Functional morphology of the gonoduct of the viviparous teleost Poeciliopsis gracilis (Heckel, 1848) (Poeciliidae)

Female teleosts do not develop Müllerian ducts; consequently, the ovary of teleosts contains two zones: germinal and gonoduct. The gonoduct lacks germinal cells, but has relevant functions in the reproductive process. We describe the functional morphology of the gonoduct in the viviparous teleost Poeciliopsis gracilis during nongestation and gestation stages. This study tests the hypothesis that the gonoduct functions as a barrier between the germinal zone and the exterior. By providing information about morphology and function of the gonoduct we show that this part of the ovary has an essential role in the reproduction of teleosts. The ovaries were processed by histological technique and stained with hematoxylin‐eosin (H‐E), Masson's trichrome, toluidine blue and periodic acid‐Schiff (PAS). The gonoduct is divided into three regions: cephalic, middle, and caudal. In the cephalic and middle regions there are mucosal folds that extend into the gonoductal lumen, forming structures similar to a cervix. The caudal region has two portions: the anterior contains a dorsal invagination and exocrine glands among columnar cells; the posterior has a ventral flexion and stratified epithelium with apical secretory cells. The morphology of this epithelium indicates two functions: (a) secretory by the apical columnar cells, and (b) protection through the stratification. Another peculiarity of the caudal region is that both ducts, reproductive and digestive, converge in a common cavity at their caudal ends, forming a cloacal region. The histology of the gonoduct indicates relevant functions including: (1) the control of the luminal diameter by the muscle and the presence of mucosal folds, like a cervix; (2) the relationship with the spermatozoa during insemination and storing them in mucosal folds; (3) the support of immunological processes; (4) secretory activities; (5) forming the duct during birth; and (6) possibly, acts as a barrier against parasite infestations.     

A new capillariid (nematoda) parasitizing Heterandria bimaculata (Heckel, 1848) (Poeciliidae) in Mexico

A new nematode species, Freitascapillaria moraveci n. sp., is described; it was obtained from specimens recovered from the gall bladder of the 2-spot livebearer Heterandrá bimaculata (Heckel, 1848) from La Antigua River, State of Veracruz, Mexico. The new species is assigned to Freitascapillaria Moravec 1982; it is largely characterized by the posterior end of the males, which is laterally expanded without distinct projections. Freitascapillaria moraveci n. sp. differs from the only other species of the genus, F. maxillosa, by the absence of wing-like cells at the esophago-intestinal junction, which are present in the latter species; stichosoma consists of 30-36 stichocytes (F. moraveci) versus 40-60 stichocytes (F. maxillosa) in both males and females and the presence of a well-developed spicule.     

Untersuchungen zur Dotterbildung in den Oocyten von Xiphophorus helleri (Heckel, 1848) (Teleostei,Poeciliidae)

Zusammenfassung Die Verteilung von Nucleinsäuren, Polysacchariden, Proteinen und Fetten in den verschiedenen Entwicklungsstadien der Oocyten von Xiphophorus helleri wurde histochemisch untersucht. Junge Oocyten enthalten viel RNS und Proteine, aber wenig Fett. Während der Vitellogenese steigt der Gehalt an Fetten, Glycoproteide werden eingebaut. Die dazu nötigen Stoffe werden aus dem mütterlichen Körper in niedermolekularer, löslicher Form über das Follikelepithel zur Oocyte transportiert. Diese histochemischen Befunde werden durch Ergebnisse der Elektrophorese gestützt. In elektronenmikroskopischen Untersuchungen wurden den histochemischen Fakten weitere morphologische Grundlagen zugeordnet. Während der Prävitellogenese tritt ein Dotterkern auf, der sich vor Beginn der Dotterbildung auflöst. Coated vesicles nehmen Material aus dem perioocytären Interzellularraum auf. Zellstrukturen der Oocyte beteiligen sich am Dotteraufbau. Besonders auffallend sind die Veränderungen an den Mitochondrien. In der Zusammensetzung des Dotters und in der Beteiligung der Organellen gibt es Unterschiede zu Lebistes. Injektionen von Myofer runden die Ergebnisse ab. Vom maternalen zum embryonalen Gewebe erfolgt ein Transport von Nährstoffen, nicht nur Gasaustausch. Die Definition der Ovoviviparie muß daher erweitert werden.

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Studies on yolk formation in oocytes of Xiphophorus helleri

Summary The distribution of nucleic acids, polysaccharides, proteins, and fats in different developmental stages of oocytes of Xiphophorus helleri was studied using histochemical methods. Young oocytes had high RNA and protein contents. During vitellogenesis, the fat content increased and glycoproteins were deposited. These substances were transported from the maternal body into the oocyte in a soluble, small molecular form. The histochemical results were supported by our studies using electrophoretic and electron microscopic methods. During previtellogenesis, a yolk nucleus appeared. Coated vesicles took up material from the intercellular space around the oocyte. Differences between Xiphophorus and Lebistes were observed in the composition of yolk and in the prevalent types of ultrastructural organelles present. In Xiphophorus, labelling by Myofer (intraperitoneal or intramuscular injections) verified the transport of nutritive material from the maternal body into oocytes (Stage III and IV) and embryonic tissues. This suggests that in Xiphophorus the definition of ovoviviparity has to be modified.

     

Length–weight and length–length relationships of four species (Barbus lacerta Heckel, 1843), Oxynoemacheilus angorae (Steindachner, 1897), Squalius lepidus (Heckel, 1843) and Pseudorasbora parva (Temminck & Schlegel, 1846) from the Sirwan River (western Iran)

The study describes the length–weight and length–length relationships for three cyprinid species, namely Barbus lacerta, Squalius lepidus and Pseudorasbora parva, and a balitorid species, Oxynoemacheilus angorae from the Sirwan River (located in Kurdistan and Kermanshah provinces, Iran. This study presents the first reference on LWR for most of the species in their distribution range.     

X-ray microanalysis of myotomal muscle in the sunbleak, Leucaspius delineatus (Heckel) and goldfish, Carassius auratus gibelio

The functioning of a group of muscle fibres as a tissue that performs a well characterized type of contraction (slow or fast) depends on their biochemical and structural organization that is already well established. The biochemical and structural diversities between three types of fish muscle fibres found also a reflection in the content of light elements. The present work demonstrates significant differences in the content of diffusible elements (Cl, K, Na, and Mg) and bound elements (P and S) between the muscle fibres types. In general all muscle fibre types of goldfish (Carassius auratus gibelio) that belongs to stationary slow-swimming fish has lower K/Na ratios than those in all three fibre types of fast swimming sunbleak (Leucaspius delineatus).     

Eggs and larvae of the 'curvina' Plagioscion squamosissimus (Heckel, 1840) (Osteichthyes, Sciaenidae) in the Baia River, Mato Grosso do Sul State, Brazil

The aim of this work was to study the eggs and larvae of the‘curvina’, specifically the examination of spatialand temporal variation, location of spawning and dispersal groundsand verification of the relationship between occurrence andenvironmental variables. Sixteen collection sites were establishedin the Baía River, Brazil, and grouped into four areas.Collections were carried out between February 1999 and April2000. Spatial and temporal variations were analysed using ANOVA.Identification of the spawning and dispersal grounds was carriedout using development stage distribution. The relationship betweenoccurrence and the environmental variables was determined usingPrincipal Components Analysis (PCA) and Pearson correlation.The eggs were found in every area practically every month, almostexclusively in the initial embryo stage, while the larvae occurredin every area mainly between October and April. The correlationbetween PCA scores and organism occurrence demonstrated thatthe highest catches occurred when the values of temperature,water level and rainfall were high and those of dissolved oxygenand pH were low. This specie spawns and develops in lentic areas,and the lotic stretch serves as a dispersal route through whichthe eggs and larvae are transported.     

The reproductive biology of Plagioscion squamosissimus (Heckel, 1840) in the Pará River estuary (Amazon Estuary)

This study describes the reproductive biology of the South American silver croaker Plagioscion squamosissimus (Heckel, 1840) in the Pará River estuary. Data were collected bimonthly from June 2007 to May 2008. In all, 334 specimens were examined. The gonads were processed with histological techniques, and the ovaries were subjected to morphometric analysis. The length at first maturity (L₅₀) values were 16.14 and 21.43 cm total length for females and males, respectively. The sex ratio based on the total number of individuals favoured the females (1.11 females: one male). Macroscopically, the gonads were classified as immature (A), maturing (B), mature (C) and spent (D). Microscopically, four germ cell types were distinguished based on the development of the ovaries. Chromatin nucleolus (I), perinucleolar (II), cortical alveoli (III) and full‐vitellogenic (IV) oocytes were observed in all ovarian stages, except that of the mature individuals which showed the largest number of full‐vitellogenic oocytes (IV), with a mean diameter of 565.4 μm (±147.4). Substantial percentages of individual P. squamosissimus were found to be in a reproductive condition. Reproductive activity was recorded throughout the year in the Pará River estuary, primarily in February/March and August/September.     

Embryonic fissure and photoreceptor differentiation in the eye of adult Garra rufa Heckel 1843 (Cyprinidae, Teleostei)

The retina of the adult teleost Garra rufa retains a curved, open embryonic fissure indicating an asymmetrical postembryonic retinal growth. Undifferentiated, oval photoreceptors are observed on both sides of the middle of the fissure with their larger diameter running parallel to the fissure to which they may attach by desmosomes. They detach from the fissure, rotate to become perpendicular to it and begin an active process of differentiation as they slide along the temporal side of the outer half of the fissure. This process is divided into stages for simplicity. The photoreceptors develop stumpy inner segments extending into a ventricular space that appears between the retinal pigment epithelium and the photoreceptors. Calycal processes arise from the inner segments and the distal centriole of each photoreceptor forms a connecting cilium. The proximal centriole is retained for some time after the outer segment develops. The formation of rod spherules and cone pedicles takes place almost concomitantly with the outer segments. Double cones appear first as single cones before pairing. One or more of the principal cone mitochondria accumulate electron-dense material and merge to form the ellipsosome. The retinal pigment epithelium undergoes a parallel differentiation. The developmental events described in the present work conform those recorded in embryonic teleostean retinas.     

Growth pattern of the endemic Neretvan roach,Rutilus basak (Heckel, 1843) in the Hutovo Blato wetlands

The growth pattern of the endemic Neretvan roach, Rutilus basak from the Hutovo Blato wetlands was analyzed. A total of 441 specimens ranging from 6.0 to 21.7 cm TL were obtained by electro fishing between December 2007 and November 2008. The male:female ratio for all fish combined was 0.34 : 1.00 but changed across length classes. The spawning period extended from February to April, with a peak in the first half of March. Maximum observed age was 10 years. Predominance of age classes 1–5 in the catch (77.0% of individuals) was noted. The length–weight relationship showed a positive allometric growth (b = 3.321; R² = 0.957). Parameters of the von Bertalanffy equation were: L_∞ = 20.201 cm; K = 0.257 per year; t₀ = ?1.554 year; R² = 0.977. This study revealed that R. basak invests energy in reproduction rather than in body size and thus has a relatively fast growth, short life span and precocious maturity. Moreover, elementary biological population parameters are provided that can be used for conservation purposes.     

A canthobrama centisquama Heckel and the validity of the genus Mirogrex Goren,Fishelson and Trewavas (Osteichthyes: Cyprinidae)

The poorly known cyprinid fish Acanthobrama centisquama is re-described and its distribution is clarified. It is found in the Orontes basin and not waters around Damascus. The genus Mirogrex is synonymised with Acanthobrama.     

Occurrence of parasites of the freshwater mugilid fish Liza abu (Heckel) from Basrah, southern Iraq

In monthly samples of Liza abu collected November 1981–October 1982 from Mehaijeran Creek, a western branch of Shatt–Al–Arab river south of Basrah, fishes were infected with the third larval stage of the nematode Contracaecum sp., the acanthocephalan Neoechinorhynchus agilis and the gill crustacean Ergasilus mosulensis.
Generally, the changes in the percentage prevalence coincided with the changes in the mean intensity of infection. There were no significant differences between the infection of male and female fishes in the cases of the monthly variations of infection with Contracaecum sp. and of infection with both Contracaecum sp. and E. mosulensis , according to fish length, but in other cases more female fishes were infected than males.
Infection with Contracaecum sp. decreased gradually in the larger fishes. In the case of both N. agilis and E. mosulensis , the infection at first increased with increase in fish length but decreased in larger fishes.
Infection with Contracaecum sp. occurred only during May–August and disappeared during September. The peak for N. agilis was in April, and it disappeared during summer. Infection with E. mosulensis disappeared during winter months.     

Annual changes in the ovarian activity of the freshwater teleost, Barbus luteus (Heckel) from Southern Iraq

The present paper describes the morphology, histology, and annual cyclical changes in the ovaries of Barbus luteus (Heckel). The ovaries are paired structures, joined by short oviducts. The ovarian structure consists of a number of lamellae, which contain the germ cells in various phases of maturation—immature, maturing and mature. Two types of yolk have been reported in the oocyte. The endocrine function of the gonads has been attributed to the follicular cells forming the 'pre-ovulatory corpus luteum' and 'postovulatory corpus luteum'. The ovaries undergo a regular annual cycle which has been divided into five stages, based on various criteria, viz, ovarian size, colour, gonosomatic index, average ova-diameter, histological composition, and the spawning activity.