/ 



O'CONNELL: PERCENTAGE OF STARVING NORTHERN ANCHOVY LARVAE 



seems a more likely cause of muscle deterioration. 

 Love (1974), in summarizing depletion in (adult) 

 fishes, states that ". . . when fish are starved the 

 lipid reserves . . . decrease to a certain point 

 beyond which the muscle protein is mobilized. As 

 the protein decreases, the water increases, and 

 this change is mainly brought about by shrinkage 

 of the cells and a corresponding increase in the 

 fluid between them." In conjunction with these 

 findings it had been shown that extracellular 

 spaces appeared in the musculature of Atlantic 

 cod, Gadus morhua (Love et al. 1968), and Ameri- 

 can plaice, Hippoglossoides platessoides (Tem- 

 pleman and Andrews 1956). Deterioration of the 

 musculature was a prominent effect following ar- 

 tificial starvation of early postyolk-sac northern 

 anchovy larvae ( O'Connell 1976) and of jack mack- 

 erel, Trachurus symmetricus, larvae (Theilacker 

 1978). Deterioration of musculature during starva- 

 tion has also been observed in larval herring, 

 Clupea harengus, and plaice, Pleuronectes platessa 

 (Ehrlich et al. 1976). 



Digestive Tract 



In most larvae the long foregut was straight with 

 a uniform lumen and a smooth surfaced mucosa of 

 cuboidal or thick squamous cells (Figure 3; see also 

 Figures 1 and 7). The foregut was considered 

 anomalous if the profile was noticeably irregular in 

 sagittal view. The mucosa usually also showed some 

 variation in cell thickness and shape. In the more 

 extreme cases the mucosa cells tended to be re- 

 duced to little more than the nucleus (Figure 4), 

 and the lumen sometimes contained a few 

 sloughed cells. 



The midgut varied greatly in appearance, de- 

 pending on the degree of longitudinal folding and 

 transverse ridge development and on the plane of 

 a particular section. Nevertheless, in most speci- 

 mens a substantial lumen, sometimes containing 

 food, and a simple mucosa of low columnar cells 

 could be traced (Figures 5, 7, 9). Although the 

 infranuclear portions of the cells were often nar- 

 rowed and slightly separated, the supranuclear 

 portions were always well joined. 



The midgut was judged anomalous when little 

 or no lumen could be traced, or when the traceable 

 lumen contained a considerable bulk of loose nu- 

 clei and necrotic cellular debris, and the mucosa 

 proper was fragmenting (Figures 6, 8, 10). In the 

 worst case the midgut was a homogeneous mass of 

 necrotic debris enclosed in only a basement mem- 



brane, with no trace of either lumen or mucosa 

 (Figure 12). This specimen, which happened to be 

 the smallest examined, also showed a severely 

 collapsed notochord and degenerate musculature. 

 The degree of organ development, including fully 

 pigmented eyes, indicated that it had shrunken. 

 Healthy specimens of comparable size, which still 

 had unpigmented eyes, showed good notochord 

 and musculature, and often a sizable remnant of 

 the yolk sac (Figure 11). Shrinkage has been 

 shown in laboratory starved larvae of both the 

 Atlantic herring (Blaxter and Hempel 1963) and 

 the northern anchovy (O'Connell 1976; O'Connell 

 and Raymond 1970). 



Whereas the muscle and foregut anomalies are 

 at least logically acceptable as consequences of 

 inadequate nourishment, interpretation of the 

 midgut anomaly is problematical. In artificially 

 starved northern anchovy larvae the midgut 

 showed thinning and increased separation of cells, 

 and the loss of some cells (O'Connell 1976), but not 

 strong contraction followed by general fragmenta- 

 tion and necrosis of the mucosa as seen in some of 

 the ocean-caught specimens. It may be, of course, 

 that the symptoms were different because the 

 laboratory and ocean situations were different. 

 Laboratory animals were starved without ever 

 having an opportunity to feed, whereas the 

 oceanic larvae showing symptoms undoubtedly 

 did have the opportunity to feed. Most in fact had 

 processed food through the digestive tract, as indi- 

 cated by the presence of supranuclear inclusion 

 bodies in the mucosa cells of the hindgut, though 

 the hindgut and the inclusion bodies were some- 

 times in a state of disintegration. Such inclusion 

 bodies were never found in laboratory specimens 

 deprived of food from time of hatching (O'Connell 

 1976). 



Contraction and congestion resembling that 

 seen in the midguts of the emaciated northern 

 anchovy larvae from the ocean have been de- 

 scribed for some other fishes, but they can be 

 symptomatic of disease as well as of starvation. 

 Clupea harengus larvae of 9-13 mm, for example, 

 are vulnerable to a nematode that grows in the 

 body cavity and deforms the gut, often resulting in 

 occlusion of the lumen that blocks food intake 

 and/or defecation (Margolis 1970). There are other 

 nematodes whose larvae attack the gut walls of 

 certain fishes, causing inflammatory and de- 

 generative changes, including localized necrosis 

 and infiltration of abundant lymphocytes (Mar- 

 golis 1970). There are also protozoans, such as 



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