Serum iron concentration and other blood parameters during the life cycle of the sea lamprey, Petromyzon marinus L

Distribution of iron during embryogenesis and early larval life in sea lampreys (Petromyzon marinus)

The distribution of ferric iron was examined in eggs, embryos, and early larvae (up to 77 d post fertilization (PF)) of the sea lamprey, Petromyzon marinus, using the Prussian blue staining technique. Iron was not detected in eggs and embryos but was detected in the lumen of the oesophagus at 17 – 33 days PF, when the newly hatched larvae burrow and commence exogenous feeding. The posterior intestine and hindgut became the primary location of iron absorption by 36 days PF, and subsequent development (36 – 63 days PF) showed an iron distribution suggesting elimination of excess metal through exfoliation of epithelial cells of the posterior intestine. The deposition of iron in macrophages of the intestine and liver (Kupffer cells) by 40 days PF may be related to both erythrophagocytosis and erythropoiesis at this time. Iron deposits in the macrophages of the pronephros and the atrium of the heart at 42 – 44 days PF were likely a consequence of endocytosis/filtration of the metal from circulating plasma. The commencement of iron deposition in specific tissues of larval lampreys seems to be correlated with the time they begin filter-feeding. Macrophages play an important role in iron metabolism in early larval life of lampreys.

Origin of iron in sea lamprey, Petromyzon marinus, tissues during embryogenesis and early larval life

Iron (Fe) concentration was measured in unfertilized eggs, embryos, prolarvae, and young larvae (up to day 56) of sea lampreys (Petromyzon marinus) raised in two substrates to determine (i) the importance of maternal transfer to Fe accumulation in sea lampreys and (ii) the influence of substrate on Fe uptake in young larvae. Unfertilized eggs contained about 35 ng of Fe, supporting the maternal transfer hypothesis. There were no significant changes in Fe concentration in developing embryos and prolarvae after hatching. Young larvae rapidly accumulated Fe from their burrowing substrate and the amount accumulated depended on the amount of Fe in the substrate. Since this rapid accumulation coincides with the beginning of exogenous feeding, as well as burrowing, environmental sources of Fe appear to be important contributors to Fe body burdens in larval sea lampreys.

Quantitative changes in a serum protein, AS, during the life cycle of the lamprey,Petromyzon marinus L

The electrophoretically fastest migrating protein in ammocoete serum, AS protein, was isolated and found to be an acidic glycoprotein with a molecular weight of 140,000 Daltons. Purified AS was injected into rabbits to produce a monospecific antiserum that was used in rocket immunoelectrophoresis to quantitate AS at different periods in the life cycle. AS was found to constitute approximately 70% of total serum protein in the ammocoete, remained at about the same value during transformation, and was reduced to 38% of total serum protein in the juvenile adult. In both male and female upstream migrant animals, AS was less than 0.5% of total serum protein. When juveniles were acclimated to seawater over a 10 week period, it was found that their AS level was reduced by 92% to 3.8% of total serum protein. These results are discussed in relation to changes in other serum proteins at various intervals of the lamprey life cycle.

An increase in the concentration of hepatic iron during the metamorphosis of the lamprey Geotria australis is accompanied by increased superoxide dismutase activity

The concentration of total non-haem iron and its ferritin iron component, and the activity of the enzyme superoxide dismutase (SOD), were measured in the livers of ammocoetes, metamorphosing animals (stages 1-7) and recently metamorphosed downstream migrants of the lamprey Geotria australis. Total non-haem iron in the liver rose significantly from 0.15-0.55 μg.mg wet weight(-1) in ammocoetes and metamorphosing stages 1-3 to 2.2-2.9 μg.mg(-1) in stages 5-7 and to 8.8 μg.mg(-1) in downstream migrants. The comparable values for ferritin iron were 0.06-0.26, 1.4-2.0, and 5.3 μg.mg(-1). Superoxide dismutase activity fell sharply from 0.39 μg.mg(-1) in large ammocoetes to between 0.07 μg.mg(-1) in stage 1 and 0.15 μg.mg(-1) in stage 6, before rising significantly to 0.26 μg.mg(-1) in stage 7 and 0.35 μg.mg(-1) in downstream migrants. The sharp fall in SOD activity at the beginning of metamorphosis is assumed to be related to the marked decline in plasma iron which occurs at the onset of this non-trophic phase in the life cycle. It is proposed that the subsequent increase in SOD activity in the liver of G. australis with increasing iron represents a mechanism aimed at reducing the potentially toxic effects of iron accumulation. This view is consistent with the significant and positive correlation found between both total non-haem and ferritin iron and SOD activity in the liver of non-trophic animals.

Ultrastructure of the pronephric kidney in upstream migrant sea lamprey, Petromyzon marinus L

The pronephric kidneys were examined in upstream migrant sea lampreys, Petromyzon marinus L., by transmission and scanning electron microscopy. Each pronephros consists of an enlarged renal corpuscle (glomus) and ciliated nephrostomes, but there are no renal tubules. The renal corpuscle contains an extensive mesangium, which consists of a highly fibrous extracellular matrix, numerous mesangial cells, granulocytes, and macrophages. The extracellular matrix contains microfibrils with a morphology similar to amyloid P microfibrils, fibrils with a periodicity similar to fibrin, and abundant collagen. Often these fibrillar components are aggregated in the region of the basement membrane, giving it a thickened appearance. Some podocytes of the visceral epithelium appear swollen, and their cytoplasm contains numerous vacuolar inclusions, and many have only primary major processes with only a few or no foot processes. The morphological features of the pronephric kidney of the lamprey at this time in the life cycle reflect the regression of this organ, but some features also resemble those seen in renal pathologies of higher vertebrates.

Tissue levels of bilirubin and biliverdin in the sea lamprey, Petromyzon marinus L., before and after biliary atresia

1. Liver, intestine, kidney, muscle and epidermis from larvae, juvenile adults and upstream migrants of the sea lamprey, Petromyzon marinus L., were assayed for the presence of biliverdin and bilirubin. Urine was also examined for these bile pigments in juveniles and upstream migrants. 2. Bilirubin concentration increased dramatically in the liver and caudal intestine following loss of larval bile ducts while biliverdin levels were highest in the liver of upstream migrants and rose sharply in the caudal intestine immediately following the atresia. 3. Small amounts of bile pigment were present in larval kidneys but high concentrations were found in this organ in upstream migrants. The urine of the latter possessed biliverdin. 4. Mucus of the epidermis may be a vehicle for transport and release of bilirubin in upstream migrants. 5. These data indicate that lampreys utilize different avenues for bile pigment storage and elimination over the course of their life cycle.