(2002b) estimated populations of 7,630,164 individuals for H. (H.) mexicana,
5,536,349 for I. badionotus, and 231,074 for A. multifidus. However, the densities
of these sea cucumbers in Panama were 50 times lower than those measured at
other Caribbean sites (Guzman and Guevara 2002b).
4.3.1 Physiology
Lawrence and Glynn (1984) studied the diet of the sea urchin Eucidaris thouarsii
(Valenciennes, 1846) through the absorption of nutrients from the predation on the
coral Pocillopora damicornis (Linnaeus, 1758) in the Gulf of Panama. The
absorption efficiency was determined to be 44.7 % for carbohydrates, 85.3 % for
protein and 69.3 % for lipids. The urchin absorbs 0.402 mg carbohydrate,
2.814 mg protein and 1.108 mg lipid for each gram of P. damicornis ingested;
0.201 mg carbohydrate, 1.407 mg protein and 0.554 mg lipid per individual per
day; and absorbs 0.824 9 10
-3 kcal carbohydrate, 7.950 9 10
-3 kcal protein and
235 9 10
-3 kcal lipid per individual per day. The authors concluded that despite
the high efficiency of digestive absorption of organic constituents of the coral
ingested, E. thouarsii needs to consume large quantities to meet its nutritional
requirements.
Work by Hendler and Byrne (1987) on Ophiocoma wendtii collected in Galeta,
Panama Caribbean, Belize and Florida, resulted in the identification and description of three structures in the dorsal arm plate (DAP) that comprise a photoreceptor
system. The upper surface of the DAP bears transparent microscopic structures
which are expanded peripheral trabeculae of the calcite stereom. These structure
are part of the photoreceptor system and can facilitate light transmission through
the DAP by decreasing light refraction, reflection and absorption that occur at
stereom/stroma interfaces. Bundles of nerve fibres located below the expanded
peripheral trabeculae function as primary photoreceptors. The third elements of the
system are the chromatophores that regulate the intensity of light impinging on the
sensory tissue are regulated by the diurnal activity cycle. During the day
the chromatophores cover the expanded peripheral trabeculae and thereby shade
the nerve fibres. At night they retract into inter-trabecular channels, uncovering the
expanded peripheral trabeculae and thereby exposing the nerve fibres to transmitted light. Thus, the transparent stereom may play a role in photoreception, in
addition to its generally recognized skeletal function. Although ciliated cells that
may be sensory are present in the epidermis of O. wendti, they do not appear to be
photoreceptors (Hendler and Byrne 1987).
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5,536,349 for I. badionotus, and 231,074 for A. multifidus. However, the densities
of these sea cucumbers in Panama were 50 times lower than those measured at
other Caribbean sites (Guzman and Guevara 2002b).
4.3.1 Physiology
Lawrence and Glynn (1984) studied the diet of the sea urchin Eucidaris thouarsii
(Valenciennes, 1846) through the absorption of nutrients from the predation on the
coral Pocillopora damicornis (Linnaeus, 1758) in the Gulf of Panama. The
absorption efficiency was determined to be 44.7 % for carbohydrates, 85.3 % for
protein and 69.3 % for lipids. The urchin absorbs 0.402 mg carbohydrate,
2.814 mg protein and 1.108 mg lipid for each gram of P. damicornis ingested;
0.201 mg carbohydrate, 1.407 mg protein and 0.554 mg lipid per individual per
day; and absorbs 0.824 9 10
-3 kcal carbohydrate, 7.950 9 10
-3 kcal protein and
235 9 10
-3 kcal lipid per individual per day. The authors concluded that despite
the high efficiency of digestive absorption of organic constituents of the coral
ingested, E. thouarsii needs to consume large quantities to meet its nutritional
requirements.
Work by Hendler and Byrne (1987) on Ophiocoma wendtii collected in Galeta,
Panama Caribbean, Belize and Florida, resulted in the identification and description of three structures in the dorsal arm plate (DAP) that comprise a photoreceptor
system. The upper surface of the DAP bears transparent microscopic structures
which are expanded peripheral trabeculae of the calcite stereom. These structure
are part of the photoreceptor system and can facilitate light transmission through
the DAP by decreasing light refraction, reflection and absorption that occur at
stereom/stroma interfaces. Bundles of nerve fibres located below the expanded
peripheral trabeculae function as primary photoreceptors. The third elements of the
system are the chromatophores that regulate the intensity of light impinging on the
sensory tissue are regulated by the diurnal activity cycle. During the day
the chromatophores cover the expanded peripheral trabeculae and thereby shade
the nerve fibres. At night they retract into inter-trabecular channels, uncovering the
expanded peripheral trabeculae and thereby exposing the nerve fibres to transmitted light. Thus, the transparent stereom may play a role in photoreception, in
addition to its generally recognized skeletal function. Although ciliated cells that
may be sensory are present in the epidermis of O. wendti, they do not appear to be
photoreceptors (Hendler and Byrne 1987).
120
S. E. Coppard and J. J. Alvarado