(1990), Wolfe and Felgenhauer (1991), Mikami and Takashima (1993) and Lemmens and Knott (1994), in which substantial morphological changes occurred in the digestive system during metamorphosis by the reduction of mandibles and the number of setae in the mouthpart appendages and poorly developed foreguts. Abrunhosa and Kittaka (1997a,b) reported similar observations during non-feeding stages in megalopae (transitory stage) of Paralithodes crabs (an important fishing resource of the Northern Pacific) related to the poorly developed feeding appendages (mouthparts and foregut) and, more recently, during the zoeal stages of the thalassinid Lepidophthalmus siriboia Felder and Rodrigues, 1993.
The present study supplies morphological descriptions of foreguts of larvae and post-larvae of three species belonging to the infra-order of Pleocyemata, Callicurus major (Say, 1818) (Thalassinidea) and Sesarma rectum Randall, 1840 (Brachyura) and Dendrobranchiata, Litopennaeus vannamei (Boone, 1931) (Penaeidea).
trivittatus and the Atlantic jackknife clam (Ensis directus), increased in occurrence in foreguts with increasing crab size.
Blue crab %FRE %VOL Number of nonempty foreguts 328 Plant material 1.5 <0.1 Hydrozoa 0.6 <0.1 Mollusca, unid.
N sampled in the guts must not have been strongly influenced by N excretion into the digestive tract, for example in the form of digestive enzymes, since these should have an N signal closer to the fish bodies than to the fish foreguts. No large consistent difference in [[delta].sup.13]C between resources and consumers is expected (DeNiro and Epstein 1978, Peterson and Fry 1987, Hesslein et al.
In their place is a wide region extention of the foregut, referred to as the "anterior bulb" (Hofer 1991).
When describing the diet of portunid crabs, Williams (1981) recommended including only individuals with foreguts more than 50% full (i.e.
Small crustaceans were frequent and predominant in the foreguts of O.
It is doubtful if digestion occurs maximally at night as reported by Modder (1983) since no significant difference was observed in the store of the foregut content of nymphs with and without food overnight collected at 6 a.m (Table 2).
Starved Source D.f Starved nymphs Fed Nymphs Adult Crushed leaves 6 319.27 ** (94%) 9.78(4.4%) 0.41(-7.1%) Intact leaves 6 250.08 *** (117%) 14.08(4.6%) 0.49(11.8%) Inflorescence 6 318.41 * (98%) 45.52(-0.76%) 6.00(5.1%) Values are significant * (p<0.05), ** (p<0.01) and *** (p<0.001) D.f-Degrees of Freedom Figures in bracket indicate the percentage growth rate TABLE 2 Mean scores of foregut content of Zonocerus nymphs with and without food Time Foregutcontent With Without Food 6 AM 1.8 [+ o -] 0.25 1.7 [+ o -] 0.23 10 AM 1.6 [+ o -] 0.15 0.6 [+ o -] 0.16 12 AM 2.3 [+ o -] 0.26 0.3 [+ o -] 0.16 RESUMEN
Small wonder, considering that even the tiniest known mammal with a foregut -- the muntjac, or toy deer, of Southeast Asia -- weighs more than five times as much as the roughly 1.5-pound hoatzin.
But Strahl and his collaborators suggest that the hoatzin's foregut, a prerequisite for digesting its leafy diet, may reflect an evolutionary tradeoff that accounts for many of its other peculiarities, including a sedentary lifestyle.