scholarly journals Another lesson from beautiful monsters: the case of 'sex reversals' in the Ammonoidea and their significance

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Camille Frau ◽  
Pierre-Yves Boursicot
Keyword(s):  
Environmental Pollutants ◽  
Temperature Fluctuations ◽  
Shell Morphology ◽  
Endocrine Disrupters ◽  
Adult Size ◽  
External Shell ◽  
Genetic Abnormalities ◽  
Adult Body ◽  
Extinct Group ◽  
Male To Female

Abstract Background Expression of sexual dimorphism is recognised in various fossil groups of molluscs such as the Ammonoidea, an extinct group of shelled cephalopods. During the Mesozoic, the best-documented sexual dimorphic examples are seen in the Jurassic superfamily Perisphinctoidea. It is usually expressed by distinct adult size and apertural modifications between the antidimorphs. Putative males (otherwise referred to as microconch) are small in size and develop lappets at the end of the shell while the females (macroconch) are larger and bear a simple peristome. Dubious cases are, however, known in that superfamily, which often relate to taxonomic biases or lack of diagnostic characters, and some others expose ontogenetic anomalies illustrated by ‘sex reversals’ in the shell morphology and ornamentation. Results The discovery of two specimens of the Callovian Aspidoceratidae Peltoceras athleta (Phillips), having both female and male features, questions the significance and causes of ‘sex reversals’ in the Ammonoidea. The two specimens have started with the macroconch ontogeny of Peltoceras athleta and show an apparent change toward maleness in the adult, as illustrated by their rounded whorl section, ribs retroversion, fading of the tubercles and lappets typical of the microconchs. Few other cases of female-to-male, as well as male-to-female ‘sex reversal’, are known in the fossil record, all belonging to the Jurassic Perisphinctoidea (families Perisphinctidae or Aspidoceratidae). Since all Jurassic Perisphinctoidea are strictly gonochoristic, these ‘sex reversals’ are pathological in nature and are herein referred to as a new forma-type pathology: namely “forma hermaphrodita”. Conclusions In the absence of any clear evidence of injury or parasitism, we hypothesize that such “forma hermaphrodita” individuals illustrate pathologic cases of intersexuality. Little is known about the ammonoid soft parts, and it is not possible to determine which internal sexual organs occur in specimens having both male and female external shell features. Abnormal feminisation and/or masculinisation also occur in modern cephalopods, the latter also grouping only gonochoric species. This phenomenon is similarly illustrated by a change in the adult body size and a mixing of both female and male structures. In that case, intersexuality is either advantageous in the population or caused sterility. The causes of intersexuality are not clearly established but environmental pollutants are evoked in modern cephalopods because they act as endocrine disrupters. ‘Sex reversals’ and/or non-functional reproductive abnormalities have also been caused by endocrine disrupters in various gonochoric gastropods species, but infestation, genetic abnormalities, temperature fluctuations or viruses are multiple causes, which can stimulate or inhibit neural-endocrinal activity by direct gonadal influence, and ultimately lead to feminisation or masculinisation in fishes, isopods, crustaceans, and gastropods as well. Regardless of whether “forma hermaphrodita” is due to an exogenic or endogenic cause, the record of intersex Perisphinctoidea in the Jurassic can be explained by the ready recognition of dimorphic pairs, and the easy collection of large and sufficiently preserved fossil palaeopopulations in which intersex specimens have statistically more chance to be found.

scholarly journals Another Lesson From Beautiful Monsters: the Case of 'sex Reversals' in the Ammonoidea and Their Significance

2021 ◽  
Author(s):  
Camile Frau ◽  
Pierre-Yves Boursicot
Keyword(s):  
High Frequency ◽  
Environmental Pollutants ◽  
Shell Morphology ◽  
Endocrine Disrupters ◽  
Adult Size ◽  
External Shell ◽  
Genetic Abnormalities ◽  
Male Sex ◽  
Extinct Group ◽  
Male To Female

Abstract Background: Expression of a sexual dimorphism is recognised in various fossil groups of molluscs such as the Ammonoidea, an extinct group of shelled cephalopods. During the Mesozoic, the best documented sexual dimorphic examples are seen in the Jurassic superfamily Perisphinctoidea. It is most usually expressed by distinct adult size and apertural modifications between the antidimorphs. Putative males (otherwise referred to as microconch) are small in size and develop lappets at the end of the shell while the females (macroconch) are larger and bear a simple peristome. Dubious cases are, however, known in that superfamily. They most often relate to taxonomic biases or lack of diagnostic characters, and some others expose ontogenetic anomalies illustrated by ‘sex reversals’ in the shell morphology and ornamentation. Results: The discovery of two specimens of the Callovian Aspidoceratidae Peltoceras athleta (Phillips), having both female and male features, questions the significance and causes of ‘sex reversals’ in the Ammonoidea. The two specimens have started with the macroconch ontogeny of Peltoceras athleta, and show an apparent change toward maleness in the adult, as illustrated by their rounded whorl section, ribs retroversion, fading of the tubercles and lappets typical of the microconchs. Few other cases of female-to-male ‘sex reversal’, as well as male-to-female ones, are known in the fossil record, all belonging to the Jurassic Perisphinctoidea (families Perisphinctidae or Aspidoceratidae). Since all Jurassic Perisphinctoidea are strictly gonochoristic, these ‘sex reversals’ are pathological in nature and are herein referred to as a new forma-type pathology: namely “forma hermaphrodita”.Conclusions: In the absence of any clear evidence of injury or parasitism, we hypothesize that such “forma hermaphrodita” individuals illustrate pathologic cases of intersexuality. Little is known about the ammonoid soft parts, and it is not possible to determine which internal sexual organs occur in specimen having both male and female external shell features. Abnormal feminisation and/or masculinisation also occur in modern cephalopods; the latter also grouping only gonochoric species. This phenomenon is similarly illustrated by a change in the adult body size and a mixing of both female and male structures. In that case, intersexuality is either advantageous in the population or caused sterility. The causes of intersexuality are not clearly established but environmental pollutants are evoked in modern cephalopods because they act as endocrine disrupters. ‘Sex reversals’ and/or non-functional reproductive abnormalities have also been caused by endocrine disrupters in various gonochoric gastropods species, but infestation, genetic abnormalities, temperature fluctuations or viruses are multiple causes which can stimulate or inhibit neural-endocrinal activity by direct gonadal influence, and ultimately lead to feminisation or masculinisation in fishes, isopods, crustaceans, and gastropods as well. Regardless of whether “forma hermaphrodita” is due to an exogenic or endogenic cause, the high frequency of intersex Perisphinctoidea in the Jurassic can be explained by the readily recognition of dimorphic pair, and the easy collection of large and sufficiently preserved fossil palaeopopulations in which intersex specimens have statistically more chance to be found.

scholarly journals Aggregations and parental care in the Early Triassic basal cynodontsGalesaurus planicepsandThrinaxodon liorhinus

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e2875 ◽  
Author(s):  
Sandra C. Jasinoski ◽  
Fernando Abdala
Keyword(s):  
Parental Care ◽  
Reproductive Biology ◽  
Fossil Record ◽  
Size Difference ◽  
Early Triassic ◽  
Adult Size ◽  
Extensive Survey ◽  
Comprehensive Survey ◽  
Extinct Group ◽  
Mixed Age

Non-mammaliaform cynodonts gave rise to mammals but the reproductive biology of this extinct group is still poorly known. Two exceptional fossils ofGalesaurus planicepsandThrinaxodon liorhinus, consisting of juveniles closely associated with an adult, were briefly described more than 50 years ago as examples of parental care in non-mammaliaform cynodonts. However, these two Early Triassic fossils have largely been excluded from recent discussions of parental care in the fossil record. Here we re-analyse these fossils in the context of an extensive survey of other aggregations found in these two basal cynodont taxa. Our analysis revealed six other unequivocal cases of aggregations inThrinaxodon, with examples of same-age aggregations among immature or adult individuals as well as mixed-age aggregations between subadult and adult individuals. In contrast, only one additional aggregation ofGalesauruswas identified. Taking this comprehensive survey into account, the two previously described cases of parental care inGalesaurusandThrinaxodonare substantiated. The juveniles are the smallest specimens known for each taxon, and the size difference between the adult and the two associated juveniles is the largest found for any of the aggregations. The juveniles ofThrinaxodonare approximately only 37% of the associated adult size; whereas inGalesaurus, the young are at least 60% of the associated adult size. In each case, the two juvenile individuals are similar in size, suggesting they were from the same clutch. Even though parental care was present in bothGalesaurusandThrinaxodon, intraspecific aggregations were much more common inThrinaxodon, suggesting it regularly lived in aggregations consisting of both similar and different aged individuals.

Effects of initial (larval) size and host body temperature on growth in trematodes

2003 ◽  
Vol 81 (4) ◽  
pp. 574-581 ◽  
Author(s):  
Robert Poulin ◽  
A David M. Latham
Keyword(s):  
Body Size ◽  
Body Temperature ◽  
Adult Stage ◽  
Species Variation ◽  
Adult Size ◽  
Model Group ◽  
Larval Size ◽  
Relative Growth ◽  
Host Body ◽  
Adult Body

For ectotherms, temperature is an important correlate of variation in body size within species. Variation in body size among related species could also be attributable in part to temperature if the different species grow under different thermal regimes. The roles of both initial (larval) size and host body temperature on final (adult) size of parasitic trematodes were investigated in a comparative analysis. Trematodes are a good model group for such a study, with almost half of known species growing at high and constant temperatures in endothermic vertebrates and the rest at lower and fluctuating temperatures in ectothermic vertebrates. The relative growth of trematodes, i.e., their growth relative to the size of their larvae, varied greatly among species. Increases in body size from the cercarial larval stage to the adult stage averaged almost 40-fold (maximum 1300-fold), whereas increases in size from the metacercarial stage to the adult stage averaged 6-fold (maximum 110-fold). There were no differences between trematodes in ectothermic hosts and trematodes in endothermic hosts with respect to these measures of relative growth, however, which suggests that host type and the thermal regime provided by the host have no effect on the growth of trematodes from larval to adult stages. In contrast, the final (adult) body size of trematodes appears to be determined to some extent by their initial (larval) size, independently of the type of host in which they developed.

scholarly journals When does diet matter? The roles of larval and adult nutrition in regulating adult size traits

2019 ◽  
Author(s):  
Gonçalo M. Poças ◽  
Alexander E. Crosbie ◽  
Christen K. Mirth
Keyword(s):  
Body Weight ◽  
Caloric Restriction ◽  
Fruit Fly ◽  
Adult Size ◽  
Larval Diet ◽  
Caloric Density ◽  
Larval Stages ◽  
Adult Body ◽  
Adult Body Weight ◽  
Adult Diet

ABSTRACTAdult body size is determined by the quality and quantity of nutrients available to animals. In insects, nutrition affects adult size primarily during the nymphal or larval stages. However, measures of adult size like body weight are likely to also change with adult nutrition. In this study, we sought to the roles of nutrition throughout the life cycle on adult body weight and the size of two appendages, the wing and the femur, in the fruit fly Drosophila melanogaster. We manipulated nutrition in two ways: by varying the protein to carbohydrate content of the diet, called macronutrient restriction, and by changing the caloric density of the diet, termed caloric restriction. We employed a fully factorial design to manipulate both the larval and adult diets for both diet types. We found that manipulating the larval diet had greater impacts on all measures of adult size. Further, macronutrient restriction was more detrimental to adult size than caloric restriction. For adult body weight, a rich adult diet mitigated the negative effects of poor larval nutrition for both types of diets. In contrast, small wing and femur size caused by poor larval diet could not be increased with the adult diet. Taken together, these results suggest that appendage size is fixed by the larval diet, while those related to body composition remain sensitive to adult diet. Further, our studies provide a foundation for understanding how the nutritional environment of juveniles affects how adults respond to diet.

scholarly journals Correlated and decoupled evolution of adult and larval body size in frogs

2020 ◽  
Vol 287 (1933) ◽  
pp. 20201474
Author(s):  
Tung X. Phung ◽  
João C. S. Nascimento ◽  
Alexander J. Novarro ◽  
John J. Wiens
Keyword(s):  
Body Size ◽  
Phylogenetic Signal ◽  
Life Cycles ◽  
Major Group ◽  
Adult Size ◽  
Larval Body ◽  
Larval Stages ◽  
Rates Of Evolution ◽  
Adult Body ◽  
Body Sizes

The majority of animal species have complex life cycles, in which larval stages may have very different morphologies and ecologies relative to adults. Anurans (frogs) provide a particularly striking example. However, the extent to which larval and adult morphologies (e.g. body size) are correlated among species has not been broadly tested in any major group. Recent studies have suggested that larval and adult morphology are evolutionarily decoupled in frogs, but focused within families and did not compare the evolution of body sizes. Here, we test for correlated evolution of adult and larval body size across 542 species from 42 families, including most families with a tadpole stage. We find strong phylogenetic signal in larval and adult body sizes, and find that both traits are significantly and positively related across frogs. However, this relationship varies dramatically among clades, from strongly positive to weakly negative. Furthermore, rates of evolution for both variables are largely decoupled among clades. Thus, some clades have high rates of adult body-size evolution but low rates in tadpole body size (and vice versa). Overall, we show for the first time that body sizes are generally related between adult and larval stages across a major group, even as evolutionary rates of larval and adult size are largely decoupled among species and clades.

scholarly journals Systematic evaluation of cryptic freshwater snails from central Chile, including the enigmatic Littoridina santiagensis (Gastropoda, Truncatelloidea)

2019 ◽  
Author(s):  
Gonzalo A. Collado ◽  
Karina P. Aguayo ◽  
Néstor J. Cazzaniga ◽  
Diego E. Gutiérrez Gregoric ◽  
Micaela De Lucía ◽  
...  
Keyword(s):  
South America ◽  
Southern Cone ◽  
Shell Morphology ◽  
Systematic Evaluation ◽  
Freshwater Snails ◽  
Allopatric Population ◽  
Type Specimens ◽  
Central Chile ◽  
Taxonomic Analysis ◽  
External Shell

Walter Biese described Littoridina santiagensis Biese, 1944 (Cochliopidae) from Estero Dehesa in 1944 based exclusively on external shell features and a second allopatric population in Yeso Spring three years later. Since 2011 different samplings have been carried out at the type locality and have only provided specimens of the morphologically similar invasive mudsnail Potamopyrgus antipodarum Gray, 1843 (Tateidae), raising doubts about the identity of the species. The recent finding of two snail morphotypes in Yeso Spring, a thick shelled form congruent with type specimens of L. santiagensis and a slender one morphologically associable to P. antipodarum, allowed comparative studies, including the taxonomic analysis of additional populations with similar shell morphology occurring in central Chile. A DNA barcoding (COI) approach identified the slender form from Yeso Spring in Maipo Basin and a second population from the contiguous Rapel Basin indeed as the invasive P. antipodarum; however, L. santiagensis was recovered among species of Potamolithus Pilsbry, 1896 (Tateidae), justifying the Potamolithus santiagensis (Biese, 1944) comb. nov. Besides recognition of three other populations as belonging to Potamolithus, the molecular analysis also suggests trans-Andean dispersal of this group of snails in the Southern Cone of South America.

Comparison of Array Comparative Genomic Hybridization (aCGH) to FISH and Cytogenetics in Prognostic Evaluation of CLL.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 4393-4393
Author(s):  
Dennis P. O'Malley ◽  
Christina Giudice ◽  
Averee S Chang ◽  
Dorothy Chang ◽  
Todd S Barry ◽  
...  
Keyword(s):  
Comparative Genomic Hybridization ◽  
Array Comparative Genomic Hybridization ◽  
Genetic Alterations ◽  
Comparative Genomic ◽  
Control Group ◽  
Female Ratio ◽  
Additional Group ◽  
Genetic Abnormalities ◽  
Male To Female ◽  
Classical Cytogenetics

Abstract Abstract 4393 INTRODUCTION Chronic lymphocytic leukemia (CLL) is a commonly encountered hematologic neoplasm. Evaluation of prognosis in CLL is strongly based on genetic findings and the most commonly used studies are classical cytogenetics and targeted interphase fluorescence in situ hybridization (FISH). High resolution array comparative genomic hybridization (aCGH) is a relatively new and robust method of evaluating chromosomal alterations over the entire genome. We compared aCGH with routine cytogenetics and FISH in detecting genetic alterations in newly-diagnosed CLL cases. MATERIALS AND METHODS aCGH testing was performed on 55 cases of CLL in addition to a standard panel of FISH probes (ATM on 11q22, trisomy 12, 13q14, p53 on 17p13 using a standard cutoff for positivity of 10%). These results were compared to a control group of 100 CLL cases upon which routine cytogenetics and FISH were performed. The frequency of detecting abnormalities was compared between the groups and discordant results between methodologies were compared. RESULTS In the control group (n=100), the mean age was 71 (52-86) with a male to female ratio of 1.6:1. Genetic abnormalities were detected by classical cytogenetics in 19% (19/100) of cases as compared to FISH which detected abnormalities in 66% (66/100) of cases (Table 1). An additional group of 55 CLL cases [male to female ratio of 2.2:1 and a mean age of 71 (52-90)] was analyzed by both aCGH and FISH. This additional group of CLL cases showed a similar frequency of genetic abnormalities by FISH (60%; 27/45). In contrast to FISH, aCGH detected genetic abnormalities in 82% (45/55) of CLL cases (Table 1). aCGH identified genetic abnormalities not detected by FISH studies in 16% (7/45) of cases whereas FISH identified abnormalities not detected by aCGH in only 7% (3/45) of cases. Rare recurring genetic alterations were detected by aCGH, which would not have been detected by a standard FISH panel, and included losses in 6q, 8p, 10q, 14q32, and 18q, and gains in 10q. DISCUSSION Classical cytogenetics is often performed in cases of CLL, but is not particularly useful as CLL cells are often difficult to grow in culture and because of the low rate of detecting common genetic alterations. Our findings suggest that aCGH is an effective and robust technique for evaluating recurring genetic abnormalities in CLL and is better than classical cytogenetics and standard FISH in detecting common genetic abnormalities in CLL. Disclosures: No relevant conflicts of interest to declare.

Keys to the Shells of Bahia la Choya, Sonora, Mexico

1987 ◽  
Vol 2 ◽  
pp. 62-103
Author(s):  
Nancy Beckvar ◽  
Richard D. Norris ◽  
Sherman Suter
Keyword(s):  
Seasonal Variations ◽  
Shell Morphology ◽  
Shell Structures ◽  
Shell Material ◽  
Sand Flat ◽  
Ecological Information ◽  
Descriptive Information ◽  
External Shell ◽  
Molluscan Species ◽  
Technical Terms

These keys are intended for use on dead shell material found on the sand flat, spit and estero of Bahia la Choya. They describe one hundred seventy molluscan species, three irregular echinoids and an inarticulate brachiopod. The taxonomic list on which the keys are based was compiled from shell material collected mainly during February and March, 1985. An attempt was made to make the keys as complete as possible. However, due to seasonal variations in shell abundances, not all shell material found at Bahia la Choya may be included in the key. Additionally, not all taxa found in the Pleistocene rock exposed around the bay are described here.The keys are based on morphological similarites, not phylogenetic relationships. Descriptive terminology has been kept to a minimum, and a glossary and labeled sketches are included for those technical terms which were employed. The reader is advised to become familiar with the anatomical parts of shells before embarking on an identification.External shell morphology can be altered by physical and biological destruction. In particular, fragile shell structures may be broken off, and shell sculpturing may be worn down. The absence of these sometimes critical features may lead to an incorrect identification. Additionally, bleaching of shells can alter or destroy the original colors. Therefore, shell color is not necessarily diagnostic and is mainly used as an additional character in the description of the species.Species are described only within the keys. When the species name has been reached, phrases within the couplet contain additional descriptive information and often some ecological information.

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.

Iterative progenesis in Upper Cretaceous ammonites

Paleobiology ◽  
1989 ◽  
Vol 15 (2) ◽  
pp. 95-117 ◽  
Author(s):  
Neil H. Landman
Keyword(s):  
Sexual Dimorphism ◽  
North America ◽  
Rare Species ◽  
Upper Cretaceous ◽  
Morphological Changes ◽  
Adult Size ◽  
Developmental Pathway ◽  
Evolutionary Pattern ◽  
Body Chamber ◽  
Adult Body

Pteroscaphites are small, rare species of scaphitid ammonites from the Upper Cretaceous (Turonian-Santonian) of the Western Interior of North America. Their evolution appears to parallel that of the larger species ofScaphitesorClioscaphites, with which they co-occur. To investigate this evolutionary pattern, I constructed a phylogeny of all these species based on their distribution of shared derived characters including ornamentation, ammonitella size, whorl shape, umbilical diameter, sutures, number of whorls, adult size, shape of the adult body chamber, and apertural modifications. This analysis revealed numerous instances of congruence in the preadult morphology of the pteroscaphites and that of the co-occurring scaphites or clioscaphites. However, there is a marked divergence at maturity. Adult pteroscaphites are uniformly small (2.5 postembryonic whorls in their phragmocone) and develop apertural projections. The scaphites and clioscaphites exhibit a number of morphological changes at approximately the same whorl number, but secrete as many as two more whorls in their phragmocone before forming a mature body chamber with a relatively unmodified aperture. Both groups display sexual dimorphism. The process of progenesis may explain this conflicting pattern of congruence prior to maturity and divergence at maturity. Adult pteroscaphites are not mature replicas of the juvenile shells of the larger scaphites or clioscaphites, because maturation produces its own set of morphological modifications. Nevertheless, such features as the apertural projections on adult pteroscaphites may be interpreted as extrapolations of juvenile patterns of growth into maturity. The repeated associations of pteroscaphites with scaphites or clioscaphites in the Upper Cretaceous suggest that progenesis was iterative and may have represented an optional developmental pathway common to all of these species.

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