Fine structure of the vessels of the hypophysial portal system of the White-crowned Sparrow,Zonotrichia leucophrys gambelii

Summary The angioarchitecture of the hypophysial portal system of the White-crowned Sparrow, Zonotrichia leucophrys gambelii, was investigated by electron microscopy in conjunction with light microscopy of serial thick sections.The small arteries or arterioles supplying the primary capillary plexus of the median eminence have the typical form of arterioles.The vessels of the primary capillary plexus, on the surface of the median eminence, with their many fenestrations and pinocytotic vesicles, are typical of the form of capillary usually found in other endocrine organs.The portal vessels in the pars tuberalis have wide perivascular spaces between the basement membrane of the endothelium and that of parenchymal lobules of the pars tuberalis. These perivascular spaces are occupied usually by the perivascular cells, but sometimes contain erythrocytes.The endothelial cells of the portal vessels often protrude into vascular lumen giving the appearance of valve-like structures. These may have a role in the regulation of blood flow.The endothelial cells of the portal vessels are invested by a definitive basement membrane and by the cytoplasm of pericytes which are oriented spirally to the longitudinal axes of the vessels. The pericytes may have a function in the mechanical support of the vascular wall and a contractile function that might regulate the flow rate of blood.The investigation reported herein was supported by a scientific research grant (No. 291049) from the Ministry of Education of Japan to Prof. Mikami; by a grant from the Deutsche Forschungsgemeinschaft to Prof. Oksche; by a grant (5 ROI-NB 06817) from the National Institutes of Health to Prof. Farner, and by a research grant (5 ROI-HE 07240 NEUA) from the National Institutes of Health to Prof. Vitums.     

Use of the lateral line and tactile senses in feeding in four antarctic nototheniid fishes

Synopsis Fishes of the family Nototheniidae (Pisces: Perciformes) dominate antarctic fish communities and have radiated to fill diverse niches. The most southern species must operate under an extended austral night and under thick sea ice, yet have eyes more typical of shallow coastal fishes. In winter, the eyes are probably useless, except for detecting bioluminescence. I compared the responses of four species to hydromechanical and tactile signals: two benthivores,Trematomus bernacchii andT. pennellii, a benthic planktivore,T. nicolai, andPagothenia borchgrevinki, which feeds near the ice undersurface and within ice cracks. The planktivores have dorsal mouths, with eyes oriented dorsally or laterally (Pagothenia); their lateral line canals and receptor organs are larger dorsally. The benthivores have more ventrally oriented mouths and eyes. All species responded to hydromechanical cues to the head, but only the two benthivores responded to trunk hydromechanical stimuli or tactile stimuli to the ventral trunk or pelvic fins. Possibly responses to plankton along the trunk are of little use if a reorientation washes pelagic prey away. In responding to trunk stimuli,T. bernacchii reorients its head to the target in two stages by slowly pivoting on its pelvic fins. In contrast,T. pennellii reorients in a single quick flip. It is argued that, becauseT. bernacchii has wider canals thanT. pennellii, it must move more slowly to reduce self-generated noise. It is likely that further studies of winter diet and prey behavior may reveal the relative advantages of the two repositioning styles.     

Attachment sites of parasitic lampreys: comparisons among species

Synopsis Distribution of attachment sites varies with the species of lamprey being considered. Large anadromous species (Petromyzon marinus and Lampetra tridentata) tend to attach ventrally, especially near the pectoral fins, while smaller freshwater species in shallow habitats (Ichthyomyzon castaneus and I. unicuspis) and species that feed on muscle tissue (Lampetra ayresi) tend to attach dorsally. Catostomids tend to be attacked on the head and, by the Ichthyomyzon species, on the paired fins. Distribution of attachments by P. marinus in laboratory studies may be affected by tank size. Attachments to the head and pectoral regions are probably associated with greater host mortality rates and may be underrepresented in field samples. Attachments to the pectoral region appear to combine low costs, in terms of handling time prior to feeding, with greater rates of energy intake once feeding has been initiated. Dorsal attachments by species that inhabit relatively shallow rivers and streams may be a compromise to avoid abrasion against the bottom. A consequence of dorsal attachments may be a reduced impact on host populations through prolonged attachments to individual hosts and reduced attack rates.     

<Emphasis Type="Italic">Cabillus atripelvicus</Emphasis>, a new species of gobiid fish from the Ogasawara Islands,with a key to species of the genus

Cabillus atripelvicus is described from three specimens, 26.1–40.6 mm in standard length, collected from depth 17–29 m in the Ogasawara Islands. In addition, two small specimens taken by dredge in 50–55 m from Sagami Bay, Honshu, and one from Tachibana Bay, Kyushu, are identified as this species but not designated as paratypes. Cabillus atripelvicus is distinguished from the four other described species of the genus by its high count of 18–20 pectoral rays, presence of median predorsal scales, longer pectoral fins, and distinctive color pattern, including black pelvic fins. The range of C. lacertops Smith, 1959 is extended east to the Marshall Islands and that of C. tongarevae (Fowler, 1927) east to American Samoa. More species remain to be described in the genus. Supplementary material to this paper is available in electronic format at     

The Fish–Tetrapod Transition: New Fossils and Interpretations

Our information on the transition between fish with fins and tetrapods with limbs and digits has increased manyfold in the last 15–20 years and especially in the last 5 or 10 years, with some spectacular finds of new material. Some of these include new tetrapod-like fish and very primitive tetrapods that help to resolve questions of the sequence of acquisition of tetrapod characters, the approximate timing of the events, the likely geographic location, and the circumstances under which it happened. Forelimbs and skulls became modified in advance of hind limbs, adapted for supporting the head and front of the body out of the water, probably in connection with air breathing. The likely time of origin for limbed tetrapods is between 385 and 380 million years ago, probably in the northern continent of Laurussia. The origin of limbed tetrapods did not coincide with the acquisition of full terrestriality, an outcome that probably arose in the Early Carboniferous. This later part of the story is documented by few fossils, though two in particular give key information. Studies of modern vertebrates, especially the evolutionary developmental genetics of Hox genes, are beginning to provide clues to the origin of digits.     

Innervation of the renal vasculature of the toad (Bufo marinus)

The innervation of the dorsal aorta and renal vasculature in the toad (Bufo marinus) has been studied with both fluorescence and ultrastructural histochemistry. The innervation consists primarily of a dense plexus of adrenergic nerves associated with all levels of the preglomerular vasculature. Non-adrenergic nerves are occasionally found in the renal artery, and even more rarely near the afferent arterioles. Many of the adrenergic nerve profiles in the dorsal aorta and renal vasculature are distinguished by high proportions of chromaffin-negative, large, filled vesicles. Close neuromuscular contacts are common in both the renal arteries and afferent arterioles. Possibly every smooth muscle cell in the afferent arterioles is multiply innervated. The glomerular capillaries and peritubular vessels are not innervated, and only 3-5% of efferent arterioles are accompanied by single adrenergic nerve fibres. Thus, nervous control of glomerular blood flow must be exerted primarily by adrenergic nerves acting on the preglomerular vasculature. The adrenergic innervation of the renal portal veins and efferent renal veins may play a role in regulating peritubular blood flow. In addition, glomerular and postglomerular control of renal blood flow could be achieved by circulating agents acting via contractile elements in the glomerular mesangial cells, and in the endothelial cells and pericytes of the efferent arterioles. Some adrenergic nerve profiles near afferent arterioles are as close as 70 nm to distal tubule cells, indicating that tubular function may be directly controlled by adrenergic nerves.     

The spleen of the cowbird

A histological study of the spleen of the Brown-headed cowbird, Molothrus ater, is presented. One of the most striking differences from the mammalian spleen is the lack of trabeculae and of smooth muscle in the capsule which would suggest that the spleen is not an organ of storage or pumping of blood. Without trabeculae to foster the close association of the major arteries and veins, these vessels take separate courses. Their support is provided by elaboration of the collagenous and reticular fibres of the stroma. A peculiar ovoid structure, the ampulla, carries the blood from the terminal arterioles of the white pulp to both the sinusoids and the reticular cords of the red pulp so that both open and closed circulations are seen but the open circulation predominates. The ampulla has perforated walls consisting of a simple cuboidal endothelium surrounded by a dense reticular sleeve. Leucocytes were seen passing through the holes in the walls of the ampullae by diapedesis. It is suggested that the ampullae may be contractile and act as sphincters controlling the flow of blood through the spleen. The major functions of the spleen appear to be haemopoiesis, production of antibodies, and filtration of blood.     

A light and electron microscopical study of the green flagellateSpermatozopsis similis spec. nova

The green flagellateSpermatozopsis similis spec. nova has been studied in culture by light and electron microscopy. The flagellate bears two flagella, is naked and has a characteristic crescent and spirally twisted cell shape. The two flagella are of subequal length, each with a prominent hair-point. Each cell contains two contractile vacuoles, a single chloroplast with an anterior eyespot but lacking a pyrenoid, an anteriorly located nucleus, a single dictyosome associated with the posterior end of the nucleus, a single mitochondrion posterior to the nucleus and associated with a small microbody, some conspicuous vacuoles, and a greater number of secondary cytoskeletal microtubules which probably are responsible for maintaining the peculiar shape of this species. SinceS. similis in culture is only biflagellate, it cannot be accommodated within the quadriflagellate, but otherwise very similar speciesS. exsultans. Spermatozopsis similis is compared with other green flagellates and is shown to share common ultrastructural characters withChlamydomonas-type green algae.     

A megapterygium larva of <Emphasis Type="Italic">Discoverichthys praecox</Emphasis> (Aulopiformes: Ipnopidae) from the tropical western Pacific

The larva of Discoverichthys (Aulopiformes: Ipnopidae) is described for the first time based on a specimen 39.5 mm in standard length collected in surface waters near the Marianas in the western North Pacific. Despite its remote location from the previous record in eastern North Atlantic (type locality), this larva was identified as Discoverichthys praecox by general agreements of meristic counts and other morphological features. It is characterized by the following possible autapomorphic features: body moderately elongate, with uniformly distended abdomen, terminating in long, stout trailing gut; all fins, particularly the pectoral and pelvic, are extensively produced; body pigmentation is scanty, but all fins except the caudal are polka-dotted distally and covered by unusually thick skin; the skeleton is largely cartilaginous, with poorly differentiated axial components and uniquely expanded dorsal- and anal-fin pterygiophores. Its peculiar morphology is discussed with special reference to transformation events.     

Zur Kenntnis vonTetrasporopsis fuscescens

The macroscopic colonies ofTetrasporopsis fuscescens consist of a tegument of irregularly folded bag-like mucilage. It contains isolated ellipsoidal cells arranged in a regular peripheral stratum and rather sparsely and irregularly beneath. They show polarity, 4 parietal chromatophors when fully developed, have a wall containing cellulose, and no contractile vacuoles. Naked protoplasts are released from them through circular openings oriented towards the surface. Flagellated cells and cysts were not observed.T. reticulata may be closely related toT. fuscescens, but probably no other species is allied.

Herrn Univ.-Prof. Dr.Walter Leinfellner zum 70. Geburtstag gewidmet.     

Periophthalmus spilotus, a new species of mudskipper from Sumatra (Gobiidae: Oxudercinae)

A new species of mudskipper,Periophthalmus spilotus, is described on the basis of 16 specimens from Sumatra, Indonesia. It differs from other species ofPeriophthalmus by the following combination of characters: pelvic fins totally united into rounded disk; first dorsal fin high, greyish, no spots on fin nor elongate spines; second dorsal fin typically with 14 total elements; anal fin typically with either 14 or 15 total elements; length of anal-fin base 21.8–29.0% SL; and length of second dorsal-fin base 22.5–26.7% SL. This species is most similar to, and probably most closely related to,P. chrysospilos.     

Early development of the flathead,Percophis brasiliensis (Teleostei: Percophididae), from Southeastern Brazil

Morphological and osteological development of the flathead,Percophis brasiliensis, is described based on specimens collected from southeastern Brazilian waters. Identification of larvae was based on pigment pattern and meristic counts. Distinct melanophores were present on the bottom of the hindbrain, between the bases of the pelvic fins and on the bases of the pectoral fins. Within the family Percophididae onlyPercophis brasiliensis has 57 myomeres, which result in the larvae having an elongated body form. The larval pigment pattern and structure of the caudal complex suggest that the subfamilies Percophinae and Bembropinae are phylogenetically close, while the Hemerocoetinae belong to an advanced group within the family.     

Internal morphology and function of paired fins in the epaulette shark,hemiscyllium ocellatum

Paired fins and associated internal structures of the epauletic sharkHemiscyllium ocellatum, were described on the basis of three specimens. A comparison with other genera showed the epaulette shark to be, characterized by two elongated basal cartilages articulating with a distally projecting articular condyle on the coracoid, a loosely separated radial series with an intermediate series, a levator pectoralis inferior muscle and an anterolaterally developed depressor pectoralis muscle in the pectoral fin, and an elongated anterior pelvic basal cartilage articulating with a distally projecting articular condyle and an anterolaterally developed depressor pelvicus muscle in the pelvic fin. In captivity, the sharks exhibited both upright and crawling behavior on the bottom by using the pectoral and pelvic fins and bending the body. The distinctive morphological characters are shared by otherHemiscyllium species and are suggested as important factors enabling their unique behavior associated with a complex coral reef habitat.     

The fine structure of Crithidia fasciculata with special reference to the organelles involved in the ingestion and digestion of protein

Summary As in other trypanosomatids, the cell membrane of Crithidia fasciculata overlies a single layer of microtubules. Each microtubule possesses a large number of periodically arranged drumstick-like appendages and adjacent microtubules are joined by fibrillar connectives. Anteriorly, the microtubules gradually taper to terminate just before or just after entering the reservoir. An attempt is made to correlate microtubule tapering with maintenance of form of the truncated anterior end of the cell. Smooth and coated vesicles are proliferated from the Golgi saccules and the prominent contractile vacuole lies nearby. The single mitochondrion is extensive and expanded at one point to form a capsule for the kinetoplast. The cristae are predominantly plate-like but other configurations do occur. The cytostome, a shallow invagination of the reservoir membrane, is found between two constrictions in the reservoir wall. Supporting the cytostome are several microtubules which penetrate deeply into the cytoplasm. Ingestion of ferritin occurs by pinocytosis from the cytostome and by coated vesicle formation from the reservoir membrane. Digestion probably occurs in multivesicular bodies which contain acid phosphatase activity.     

Myogenesis and contraction in the early embryonic heart of the rainbow trout

Summary Myogenesis in the embryonic heart of the rainbow trout, Salmo galrdneri (Rich.), was investigated electron microscopically from the 29th to the 41st somite stage. Thick and thin myofilaments are formed simultaneously as well as precursors of Z-lines, to which the thin filaments are attached. The genesis of filaments takes place in the region around the intracellular yolk droplets. The first myofibrils appear by the 33rd somite stage, probably formed by a mechanism of self-assembly in which the binding sites of actin and myosin participate. A- and I-bands do not develop before the 38th somite stage. The contraction already begins during the 33rd somite stage in the middle of the tubular heart. Gradually, the peristaltic waves spread increasingly to other parts of the heart. In the 41st somite stage the entire heart is contractile and all myocytes contain myofibrils.     

Trypanosoma cruzi: correlation of muscle lesions with contractile properties in the acute phase of experimental infection in mice (Mus musculus)

Parasitism in skeletal muscles and myositis are commonly observed during experimental Trypanosoma cruzi infection. The effect of T. cruzi infection on contractile properties of skeletal muscles in consecutive periods of the acute infection in BALB/c mice was studied. Albarrada strain (clone 4) which was isolated in Mexico and has demonstrated a high level of blood parasitemia and parasitism in skeletal muscles was used. Isolated strips of rectus abdominis muscle were subjected to direct electrical field in vitro. Alternatively, plantaris muscles were stimulated in situ through the sciatic nerve. The peak amplitudes of a single twitch and tetanus contractions were considered to estimate the mechanical properties of muscles. Histopathological analysis was performed to correlate functional changes with the evolution of tissue parasitism and tissue injury. Contractile properties of muscles were significantly attenuated during acute T. cruzi infection. The percentage of damaged muscles rather than the character of tissue pathology affected their contractile properties significantly.     

Brush-border formation in the midgut of an insect,Calliphora erythrocephala meigen

Summary The embryonic development of the brush-border of anterior midgut cells of Calliphora was studied by electron microscopy. Dense surface-forming vesicles, as described by Bonneville (1970), are found prior to microvillus formation. These dense vesicles provide membranous and coating material for the moulding of the microvilli. The number of dense vesicles increases rapidly to a maximum just before brush-border formation, after which it decreases very rapidly, accompanied by an increase in the number of microvilli. Formation of microvilli proceeds in essentially the same way as in Xenopus. First, some of the vesicles fuse with the apical cell membrane, resulting in an increase of the cell surface, part of which is coated with filamentous material deriving from the dense vesicles. This in turn leads to bulging, and short irregular microvilli appear. These are erected and elongated.Prefabricated tubular elements are believed to play a part in this erection and elongation, probably due to the unwinding of spirally coiled strands.Microvillus formation proper lasts 2 to 3 hours in Calliphora. Almost the entire amount of membranous and coating material is prefabricated prior to the formation of microvilli.     

A reassessment of the taxonomic and phylogenetic affinities of the fossil catarrhines from fort Ternan,Kenya

This paper presents a reassessment of the taxonomic and phylogenetic affinities of the fossil catarrhine primates from the important middle Miocene site of Fort Ternan in Kenya. Although the sample of specimens is rather small, the material can be attributed to at least five different species, identified here asKenyapithecus wickeri, Proconsul sp., a large species of oreopithecid,Simiolus sp., and a small species of catarrhine of indeterminate status.Kenyapithecus wickeri probably represents a conservative sister-taxon of the extant large hominoids. It is more derived than“Sivapithecus” africanus from Maboko Island, from which it can be distinguished at the generic level. A small species of catarrhine from Fort Ternan can be attributed toSimiolus. It is probably a different species fromSimiolus enjiessi from the early Miocene of East Africa, but additional material is needed to confirm its taxonomic distinctiveness. The occurrence of at least five species of catarrhine primates at Fort Ternan confirms that species diversity levels were as high during the middle Miocene as they had been during the early Miocene. However, the overall taxonomic and ecological composition of the middle Miocene catarrhine community was quite different, evidently due to a significant change in the local ecological setting. Taxonomic differences between the catarrhine faunas at Fort Ternan and Maboko Island can probably be explained as a consequence of a chronological separation between the two sites, and, to a lesser degree, to paleoecological differences.     

Actinotrichia collagens and their role in fin formation

The skeleton of zebrafish fins consists of lepidotrichia and actinotrichia. Actinotrichia are fibrils located at the tip of each lepidotrichia and play a morphogenetic role in fin formation. Actinotrichia are formed by collagens associated with non-collagen components. The non-collagen components of actinotrichia (actinodins) have been shown to play a critical role in fin to limb transition. The present study has focused on the collagens that form actinotrichia and their role in fin formation. We have found actinotrichia are formed by Collagen I plus a novel form of Collagen II, encoded by the col2a1b gene. This second copy of the collagen II gene is only found in fishes and is the only Collagen type II expressed in fins. Both col1a1a and col2a1b were found in actinotrichia forming cells. Significantly, they also expressed the lysyl hydroxylase 1 (lh1) gene, which encodes an enzyme involved in the post-translational processing of collagens. Morpholino knockdown in zebrafish embryos demonstrated that the two collagens and lh1 are essential for actinotrichia and fin fold morphogenesis. The col1a1 dominant mutant chihuahua showed aberrant phenotypes in both actinotrichia and lepidotrichia during fin development and regeneration. These pieces of evidences support that actinotrichia are composed of Collagens I and II, which are post-translationally processed by Lh1, and that the correct expression and assembling of these collagens is essential for fin formation. The unique collagen composition of actinotrichia may play a role in fin skeleton morphogenesis.