1,721,059 research outputs found
The embryological origin of the juxtatesticular body in jawfishes (Opistognathidae)
No full textA male accessory sex organ, termed the juxtatesticular body (JTB), is located in the posterior part of the trunk, outside the coelomic cavity, lying ventral to the urinary ducts and dorsal to the urinary bladder and testes in jawfishes. Its microscopic structure is unusual for an accessory sex organ because it is highly vascularized, organized in small follicles, and ductless. The embryological origin of the JTB and the development of the urogenital apparatus was studied in juveniles of Opistognathus whitehurstii and O. maxillosus. Both sexes possess a structure located outside the coelomic cavity in the posterior part of the trunk. In females this structure showed the same histological organization as the kidney, however in males it was different and recognized as the JTB. The degree of development of the JTB followed that of the testes, being represented in youngest recognizable males only by a small mass of mesenchymal cells while it was fully developed in males with spermatogenic testes. In most immature males renal structures, such as tubules and glomeruli, were found in the dorsal part of this structure. On the basis of anatomical and cytological features a nephrogenic origin for the JTB is proposed
Male reproductive apparatus of some blennioidei (Pisces: Teleostei)
No full textI performed a comparative study of the morphology of the male genital apparatus on 11 species of blennies: Acanthemblemaria spinosa (Chaenopsidae), Enneanectes pectoralis, E. boelkei (Tripterygiidae), Gillellus rubrocinctus (Dactylopteridae), Labrisomus nuchipinnis, L. haitiensis, L. bucciferus, Paraclinus nigripinnis, Malacoctenus versicolor, M. triangulatus, and M. macropus (Labrisomidae). In the chaenopsid fish, an unpaired testis and a single seminal vesicle occurred. The seminal vesicle consisted of a single chamber containing no sperm and was filled with an homogeneous secretion. In the tripterygiid, dactyloscopid, and labrisomid species testes were paired, with a testicular gland interposed between the seminiferous lobules and the spermduct of each testis. Interspecific differences were noted in the volume of the testicular gland, relative to that of the testis, and in the development of the spermduct. Histochemical stainings in the testicular gland of Malacoctenus triangulatus and M. macropus revealed the secretion of glycogen and nonsulphated mucins. The possible involvement of the testicular gland, seminal vesicle, and spermduct in the nutrition of germ cells, production of a viscous seminal fluid and storage of sperm is discusse
Alternative male mating tactics in the black goby, Gobius niger
No full textIn the field, parental males of the black goby Gobius niger were always>9 cm LT, showed a conspicuous elongation of the first dorsal fin, and were darkly coloured. Larger parental males did not occupy larger nests or obtain more eggs, suggesting that over a threshold size reproductive success was not correlated with male size. The mating system was polygynous with different egg clutches simultaneously present in a nest. Smaller sexually mature males were observed around and inside nests in which spawning was occurring. These opportunistic males
ranged in body size between 6 to 8 cm LT. In contrast to parental males, they did not show an exaggeration of the first dorsal fin and were cryptically coloured, thus resembling small females in their external morphology. Aquarium experiments confirmed that smaller males perform a sneaking behaviour, releasing sperm when parental males spawn. As a consequence, it is
possible to define three male types: type I are small, without an elongated dorsal fin and adopt a sneaking mating tactic; type III are large, have a pronounced elongation of the dorsal fin and perform parental behaviour; type II are intermediate both in size and elongation of the first dorsal fin and behave as either as sneakers or, possibly, as parental males according to nest availability and male competition
The biology of a population of spined loach,Cobitis taeniaL.
No full textA spined loach (Cobitis taenia L.) population inhabiting a small river in northern Italy was studied. At each age, females were larger than males and both sexes showed a marked seasonal pattern of growth with a high rate from May through November. Total population density averaged 2.38 ± 1.6 ind/m2 and the annual production in the study area was 3.3 g/m2. The first year class during the summer accounts for more than half the production. The sex‐ratio did not significantly depart from unity. Most individuals achieved sexual maturity in their second spring after hatching and spawning occurred in late May and June. The relationship between female total length and fecundity was lnF=l.07+0.065L. Males showing three different liveries were found throughout the year; the seasonal variation in their frequency suggested that males change livery in relation to their reproductive conditions
Mating preferences of the female river bullhead,Cottus gobio(Cottidae, Teleostei)
No full textField observations on the influence of site and male quality on choice by the female river bullhead (Colitis gobio) are reported. Females appeared to choose males of large size, and apparently they preferred to spawn with males whose nests contained eggs
Abnormal hermaphroditism in Gambusia affinis holbrooki from a hot spring of north-eastern Italy
No full textExtended breeding season in the marbled goby, Pomatoschistus marmoratus (Teleostei: Gobiidae), in the Venetian Lagoon
No full textLife cycle and reproductive biology of the marbled goby, Pomatoschistus marmoratus, was studied in the Venetian Lagoon. Lifespan was determined by reading otoliths. The maximum age recorded was 17 months, juveniles occurred in samples from July to November. Nests were found in two different periods: from the middle of April to the middle of July, and from the middle of August to the end of September. While individuals in a wide range of body size (35-62 mm total length) mated during the first spawning peak, during the second one only small individuals (28-32 mm total length), developed during the first peak, were in reproductive activity. Histological analyses showed that most of the juveniles, developed during the first spawning peak, delayed sexual maturation to the following year. Ripe females appeared to be multiple spawner, showing an asynchronous ovary, with oocytes at different stages of development. From nesting male body sizes, gonadosomatic indices, and histological analyses,..
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