Gonad Length Research Articles

Sexual differentiation in the spiny softshell turtle (Apalone spinifera), a species with genetic sex determination.

It is hypothesized on the basis of sex determination theory that species exhibiting genetic sex determination (GSD) may undergo sexual differentiation earlier in development than species with environmental sex determination (ESD). Most turtle species exhibit a form of ESD known as temperature-dependent sex determination (TSD), and in such species the chronology of sex differentiation is well studied. Apalone spinifera is a species of softshell turtle (Trionychidae) that exhibits GSD. We studied sexual differentiation in this species in order to facilitate comparison to TSD species. Eggs were incubated at two different temperatures and embryos were harvested at various stages of mid to late development. Gonad length was measured with image analysis software, then prepared histologically. Indifferent gonads have differentiated in stage 19 embryos. Histological details of gonadogenesis follow the same pattern as described for other reptiles. Regression of the male paramesonephric duct closely follows testicular differentiation. Gonad lengths are longer at the warmer incubation temperature, and ovaries are generally longer than testes at each stage and for each temperature. Although sexual differentiation takes place at about the same stage as in other turtles with TSD (18-20), in A. spinifera this differentiation is irreversible at this stage, while in some of the TSD species sex is reversible until about stage 22. This immutable, definitive sexual differentiation may support the hypothesis of an accelerated chronology of sex differentiation for this species. We also note that sexual dichromatism at hatching is known in this species and may provide additional evidence of early differentiation. J. Exp. Zool. 290:190-200, 2001.

Seasonal changes in feeding, gonad development and lipid stores in Calanusfinmarchicus and C . hyperboreus from Malangen, northern Norway

Seasonal dynamics of feeding activity, oil sac volume, gonad development, sex ratio and spawning periods in the two sibling species Calanusfinmarchicus and C. hyperboreus, the key zooplankton copepod organisms throughout the northern Atlantic waters, were studied simultaneously in Malangen, northern Norway, during 1992. We were also tracing differences in surface- and deep-dwelling components of these populations in terms of oil sac volume and gonad development during the time period when the G1 is preparing for a subsequent generation (G2) or hibernation. The main difference in the life cycle strategies of these species is the earlier maturation and spawning of C. hyperboreus. No feeding activity in either of the two species was found in February, but both commenced feeding in March, prior to the spring phytoplankton peak. The larger copepod, C. hyperboreus, had a more intensive energy deposition than C. finmarchicus. The period of active feeding was much shorter for the former species, only from March through July in copepodite stages CIV and CV, and even less in females – March and April. Basically, a similar pattern of seasonal changes in gonad length and lipids was observed in the two species. In June, oil sacs in the surface- and deep-dwelling specimens were about equal, during the rest of the year, lipids in the deep CVs exceeded those in the surface. We propose that as copepods accumulated sufficient lipid reserves, they started to descend, while others, containing less fat, stayed in the upper layers feeding. The mean length of the gonads in the surface-dwelling copepods was consistently less than in their deep counterparts from October to February, so that gonad development at the expense of accumulated reserves during resting stage was confirmed. C. finmarchicus males were found in considerable numbers only in February and March, and were only occasionally found in the upper layers (0–100 m), while adult male C. hyperboreus were present from October to March, but were never found in the surface layers. The differences in life cycle timing among the two species are discussed in relation to tradeoffs with regard to foraging strategies, generation numbers, bioenergetics and predator avoidance.

Morphology of the gonads in the reproductive cycle of Synodontis schall (Pisces: Mochokidae) in Asa Lake Ilorin, Nigeria

The gonads of specimens of Synodontis schall (N = 813) in Asa lake were observed for morphological changes for 24 months. The female population (54.6%) was more than the male (45.4%) and all the gonad stages were observed in both sexes. The juveniles constituted (12.7%) of the total population. Gonad and body weight relationship in female (0.54) was positively correlated. Similarly the gonad and body length relationship in male (0.77) and female (0.68) were positively correlated. The months of July and August were the peak spawning periods during which the littoral zone became flooded due to the rains. The male and female S. schall in the lake were ready for spawning about the same time hence there was the tendency for a high percentage of the male population pairing with the female for fertilization. Fecundity was high (7,910 to 64, 450 eggs) and the mean eggs diameter at the spawning stage was 1.03 mm. There is need for enhanced monitoring actives in order to enforce fishing rules and regulation around the water body to protect gravid specimen from being over exploited. The advantages of higher female population were discussed. JOURNAL OF AQUATIC SCIENCES Volume 16, Number 2, October 2001, pp. 105-110 KEY WORDS: Synodontis schall, gonads, fecundity, spawning

Rhabditis (Rhabditis) Necromena Sp. N. (Nematoda: Rhabditidae) From South Australian Diplopoda With Notes On Its Siblings R. Myriophila Poinar, 1986 and R. Ca Uller Yi Maupas, 1919

Based on a laboratory culture, R. necromena from Diplopoda in South Australia is described. Is is a self-fertilizing hermaphrodite with males occurring rarely. It can be distinguishcd from other Rhabditis species by its long reflexion of the testis (about 43-56% of gonad length). Otherwise it differs slightly morphologically from other members of the Insectivora-group. A critical comparison is made in particular to R. myriophila Poinar, 1986, originally cultured from millipedes as well. R. necromena is shown to be of economic importance as a biological control agent against the introduced millipede Ommatoiulus moreletii in South Australia.

Ecological significance of individual variability in copepod bioenergetics

High interstage variability in body length and mass, reproductive state, and metabolic activity is characteristic of copepod populations from the Barents Sea and coastal waters in Sweden and Norway. The dry weight of a given copepodite stage, sampled at a given time from a homogeneous water mass, may vary by a factor of 4–5 between extreme individuals, protein and particularly lipid content being even more variable. Similarly, high variability in gut fullness and grazing rate within defined copepodite stages typically occurs at all times of the year, both when measured as in situ rate or experimentally determined rate, using homogeneous food suspensions. In accordance with this, maturation state (measured as length of gonads) and spawning (measured as rate of egg production over 24 h) are highly variable factors at the individual level. Since all these factors also influence the metabolic rate of the animals the respiratory rate (measured as ETS activity) of comparable individuals may vary by a factor of 5 or more. The results indicate that high individual variability in size and activity parameters is universal. This can not be explained by existing models of feeding behaviour, growth and development, and calls for new models, in which the nutritional history of the individual may play an important role.

Potato rot nematode,Ditylenchus destructor(Nematoda: Tylenchidae), infecting hops in New Zealand

Abstract The potato rot nematode, Ditylenchus destructor Thorne, 1945, is recorded for the first time in New Zealand. It was found infecting the roots of hop plants (Humulus lupulus L.) on two properties in the Motueka district, South Island. Distribution was patchy on both properties, but damage to plants was severe. The nematode readily established on laboratory cultures of the fungi Alternaria tenuis and A. solani, and on tubers and root systems of the potato. Specimens from the field were smaller than those reared in the laboratory, and gonadal length was shorter.

Physiological Attributes of Reproductively Active and Dormant Mexican Bean Beetles 12

Measurements of several physiological parameters of adult Mexican bean beetles, Epilachna varivestis Mulsant (Coleoptera: Coccinellidae), throughout the season indicate a reproductive diapause. Both sexes of diapausing Mexican bean beetles had an increased dry weight, enlarged fat bodies, reduced inactive gonads, reduced respiration rates and lower water contents than reproductively active beetles. The type of host plant (i.e., lima bean vs soybean) influenced values of certain parameters, e.g., dry weight, fat body index and gonad length of male beetles were significantly higher for individuals reared on lima bean rather than soybean.

The effects of population density on fecundity and fertility in the guppy, Poecilia reticulata (Peters)

Experiments were performed to examine the influence of population density on the fecundity and fertility in the guppy, Poecilia reticulata. The frequency of females with only ova or with different combinations of reproductive units and developmental stages in the ovary was significantly different between different densities but not between females with one and two gestations from the same population density. The ovarian width of females with one gestation from the lowest density was significantly larger than in the highest population density. Gonad length and height and ovarian volume of females with two gestation periods were larger in the lowest compared with the highest density. After one gestation, females at the lowest population level had greater ovarian length, height, gonad weight, width and volume compared with those from the higher density. Ovarian length, height and volume and gonad weight were also significantly greater among females of two gestation periods in the lowest than in the second lowest density. The average gonadosomatic ratio was highest in the lowest population density. A significant correlation was found between gonad volume and total body weight and between gonad volume and ovarian weight of females at every population level. This was also the case when ovarian weight vs. total body weight was examined in each population density. Only at the lowest population level was there a significant correlation between fecundity and total body length and between fertility and body length. A significant relationship was also found between gonad volume and total body length and between gonad weight and body length at the same population level. No significant difference of fecundity and ovum size was found between females of one and two gestation periods from the same density. Fecundity and fertility were significantly higher among females of one and two gestation periods from the lowest than from the highest density.

Embryonic and Post-Embryonic Development of Cylindrocorpus Longis'Toma (Nematoda: Cylindrocorporidae)

Embryonic development in C. longistoma follows the general pattern of other nematode species. Embryonic development lasts 30-34 hours. The relationship between larval movement and the hatching mechanism is discussed. The proportional changes which occur in gross body form during postembryogenesis are studied through a biometrical analysis of morphometric and allometric characters. The greatest increase in body length occurs during the third stage, coinciding with the greatest increase in gonad length. Due to lack of allometry between pairs of morphometric characters, 'a', 'b', and 'c' ratios are unacceptable for taxonomic purposes pertaining to this species. Growth of the reproductive system is relatively stable and the use of 'V' and 'T' for taxonomic purposes is acceptable. The genital primordium of first- and second-stage larvae consists of two germinal and two somatic cells. Sexual differences are discernible during the second molt by the presence or absence of specialized ventral chord nuclei and differential development of the genital primordium. Specialized ventral chord nuclei take part in the formation of the vagina. A specialized somatic nucleus separates from the uterine wall and initiates the vaginal primordium. Specialized ventral chord nuclei are absent in male larvae. During the third molt the anterior portion of the male gonad turns posteriad and grows along the ventral side of the body. Primordia of spicules and gubernaculum begin development during the third molt and male accessory structures are completed during the final molt. Nuclear divisions in the reproductive system occur throughout molts and stages.

Effects of X-rays on the spermaries and ovaries of Xenopus tadpoles.

The results show that irradiation affects both the size of the gonads and the number of germ cells they contain. At stage 64, gonads from irradiated animals were smaller than those from unirradiated ones. The reduced length and thickness of gonads of the test animals were probably due to cell killing. The variation in size of gonads of different test animals and the difference between the left and right ovary of a single individual are indicative of the degree of radiation sensitivity.

The Cystic Stage of Octomyomermis itascensis (Nematoda: Mermithidae) in Chironomus plumosus (L.) (Diptera)

Surveys of Chironomous plumosus larvae in Lake Itasca, Minnesota, in the summers of 1959 and 1961 document the existence of a cystic larval stage of Octomyomermis itascensis. The cysts are concentrated in the thoracic hemocoel and vary in number from 1 to 5 per insect. Each cyst contains a single juvenile nematode. Apparently the nematode reaches a given stage of development in the cyst and must excyst to continue development. Evidence is presented for the parasite origin of the cyst wall. Humoral factors of the host may play a role in excystation of the nematode. Couturier (1951) reported the presence of a capsule investing a mermithid juvenile in the development of Tunicamermis melolonthae in grubs of Melolontha melolontha in France. Couturier (1963) indicated that the preparasitic juvenile penetrates the grub and induces proliferation of host tissue around the parasite. The capsule enlarges as the nematode grows in size. The final capsule is large, irregular, and attached to the host by a stalk. This is the only record of encapsulation of mermithids as a normal developmental event. In July of 1959 an examination of 1,844 fourth-stage larvae of Chironomus plumosus from the benthos of Lake Itasca, Minnesota, revealed the presence of a small encysted nematode in 34.4% of the insects. Johnson (1963) described the adult of this form, Octomyomermis itascensis. Three other undescribed species of mermithids are known by the investigator to be present in the same host in the same habitat. One of these nematodes is imagocidal and the other two larvicidal. Early stages of the two larvicidal forms are known and do not have a cyst enclosing them. The small, round, flattened cysts of O. itascensis contain a single juvenile reaching a maximum size of 1.7 mm in length. The cysts are contiguous with muscles, fat bodies, imaginal discs, salivary glands, and other structures of the host. The cyst wall is not connected to host tissues or the juvenile. The red, transparent larvae of C. plumosus possess a head capsule, prothoracic prolegs, 12 body segments (3 thoracic, 9 abdominal), Received for publication 12 July 1973. posterior prolegs, and posterior gills. A sample of 172 infected host larvae was documented as to the number of cysts per host; 121 or 70% had one cyst, 34 or 20% had 2, 8 or 5% had 3, 7 or 4% had 4, and 2 or 1% had 5. Despite the presence of more adequate hemocoelic space posteriorly the cystic nematodes were more abundant in anterior segments. Two hundred twenty-six cysts were di tributed as follows: thoracic segment I, 51; II, 65; III, 45; abdominal segment I, 30; II, 8; III, 5; IV, 2; V, 1; VI, 1; VII, 0; VIII, 1; IX, 5; and posterior prolegs, 12. As many as three cysts have been found in one segment. No mechanical problems were observed in the insects. The acellular membrane composing the cyst wall is transparent, homogeneous, without pigmentation, and about twice the thickness of the cuticle of the nematode. The entire cyst can be readily dissected out of the host. The staining properties of the membrane resemble those of the nematode cuticle very closely. The size and structure of the cystic nematode was uniform. Measurements of six cystic juveniles indicate the following ranges: Length 1.4 to 1.7 mm, greatest diameter 87 to 97 It, stichosome length 600 to 900 u and gonad length 87 to 230 j/. The prominent structures in the cystic juvenile (Fig. 1) are the two large granular cells with oval nuclei anterior to the stichosome, the 16 linearly arranged irregular nuclei of the stichocytes, a rudimentary gonad posterior and ventral, and a trophosome occupying most of the posterior pseudocoel. The cuticular esophagus was present but could not be traced posterior to the granular cells.

Aphelenchoides Rutgersi N. Sp. (Nematoda: Aphelenchoidea), Description and Morphometrics, With Observations On a. Dactylocercus Hooper, 1958 and a. Cibolensis Riffle, 1970

The Aphelenchoides sp. studied for several years at Rutgers University, U.S.A., and formerly thought to be A. sacchari or A. dactylocercus is described as Aphelenchoides rutgersi n. sp. Some variants resemble A. cibolensis, the male of which is also described. The body length, gonad length and tail shape of females, the progeny of single females cultured on Pyrenochaeta terrestris or Botrytis cinerea, vary greatly according to type and age of culture. Small but consistent differences distinguish A. rutgersi from the above species. The female has three lateral incisures, a short post-vulval sac about one and a half vulval body-widths long and a conoid tail about three anal body-widths long. The shape of the tail terminus is variable but usually has a short ventral mucro. The stylet is 10 μm long. Males are very rare.

Reproductive Biology of the Mola Carplet <i>Amblypharyngodon mola</i> (Hamilton) (Cypriniformes: Cyprinidae) from Netrakona Water

Some aspects of the reproductive biology viz. sex ratio, fecundity and reproductive periodicity of Amblypharyngodon mola were studied during March 2004 through February 2005 in Netrakona. Sex ratio was found to be 1:2.03. Fecundity varied from 1,291 to 12,797 with a mean value 5,751.46 ± 3,321.73 eggs. The relationships between Fecundity (F) and Total Length (TL), Standard Length (SL), Total Weight (TW), Gonadal length (GL) and Gonadal Weight (GW) were calculated and found to be highly significant. The mean of ova diameter was 1.4 ± 0.35mm. Different methods used to study the reproductive periodicity showed that the periodicity of A. mola starts from March and continues up to August with a peak in May. Key words: Reproductive biology, Reproductive periodicity, Amblypharyngodon mola. DOI: 10.3329/bjsir.v44i3.4414 Bangladesh J. Sci. Ind. Res. 44(3), 377-379, 2009