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Fishery Bulletin 96(1 ), 1998 
130 mm, matures at 70 mm), S. kyaropterygium (ca. 
120 mm, matures at ca. 74-85 mm), S. plagusia (ca. 
130 mm, matures at ca. 85 mm), S. caribbeanus (ca. 
130 mm, matures at 70-80 mm), and S. trewavasae 
(ca. 139 mm, matures at ca. 70-80 mm). 
Large species of Symphurus are those ranging in 
size from ca. 150 to 320 mm and maturing at sizes 
usually greater than 90 mm. As a group, large-size 
western Atlantic tonguefishes are also those species 
that reach maturity at the largest sizes observed for 
any tonguefish in the other size categories. The larg- 
est western Atlantic tonguefishes are (in order of 
increasing maximum sizes) S. civitatium (ca. 152 
mm, matures at sizes slightly greater than 90 mm), 
S. urospilus (ca. 166 mm, matures at ca. 100 mm), S. 
plagiusa (ca. 175 mm, matures at 85-95 mm), S. 
diomedeanus (207 mm, matures at 90-120 mm), S. 
oculellus (190 mm, matures at ca. 110 mm), S. 
tessellatus (ca. 220 mm, matures at 104 to 120 mm), 
and S.jenynsi, the largest species in the genus (maxi- 
mum sizes of ca. 320 mm, matures ca. 115 mm). 
Because body size is considered to be among the 
most important determinants of organismal function 
and ecological role (Peters, 1983; LaBarbera, 1986; 
Hanken and Wake, 1993), comparison of size-related 
features among the species studied could reveal in- 
teresting patterns among the species groups. The 
smallest tonguefishes are those ( S . arawak, S. 
rhytisma, S. ommaspilus) inhabiting sandy sub- 
strates on and adjacent to coral reefs. In fact, a total 
of five Atlantic species of dwarf tonguefishes (three 
western Atlantic species and S. lubbocki and S. 
reticulatus from central and eastern Atlantic locali- 
ties) occur on sand substrates in tropical seagrass 
beds, or on sand habitats on or adjacent to coral reefs. 
Other dwarf species (S. minor , S. pelicanus, and S. 
pusillus ) that inhabit a variety of substrates on the 
inner continental shelf {S. minor on live-bottom sub- 
strates, S. pelicanus and S. pusillus on soft mud sub- 
strates) attain somewhat larger sizes than the dwarf 
species occurring in coral reef environments. Among 
western Atlantic dwarf tonguefishes, S. pusillus is 
quite unusual in being the only one occurring in rela- 
tively deep waters ( 100-230 m) and frequently found 
beyond tropical and warm-temperate regions (Fig. 
29). Eight Atlantic species of dwarf tonguefishes be- 
long to two of nine species groups recognized by 
Munroe ( 1992 ). Six are members of the species group 
characterized by the 1-3-2 ID pattern. Two others (S. 
ommaspilus and S. minor) possess a 1-4-2 ID pattern. 
No western Atlantic dwarf tonguefishes are known from 
other ID pattern species groups. Species with different 
ID patterns may reflect divergent lineages within the 
genus, indicating that small body size has evolved in 
at least two different lineages within the genus. 
Many specialized niches or habitats demand tiny 
body size (Hanken and Wake, 1993). Because many 
dwarf tonguefishes inhabit shallow-water, sandy 
habitats on or adjacent to coral reefs and tropical 
seagrass beds, it would appear that small size is fa- 
vorable for survival in these habitats. Robins and 
Randall (1965) suggested that, for fishes living on 
exposed sandy substrates near coral reefs, small body 
size may reflect a generalized adaptational response 
to the extreme predation pressure exerted by the high 
concentration of predators generally associated with 
the coral reef environment. Evidence they used to 
support this hypothesis is that dwarf species are 
known for tonguefishes and also for unrelated taxa 
such as cuskeels ( Ophidion ), which inhabit areas 
with similar types of substrates. 
Information based on recent collections on verti- 
cal faces of Caribbean coral reefs (Hensley) 11 where 
sizeable numbers of dwarf tonguefishes have been 
captured from extremely small (<1 m), isolated sand 
patches located in small depressions on the reef pro- 
vides alternative hypotheses that may explain the 
successful exploitation of these habitats by dwarf 
tonguefishes. Given the limited size of the sand 
patches (<1 m in area) where dwarf tonguefishes have 
been taken, small body size may reflect morphologi- 
cal specialization to the limiting physical size of suit- 
able substrates available in these isolated sand 
patches. Alternatively, small size in tonguefishes may 
reflect morphological specialization to potentially 
limiting trophic resources, i.e. the reduced abundance 
of benthic organisms, that would be available as prey 
items for tonguefishes in these small, specialized 
habitats. Hypotheses regarding ecological success of 
dwarf tonguefishes inhabiting coral reef areas are 
untested, however, because nothing is known regard- 
ing predation rates on these or other dwarf fishes in 
this region. Nor is there any information available 
concerning movements and patterns of substrate use, 
diet composition, or relative degree of food selection 
(if any) exhibited by tonguefishes within these spe- 
cialized habitats. 
More than one species group is represented among 
the species comprising the other size categories of 
tonguefishes. Three species, from three different spe- 
cies groups, are categorized as diminutive tongue- 
fishes ( S . nebulosus, 1-2-2 group; S. ginsburgi, 1-3-2 
group; and S. parvus, 1-4-2 group). Four species 
groups are represented among those categorized as 
medium-size tonguefishes. Deepwater medium-size 
species inhabiting the outer continental shelf and 
upper continental slope include S. marginatus, S. 
11 Hensley, D. A. 1990. Department of Marine Sciences, Univ. 
Puerto Rico, Mayagez, Puerto Rico 00708. Personal commun. 
