OCONNELL: PERCENTAGE OF STARVING NORTHERN ANCHOVY LARVAE 



mummichog, Fundulus heteroclitus, up to 8 days 

 resulted in a decrease in the quantity of lipid drop- 

 lets in cells of the digestive tract and contraction of 

 the intestine such that the lumen was small, some- 

 times scarcely traceable (Ciullo 1975). While these 

 considerations suggest that disease could be the 

 cause of the midgut anomaly present in certain of 

 the ocean-caught northern anchovy larvae, starva- 

 tion is the more tenable explanation because there 

 was no evidence of parasites or pathogens in the 

 hematoxylin- and eosin-stained specimens, and 

 other anomalies in these specimens were consistent 

 with demonstrated effects of starvation. 



Other Organs 



Deterioration was sometimes evident in other 

 organs, particularly in the specimens with the 

 most severe anomalies in the musculature and 

 digestive tract. The pancreas and liver, for exam- 

 ple, showed good integrity in most larvae (Figures 

 1, 9), but some showed an unusual degree of dis- 

 sociation in these organs (Figures 8, 10), and in a 

 few, both organs had undergone considerable 

 lysis. The kidney ducts were intact in all speci- 

 mens, but in a few the cells of the ducts were 

 unusually thin, or necrotic (Figure 12). In several 

 the mantle layer of the brain showed poor integ- 

 rity, perhaps from a reduction of neuroglia. 



Classification of Larvae 



During the course of microscope examination, 

 each larva was designated healthy, incipient 

 emaciation, moderate emaciation, or severe 

 emaciation. The three classes pertaining to larvae 

 with anomalies are not rigorous, but they imply 

 the following: incipient, slight looseness of the 

 trunk muscles; moderate, obvious separation of 

 the trunk muscle fibers, some irregularity of the 

 notochord and possibly the foregut, strong contrac- 

 tion of the midgut, and sometimes a high incidence 

 of hypertrophic cells in the midgut mucosa; and 

 severe, obvious separation and hyalinization, and 

 sometimes disarray, of the muscle fibers, notable 

 irregularity in the profile of the notochord and 

 foregut, depletion of foregut muscosa cells, and 

 fragmentation of midgut mucosa, with a central 

 core of dissociated and necrotic cellular debris. Of 

 the 318 larvae sectioned, 26 were classified as se- 

 verely or moderately emaciated, and another 11 

 were classified as incipient. These are listed by net 

 tow in Table 1 along with the raw data for all tows. 



The larvae classified as incipient are included with 

 the healthy rather than with the emaciated or 

 "starving" group in the sections that follow. 



Relation of Emaciated Larvae to 

 Other Variables 



Standard Length 



Emaciated larvae were all < 10 mm SL and were 

 distributed almost proportionately over the range 

 2-10 mm SL (Table 2). Larvae classified incipient 

 were similarly distributed. In the lowest size 

 category, 2.1-4.0 mm SL, only half of the 46 larvae 

 examined had exhausted their yolk and become 

 vulnerable to starvation. The emaciated individu- 

 als were part of this contingent. The absence of 

 emaciated larvae in the categories above 10 mm 

 SL may be a chance result of the relatively fewer 

 numbers of larger larvae present in the tows, but 

 there may also be some actual reduction in starva- 

 tion effects at this size because of increasing lipid 

 reserves with growth (Love 1974). 



Table 2. — Standard length distribution of the northern an- 

 chovy larvae sectioned and examined and of those classified as 

 emaciated or incipient. 



Geographical Distribution 



More than half of the tows were spread over a 

 large offshore area where abundance of northern 

 anchovy larvae was generally low (Figure 13, 

 Table 1) and where samples from six tows each 

 contained a single emaciated larva. The remain- 

 der of the tows occurred in an area of a few 

 hundred square miles off Newport Beach where 

 larval abundance was high (Figure 14, Table 1) 

 and where samples from four tows each contained 

 several emaciated larvae. The fact that these four 

 samples showed a high proportion of emaciated 

 larvae, while others from nearby tows showed only 

 healthy larvae, indicates that there was a conta- 

 gious or patchy distribution of such larvae off 

 Nevqjort Beach. 



481 



