Later Stages Of Metamorphosis Research Articles

Barnacle biology before, during and after settlement and metamorphosis: a study of the interface.

Mobile barnacle cypris larvae settle and metamorphose, transitioning to sessile juveniles with morphology and growth similar to that of adults. Because biofilms exist on immersed surfaces on which they attach, barnacles must interact with bacteria during initial attachment and subsequent growth. The objective of this study was to characterize the developing interface of the barnacle and substratum during this key developmental transition to inform potential mechanisms that promote attachment. The interface was characterized using confocal microscopy and fluorescent dyes to identify morphological and chemical changes to the interface and the status of bacteria present as a function of barnacle developmental stage. Staining revealed patchy material containing proteins and nucleic acids, reactive oxygen species amidst developing cuticle, and changes in bacteria viability at the developing interface. We found that as barnacles metamorphose from the cyprid to juvenile stage, proteinaceous materials with the appearance of coagulated liquid were released into and remained at the interface. It stained positive for proteins, including phosphoprotein, as well as nucleic acids. Regions of the developing cuticle and the patchy material itself stained for reactive oxygen species. Bacteria were absent until the cyprid was firmly attached, but populations died as barnacle development progressed. The oxidative environment may contribute to the cytotoxicity observed for bacteria and has the potential for oxidative crosslinking of cuticle and proteinaceous materials at the interface.

Changes in the distribution of corticotropin-releasing factor (CRF)-like immunoreactivity in the larval bullfrog brain and the involvement of CRF in the cessation of food intake during metamorphosis

In submammalian vertebrates, corticotropin-releasing factor (CRF) acts as an anorexigenic neuropeptide as well as a potent stimulator of corticotropin and thyrotropin release from the pituitary. As a step for demonstrating the involvement of CRF in the feeding regulation of anuran larvae, which are known to stop feeding toward the metamorphic climax, we studied firstly the changes in the distribution of CRF-like immunoreactivity (CRF-LI) in the brain of metamorphosing bullfrog larvae. Neuronal cell bodies showing CRF-LI were invariably present in the thalamic regions throughout larval development. Cells with CRF-LI were also found in the hypothalamus. The number of cells with CRF-LI in the hypothalamus, but not in the thalamus, showed a significant increase as metamorphosis progressed. Immunoreactive nerve fibers were observed mainly in the median eminence, and became abundant as metamorphosis proceeded. The number of cells showing CRF-LI in the hypothalamus as well as the density of immunoreactive fibers in the median eminence decreased at the end of metamorphosis. Secondly, we examined the effect of intracerebroventricular (ICV) injection of CRF on the food intake in the premetamorphic larvae. ICV injection of CRF at 10 pmol/g body weight (BW) induced a significant decrease of food intake during 15 min. The CRF-induced anorexigenic action was blocked by the treatment with a CRF receptor antagonist [α-helical CRF (9–41)] at 100 pmol/g BW. The results suggest the involvement of CRF in the accomplishment of metamorphosis through the pituitary and in the feeding restriction that occurs during the later stages of metamorphosis through the central nervous system.

Aspects of the early life history of the European conger eel ( Conger conger ) inferred from the otolith microstructure of metamorphic larvae

The life cycle of the conger eel (Congerconger L.) is still fairly unknown, especially its larval leptocephalus phase. The morphology, biometry and meristic characteristics of 184 metamorphosing conger eel larvae collected from the Minho River, northern Portugal, between December 1998 and April 1999 were analysed. The total number of myomeres, the general body morphology and the pigmentation pattern of leptocephali are in agreement with the corresponding data found by other authors for this species. The sagitta microstructure of 90 specimens was viewed by scanning electron microscopy. The numbers of daily increments obtained in the otolith's countable zone were between 205 and 324. The final part of the countable zone is characterised by a sharp increase in width of the daily increments (transition zone), followed by a peripheral diffuse zone. In the diffuse zone no narrow circumscribed rings are visible, which prevents an accurate estimate of the duration of metamorphosis. The data indicates that the size variation of metamorphosing leptocephali is large, suggesting that their hatching time must be variable. Our data also show that the largest larvae, in later stages of metamorphosis, arrive first to the northern Portuguese coastal waters.

Extent of ossification at the amputation plane is correlated with the decline of blastema formation and regeneration in Xenopus laevis hindlimbs.

Xenopus laevis larvae gradually lose the ability to regenerate lost hindlimb structures as they progress through metamorphosis. Previous studies have suggested that this loss of regenerative capacity occurs in a proximal-to-distal fashion. We assessed the quality of overall regeneration and early bud blastema formation in order to evaluate previous explanations for this loss of regenerative ability in Xenopus. We further examined the extent to which epidermis, basement membrane, dermis, cartilage, bone, periosteum, and accumulated mesenchyme within the blastema are involved in the decline of regenerative abilities during mid-metamorphic stages of development. Each tissue was scored based on its contributions to the regeneration blastema, in accordance with previously reported blastemal descriptions. Tadpoles amputated at the ankle and tarsal-metatarsal joints scored objectively higher within the overall regeneration and blastema quality rating systems. Both joint sites met more criteria associated with regeneration-capable blastemas than tadpoles amputated through the middle of the tarsus, especially at later stages of metamorphosis. The three amputation sites studied began to vary in their ability to regenerate skeletal elements and to generate productive blastemas during the same stages at which we initially observed ossification of the tarsus. These results suggest that the decline of Xenopus hindlimb regeneration does not occur in a strictly proximal-to-distal fashion but rather is dependent at later stages on the state of ossification of the structure through which amputation occurs. Our morphological and cellular observations reveal specific times and places during Xenopus hindlimb development at which further investigations into tissue-specific molecular events during early regeneration should be focused.

Retinoic acid stimulates development of adult-type chromatophores in the flounder

Premetamorphic flounder larvae were administered different doses of 9-cis retinoic acid (9cRA). 9cRA at 25 nM (the highest dose) not only stimulated adult-type (ad-) chromatophore development on the ocular (eyed) side, but also induced the development of ad-chromatophores on the blind (non-eyed) side of the metamorphosed fish. The ad-chromatophore development was stimulated by 9cRA only when administered to the larvae that were at late premetamorphosis and at early prometamorphosis. Ad-chromatophores actually appear much later, at the end of metamorphosis. 9cRA was not effective at later stages of metamorphosis. These results suggest that 9cRA stimulated the development or determination of the developmental fate of neural crest cells for chromatophores. The present results also suggest the presence of immature chromatophores or neural crest cells on both sides of the larval body of the flounder and that the ad-chromatophore development is somehow inhibited on the blind side in spontaneous metamorphosis. All-trans retinoic acid (atRA) had a similar effect on the ad-chromatophore development. In addition, both types of RAs affected the development of fin rays of the fish, resulting in deformity of fins when administered at high doses early in metamorphosis. The teratogenic effect of atRA was greater than that of 9cRA. J. Exp. Zool. 284:317–324, 1999. © 1999 Wiley-Liss, Inc.

Retinoic acid stimulates development of adult-type chromatophores in the flounder.

Premetamorphic flounder larvae were administered different doses of 9-cis retinoic acid (9cRA). 9cRA at 25 nM (the highest dose) not only stimulated adult-type (ad-) chromatophore development on the ocular (eyed) side, but also induced the development of ad-chromatophores on the blind (non-eyed) side of the metamorphosed fish. The ad-chromatophore development was stimulated by 9cRA only when administered to the larvae that were at late premetamorphosis and at early prometamorphosis. Ad-chromatophores actually appear much later, at the end of metamorphosis. 9cRA was not effective at later stages of metamorphosis. These results suggest that 9cRA stimulated the development or determination of the developmental fate of neural crest cells for chromatophores. The present results also suggest the presence of immature chromatophores or neural crest cells on both sides of the larval body of the flounder and that the ad-chromatophore development is somehow inhibited on the blind side in spontaneous metamorphosis. All-trans retinoic acid (atRA) had a similar effect on the ad-chromatophore development. In addition, both types of RAs affected the development of fin rays of the fish, resulting in deformity of fins when administered at high doses early in metamorphosis. The teratogenic effect of atRA was greater than that of 9cRA.

Development of the adult endocrine pancreas during metamorphosis in the sea lamprey, Petromyzon marinus L. I. Light microscopy and autoradiography.

The results of this study were found to support the hypothesis put forth by Boenig (Z. Mikrosk-Anat. Forsch., 17:125-184, 1929) that the caudal pancreas of adult lamprey develops from the epithelium of the extrahepatic common bile duct in that the bile duct cells were found to undergo a great proliferation during the early stages of metamorphosis, with a large number of the cells incorporating 3H-thymidine. If the bile duct degenerated as suggested by Barrington (The Biology of Lampreys. Academic Press, London, pp. 135-169, 1972), this uptake would not be expected. The cranial pancreas was determined to develop in a similar manner to the larval islets, with formation of the islets taking place within the intestinal/diverticular epithelium. The newly formed islets would migrate into the surrounding connective tissue. During the later stages of metamorphosis a small number of cells was found to incorporate the tritiated thymidine within mature islets.

Skeletal development in Xenopus laevis (Anura: Pipidae).

Postembryonic skeletal development of the pipid frog Xenopus laevis is described from cleared-and-stained whole-mount specimens and sectioned material representing Nieuwkoop and Faber developmental Stages 46-65, plus postmetamorphic individuals up to 6 months old. An assessment of variation of skeletogenesis within a single population of larvae and comparison with earlier studies revealed that the timing, but not the sequence, of skeletal development in X. laevis is more variable than previously reported and poorly correlated with the development of external morphology. Examination of chondrocranial development indicates that the rostral cartilages of X. laevis are homologous with the suprarostral cartilages of non-pipoid anurans, and suggests that the peculiar chondrocranium of this taxon is derived from a more generalized pattern typical of non-pipoid frogs. Derived features of skeletal development not previously reported for X. laevis include 1) bipartite formation of the palatoquadrate; 2) precocious formation of the adult mandible; 3) origin of the angulosplenial from two centers of ossification; 4) complete erosion of the orbital cartilage during the later stages of metamorphosis; 5) development of the sphenethmoid as a membrane, rather than an endochondral bone; and 6) a pattern of timing of ossification that more closely coincides with that of the pelobatid frog Spea than that recorded for neobatrachian species.

Immunohistochemical localization of corticotropin-releasing factor- and arginine vasotocin-like immunoreactivities in the brain and pituitary of the American bullfrog ( Rana catesbeiana) during development and metamorphosis

Immunoperoxidase staining for corticotropin-releasing factor (CRF) in the median eminence was sparce or absent from premetamorphic tadpoles, but increased dramatically by late prometamorphosis. Quantitative photometry revealed that CRF-like immunostaining material in the median eminence was most dense in metamorphic climax tadpoles. Arginine vasotocin (AVT)-like immunostaining material was visualized in perikarya of the magnocellular nucleus, with extensive fiber staining seen in the medial basal and infundibular hypothalamus as well as in the median eminence and pars nervosa of the pituitary. AVT-like immunoreactive perikarya were virtually absent in premetamorphic tadpoles, but their number increased greatly by Taylor-Kollros stage XII and continued to increase after this stage. Quantitative photometry revealed that AVT-like immunoreactivity in the pars nervosa increased greatly at Taylor-Kollros stage XII and remained intense after this stage. AVT-like immunoreactivity did not appear in the median eminence until Taylor-Kollros stage XVI. Localization of AVT-like immunoperoxidase staining around portal vessels in the median eminence suggests an anatomical mechanism for delivery of AVT to anterior pituitary corticotropes. These results indicate that both CRF and vasotocinergic neuronal systems develop just before the activation of interrenal steroidogenesis which occurs during the later stages of metamorphosis in this species.

An association of melanophores appearing at metamorphosis as vehicles of asymmetric skin color formation with pigment anomalies developed under hatchery conditions in the Japanese flounder, Paralichthys olivaceus.

The mechanisms for asymmetric skin color formation in the Japanese flounder are studied with particular concerns to causes for pigment disorder (hypomelanosis) occurring under hatchery conditions. For an analysis of normal pigmentation, fish were raised with wild zooplanktons in an indoor hatchery, whilst for hypomelanosis, they were raised with Brazilian Artemia nauplii, a diet used in the hatcheries. Morphological observations, counting of melanophores, histochemical assay of DOPA-positive immature cells (melanoblasts), and radiometric estimation of tyrosinase activities in skins of developing larvae and juveniles indicate that 1) the structural plan for pigmentation in this species is bilaterally symmetric until metamorphosis, utilizing large-sized melanophores (hence larval melanophores) as main vehicles, and 2) an asymmetric coloration characteristic to metamorphosed juveniles is formed by an intensive development of smaller-sized melanophores (hence adult-type melanophores) appearing selectively in the ocular side at the later stages of metamorphosis and by an absence of it in the blind. These findings apparently indicate that 1) two types of melanophores occur in this species which differ with respect to morphological properties and developmental fate, and 2) selective differentiation of adult type melanophores in the ocular side of the body at or after metamorphosis is primarily responsible for an asymmetric coloration of its adult form. The similar assays on the fish fed with Artemia nauplii indicate that defective development of adult-type melanophores results in hypomelanosis in their ocular-sided skins, yielding a pigmentary pattern seen in the blind side of the metamorphosed juveniles with normal pigmentation.(ABSTRACT TRUNCATED AT 250 WORDS)

Gap junctions and zonulae occludentes of hepatocytes during biliary atresia in the lamprey

Gap junctions and zonulae occludentes of hepatocytes were examined in thin sections and freeze-fracture replicas from livers of larval and juvenile adult lampreys and during the phase of metamorphosis when bile ducts and bile canaliculi disappear (biliary atresia). Larvae possess zonulae occludentes at the canaliculi which are composed of one to five (mean = 2.81) junctional strands that provide a bile-blood barrier. Morphometry demonstrates that during biliary atresia the decreases in number of junctional strands and apico-basal depth of the zonulae occludentes are accompanied by an increase in the frequency of gaps or interruptions in the strands and in a breakdown of the bile-blood barrier. The zonulae occludentes completely disappear during metamorphosis and are not found in the adult liver. Gap junctions of the larval liver occupy 1% of the surface of the plasma membrane and have a mean area of 0.167 μm 2 but, following an initial decline in these parameters during early biliary atresia, they rise sharply in later stages of metamorphosis and in adults are 3.2% and 0.502 μm 2, respectively. The events of alteration in junctional morphology during lamprey biliary atresia is in many ways comparable to the changes in gap junctions and zonulae occludentes during experimental and pathological intra- and extrahepatic cholestasis in mammals.

Uptake of 125I-labelled prolactin by bullfrog kidney tubules: an autoradiographic study.

The uptake of 125I-labelled ovine prolactin in the bullfrog kidney was studied by autoradiography. Five minutes after the intracardiac injection of 125I-labelled prolactin, no labelling was detected in the kidneys of premetamorphic tadpoles or in animals whose forelimbs had just emerged (climax tadpoles). After 15 min, a few isolated tubules were labelled in the premetamorphic tadpole kidneys and many kidney tubules were labelled in climax tadpoles. In the froglet kidneys, extensive labelling was seen by 5 min after injection, and only distal tubules seemed to be consistently unlabelled. The radioactive label was displaced by an excess of unlabelled ovine prolactin, but not by ovine growth hormone or bovine LH. These findings provide the first morphological demonstration of specific binding of prolactin by the nephric tubules of an amphibian. They show that the receptors, present in small numbers in the premetamorphic state, proliferate during the later stages of metamorphosis. The change in receptor density involves both an increase in the number of tubules having receptors and in the density of receptors per tubule.

Morphogenesis and growth of the definitive opisthonephros during metamorphosis of anadromous sea lamprey,Petromyzon marinusL

ABSTRACTThe definitive opisthonephros of the adult lamprey, Petromyzon marinus L., develops during metamorphosis from the nephrogenic cord confined within a nephric fold and extending from the posterior tip of the larval opisthonephros to the cloaca. This development is initiated prior to the first signs of external metamorphosis and begins with the simultaneous appearance of clusters of cells scattered along the entire length of the cord. Proliferation of these cell clusters and their elongation to connect to the closely associated archinephric duct results in the formation of rudimentary nephron units. Subsequent development involves the formation of tubular lumina, branching of the tubules, and the participation of the proximal ends of the newly formed tubules in the formation of the single renal corpuscle. Growth in size of the kidney is the result of lengthening of the existing tubules through cell proliferation rather than through the addition of new nephrons. This growth appears to be at the expense of adipose tissue within the nephric fold. During later stages of metamorphosis, cell proliferation is more prevalent in the ventral part of the nephric fold where a parallel system of tubules develops.The development of the definitive opisthonephros during metamorphosis of lamprey may prove to be a useful model for further studies of tissue differentiation and interaction during kidney development in vertebrates.

A combined biochemical and morphometric study on tissue changes inXenopuslarvae during induced metamorphosis

The metamorphic tissue changes in liver and tail muscle of Xenepus larvae have been followed with the aid of biochemical and morphc metric characteristics. After induction cf metamorphosis by thyroxir.e the larval liver shows an increase and then a marked decrease in weight, but no change in water content. Coincident with this, there are similar, but differential fluctuations in the amount of DNA, total RNA and acid precipitable protein. The concentiation of RNA and protein (per unit fresh weight) remains constant throughout metamorphosis, whereas that of DNA decreases during the growth period and increases during late metamorphosis. In tail muscle, which undergoes involution at metamorphosis, there is no change in water content. The concentration of macromolecular constituents does not show any significant change, except for DNA the concentration of which increases during later stages of metamorphosis. The morphometric analysis of the liver tissue reveals that the initial growth response occurs without any significant change in the volume proportion between extrahepatocytic space and hepatocytes, and that liver atrophy during later stages of metamorphosis coincides with similar decreases in the fractional volumes of hepatocytes and their cytoplasmic constituents (mitochondria, ER, ground substance). It is deduced that the larval liver of Xenopus — in contrast to tail muscle — responds to thyroid hormone by transient growth followed by a marked atrophy of the hepatocytes. Biochemical and morphometric data support the view that this response primarily involves cell mass, and possibly to some extent also cell number, but does not affect the volume proportions of cytoplasmic constituents of the hepatocytes.

Comparison of blood glucose and liver glycogen of larval and adult frogs ( Rana pipiens)

Blood glucose levels are lower in tadpoles than adults. Transition to adult levels occurs during the later stages of metamorphosis, but the rise is interrupted by a brief decline in blood glucose at the beginning of metamorphic climax. Liver glycogen rises from 4.6% to 8% during larval life, falls to 1.7% at the beginning of metamorphic climax then returns to 5–7% during late climax and in the frog. Possible mechanisms responsible for the differences in carbohydrate regulation in larval and post metamorphic amphibians, and the biological significance of the differences are briefly discussed.

Glycoproteins and glycolipids of oxyntic cell microsomes I. Glycoproteins: Carbohydrate composition, analytical and preparative fractionation

Isotopically-labeled sugars were incorporated into glycoproteins of isolated bullfrog gastric mucosa. The majority of the label was found in gastric microsomal fractions which were shown to contain membranes derived from the oxyntic cell tubular membrane system and were not significantly contaminated with mucus. The tubular membranes contained exceptionally large quantities of carbohydrate (approx. 260 μg/mg protein). Most of the sugar (73%) was associated with protein in the following molar ratios: hexose, 1.0: fucose, 0.42; hexosamine, 0.62; sialic acid, <0.02. The remaining sugar, predominantly hexose, could be extracted into lipid solvents and was presumably glycolipid. Gastric microsomes were dissolves in sodium dodecyl sulfate and subjected to acrylamide gel electrophoresis and Sephadex G-200 fractionation. The latter preparative procedure yielded several molecular weight classes, each of which contained different sets of proteins and/or glycoproteins; however, the molar ratios of the sugars found in the two carbohydrate containing classes were quite similar. Significant quantities of carbohydrate were also found in gastric microsomal fractions from other species, e.g. pig and rabbit. Furthermore, characteristic proteins and glycoproteins were not present in tadpole gastric microsomes until the later stages of metamorphosis when HCl secretory capability had been established. The above findings suggest that glycoproteins may play an important role in oxyntic cell functions; the possibility of a membrane protective role is discussed.

Metamorphosis of the perirectal malpighian tubules in the mealworm Tenebrio molitor L. (Coleoptera, Tenebrionidae). II. Ultrastructure and role of autophagic vacuoles.

The perirectal Malpighian tubules of T. molitor are highly specialized for ion and fluid transport. Although they survive metamorphosis, being similar in structure and function in both larva and adult, they undergo a sequence of dramatic alterations in subcellular organization. In the early stages of metamorphosis there is a phase of dedifferentiation during which the perirectal tubule cells undergo degenerative changes. The highly specialized brush border, which in the larva is formed of closely packed microvilli containing mitochondria, is partially broken down and a large number of mitochondria undergo autophagic isolation and digestion. A conspicuous result of the autophagic processes is the accumulation of membrane lipid within autophagic vacuoles which are eventually transformed into 'osmiophilic bodies.' During the later stages of metamorphosis the cells progressively redifferentiate and the brush border is reconstituted. The number of osmiophilic bodies declines markedly, concomitant with an apparent increase in the number of mitochondria.

Metamorphosis of the perirectal Malpighian tubules in the mealworm Tenebrio molitor L. (Coleoptera, Tenebrionidae). I. Histology and histochemistry.

The perirectal Malpighian tubules of both larva and adult T. molitor are highly specialized for a fluid transport role. Related to this function are a number of structural specializations, including a thick brush border which lines the lumen of the tubules. The brush border consists of closely packed microvilli containing mitochondria. Although the perirectal tubules survive the transformation from larva to adult they undergo at the cellular level a sequence of dramatic changes. During the early stages of metamorphosis there is a phase of dedifferentiation and autolysis involving the partial breakdown of the brush border and the destruction of large numbers of mitochondria. A conspicuous cytological manifestation of these processes is the transfer of membrane lipids from the brush border into intracellular osmiophilic bodies (autolysosomes). During the later stages of metamorphosis, i.e. adult development, the cells progressively redifferentiate. As the brush border is rebuilt there is an increase in the number of mitochondria concomitant with a decline in the number of osmiophilic bodies, indicating that the membrane lipid is reutilized for mitochondrial genesis.The results show that the processes of isolation and digestion of mitochondria, the accumulation and retention of valuable breakdown products, and their subsequent reutilization are integral parts of the economy of the perirectal tubule cells during metamorphosis.

The development of intracellular membranes concomitant with the appearance of HCl secretion in oxyntic cells of the metamorphosing bullfrog tadpole.

ABSTRACT Bullfrog tadpole stomachs of various metamorphic stages were examined to determine the fine-structural development of oxyntic cells and to correlate observed morphological development with the capacity to secrete HCL It was found that in vitro tadpole stomachs can consistently be stimulated to secrete acid by stage XXIV of metamorphosis, when tail reabsorption is nearly complete. Concomitant with the appearance of HC1 secretion, identifiable oxyntic cells were found in the gastric glands. Prior to stage XXIV (stages XXI and XXII) the majority of cells present in the developing gastric glands exhibit features of cytological organization characteristic of undifferentiated cells: large nuclei, relatively scanty cytoplasm, and numerous ribosomal particles within the cytoplasmic matrix. The newly differentiated oxyntic cells of stage XXIV tadpole stomachs are recognizable by the accumulation of tubular members of the smooth-surfaced endoplasmic reticulum in the apical portion of the cells. These membranous structures appear to be formed by the Golgi complex which is extremely elaborate at this stage of development. As the animals complete metamorphosis (stage XXV) further development of the oxyntic cells occurs, especially the elaboration of the tubular components of the smooth-surfaced endoplasmic reticulum. The abundance of these membranous tubules within the apical cell regions and the pattern of their packing is similar to that observed in oxyntic cells of adult frogs. Also consistent with studies on adult frogs, structural alterations associated with HC1 secretion were seen in the later stages of metamorphosis. In stages XXIV and XXV tadpole stomachs, which had been stimulated to secrete acid by addition of histamine, the apical surfaces of oxyntic cells were invested with long filamentous microvilli which projected into the glandular lumen. These observations support the hypothesis that membrane transformations play an integral role in the mechanism of HC1 secretion and they implicate the morphogenesis of the smooth-surfaced endoplasmic reticulum as a basic prerequisite in the development of gastric secretory function.

In vitro conversion of 17α-hydroxyprogesterone to androstenedione by mashed gonads from metamorphic stages of Xenopus laevis

After incubation of [4- 14C] 17α-hydroxyprogesterone with testes and ovaries of Xenopus laevis larvae at three stages of climactic metamorphosis and with testes of one group of postmetamorphic animals, [4- 14C] androst-4-ene-3,17-dione was found as the only C 19-steroid metabolite. At the youngest stage (larvae before forearm break through; stage 29–30), the formation of androst-4-ene-3,17-dione per animal was equally low in both sexes. It remained at that same low level for the ovaries, but more than doubled for testes at the later stages of metamorphosis. There was no indication for the formation of testosterone or estrogens. These studies demonstrate the presence of a 17α-hydroxyprogesterone C 17C 20 lyase; they also indicate a pathway for the formation of androst-4-ene-3,17-dione from 17α-hydroxyprogesterone similar to that in mammalian testes and ovaries.