Temporal and spatial variation in egg size of thirteen Panamanian echinoids was
studied by Lessios (1987). His results showed that mean egg size from different
females collected from the same locality on the same day were significantly different
in all species studied. However, daily (within-month) variation in egg size was only
significant in E. tribuloides, D. antillarum, and L. variegatus, while no significant
differences were found in the daily means of egg volume in D. mexicanum and E.
viridis. Monthly means of egg volume were different in L. variegatus, L. williamsi,
T. ventricosus, E. viridis, E. vanbrunti, C. rosaceus and C. subdepressus. Betweenyears variation was also significant in all of these species except L. variegatus. All
Caribbean species showed a decline in egg size after September, however, this could
not be explained by any obvious environmental fluctuation. Echinometra lucunter
showed no significant variation between months of the same year but exhibited
differences between years. No significant monthly or annual variation was observed
in E. tribuloides, E. thousarii (Valenciennes, 1846), D. antillarum, D. mexicanum or
Leodia sexiesperforata. Correlations between size of eggs collected at a particular
time and the intensity of spawning by the population at that time was not significant,
suggesting that size of mature eggs is not determined by the reproductive state of the
parental population (Lessios 1987).
Lessios (1990) looked at adaptation and phylogeny as determinants of egg size
in twenty-two species of echinoids and two species of asteroids from the Caribbean and Pacific coasts of Panama. Lessios (1990) identified four trends: (1)
species have eggs that are significantly different from those of other congeneric
species; (2) species evolving for three million years in separate environments have
accumulated differences in their egg sizes and the direction of these differences is
not random; (3) egg size of congeneric species is similar where developmental
modes are similar (n.b. the volume of Clypeaster rosaceus eggs is eight times
greater than that of its congener C. subdepressus, an adaptation that reflects
developmental mode as the larvae of C. rosaceus are facultative planktotrophs,
while those of C. subdepressus are obligate planktotrophs); (4) there is no similarity between the egg sizes of species belonging to the same family or higher
taxonomic category, even if these species inhabit the same ocean. He concluded
that because the phenomena of smaller eggs in the Pacific (a pattern attributed to
higher levels of primary productivity in the eastern Pacific) holds for lineages that
have not shared a common ancestor for a long time, it is likely that independent
adaptation by the members of each pair has occurred due to the environments of
the two oceans during the last three million years.
McAlister (2008) studied the plasticity of larval feeding arms for geminate
species pairs to determine how food availability can influence growth and the arm
length of the larvae. No plasticity in arm length was found in either Caribbean or
Pacific species, however, arm length was significantly longer in Caribbbean species (including in D. antillarum). McAlister (2008) suggests that historical changes
in food levels led to the development of longer feeding arms in Caribbean species,
while plasticity may be limited by egg size or the timing of reproduction.
The evolution of gametic incompatibility in neotropical Echinometra was
investigated by Lessios and Cunningham (1993). They used fertilization
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S. E. Coppard and J. J. Alvarado
studied by Lessios (1987). His results showed that mean egg size from different
females collected from the same locality on the same day were significantly different
in all species studied. However, daily (within-month) variation in egg size was only
significant in E. tribuloides, D. antillarum, and L. variegatus, while no significant
differences were found in the daily means of egg volume in D. mexicanum and E.
viridis. Monthly means of egg volume were different in L. variegatus, L. williamsi,
T. ventricosus, E. viridis, E. vanbrunti, C. rosaceus and C. subdepressus. Betweenyears variation was also significant in all of these species except L. variegatus. All
Caribbean species showed a decline in egg size after September, however, this could
not be explained by any obvious environmental fluctuation. Echinometra lucunter
showed no significant variation between months of the same year but exhibited
differences between years. No significant monthly or annual variation was observed
in E. tribuloides, E. thousarii (Valenciennes, 1846), D. antillarum, D. mexicanum or
Leodia sexiesperforata. Correlations between size of eggs collected at a particular
time and the intensity of spawning by the population at that time was not significant,
suggesting that size of mature eggs is not determined by the reproductive state of the
parental population (Lessios 1987).
Lessios (1990) looked at adaptation and phylogeny as determinants of egg size
in twenty-two species of echinoids and two species of asteroids from the Caribbean and Pacific coasts of Panama. Lessios (1990) identified four trends: (1)
species have eggs that are significantly different from those of other congeneric
species; (2) species evolving for three million years in separate environments have
accumulated differences in their egg sizes and the direction of these differences is
not random; (3) egg size of congeneric species is similar where developmental
modes are similar (n.b. the volume of Clypeaster rosaceus eggs is eight times
greater than that of its congener C. subdepressus, an adaptation that reflects
developmental mode as the larvae of C. rosaceus are facultative planktotrophs,
while those of C. subdepressus are obligate planktotrophs); (4) there is no similarity between the egg sizes of species belonging to the same family or higher
taxonomic category, even if these species inhabit the same ocean. He concluded
that because the phenomena of smaller eggs in the Pacific (a pattern attributed to
higher levels of primary productivity in the eastern Pacific) holds for lineages that
have not shared a common ancestor for a long time, it is likely that independent
adaptation by the members of each pair has occurred due to the environments of
the two oceans during the last three million years.
McAlister (2008) studied the plasticity of larval feeding arms for geminate
species pairs to determine how food availability can influence growth and the arm
length of the larvae. No plasticity in arm length was found in either Caribbean or
Pacific species, however, arm length was significantly longer in Caribbbean species (including in D. antillarum). McAlister (2008) suggests that historical changes
in food levels led to the development of longer feeding arms in Caribbean species,
while plasticity may be limited by egg size or the timing of reproduction.
The evolution of gametic incompatibility in neotropical Echinometra was
investigated by Lessios and Cunningham (1993). They used fertilization
122
S. E. Coppard and J. J. Alvarado