Age, reproduction and fecundity of the spined loach Cobitis taenia L. (Pisces, Cobitidae) from Lake Klawój (Poland)

This is the first study concerning the features of the reproduction process of the karyologically identified spined loach C. taenia (2n=48). The histology of 71 ovaries, and gonadosomatic index (GSI) of karyologically identified spined loach Cobitis taenia L. from Lake Klawój (Northern Poland) were examined. The absolute and relative fecundity of 25 females was estimated by gravimetric method. The age of fish was determined according to the annual increments of otholits. The spawning of C. taenia from Lake Klawój took place from May to July, at a water temperature exceeding 18.5 degrees C. The GSI values at the beginning of the reproduction period ranged from 7 to 19%. The average absolute fecundity of females was 2078 eggs, with the number ranging from 869 to 3371 eggs. High individual variability in the gonad histology and the GSI values during the reproductive period was observed. Such variability could be the result of beginning the reproduction process in the fish at various times and, probably, due to the various numbers of batches laid and various numbers of eggs per batch.     

Genetic structure of a diploid-polyploid complex of the spined loach Cobitis taenia (Cypriniformes: Cobitidae) from the middle Dnieper bassin

Biochemical genetic typing and cytometry showed that polyploid females account for 87% of the spined loach Cobitis taenia population from the middle Dnieper basin. The polyploidy series included triploids, tetraploids, and, possibly, a few pentaploids. A characteristic feature of the genetic structure of polyploids was that their genetic variation was due to the clonal variation in the haploid portion of the genome originating from Cobitis sp. and to polymorphism of the diploid portion originating from C. taenia. The results are discussed with regard to comparative evolution of alloploid complexes in fish and terrestrial vertebrates.     

In vitro maturation,fertilization and development of domestic cat oocytes recovered from ovaries collected at three stages of the reproductive cycle

This study was conducted to examine the effect of the donor cat's reproductive cycle stage on in vitro maturation (IVM), in vitro fertilization (IVF), and in vitro development of oocytes recovered from ovaries that were collected and stored at 35 degrees C for a short period (1-6 h). Based on the presence or absence of follicles and corpora lutea, the ovarian pairs collected were classified into inactive, follicular, or luteal stages. Nuclear status of 161 cumulus-oocyte complexes (COCs) were examined immediately after recovery; 91.3% of the oocytes were found to be at the immature germinal vesicle (GV) stage, and 3.7% of the oocytes were at metaphase II (MII) stage. The percentage of the oocytes at the GV stage was significantly lower in the follicular stage than in the inactive stage (P < 0.01). Of the oocytes from the follicular stage, 9.1% were at MII stage. After culture for 24 h, however, the proportions of oocytes that reached metaphase I and MII were not different among the reproductive cycle stages of the ovaries collected (P > 0.05). After co-incubation with sperm, 63.1% of oocytes were fertilized, but there were no significant differences among the reproductive cycle stages of the ovaries with respect to the proportions of normal and polyspermic fertilization. However, the number of oocytes reaching cleavage stage and development to the morula and blastocyst stages from follicular stage ovaries were significantly lower (P < 0.05) than those obtained from inactive and luteal stage ovaries. These results indicate that the reproductive cycle stage of donor cat ovaries, stored at 35 degrees C, has no apparent effects on the frequencies of maturation and fertilization of oocytes, but influences developmental competence of the oocytes following IVM or IVF.     

Histological investigation on the ovarian cycle of the bluefin tuna in the western and central Mediterranean

The histological analysis of eastern Atlantic bluefin tuna Thunnus thynnus ovaries caught from February to September 1999–2000, made it possible to distinguish the presence of seven oocyte developmental stages and allowed the characterization of six time-dependent ovary maturity stages. The ovaries of mature (fork length, L _F ≥ 110 cm) bluefin tuna were non-active from August (spent period) to March (quiescent period) when they contained only perinucleolar-stage oocytes. Ovary development started in April to early May (recrudescent period) with the appearance of oocytes at the lipid stage. Vitellogenesis appeared in mid-May (ripening period) and post-vitellogenesis occurred in late May to mid-June (pre-spawning period). In late June to early July, hydrated oocytes, a sign of imminent spawning, were found only in specimens caught in Balearic waters. Females ranging between 100 and 110 cm L _F, captured during the recrudescent and ripening periods, had the largest oocytes at the lipid stage, most of which were degenerating. An extensive vitellogenic atresia was observed in the ovaries of five females caught during the spawning period in non-spawning areas.     

Evolutionary history of asexual hybrid loaches (Cobitis: Teleostei) inferred from phylogenetic analysis of mitochondrial DNA variation

Reconstruction of the evolutionary history of asexual lineages undermines their suitability as models for the studies of evolutionary consequences of sexual reproduction. Using molecular tools we addressed the origin, age and maternal ancestry of diploid and triploid asexual lineages arisen through the hybridization between spiny loaches Cobitis elongatoides, C. taenia and C. tanaitica. Reconstructions of the phylogenetic relationships among mitochondrial DNA (mtDNA) haplotypes, revealed by sequence analyses, suggest that both hybrid complexes (C. elongatoides-taenia and C. elongatoides-tanaitica) contained several asexual lineages of independent origin. Cobitis elongatoides was the exclusive maternal ancestor of all the C. elongatoides-tanaitica hybrids, whereas within the C. elongatoides-taenia complex, hybridization was reciprocal. In both complexes the low haplotype divergences were consistent with a recent origin of asexual lineages. Combined mtDNA and allozyme data suggest that the triploids arose through the incorporation of a haploid sperm genome into unreduced ova produced by diploid hybrids.     

Genetic diversity, origin and patterns of geographic distribution of polyploid spiny loach (Cypriniformes, Cobitidae, Cobitis) in Ukraine

Only 16 biotypes from 28 possible ones, which could be generated during hybridization of C. elongatoides, on the one hand, and representatives of superspecies C. taenia s. lato (C. taenia, C. tanaitica, C. species-1), on the other hand, were discovered in water areas of Ukraine. Furthermore. two biotypes, presumably C. aff. melanoleuca-tanaitica, were discovered in the north-western regions. Polyploids have compounded 65% of investigated individuals of Cobitis genus, the average quantity of males has compounded less than 1% and it was equal among triploids and tetraploids. Absence of amphidiploids and also lack of sufficiently large number of individuals with recombined genotype and abnormal electrophoretic spectra should be stressed. Two loci of polyploid biotypes formation are marked out: southern (the Lower Danube) and northern (the Upper Danube, Oder and Rhine). C. taenia and non-specified C. species, typical of the north-western basins of Ukraine, participate in formation of polyploids in the last mentioned river alongside with C. elongatoides and C. tanaitica. It is established that in spite of clearly evident expansion capacity, so-called southern biotypes (C. 2 (3) elongatoides-tanaitica, C. elongatoides--2 (3) tanaitica) in comparison with the northern ones, which genome includes chromosomal complement C. taenia or C. species-1, are sharply limited in their spread to the East. The reason of such a situation is unbalanced gynogenetic crossing between females of the southern biotypes and C. taenia males, accompanied by introgressions, genetic instability and reduced posterity viability.     

Ice age cloning--comparison of the Quaternary evolutionary histories of sexual and clonal forms of spiny loaches (Cobitis; Teleostei) using the analysis of mitochondrial DNA variation

Recent advances in population history reconstruction offered a powerful tool for comparisons of the abilities of sexual and clonal forms to respond to Quaternary climatic oscillations, ultimately leading to inferences about the advantages and disadvantages of a given mode of reproduction. We reconstructed the Quaternary historical biogeography of the sexual parental species and clonal hybrid lineages within the Europe-wide hybrid complex of Cobitis spiny loaches. Cobitis elongatoides and Cobitis taenia recolonizing Europe from separated refuges met in central Europe and the Pontic region giving rise to hybrid lineages during the Holocene. Cobitis elongatoides due to its long-term reproductive contact with the remaining parental species of the complex--C. tanaitica and C. spec.--gave rise to two clonal hybrid lineages probably during the last interglacial or even earlier, which survived the Würmian glaciation with C. elongatoides. These lineages followed C. elongatoides postglacial expansion and probably decreased its dispersal rate. Our data indicate the frequent origins of asexuality irrespective of the parental populations involved and the comparable dispersal potential of diploid and triploid lineages.     

Morphology of the female reproductive system and reproductive cycle of the mangrove land crab Ucides cordatus (L.) in the Baía de Antonina,Paraná, Brazil

Ucides cordatus is a species of considerable ecological and socioeconomic importance. The goal of this study is to contribute to the understanding of the reproduction biology of this species by describing the macroscopic anatomy, the histology of the female reproductive system and the reproductive cycle of U. cordatus. A total of 367 females were obtained from October of 2002 to March of 2005 during monthly collections in the Baía de Antonina, Paraná, Brazil. Specimens were submitted to necropsy and their reproductive systems (ovary and spermathecae) were analysed histologically. Permanent slides were stained with Harris' hematoxylin and eosin, Mallory's trichromic and the periodic acid‐Schiff reaction. Ovarian analysis allowed for the determination of five developmental stages based on the prevalence of oocytes in different phases of vitellogenesis. During stage V, when ovaries recover from spawning, the presence of oocytes in advanced stages of vitellogenesis was detected, suggesting that there could be more than one spawning in a single reproductive period. Females in stage IV were most common in the spring (November through February), whereas females with their egg mass exposed were most frequent from November through March. The reproductive period of U. cordatus in mangroves of the study region occurred from October to March. The reproductive events observed in the present study suggest that spermatophores acquired during copulation, which takes place during the ‘andada’, are only used in the reproductive period of the following year.     

Feeding habits and diet in two populations of spined loach, Cobitis taenia (L.)

SUMMARY. The feeding habits of Cobitis taenia were studied by means of monthly samples taken over a 2-year period, October 1972-October 1974, from two sites, one on the River Great Ouse at Newport Pagnell and the other at some neighbouring gravel pits. Dietury components, seasonal variation in these components, and seasonal and diurnal variation in feeding intensity were examined. The ecological niche of the food items and their size range are discussed, since both these factors appeared important in governing the micro-habitat of the fish.
The feeding activity followed a seasonal cycle with little or no feeding in the winter and a high level of feeding activity in mid-summer.
The diet showed a predominance of small food items, such as chydorids. copepods and rhizopods. These items varied in occurrence during the feeding period which appeared to be related to their own abundance, pointing to non-seleclive feeding by the fish. The small size and benthic habits of the food items, many of which are closely associated with surface layers of mud and weed, indicated a preference by Cobitis taenia (L.) for feeding in this type ot habitat and on this type of food, in contrast to the stone loach. Noemacheilus barbatulus (L.), which is believed to inhabit stony areas and take larger food items.     

European colonization by the spined loach (Cobitis taenia) from Ponto-Caspian refugia based on mitochondrial DNA variation

In the last 20 years, new species, asexual reproduction, polyploidy and hybridization have all been reported within the genus Cobitis. An understanding of the current distribution and baseline phylogeographical history of 'true' nonhybrid Cobitis species is crucial in order to unravel these discoveries. In the present work, we investigated the phylogeography of the spined loach, Cobitis taenia, using 1126 bp of the mitochondrial cytochrome b gene from 174 individuals collected at 47 sites. In total, 51 haplotypes that differed at 49 positions (4.35%) were detected. We deduce that C. taenia survived European glaciations in at least three refugees in the Ponto-Caspian area. Two of these refugees each provided a major lineage that recolonized Europe in separate directions: one westward to England and the other spreading north into Russia before moving west. A third (minor) lineage that contributed little to the recolonization of Europe was also revealed--remaining near its Black Sea refuge. However, more recent history was difficult to resolve with colonization from a more western refugium during the last glacial maximum (LGM) a distinct possibility. Nested clade analysis indicates a pattern of restricted gene flow with isolation by distance at the first two levels and overall. Unlike many other European freshwater fish species, the Danube is not part of the current distribution of C. taenia, nor was it used as either a refuge or a source of colonization of Europe. Low genetic diversity within C. taenia suggests that its colonization of Europe is relatively recent. Demographic analyses revealed a history of recent expansion and isolation by distance.     

Development of nine polymorphic microsatellite loci in the spined loach, Cobitis taenia, and cross-species amplification in the related species C. elongatoides, C. taurica and C. tanaitica

Nine polymorphic microsatellite loci were developed for the spined loach, Cobitis taenia (Teleostei: Cobitidae). The loci were validated using 50 individuals from a population in Belgium. Moderate to high levels of polymorphism were detected (two to 11 alleles). In addition, most markers amplified successfully in three closely related taxa that are known to hybridize with C. taenia: C. elongatoides, C. taurica and C. tanaitica. Some of the loci are most likely diagnostic among species. These markers will be valuable for the study of the historical and contemporary interactions within C. taenia and the Cobitis species complex.     

Biochemical genetic evidence for a hybrid origin of spined loach, Cobitis taenia taenia, in Japan

Starch gel electrophoresis and isoelectric focusing were performed on sarcoplasmic proteins from three taxa of cobitid fish in Japan, Cobitis biwae , C. taenia striata and C. l. taenia . These taxa are hardly distinguishable from each other by external appearance or morphological characters. Electrophoretic patterns of sarcoplasmic proteins from white muscle suggested fixed allelic differences between C. biwae and C. t. striata at two protein-coding loci (parvalbumin and creatine kinase). The third taxon, C. t. taenia , showed composite banding patterns with respect to the above two proteins, suggesting C. t, taenia originated from hybridization between C. biwae and C, t. striata . Previously, C. t, taenia and C. t. striata were believed to have shared a common ancestor subsequent to their divergence from C. biwae .     

Reproduction of spined loach, Cobitis taenia, (Cypriniformes; Cobitidae) under laboratory conditions

A simple and reliable method is described for breeding spined loach, Cobitis taenia Linnaeus, 1758, under laboratory conditions. Three 40 L aquaria were each provided with a thick tuft of moss placed on top of a gauze-covered plastic box to serve as a spawning site. Ovoposition always occurred in the most densely available vegetation. The nonadhesive eggs fell through the gauze into the box. The spined loach is a fractional spawner releasing eggs in 14–18 batches at intervals of 2–23 (median 6) days. The total number of eggs per female was 2905–4282 during the reproductive season of 101–120 days. Yolks measured 1.14 ± 0.07 mm and eggs were 2.54 ± 0.22 mm in diameter. Total larval length was 5.03 ± 0.34 mm at hatching and 6.77 ± 0.34 mm at the beginning of exogenous feeding. The method allowed the rearing of numerous young for conservation measures and experimental investigations.     

The Genetic Structure of the Diploid–Polyploid Complex of the Spined Loach Cobitis taenia (Cypriniformes: Cobitidae) from the Middle Dnieper Basin

Biochemical genetic typing and cytometry showed that polyploid females account for 87% of the spined loachCobitis taeniapopulation from the middle Dnieper basin. The polyploidy series included triploids, tetraploids, and, possibly, a few pentaploids. A characteristic feature of the genetic structure of polyploids was that their genetic variation was due to the clonal variation in the haploid portion of the genome originating from Cobitis sp. and to polymorphism of the diploid portion originating fromC. taenia. The results are discussed with regard to comparative evolution of alloploid complexes in fish and terrestrial vertebrates.     

Maturity, oocyte dynamics and fecundity of the roundnose grenadier from the Rockall Trough

The reproductive biology of roundnose grenadier Coryphaenoides rupestris was investigated against a background of increasing commercial exploitation. Samples were taken from surveys carried out in Rockall Trough between 1993 and 1995. An eight-point maturity scale was developed based on both visual inspection of the ovaries and histological screening. The various stages of development of roundnose grenadier oocytes were described and the relative proportion of oocyte types and their respective size range in each maturity stage were investigated. The dynamic organization of the ovary indicated a determinate maturation cycle in this species. Population spawning appears to be prolonged, extending from July to at least November. However, data were insufficient to clarify individual spawning duration. The potential fecundity of 29 mature fish ranged from 11 083-55 175 (63-95 cm total length). The results were very similar to previous values from the North Atlantic. The reproductive strategy of the roundnose grenadier is discussed in the light of the current commercial exploitation of the Species.     

Phylogenetic relationships and historical biogeography of spined loaches (Cobitidae, Cobitis and Sabanejewia) as indicated by variability of mitochondrial DNA

For sequence analysis of the 12S rRNA gene in spined loaches, specimens of the following taxa were used: Sabanejewia balcanica, Cobitis paludica, C. bilineata, C. fahireae, C. elazigensis, C. elongata , two different sub-populations of C. taenia and four different sub-populations of C. turcica . Phylogenetic relationships among taxa were estimated using parsimony, neighbor-joining, and maximum likelihood algorithms. The calculation of the transition-tranversion ratio indicated that the taxa analysed were rather distantly related. Our analyses using the genus Sabanejewia as an outgroup suggest that C. bilineata is separated from the subgenus Cobitis sensu stricto and placed together with C. elongata as basal to all other species of the genus Cobitis . Support for the placement of C. paludica as basal to both the subgenera Bicanestrinia and Cobitis s. s. (without C. bilineata ) is given by outcomes from three independent methods of phylogenetic reconstruction. A sister-taxon relationship for the subgenera Bicanestrinia and Cobitis s. s. without C. bilineata was consistently found. C. elazigensis was closely related to the population of C. turcica from Lake Beysehir in Turkey. Both formed a sister-group to the remaining populations of C. turcica , while C. fahireae was basal to C. taenia . A molecular clock was calculated based on sequence divergence values and palaeogeographical data. This suggests that different historical colonization routes must have been used by different clades of spined loaches.     

Seasonal prevalence and intensity of follicular atresia in Baltic cod Gadus morhua callarias L.

In the present study, 307 ovaries of eastern Baltic cod Gadus morhua callarias sampled during the prespawning and spawning season 2000 were analysed histologically to estimate the seasonal prevalence and intensity of atresia. The number of atretic oocytes per ovary was estimated using a combination of the physical disector method and volume fraction (Delesse principle). Atretic oocytes were observed in 32% of the ovaries. Prevalence of atresia was independent of female size, but increased significantly with declining female condition from prespawning and through the spawning stages. The relative intensity of atresia, i.e. number of atretic oocytes in relation to normally developed vitellogenic oocytes, was low amounting to 1·4% on average. Similar to prevalence, relative intensity of atresia differed significantly between maturity stages and increased with decreasing female condition. The population egg loss due to atresia amounted to 4·6% indicating that Baltic cod was performing close to maximum productivity, i.e. potential egg production.     

Preliminary observations on different reproduction strategies in the bullhead (Cottus gobio L.) in northern and southern England

The size distribution and numbers of oocytes were examined in samples of ovaries from two sites and in fish in tanks whose past spawning activities were known. In an upland stream in northern England Cottus gobio would seem to be an annual spawner, maturing a single batch of eggs each year. In a more productive stream in southern England, where the reproductive life is short, fish mature and lay a succession of batches of eggs during a long spawning season. The physiological and ecological implications of these characteristics are discussed.     

Reproductive biology of little tunny,Euthynnus alletteratus (Rafinesque), from the north‐eastern Mediterranean Sea

The study aimed at identifying spawning season and potential year classes reaching maturity in the north‐eastern Mediterranean, an area where little information on tuna spawning is available. Gonads (60 ovaries and 36 testis) were obtained from little tunny, Euthynnus alletteratus. The fish were caught between November 2002 and May 2005 in the north‐eastern Mediterranean Sea. The ovaries were histologically examined to determine the reproductive conditions and developmental stages of oocytes. Seven females sampled in May, July, and August were sexually mature (stage III or IV). The gonado‐somatic index (GSI) indicated that spawning generally occurred between May and September. The most intensive spawning period was observed between July and August. The sex ratio was calculated as 1 : 1.7 M/F (total n = 96). The length and weight relationship was calculated with W = 0.038 L^2.77, ages from year I to IV being included in the analysis.