An Experiment with Medaka, Oryzias latipes, and a Critique of the Hypothesis that Teleost Egg Size Controls Vertebral Count

1971 ◽  
Vol 28 (9) ◽  
pp. 1235-1240 ◽  
Author(s):  
C. C. Lindsey ◽  
M. Y. Ali
Keyword(s):  
Related Species ◽  
Egg Size ◽  
Oryzias Latipes ◽  
Causal Connection ◽  
Adult Size ◽  
Vertebral Number ◽  
Vertebral Count ◽  
Large Adult

In each of two sets of experiments, two female medaka, Oryzias latipes, that laid different-size eggs were crossed reciprocally with two males. Vertebral counts of the offspring differed significantly between batches, but there was no consistent correlation between egg size and vertebral count. Both the highest and lowest counts resulted from crosses with females laying large eggs. Other experiments are reviewed, and it is concluded that within the same race of fish there is no causal connection between vertebral number and egg size, although between different races or related species large adult size is often correlated with high vertebral count. The possible advantages of variation in vertebral number are discussed.

scholarly journals Sex allocation in haplodiploids is mediated by egg size: evidence in the spider mite Tetranychus urticae Koch

2010 ◽  
Vol 278 (1708) ◽  
pp. 1054-1063 ◽  
Author(s):  
Emilie Macke ◽  
Sara Magalhães ◽  
Hong Do-Thi Khan ◽  
Anthony Luciano ◽  
Adrien Frantz ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Tetranychus Urticae ◽  
Egg Size ◽  
Spider Mite ◽  
Sex Ratios ◽  
Size Difference ◽  
Adult Size ◽  
External Fertilization ◽  
Offspring Sex Ratio ◽  
Egg Provisioning

Haplodiploid species display extraordinary sex ratios. However, a differential investment in male and female offspring might also be achieved by a differential provisioning of eggs, as observed in birds and lizards. We investigated this hypothesis in the haplodiploid spider mite Tetranychus urticae , which displays highly female-biased sex ratios. We show that egg size significantly determines not only larval size, juvenile survival and adult size, but also fertilization probability, as in marine invertebrates with external fertilization, so that female (fertilized) eggs are significantly larger than male (unfertilized) eggs. Moreover, females with on average larger eggs before fertilization produce a more female-biased sex ratio afterwards. Egg size thus mediates sex-specific egg provisioning, sex and offspring sex ratio. Finally, sex-specific egg provisioning has another major consequence: male eggs produced by mated mothers are smaller than male eggs produced by virgins, and this size difference persists in adults. Virgin females might thus have a (male) fitness advantage over mated females.

The world's biggest trilobite—Isotelus rex new species from the upper Ordovician of northern Manitoba, Canada

2003 ◽  
Vol 77 (1) ◽  
pp. 99-112 ◽  
Author(s):  
David M. Rudkin ◽  
Graham A. Young ◽  
Robert J. Elias ◽  
Edward P. Dobrzanski
Keyword(s):  
New Species ◽  
Rapid Onset ◽  
Adult Size ◽  
Upper Ordovician ◽  
Low Latitude ◽  
Large Size ◽  
Extinction Event ◽  
Widespread Phenomenon ◽  
Climatic Cooling ◽  
Large Adult

The largest known trilobite fossil, a virtually complete articulated dorsal shield of the asaphid Isotelus rex new species, has been recovered from Upper Ordovician (Cincinnatian, Richmondian) nearshore carbonates of the Churchill River Group in northern Manitoba. At over 700 mm in length, it is almost 70 percent longer than the largest previously documented complete trilobite, and provides the first unequivocal evidence of maximum trilobite length in excess of one-half metre. Comparisons with other fossil and extant members of the phylum suggest that in terms of maximum linear dimensions it was among the biggest arthropods ever to have lived. Sediments of the Churchill River Group were deposited in an equatorial epeiric setting and the extremely large size of I. rex n. sp. thus marks a striking example of low-latitude gigantism, in sharp contrast to the widespread phenomenon of “polar gigantism” in many modern marine benthic arthropods. Lack of extensive epibiontic colonization of the exoskeletal surface and the presence of large distinctive trace fossils in the same unit suggest that I. rex n. sp. may have been a semi-infaunal predator and scavenger that employed a shallow furrowing and probing mode of benthic feeding. The extinction of the isotelines (and virtually the entire asaphide lineage) at the end of the Ordovician cannot be related to the near contemporaneous achievement of exceptionally large adult size in some representatives. Failure to survive the terminal Ordovician extinction event was most likely a consequence of a pelagic larval life-style that proved ill-adapted to the rapid onset of global climatic cooling and loss of tropical shelf habitats.

Reproductive investment by green turtles nesting on Ascension Island

1993 ◽  
Vol 71 (6) ◽  
pp. 1098-1103 ◽  
Author(s):  
Graeme C. Hays ◽  
Colin R. Adams ◽  
John R. Speakman
Keyword(s):  
Egg Size ◽  
Reproductive Investment ◽  
Chelonia Mydas ◽  
The Body ◽  
Adult Size ◽  
Green Turtles ◽  
Female Body Size ◽  
Ascension Island ◽  
Egg Chamber ◽  
The Relationship

Clutch sizes and egg sizes were measured for green turtles (Chelonia mydas) nesting on Ascension Island in the South Atlantic (7°57′S, 14 °22′W) in 1992. The mean number of eggs per clutch was 127.5 (SD = 22.9; n = 46 clutches). The number of eggs per clutch increased in larger turtles and declined as the nesting season progressed. Mean egg size was 45.5 mm (SD = 1.45 mm; n = 47 clutches). Three turtles laid significantly smaller eggs than the rest of the sample. When these three clutches were removed from the analysis, mean egg size increased in larger turtles. When the effect of female body size was removed there was no relationship between the number and size of the eggs in a clutch. The depth from the top to the bottom of the egg chamber, the depth from the top of the egg chamber to the topmost egg, and the depth of the body pit were all independent of adult size. Egg size varied systematically within clutches, the largest eggs being laid first and the smallest eggs last. This intraclutch variation in egg size had important consequences for the calculated gradient of the relationship between egg size and adult size.

2 New Kidney Flukes (Digenea, Renicolidae) From Marine Birds of Heron Island, Australia

1989 ◽  
Vol 37 (1) ◽  
pp. 59 ◽  
Author(s):  
HL Ching
Keyword(s):  
New Species ◽  
Body Size ◽  
Oral Sucker ◽  
Related Species ◽  
Egg Size ◽  
Marine Birds ◽  
The Family ◽  
Two New Species ◽  
Planaxis Sulcatus

Four members of the family Renicolidae are described from Heron I., Australia. Adults of two new species are found in the kidneys of the black noddy, Anous minutus. Of these, Renicola foliata, sp. nov., differs from related species in the position of the ovary and testes, in the lobate gonads, in egg size, and in the presence of an oesophagus. R. caudescens, sp. nov., is distinguished by its body size, the lobation and position of the testes, the distribution of the vitellarian follicles and the size of the oral sucker. Also described are a renicolid metacercaria from the musculature of an atherinid fish, and a renicolid cercaria (cercaria F of Rohde, 1981) from the gastropod Planaxis sulcatus.

scholarly journals Male–only care and classical polyandry in birds: phylogeny, ecology and sex differences in remating opportunities

2002 ◽  
Vol 357 (1419) ◽  
pp. 283-293 ◽  
Author(s):  
I. P. F. Owens
Keyword(s):  
Sex Differences ◽  
Related Species ◽  
Egg Size ◽  
Breeding Systems ◽  
Female Size ◽  
Huge Number ◽  
Closely Related Species ◽  
Significant Difference ◽  
Low Rate ◽  
Ecological Differences

It has been argued recently that the combination of male–only parental care and classical polyandry in birds is the most interesting and yet the least understood of all avian breeding systems. Despite a huge number of hypotheses, careful comparative analyses have repeatedly failed to identify consistent ecological differences between species showing male–only care and closely related species showing other patterns of care. This has led to the suggestion that such analyses fail because the crucial differences are between ancient lineages rather than between closely related species. Here, therefore, I use comparisons between families to test three well–known hypotheses: that male–only care is associated with: (i) a low rate of fecundity; (ii) large egg size relative to female size; or (iii) female–biased opportunities for remating. Families showing male–only care do not differ from families showing female–only care with respect to rate of fecundity or relative egg size. There is, however, a significant difference between these two groups of families with respect to an index of remating opportunities, nesting density. Families showing female–only care nest at high density, while those showing male–only care nest at very low density. This is one of the first times a consistent ecological correlate has been identified for male–only care in birds. It suggests that female–only care arises (or persists) in families where remating opportunities are abundant for both sexes, whereas male–only care arises (or persists) in families where remating opportunities are rare for both sexes and particularly scarce for males. This in turn suggests that sex differences in remating opportunities are the key ecological factor in determining male–only care and classical polyandry in birds.

A new species of Plestiodon (Squamata: Scincidae) from Sierra Madre del Sur of Guerrero, México

Zootaxa ◽  
2012 ◽  
Vol 3339 (1) ◽  
pp. 57 ◽  
Author(s):  
MANUEL FERIA-ORTIZ ◽  
URI OMAR GARCÍA-VÁZQUEZ
Keyword(s):  
New Species ◽  
Lateral Line ◽  
Adult Size ◽  
Sierra Madre ◽  
Sierra Madre Del Sur ◽  
Large Adult ◽  
A New Species

We describe a new species of lizard of the genus Plestiodon from the Sierra Madre del Sur of Guerrero, Mexico. Plestiodonnietoi sp. nov. shares a characteristic with all members of the P. brevirostris group in that the scale that medially bordersthe postgenial is wider than long. This species is most similar to P. brevirostris and P. indubitus from which it differs byhaving the following combination of characters: large adult size, interparietal enclosed posteriorly by parietals, and a pale lateral line on the neck.

scholarly journals Geographical variation in larval host-plant use by Heliconius erato (Lepidoptera: Nymphalidae) and consequences for adult life history

2002 ◽  
Vol 62 (2) ◽  
pp. 321-332 ◽  
Author(s):  
D. RODRIGUES ◽  
G. R. P. MOREIRA
Keyword(s):  
Life History ◽  
Body Size ◽  
Larval Stage ◽  
Egg Size ◽  
Geographical Variation ◽  
Size Range ◽  
Adult Size ◽  
Experimental Station ◽  
Female Body Size ◽  
Adult Body

Adult body size, one of the most important life-history components, varies strongly within and between Heliconius erato phyllis (Lepidoptera: Nymphalidae) populations. This study determines if this variation is caused by geographical changes in host-plant used by the larval stage, whose reproductive parameters are influenced by female body size, with estimates of the corresponding heritability. The variation in adult body size was determined together with a survey of passion vine species (Passifloraceae) used by the larvae in seven localities in Rio Grande do Sul State: three located in the urban area of Porto Alegre and Triunfo Counties, two within Eucalyptus plantations (Barba Negra Forest, Barra do Ribeiro County, and Águas Belas Experimental Station -- Viamão County), one in a Myrtaceae Forest (Itapuã State Park -- Itapuã County) and one in the Atlantic Rain Forest (Maquiné Experimental Station -- Maquiné County). Effects of female body size on fecundity, egg size and egg viability were determined in an outdoor insectary. Size heritability was estimated by rearing in the laboratory offspring of individuals maintained in an insectary. The data showed that adults from populations where larvae feed only upon Passiflora suberosa are smaller than those that feed on Passiflora misera. The larvae prefer P. misera even when the dominant passion vine in a given place is P. suberosa. Fecundity increases linearly with the increase in size of females, but there is no size effect on egg size or viability. Size heritability is null for the adult size range occurring in the field. Thus, the geographical variation of H. erato phyllis adult size is primarily determined by the type, corresponding availability and quality of host-plants used by the larval stage. Within the natural size range of H. erato phyllis, the variation related to this caracter is not genetically based, thus being part of H. erato phyllis phenotypic plasticity.

THE EFFECT OF ALTERNATING TEMPERATURE ON VERTEBRAL COUNT IN THE MEDAKA (ORYZIAS LATIPES)

1965 ◽  
Vol 43 (1) ◽  
pp. 99-104 ◽  
Author(s):  
C. C. Lindsey ◽  
M. Y. Ali
Keyword(s):  
Oryzias Latipes ◽  
Vertebral Count ◽  
Alternating Temperature

Eggs reared at different sustained temperatures ranging from 20° to 34 °C produced young with vertebral counts progressively lower at higher temperatures. Eggs transferred from 20° to 30° 2 days after fertilization produced significantly fewer vertebrae, and eggs transferred 6 days after fertilization produced significantly more vertebrae than did those reared at either sustained temperature. Eggs subject to temperatures alternating between 22° and 30° every 12 hours throughout development produced intermediate counts, corresponding to those resulting from sustained rearing at 26°, and showed the highest survival and no abnormalities.

Atlantic Cod Populations along the Southern Canadian Mainland as shown by Vertebral Count Studies

1955 ◽  
Vol 12 (5) ◽  
pp. 698-705 ◽  
Author(s):  
R. A. McKenzie ◽  
G. F. M. Smith
Keyword(s):  
Nova Scotia ◽  
Atlantic Cod ◽  
South Coast ◽  
The South ◽  
Vertebral Number ◽  
Vertebral Count ◽  
Seasonal Migrations

Analysis of vertebral counts of 28,097 cod (Gadus callarias L.) in 184 samples from the Canadian mainland coast demonstrates some segregation of inshore and offshore populations and little mixing between the cod on various sections of the coast. Four populations are recognized in the Gulf of St. Lawrence. Three offshore populations and at least four inshore populations are also recognized along the south coast of Nova Scotia. Seasonal migrations northward in summer and southward in winter are indicated by changes in vertebral numbers. Small cod (less than 21/2 lb.) exhibit less variability in vertebral number than larger ones, suggesting increased mixing with growth.

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