Pre-adult Instars Research Articles

Life Cycle of a New Bosminid Cladocera: Bosmina (Bosmina) tripurae (Korinek, Saha, and Bhattacharya, 1999)

Bosmina tripurae was first reported as a new species of subgenus Sinobosmina (Cladocera, Bosmina) in 1999 in Tripura, India. However, no further research work was done on this species. The present investigation has been carried out to provide the basic knowledge of life history aspects of B. tripurae on its length increment, instar number, instar duration, fecundity, hatching success, life span and embryonic development. The species was cultured in the laboratory for ten generations. The experiment was conducted under controlled conditions at 20 ± 0.29 °C and animals were fed with Chlorella sp. (2 × 104 cells ml−1). Parthenogenetic female showed three preadult and ten adult instar stages. Female produced around 22 eggs in its total life span of about 25 days. The length of first instar juvenile was 261 μm and the last adult instar was 590 μm. Duration of preadult instars ranged from 1.05 to 1.27 days whereas adult instars ranged from 1.93 to 2.30 days. Age at first reproduction was about 3.65 days. The species showed maximum ten clutches in the present study however, the sixth clutch produced and released significantly (P < 0.05) higher number of both eggs and neonates as compared to other clutches. In laboratory condition, about 89 % eggs were hatched out into neonates. The gestation period of the embryo was around 2.03 days with 12 developmental stages in the brood pouch of the mother.

The influence of cropping rotations and soil cultivation practice on the population ecology of carabids (Coleoptera: Carabidae) in arable land

Summary Use is made of detailed information on the lifecycles and phenology of carabid beetles in arable fields to analyse pitfall catches and seek evidence for the hypothesis that pre-adult instars in the soil are susceptible to soil tillage operations at particular times of the year. Strictly autumn-breeding species were trapped less frequently at the time of adult emergence in early summer when soil cultivation was done for crop establishment in late spring compared with uncultivated or autumn-sown fields. Analysis of data for species with distinct reproductive cohorts in autumn and spring produced evidence that the larval over-wintering cohort, but not the adult hibernating cohort, was similarly affected by soil cultivation. No evidence was found to suggest that cultivation at the time of egg or early larval instars directly influences the survival of populations and it is concluded that probably only cultivation-induced mortality of late larval and pupal instars has a significant population effect. The longer-term survival of most carabids in arable fields probably depends on either flexibility in their time of breeding or, for strictly autumn-breeding species, on a well-developed phase of post-emergence dispersal by adult beetles. It is concluded that soil cultivation directly impacts on the incidence of larval over-wintering populations and limits the range of lifecycles and phenologies that are possible in arable land. Such constraints may explain the phenomenon of long-term population robustness that is often exhibited by carabid populations in arable crops when they are subject to non-target pesticide effects.

The effect of size at birth, maturation threshold and genetic differences on the life-history of Daphnia magna.

Life-history traits of 101 clones from two populations of Daphnia magna were measured under controlled environmental conditions in the laboratory. Some individuals had four juvenile instars, others had five. This depended on their length at birth and on the population they came from. Females in the group with five juvenile instars were smaller at birth but larger and older at maturity than those with four juvenile instars. Within groups of females with equal numbers of preadult instars (instar groups) age and size at maturity increased with size at birth. This relationship differed significantly among instar groups for both age and size at maturity. Significant differences in age and size at maturity between two populations became non-significant when size at birth was used as a covariable in AN-COVA. Within populations, size at birth depended on the clone and on the parity of the clutch. First-clutch offspring were considerably smaller than those from later clutches. The results suggest that variability in life-history traits is common within and between clones, but that most of this variation can be accounted for by size at birth and the number of pre-adult instars.

Influence of various concentrations of rice bran with tap water and pond water on the longevity, egg production and body size ofDaphnia similis Claus (Crustacea: Cladocera)

Daphnia similis Claus is a tropicopolitan and dominant species of temporary ponds of South India Laboratory cultures were made to study the longevity, preadult instars, egg production and growth using different concentrations of rice bran, an agro-industrial waste which is available readily and cheaply. Rice bran dissolved in pond water resulted not only in higher fecundity but also in an additional increase in size and as such rice bran may form an ideal nutrient medium for mass production of daphnids. Egg production is 6 times higher and growth is two fold greater in cultures with rice bran in pond water than in tap water with rice bran. From the present study it is hoped that, the use of rice bran in mass culture ofDaphnia similis will be profitable.

Laboratory culture ofDiaphanosoma Senegal Gauthier, (Crustacea, Cladocera) from south India

Laboratory studies on growth and reproduction of Diaphanosoma Senegal Gauthier show that this species has a life span of 18–7 days. Three preadult and sixteen adult instars were recorded at a temperature range of 28–30°C. Maximum body size is attained at the end of its life-cycle and the growth increment is more during preadult instars. The present observations are compared with other laboratory studies on tropical South Indian cladocerans.

Chronic effects of selenite-selenium onDaphnia pulex

Acute and chronic toxicity tests with selenite-selenium (selenite-Se) were conducted onDaphnia pulex. The 48-hr static LC50 was 3.87 mg/L selenite-Se. The sublethal effects of 0.2, 0.4, 0.6, and 0.8 mg/L selenite-Se on the survival, growth, and reproduction ofD. pulex were monitored for 28 days, and the results were analyzed statistically by brood. Appreciable mortality occurred only at 0.8 mg/L Se. Growth, as measured by body length, was depressed at the highest concentration during the preadult instars and was slightly stimulated during the later adult instars. Number of live young per brood was depressed at 0.4, 0.6, and 0.8 mg/L Se during the early broods and apparently was stimulated in later broods. Reproductive dysfunction (i.e., dead young, deteriorated eggs, and abortions) was significant only at higher concentrations in the early broods. Results of the chronic study based on the brood method of analysis indicated safe concentrations between 0.2 and 0.4 mg/L selenite (Se).

Patterns of Variation in The Prosome Length of Overwintering Stage V Copepodites of Calanus Finmarchicus in The Firth of Clyde

In attributing variations in growth and metabolism within a population to environmental fluctuations, and in interpreting the biological response to environmental fluctuations, it is important to recognize the variations that are intrinsic to the population or species. Consequently, it is common practice in studies on the growth and metabolism of calanoid copepods to separate instars and, in the case of adults, males and females when analysing measurements. Although studies on calanoids, in particular species of Calanus and Euchaeta, have demonstrated the existence of pronounced sexual differences in parameters such as dry weight, biochemical composition and respiration rate (e.g. Comita, Marshall &amp; Orr, 1966; Marshall, 1973; Bamstedt, 1975, 1979; Gatten et al. 1979, 1980), the possibility that similar differences might occur in pre-adult instars has not been examined, this despite the fact that in many species in this group it is possible to distinguish the sex of copepodites IV and V, the two instars preceding the adult.

Multiple mimetic forms in an ant-mimicking clubionid spider.

Castianeira rica mimics about five classes of ant models. The multiple mimetic forms result from (i) sexual dimorphism, (ii) color variation in the adult female, and (iii) developmental changes in the preadult instars. A congeneric, sympatric, and nonmimetic species, Castianeira alba, acts as an evolutionary "control" for comparison.

A TIME STUDY OF EVENTS IN THE LIFE SPAN OF DAPHNIA MAGNA

Hourly observations were made on 159 Daphnia magna individually reared in manure-soil medium at 25° C. throughout their whole life span.The number of pre-adult instars varied from four to six, the most frequent number being five.The average longevity was approximately 960 hours or 17 instars.In general the duration of the instars increases with age. The pre-adult instars with the exception of the last require about a day, the final taking about 30 to 32 hours. Beginning with the first adult the instars last approximately two days and increase slightly with each instar.The number of young produced increases with each adult instar up to the fifth, followed by a decrease. The use of the number of young produced as an index of the general metabolic condition of a daphnid is analysed and believed justified.The brooding periods, i.e. the time between the deposition of eggs and their subsequent release as young, vary with the duration of the instars.The need for a more readily controllable and reproducible cultu...

GROWTH AND VARIABILITY IN DAPHNIA PULEX

Eighty-two individually reared female Daphnia pulex were observed from the time they were released from the brood chamber of their mothers until they died. Measurements of total length, carapace length, and height were made daily on each animal. The number of young released during each instar was recorded.Seventy-one animals were primiparous during the fifth instar and 9 during the sixth. Consequently the number of pre-adult instars is variable, the minimum being four.Data from the 47 animals which were primiparous during the fifth instar and which lived for twenty instars or more were used in constructing growth curves. Growth in the three dimensions studied is sigmoid. The point of inflection in all curves comes during the fourth instar, the last pre-adult.The Robertson and the Gompertz equations do not fit the data satisfactorily. This may be due to the time unit employed, which in this case is the instar.The growth increment is greatest during the fourth instar. The increments increase up to the fourth instar, then decrease gradually until the eleventh instar, after which they remain low and relatively constant.A significant negative correlation exists between initial body size and initial growth rate, also between duration of growth and final body size. Other characteristics of the growth process investigated appear to vary independently.The number of young released during the adult instars increases to a maximum at the tenth instar followed by a gradual decrease.The number of young released during any adult instar is significantly correlated with the growth increment for the instar preceding the one during which the young are released.Relative growth in the dimensions studied may be expressed satisfactorily by the equationy = bxα.No marked changes occur in the relations between total length and carapace length. Marked changes in the relations between carapace length and height and between total length and height occur at the thirteenth instar.The standard deviation and coefficient of variation of total length tend to increase somewhat during the early instars, but after the eighth instar both decrease rather steadily.Relative variability in body size, as measured by the coefficient of variation of total length, is roughly directly proportional to the logarithm of the growth rate. The existence of this relationship is ascribed largely to the mode of action of environmental factors during growth. It may perhaps also be explicable in terms of Rahn's theory of the physico-chemical origin of variability in growth rate.Size-frequency analyses of natural populations as methods of studying growth are shown to be inferior to the method using individually reared animals.

ON THE PRE‐ADULT INSTARS OF PSEUDOCOCCUS LONGISPINUS TARG., WITH SPECIAL REFERENCE TO CHARACTERS OF POSSIBLE GENERIC SIGNIFICANCE (HEM.)

Transactions of the Royal Entomological Society of LondonVolume 86, Issue 5 p. 73-84 ON THE PRE-ADULT INSTARS OF PSEUDOCOCCUS LONGISPINUS TARG., WITH SPECIAL REFERENCE TO CHARACTERS OF POSSIBLE GENERIC SIGNIFICANCE (HEM.) H. C. James B.Sc., Ph.D., H. C. James B.Sc., Ph.D. Entomological Department, Zoological Laboratory, Cambridge.Search for more papers by this author H. C. James B.Sc., Ph.D., H. C. James B.Sc., Ph.D. Entomological Department, Zoological Laboratory, Cambridge.Search for more papers by this author First published: April 1937 https://doi.org/10.1111/j.1365-2311.1937.tb00425.xCitations: 2AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume86, Issue5April 1937Pages 73-84 RelatedInformation

THE NUMBER OF PRE-ADULT INSTARS, GROWTH, RELATIVE GROWTH, AND VARIATION IN DAPHNIA MAGNA

Observations as to the number of pre-adult instars have been made on over 200 individually reared female Daphnia magna of seven clones. In all cases measurements of the total length during each instar were taken. For well over a hundred individuals measurements of carapace length and height were taken in addition to those of total length.The number of pre-adult instars varied upward from five. This variation was found in all clones tested.Growth curves have been constructed for various groups based on the number of pre-adult instars. The inflection in the growth curve of any dimension in any group coincides with the time of sexual maturity.Brooks' Law holds only for those groups which were primiparous during the sixth instar and then only approximately.Relative growth in the dimensions studied, x and y, may be expressed by the equation[See equation in the PDF file]Relative growth changes at sexual maturity, i.e., a change occurs in the values of the constants b and k.The above equation may perhaps be us...