia.
Morphological studies of the osteology and myology of the heads
of adult parrotfishes revealed two morphological groups within the
genus Scarus, vtz. the 'sordidus' and 'frenatus' groups. species
in the 'sordidus' group are characterized by: uneven cutting edges
on the jaws, an entopterygoid lateral process, a tightly bound
interdigitating maxilla and premaxilla, three rows of teeth on the
upper pharyngeal bones, well developed adductor mandibulae sections
~, A2 and A3 and an additional unique muscle, the Awy. Species in
the 'frenatus' group are characterized by: even cutting edges on
the jaws, a slightly protrusible premaxilla, two rows of teeth on
the upper pharyngeal bones, fusion of the abductor muscle section
~a and A2 in some species and a thin strap-like A3 section which
inserts only on the articular. The morphology of the heads of
species in other genera, namely, Cetoscarus btcoLor, BoLbometopon
murtcatum and Htpposcarus Longtceps was marked by their possession
of a quadrato mandibularis internus muscle and the non-articulatory
articular-dentary joint in C. btcoLor and B. murtcatum.
iv
Analyses of the two morphological groups indicated a marked
difference in the functional abilities of species in the two groups.
The morphological characteristics of 'sordidus' group species enable
them to bite the substratum with a large powerful cracking bite.
Species in this group are therefore described as 'biters', The
morphological characteristics of 'frenatus' group species are
consistent with the requirements necessary for scraping
substratum with small, weak bites.
therefore described as 'scrapers'.
Species in this group are
Of the species examined in this study, the following species
are functional 'biters'~ S. bteekert, S. gtbbUS and S. sordtdus,
whereas the folloWing are functional 'scrapers': S. brevtfttts,
s. dtmtdtatus, s. ftavtpeatoratts, S. jrenatus, S. ghobban,
S. gtobtceps, S. tongtptnnts, S. ntger, S. ovtaeps, S. pstttacus,
S. rtvutatus, S. rUbrovtotaaeus, S, sahtegett, S. sptnus,
S. trtaotor and Scarus sp. (af. tunuta). Because they lack some
specialized morphological features associated with the biting or
scraping strategies of species in the genus Scarus, Cetoscarus
btcotor and Botbometopon murtcatum are considered 'proto-biters',
whilst Htpposaarus tongtaeps is considered a 'proto-scraper'.
These differences are not apparent in juvenile specimens less
than 50 mm standard length. specimens of Saarus smaller than this
are extremely similar. Small specimens « 14 mm S.L.), in
particular, differ markedly from the adults in the possession of
caniform teeth and a simple, non-sacculated intestine.
v
Functional interpretations of the anatomy of the head and
intestine of juvenile scarids suggest that they progress from an
initial carnivorous phase to a selective grazing stage before
becoming functional 'scrapers' at about 50 rom S.L. 'Biting' species
only possess the full complement of biting characteristics above
90 mm S.L,
Field observations of adults revealed two feeding guilds within
the genus Scarus which correspond with the two functional groups.
(1) 'Biting' t,e. 'sordidus' group species are characterized by: i)
infrequent, large bites which scar the Substratum, ii) a propensity
to feed upon convex substrata, and iii) aggressive interspecific
interactions, when displayed, predominantly directed towards other
'sordidus' group species. (2) 'scraping' t.e. 'frenatus' group
species are characterized by: i) numerous small bites which rarely
scar the substratum, ii) a tendency to feed on a range of substrata,
and iii) aggressive interspecific interactions, when displayed,
predominantly directed towards other 'frenatus' group species,
These feeding strategies strongly influence the roles played by
parrotfishes as coral predators and bioeroding agents. The major
coral predator is Botbometopon muricatum. Bioerosion is primarily
the result of feeding by 'sordidus' group species, Cetoscarus
bicotor and B. murtcatum. It is therefore proposed that the
distribution of these species within and between reefs may influence
the extent and rates of bioerosion, the topography of the substratum
and the distribution of various coral morphs.
viField observations of juvenile scarids revealed a wide range of
behavioural traits, although these did not correspond with the
'sordidus' and 'frenatus' groupings. s. frena~us in particular,
differed from other juvenile 'frenatus' group species in its feeding
behaviour. An analysis of the gut contents of the juveniles of
several species showed marked changes in the diet, from being
initially predominantly carnivorous to herbivorous. These changes
were strongly correlated with changes in morphology and behaviour.
In addition to functional considerations, the morphological
analyses in this study were used to examine the systematic
relationships between genera in the subfamily Scarinae. The present
generic status of Ce~oscarus, Bo~bome~opon and Htpposcarus is
supported. The genus Scarus contains two distinct groups which may
be recognized at the generic level.
A descriptive account of the ontogeny of the colour patterns of
the juvenile phase of 22 species is presented to facilitate the
study of juvenile scarids in the field. The colour patterns of
juvenile scarids are interpreted in terms of concealment
colouration, including crypticism, camouflage and mimicry. In the
species examined, there is a strong correlation between schooling
behaviour, the range of patterns displayed, and the speed with which
the patterns may be changed.
TABLE OF CONTENTS
ABSTRACT
TABLE OF CONTENTS
LIST OF FIGURES
LIST OF TABLES
ACKNOWLEDGEMENTS
GENERAL INTRODUCTION
vii
iii
vi.i
ix
xv
xviii
1
PART I MORPHOLOGY (Volume 1)
Chapter 1 THE MORPHOLOGY OF ADULT SCARIDS 5
1. 3.51. 3.61.3.7
1.1
1.2
1.3
Introduction
Materials, Methods and Terminology
A The Muscular and Skeletal System
Observations1.3.1 External appearance and integument1.3.2 Osteology1.3.3 Myology1.3.4 The 'sordidus' and 'frenatus' groups
1.3.4.1 The 'sordidus' group1.3.4.2 The 'frenatus' groupCe~oscarus btcoLorBoLbome~opon murtca~um
'Prenatus' group species as 'scrapers'C. btcoLor and B. murtca~us
Htpposcarus LongtcepsThe pharyngeal apparatus
107107115120123123
1.5
1.6
1.7
B - The Visceral Anatomy
Observations
Functional Interpretations
Discussion
132
139
150
Chapter 2 THE MORPHOLOGY OF JUVENILE SCARIDS 153
2.12.22.32.42.5
IntroductionMaterials and MethodsObservationsFunctional InterpretationsDiscussion
153155155173178
PART II SYSTEMATICS (Volume ~)
viii
Chapter 3 SYSTEMATICS OF THE SCARIDAE:PHYLOGENY AND GENERIC CLASSIFICATION
Chapter 4 SYSTEMATICS OF THE SCARIDAE:ONTOGENY OF JUVENILE COLOUR PATTERNS
184
209
4.i4.24.3
4.4
IntroductionMaterials and MethodsResults4.3.1 Meristic data4.3.2 Field observations4.3.3 Colour patterns4.3.4 Species descriptionsDiscussion
209U3U42~4
21.5U7223277
PART III ECOLOGY (Volume 2)
Chapter 5 THE BEHAVIOURAL ECOLOGY OF ADULT SCARIDS
A Feeding Biology
290
5.15.25.35.4
5.55.65.75.8
IntroductionMaterials and MethodsResultsDiscussion
B General Biology
IntroductionMaterials and MethodsResultsDiscussion
29029629931.2
318321322330
Chapter 6 THE BEHAVIOURAL ECOLOGY OF JUVENILE SCARlDS
Part A - Feeding Biology
364
6.16.26.36.4
6.56.66.76.8
IntroductionMaterials and MethodsResultsDiscussion
Part B - General Biology
IntroductionMaterials and MethodsResultsDiscussion
364365369384
392394399423
CONCLUDING DISCUSSION
APPENDIX 1
APPENDIX 2
REFERENCES
434
454
455
461
Figure
1.1 A
1.1 B
1.2
1.3
1.4 A
1,4B
1.5 A
1.5 B
1.5 C
1.5 0
1.6 A
1.6 B
1.6 C
1.6 0
1.7 A
1.7 B
1.7 C
1.7 0
1.8 A
1.8 B
1.8 C
1.8 0
1.9 A
1.9B
ix
LIST OF FIGURES
Page
The external anatomy of the head of Scarus sordtdus .... 13
The external anatomy of the head of Scarus frena~us.... 13
The osteology of the head of Scarus sordtdus 15
The osteology of the head of Scarus frena~us 16
A lateral view of the suspensorium of S. sordtduS 18
A lateral view of the suspensorium of S. frena~us 18
A lateral view of the maxilla of S. sordtdus 22
A medial view of the maxilla of S. sordtdus 22
A lateral view of the maxilla of S. sordtdus 22
A medial view of the maxilla of S. frena~us..•......... 22
A lateral view of the premaxilla of S. sordtdus 25
A lateral view of the premaxilla of S. frena~us 25
A ventro-medial view of the premaxilla of S. sordtdus .. 25
A ventro-medial view of the premaxilla of S. frena~us .. 25
A lateral view of the articular of S. sordtdus 29
A medial view of the articular of S. frena~us 29
A lateral view of the articular of S. sordtdus 29
A medial view of the articular of S. frena1;us 29
A lateral view of the dentary of S. sordtdus ........... 32
A lateral view of the dentary of S. frena~us........... 32
A medial view of the dentary of S. sordtdus ............ 32
A medial view of the dentary of S. frena~us............ 32
An anterior view of the dentary cutting edge ofS. sordidus 33
An anterior view of the dentary cutting edge ofS. frena1;us 33
1. 10
1.11 A
1.1.1 B
1.J.2 A
1.J.2 B
1.B A
1.13 B
1.14 A
1.14 B
1.15 A
1.15 B
1.16
1.17 A
1.17 B
1.18 A
1.18 B
1.18 C
1.18 D
1.18 E
x
The head of scarus sordtaus with the integument, nasal,lacrymal, circumorbitals, A1a and part of A1~ removed,showing the shading conventions used in this section ... 39
The head of S. sordtaus with the integument andcircumorbitals removed 41
The head of S. soratd:u.s with the integument, nasal,lacrymal, circumorbitals, A1a and part of A1~ removed .. 41
The head of S. frenatus with the integument removed.... 45
The head of S. frenatus with the integument, nasal,lacrymal, circumorbitals and parts of Ala/A2 removed ... 45
A medial view of the upper jaw musculature ofS. sordtdus 46
A medial view of the upper jaw musculature ofS. frenai;us 46
A medial view of the lower jaw musculature ofS. sordtdus 47
A medial view of the lower jaw musculature ofS. frena1;us 47
A lateral view of the pharyngeal apparatus ofS. soratdus 51
A lateral view of the pharyngeal apparatus ofS. frenatus 51
The head of a 388 rom S.L. Cetoscarus btcoLor withthe integument, nasal, lacrymal, circumorbitalsand part of A1 removed 79
A lateral view of the neurocranium of BoLbometoponmurtcatum 80
A lateral view of the neurocranium of CetoscarusbtcoLor 80
A ventral view of the neurocranium of CetoscarusbtcoLor 81
A ventral view of the neurocranium of BOLbometoponmurtcatum 81
A ventral view of the neurocranium of HtpposcarusLongtceps 81
A ventral view of the neurocranium of Scarus sorataus .. 81
A ventral view of the neurocranium of Scarus frenatus .. 81
1.1.9
1.20
1.21 A
1.21 B
1.21 C
1.22 A
1.22 B
1.23
1.24
2.1 A
2.1 B
2.2
2.3
3.1
3.2
4.1
xi
The head of a 530 rom S.L. BoLbome~opon murtca~um wi~h
~he in~egument, nasal, lacrymal, circumorbitals andpart of Al removed 92
rrhe head of a 329 rom S.L. Htpposcarus "Longtceps withthe integument, nasal, lacrymal and circumorbitalsremoved 101
A lateral view of the neurocranium of Htpposcarustongtceps 102
A lateral view of the neurocranium of S. sorataus ..... 102
A lateral view of the neurocranium of S. frena~us..... 102
The dentary of S. soratdus showing the theoreticalforces acting upon the dentary during musclecontraction 110
A diagrama~ic figure describing ~he relationshipbetween the angle of a muscle and its mechanicalefficiency .............•.............................. 114
A diagramatic figure describing the properties ofmuscles wi~h weakly pinnate or strongly pinnatefibres .......................•........................ 114
The three types of intes~inal pattern found inscarue species 136
A lateral view of the anterior edge of thepremaxilla of a 9.0 rom S.L. S. sorataus 157
A lateral view of the anterior edge of thepremaxilla of a 8.7 mm S.L. S. frena~us 157
The head of S. sorataus at 25.0 rom S.L. with theintegument, nasal, lacrymal and circumorbitalsremoved 161
The head of S. frena~us at 26.5 mm S.L. with theintegument, nasal, lacrymal and circumorbitalsremoved 165
A cladogram showing the proposed phylogeny of thegenera in the subfamily Scarinae 188
The phylogeny of the genera in the family Scaridaeas proposed by schultz (1958) 194
A series of diagrams showing the ontogenetic changesin the colour pattern of juvenile Scarus speciesleading to the formation of the four primary stripesshown in Figure 4.2 218
xii
4.2 The 'typical' colour pattern of a juvenile Scarusspecies showing the position of the four primary darklongitudinal stripes and the six vertical bands 2~9
S. dt.mtdta1;us : 30.5 nun S. L ....•........•. 0 •• 0 0 0 •••••. 248
A summary of the ontogenetic changes in thebehaviour, diet and morphology of juvenile scarids .... 385
The relative abundance of juvenile scarids at theNorth Reef and lagoon study sites during the 1982-3and 1983-4 November-January recruitment periods 400
The relative abundance of juvenile scarids at threedepths in the North Reef study site and at two depthsin the lagoon study site, during the 1982-3 November-January recruitment period 401
The relationship between horne range/territoryarea and total length of juvenile scarids 406
The horne ranges of two juvenile S. sordtdusin the lagoon study site 407
A vertical profile of the primary study area at theNorth Reef study site, showing the distribution ofhorne ranges/territories of juvenile scarids inthe study area 412
The relative rates of aggression by pomacentridstowards juvenile scarids in the lagoon study site ..... 419
The relative rates of aggression by pomacentridsand Acan~hurus ttnea~us towards juvenile S. frena~us
in the lagoon study site 419
The feeding preferences of juvenile scarids: Themean number of juvenile scarids feeding on sixexperimental algal-covered substratum types 422
The proposed distribution of early scarids duringthe late Eocene period 448
The proposed distribution of the major scaridgroups approximately 4 million years ago.~ 448
The present di~tribution of the major scarid groups ... 448
Table
1.J.
1.2
1.3
1.4
1.5 A
1.5B
1.5 C
1.6
1.7
2.1
2.2
2.3
3.1
5.1
5.2
5.3
5.4
5.5 A
5.5 B
LIST OF TABLES
Page
A partial synonomy of the Scaridae of theGreat Barrier Reef 7
The morphology of adult scarids: Material examined .... 8
Abbreviations used in the figures 9
A comparative list of relative liver weights 134
The liver weights of two Scarus species 135
The intestinal length va. standard length of twoscarus species 135
The intestinal length vs. body weight of twosoar-us species 135
The distribution of intestinal types in Scarusspecies 138
Gut lengths of herbivorous reef fishes •............. 143
The morphology of juvenile scarids: materialexamined 156
Ontogenetic changes in the morphology of theintestinal tract of juvenile scarids 172
The functional morphology of juvenile scarids:a summary 179
The distribution of morphological charactersamong the scarid genera 189
Variability in the colour patterns of somejuvenile Scarus species 212
The feeding rates of six Scarus species 300
Observations of the feeding rates and the extentof scarring of the substratum by scarids 301
The size of substratum scars which result fromthe grazing activity of scarids 304
Patterns of substratum utilization byS. sordtdus and S. frena~us 307
An analysis of the curvature of the substratagrazed by S. sordtdus and S. frena~us 308
A comparison of the bite-scar lengths ofS. sordtdus and S. frena~us 308
xv
5.6
5.7
5.8 A
5.8 B
5.9
5.10
5.21 A
5.11 B
5.22 A
5.12 B
6.1
6.2
6.3 A
6.3 B
6.3 C
6.4
6.5
6.6
xvi
Coral species eaten by scarids 320
A summary of the morphological and behaviouralcharacteristics of 'sordidus' and 'frenatus'group species 323
Duration and size of home ranges/territories ofscarids: A - known individuals, at North Reef 323
Ouration and size of home ranges/territories ofscarids: B - permanent sites, unknownindividuals, at North Reef ... , .. ", " .... ,., , .. '" .. 323
Aggressive interactions between scarids .. ". "" .... 325
Differences in the extent of interspecificaggression by terminal and initial phaseS. jrenat;us 329