摘要:

AbstractSaccules from 10 adult (five female, five male) toadfish (Opsanus tau), 13.5–26 cm standard length, were examined for individual/sexual variation in the hair cell orientation pattern. In addition, saccules from two juveniles (5 and 6 cm standard length) were compared with those of the adults to determine whether maturational differences exist in the hair cell orientations. The hair cell orientation pattern is unlike any reported previously for this species or its congener,O. beta. There are no major differences between the hair cell orientations of males and females, nor between the juveniles and the adults. A slight individual variation is present in the proportion of hair cells oriented in a particular direction in a specific area of the sensory epithelium. Potential ramifications of this hair cell orientation pattern are discussed with regard to development and auditory processin

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1995.tb00998.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractSpermatogonia and both generations of spermatocytes ofTenebrio molitorpossess conventional bipolar spindles with only few aster MTs. Spindles in metaphase spermatogonia are surrounded by fenestrated two‐layered cisternae and do not contain intraspindle membranes. In metaphase spermatocytes, a spindle envelope is missing, but intraspindle membranes are abundant. Mitochondria form long threads lateral to the nucleus in prophase I of meiosis. The elongated mitochondria also align parallel to the spindle apparatus in prometaphase I. As a consequence, the spindles reside in a cage formed of mitochondria. This arrangement may guarantee proper bisection of the chondriome during division. Cells are tightly packed during spermatogonial divisions and in prophase I, but large intercellular spaces develop when the first meiotic spindle assembles. Then, cytoplasmic bridges which persist between the cells as a result of incomplete cytokinesis appear as slender tubes. Anti‐tubulin immunofluorescence using an antibody against acetylated α‐tubulin revealed intense acetylation throughout spermatogonial mitosis but a low degree of α‐tubulin acetylation in meiotic spindles prior to telophase. This may indicate a high microtubule turnover i

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1995.tb00999.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe bacterial symbiosis in 13 different species of the gutless phallodriline generaInanidrilusandOlavius(Tubificidae, Oligochaeta) from Carrie Bow Cay (Belize), Florida and Bermuda is structurally compared. The result is an essentially consistent symbiotic pattern regarding the position and ultrastructural design of the prokaryotic partners and their integration in the anatomy of the animal hosts. Based on numerous micrographs, it is calculated that the endobacteria comprise about 25% of the host's volume. This corresponds to at least 0.6 × 106bacterial cells per worm of (fixed) 6 mm length, a figure that underlines the high nutritive importance of the bacteria in this symbiotic association. This importance is also endorsed by the percentage of bacteria in digestion (on average 8–10%, up to 24%) by the phagocytotic epidermal cells of the host. The symbiosis always involves two different morphological types of bacteria, apparently without intermediate stages. Detailed biometrical analyses demonstrate the significantly different size ranges of the two morphotypes, even though in two of the species, the normally rod‐shaped Type S‐bacteria are much longer than usual. About 1% of the larger, oval ‘Type L’ is regularly found in division; in some sections, this value can reach 11%. Formation of sulfur‐containing globules in this type was proven by histochemical analysis. The trophic relevance of the symbiosis is considered. Zoogeographical and evolutionary implications of the observed consistency in the symbiotic pattern in all the species studied a

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1995.tb01000.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractHuber, B. A.1994. Copulatory mechanism inHolocnemus plucheiandPholcus opilionoides, with notes on male cheliceral apophyses and stridulatory organs in Pholcidae (Araneae).—Acta Zoologica(Stockholm) 76: 291–300.The pholcid spidersHolocnemus pluchei(Scopoli, 1763) andPholcus opilionoides(Schrank, 1781) are investigated with respect to functional morphology of their genital organs using freeze‐fixation of spiders during copula in liquid nitrogen and subsequent preparation of histological serial sections of the copulatory organs in functional contact. Special attention is paid to the mode of male pedipalpal arrestation before copulation, which is achieved in two quite different ways: inPholcusby contact of the lateral cheliceral apophysis with the pedipalpal trochanter‐apophysis, inHolocnemusby locking the pedipalpal trochanter between chelicera and pedipalpal coxa. The condition inPholcusis considered to be apomorphic and to present a synapomorphy of about a dozen genera for which the name “Pholcus‐group” is proposed. The stridulatory apparatus ofHolocnemus plucheiis described, its biological significance discussed and an overview of accounts on stridulation in Ph

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1995.tb01001.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractHammerhead sharks (genus Sphyrna) show two large arterial coilings in a posteroventral hollow of the orbitary cavity. The posterior is made up of the hyoid artery which, after giving rise to the stapedial artery, enters the chondrocranium to originate the internal carotid and the cerebral arteries. The efferent pseudobranchial artery forms the anterior coiling, gives rise to the ophthalmic artery, enters the orbitary wall and joins the internal carotid artery. The histological sections of the arterial coilings showed the scarcity of smooth muscle cells in the tunica media as well as an important collagenic and elastic component in the arterial wall. Several venous vessels percolate through the coilings. A large amount of small (mean diameter = 73 μm), spheric corpuscles were observed in the connective tissue around the coilings. These corpuscles were also present in the palate and under the skin of the head of these sharks. They are comprised of spirally‐arranged cells around a bundle of collagen fibres. We hypothesize that their association with the coilings could suggest some kind of involvement in detecting pressure changes in the blood supply to the he

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1995.tb01002.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractMyzostoma cirriferumfeeds by diverting food particles carried by the ambulacral grooves of its comatulid hostAntedon bifida. When searching for food, the myzostome uses its protrusible introvert to fulfil two major functions: sensory perception and the capture of food particles. The digestive system is composed of four parts, viz. a pharynx, that is contained within the introvert, a stomach, a series of paired caeca and an intestine that lie in the myzostome's trunk. The pharynx is supplied with a thick muscle which, thanks to peristaltic movements, carries food particles from the mouth to the stomach. Both stomach and caecal cells are able to absorb dissolved nutriments and to store lipids, whereas intestinal cells are only capable of absorption. Due to the beating of their cilia, stomach cells also carry food particles into the caecal lumen, where they are subjected to endocytosis and intracellular digestion by caecal cells. Undigested food fragments eventually gather in a very large, apical vacuole, and the cell apices containing vacuoles are eliminated into the caecal lumen by an apocrinal process. Detached cell apices reach the stomach, where they are embedded in a matrix, together forming a spindle‐shaped faecal mass that is expelled through the postero‐ventral anus. The observed digestive process—entailing the regular elimination of the apical part of the caecal digestive cells—appears to be unique among the S

ISSN:0001-7272    

DOI:10.1111/j.1463-6395.1995.tb01003.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY