The Feeding Habits of the Shovel-Tusked Gomphotheres: Evidence From Tusk Wear Patterns

Paleobiology ◽  
1992 ◽  
Vol 18 (2) ◽  
pp. 132-147 ◽  
Author(s):  
W. David Lambert
Keyword(s):  
Sexual Dimorphism ◽  
Feeding Behavior ◽  
Direct Evidence ◽  
Feeding Habits ◽  
Theoretical Models ◽  
African Elephants ◽  
Water Plants

The shovel-tusked gomphotheres are normally portrayed scooping up water plants with their shovellike mandibular tusks. This portrayal is based on speculation about the possible functions of the lower tusks and misinterpretation of mandibular-tusk wear patterns that goes back to the 1920s and 1930s. In addition, most literature concerning shovel-tusker feeding behavior ignores the possibility that the upper tusks may have had a role in feeding, as they do in modern African elephants. Because wear patterns on tusks provide direct evidence as to how tusks were used during feeding, I examined and interpreted patterns on the lower and upper tusks of shovel-tusked gomphotheres on the basis of theoretical models of tusk wear to determine how the tusks were used in feeding.This examination led to the following conclusions. (1) The genus Amebelodon was characterized by feeding opportunism, gathering food with both its lower and upper tusks in a variety of ways. (2) There is evidence for similar flexibility within the genus Serbelodon. (3) Wear patterns on mandibular tusks of Platybelodon grangeri and Torynobelodon barnumbrowni indicate that these taxa did not practice mandibular shoveling but used these tusks to cut tough vegetation in a specialized fashion. (4) The flaplike trunks (probosces) generally attributed to shovel-tusked gomphotheres in restorations are shown almost certainly to be erroneous; morphological and functional evidence suggests that these animals had trunks similar to those of modern elephants. (5) Strong tusk sexual dimorphism is unknown in the shovel-tusked gomphotheres except for Platybelodon and should not be found in any taxa that relied on their tusks for procuring food. New restorations of both Amebelodon and Platybelodon are provided that are more consistent with the actual evidence bearing on their feeding behavior.

The melanocortin-3 receptor is a pharmacological target for the regulation of anorexia

2021 ◽  
Vol 13 (590) ◽  
pp. eabd6434
Author(s):  
Patrick Sweeney ◽  
Michelle N. Bedenbaugh ◽  
Jose Maldonado ◽  
Pauline Pan ◽  
Katelyn Fowler ◽  
...  
Keyword(s):  
Sexual Dimorphism ◽  
Feeding Behavior ◽  
Critical Role ◽  
Brain Regions ◽  
Sexually Dimorphic ◽  
Male And Female ◽  
Female Mice ◽  
Bidirectional Regulation ◽  
Fear And Anxiety ◽  
Agouti Related Protein

Ablation of hypothalamic AgRP (Agouti-related protein) neurons is known to lead to fatal anorexia, whereas their activation stimulates voracious feeding and suppresses other motivational states including fear and anxiety. Despite the critical role of AgRP neurons in bidirectionally controlling feeding, there are currently no therapeutics available specifically targeting this circuitry. The melanocortin-3 receptor (MC3R) is expressed in multiple brain regions and exhibits sexual dimorphism of expression in some of those regions in both mice and humans. MC3R deletion produced multiple forms of sexually dimorphic anorexia that resembled aspects of human anorexia nervosa. However, there was no sexual dimorphism in the expression of MC3R in AgRP neurons, 97% of which expressed MC3R. Chemogenetic manipulation of arcuate MC3R neurons and pharmacologic manipulation of MC3R each exerted potent bidirectional regulation over feeding behavior in male and female mice, whereas global ablation of MC3R-expressing cells produced fatal anorexia. Pharmacological effects of MC3R compounds on feeding were dependent on intact AgRP circuitry in the mice. Thus, the dominant effect of MC3R appears to be the regulation of the AgRP circuitry in both male and female mice, with sexually dimorphic sites playing specialized and subordinate roles in feeding behavior. Therefore, MC3R is a potential therapeutic target for disorders characterized by anorexia, as well as a potential target for weight loss therapeutics.

scholarly journals Sensory exploitation and sexual conflict

2006 ◽  
Vol 361 (1466) ◽  
pp. 375-386 ◽  
Author(s):  
Göran Arnqvist
Keyword(s):  
Sexual Dimorphism ◽  
Sexual Conflict ◽  
Theoretical Models ◽  
Sensory Exploitation ◽  
Subsequent Evolution ◽  
Female Preferences ◽  
General Importance ◽  
Evolution Of Resistance ◽  
Sexual Traits ◽  
Sexually Antagonistic Coevolution

Much of the literature on male–female coevolution concerns the processes by which male traits and female preferences for these can coevolve and be maintained by selection. There has been less explicit focus on the origin of male traits and female preferences. Here, I argue that it is important to distinguish origin from subsequent coevolution and that insights into the origin can help us appreciate the relative roles of various coevolutionary processes for the evolution of diversity in sexual dimorphism. I delineate four distinct scenarios for the origin of male traits and female preferences that build on past contributions, two of which are based on pre-existing variation in quality indicators among males and two on exploitation of pre-existing sensory biases among females. Recent empirical research, and theoretical models, suggest that origin by sensory exploitation has been widespread. I argue that this points to a key, but perhaps transient, role for sexually antagonistic coevolution (SAC) in the subsequent evolutionary elaboration of sexual traits, because (i) sensory exploitation is often likely to be initially costly for individuals of the exploited sex and (ii) the subsequent evolution of resistance to sensory exploitation should often be associated with costs due to selective constraints. A review of a few case studies is used to illustrate these points. Empirical data directly relevant to the costs of being sensory exploited and the costs of evolving resistance is largely lacking, and I stress that such data would help determining the general importance of sexual conflict and SAC for the evolution of sexual dimorphism.

Digenean parasite communities in flatfishes of the Scotian Shelf and southern Gulf of St. Lawrence

1982 ◽  
Vol 60 (11) ◽  
pp. 2804-2811 ◽  
Author(s):  
J. S. Scott
Keyword(s):  
Feeding Behavior ◽  
Feeding Habits ◽  
Stomach Contents ◽  
Parasite Prevalence ◽  
Winter Flounder ◽  
Fish Length ◽  
Pseudopleuronectes Americanus ◽  
Scotian Shelf ◽  
Yellowtail Flounder ◽  
Limanda Ferruginea

Prevalence of digenean parasites in four major flatfishes of the Scotian Shelf and southern Gulf of St. Lawrence, American plaice (Hippoglossoides platessoides), yellowtail flounder (Limanda ferruginea), witch flounder (Glyptocephalus cynoglossus), and winter flounder (Pseudopleuronectes americanus), is compared between hosts in relation to geographic distribution, season, feeding behavior, and fish length. The 13 parasite species indicate overlap of feeding habits among hosts but also considerable diversity in feeding behavior, supporting the evidence from examination of stomach contents. Prevalence of digeneans in different final hosts varied between geographic areas and may be used to characterize the populations of the comparatively sedentary flatfish populations. Seasonal variation in prevalence was consistent from area to area but differed between parasites, from the expected increase in summer in some, concomitant with increased feeding, to a winter increase in others, probably related to a seasonal change of diet. Fish length had little effect on parasite prevalence in yellowtail flounder and witch flounder but had a notable effect on plaice and winter flounder from the Gulf of St. Lawrence, again apparently related to change of diet.

The evolution of sexual dimorphism in the lizard Anolis polylepis (Iguania): evidence from intraspecific variation in foraging behavior and diet

1996 ◽  
Vol 74 (7) ◽  
pp. 1238-1245 ◽  
Author(s):  
Gad Perry
Keyword(s):  
Sexual Selection ◽  
Sexual Dimorphism ◽  
Feeding Behavior ◽  
Rain Forest ◽  
Sexual Size Dimorphism ◽  
Costa Rican ◽  
Agonistic Interactions ◽  
Size Dimorphism ◽  
Food Items ◽  
Competing Hypotheses

Two main explanations, intraspecific niche divergence and sexual selection, have been proposed to explain the origin of sexual size dimorphism. To test these competing hypotheses I studied the ecology, feeding behavior, and diet of the lizard Anolis polylepis in a Costa Rican rain forest. Male A. polylepis were significantly larger and heavier than females but ate smaller food items and had lower stomach volumes, despite possessing longer and wider heads. Males were more sedentary than females or juveniles, chose higher perches, and were more likely to be involved in agonistic interactions. Diets of males, females, and juveniles were also significantly different taxonomically. These data are consistent with the sexual selection origin theory but not with an ecological one. Thus, observed dietary differences probably evolved once dimorphism had been attained through sexual selection.

scholarly journals Sympatric Speciation in Threespine Stickleback: Why Not?

2011 ◽  
Vol 2011 ◽  
pp. 1-15 ◽  
Author(s):  
Daniel I. Bolnick
Keyword(s):  
Sexual Dimorphism ◽  
Assortative Mating ◽  
Intraspecific Competition ◽  
Gasterosteus Aculeatus ◽  
Theoretical Models ◽  
Sympatric Speciation ◽  
Threespine Stickleback ◽  
Disruptive Selection ◽  
Evolutionary Diversification ◽  
Trait Variance

Numerous theoretical models suggest that sympatric speciation is possible when frequency-dependent interactions such as intraspecific competition drive disruptive selection on a trait that is also subject to assortative mating. Here, I review recent evidence that both conditions are met in lake populations of threespine stickleback (Gasterosteus aculeatus). Nonetheless, sympatric speciation appears to be rare or absent in stickleback. If stickleback qualitatively fit the theoretical requirements for sympatric speciation, why do they not undergo sympatric speciation? I present simulations showing that disruptive selection and assortative mating in stickleback, though present, are too weak to drive speciation. Furthermore, I summarize empirical evidence that disruptive selection in stickleback drives other forms of evolutionary diversification (plasticity, increased trait variance, and sexual dimorphism) instead of speciation. In conclusion, core assumptions of sympatric speciation theory seem to be qualitatively reasonable for stickleback, but speciation may nevertheless fail because of (i) quantitative mismatches with theory and (ii) alternative evolutionary outcomes.

scholarly journals Antennal and palpal sensilla of three predatory Lispe species (Diptera: Muscidae): an ultrastructural investigation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Genting Liu ◽  
Qike Wang ◽  
Xianhui Liu ◽  
Xinyu Li ◽  
Xiunan Pang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Sexual Dimorphism ◽  
Feeding Habits ◽  
Visual Signal ◽  
Chemical Signal ◽  
Basiconic Sensilla ◽  
Unique Character ◽  
Maxillary Palps ◽  
Scanning Electron

AbstractAntennae and maxillary palps are the most important chemical reception organs of flies. So far, the morphology of antennae and maxillary palps of flies of most feeding habits have been well described, except for that of relatively rare aquatic predatory species. This study describes sensilla on antennae and maxillary palps of three aquatic predatory Lispe species: Lispe longicollis, L. orientalis and L. pygmaea. Types, distribution, and density of sensilla are characterised via light and scanning electron microscopy. One type of mechanoreceptors is found on antennal scape. Mechanoreceptors (two subtypes) and one single pedicellar button (in L. pygmaea) are located on antennal pedicel. Four types of sensilla are discovered on antennal postpedicel: trichoid sensilla, basiconic sensilla (three subtypes), coeloconic sensilla and clavate sensilla. A unique character of these Lispe species is that the coeloconic sensilla are distributed sparsely on antennal postpedicel. Mechanoreceptors and basiconic sensilla are observed on the surface of maxillary palps in all three species. We demonstrated clear sexual dimorphism of the maxillary palps in some of the Lispe species, unlike most other Muscidae species, are larger in males than females. This, along with their courtship dance behaviour, suggest their function as both chemical signal receiver and visual signal conveyer, which is among the few records of a chemical reception organ act as a signal conveyer in insects.

scholarly journals Feeding habits, sexual dimorphism and size at maturity of the lizard Cnemidophorus ocellifer (Spix, 1825) (Teiidae) in a reforested restinga habitat in northeastern Brazil

2010 ◽  
Vol 70 (2) ◽  
pp. 409-416 ◽  
Author(s):  
GG. Santana ◽  
A. Vasconcellos ◽  
YEA. Gadelha ◽  
WLS. Vieira ◽  
WO. Almeida ◽  
...  
Keyword(s):  
Sexual Dimorphism ◽  
Sexual Maturity ◽  
Feeding Habits ◽  
Structural Complexity ◽  
Northeastern Brazil ◽  
Size At Maturity ◽  
Insect Larvae ◽  
The Poor ◽  
Significant Difference ◽  
Poor Soil

The feeding habits, the sexual dimorphism in size and sexual maturity of the actively foraging lizard Cnemidophorusocellifer were analysed in an area of a reforested Restinga habitat located in the municipality of Mataraca, along the northern-most coast of Paraíba State, Brazil. Seventy-five specimens of C. ocellifer were examined (46 males and 29Â females). Of this total, only 23 specimens had prey in their stomachs. The most frequent prey consumed items were orthopterans (50%), coleopterans (23.9%) and arachnids (10.9%); termites and insect larvae were less consumed (both with 2.2%). There were no significant differences observed between the numbers of prey consumed by either males or females. There were significant differences in SVL (snout-vent length) between the sexes, with males attaining larger SVL values. When the influence of SVL was removed from the analyses, sexual dimorphism in the form was still reflected in the head size of these lizards. Sexual maturity in females and males was attained with SVL of 42.2 and 49.0 mm respectively. Although no significant difference was observed between the SVL of the females and the number of eggs produced, there was a clear tendency for larger females to produce more eggs. The low structural complexity of the vegetation and the poor soil quality in the reforested restinga area examined does not furnish favourable habitat for insect and termite larvae, contributing to the marked differences in the diet of the population of C. ocellifer observed in the present study in relation to the diet of their conspecifics in undisturbed areas of restinga, cerrado and caatinga.

scholarly journals First gut contents in a Cretaceous sea turtle

2005 ◽  
Vol 2 (1) ◽  
pp. 113-115 ◽  
Author(s):  
Benjamin P Kear
Keyword(s):  
Direct Evidence ◽  
Feeding Habits ◽  
Sea Turtles ◽  
Sea Turtle ◽  
Benthic Invertebrate ◽  
The Body ◽  
Gut Contents ◽  
Feeding Strategies ◽  
Shell Fragments ◽  
Correct Size

Modern sea turtles utilize a variety of feeding strategies ranging from herbivory to omnivory. In contrast, the diets of fossil sea turtles are poorly known. This study reports the first direct evidence: inoceramid bivalve shell pieces (encased in phosphatic material) preserved within the body cavities of several small protostegid turtles (cf. Notochelone ) from the Lower Cretaceous of Australia. The shell fragments are densely packed and approximately 5–20 mm across. Identical shell accumulations have been found within coprolite masses from the same deposits; these are of a correct size to have originated from Notochelone , and indicate that benthic molluscs were regular food items. The thin, flexible inoceramid shells (composed of organic material integrated into a prismatic calcite framework) appear to have been bitten into segments and ingested, presumably in conjunction with visceral/mantle tissues and encrusting organisms. Although protostegids have been elsewhere interpreted as potential molluscivores, their primitive limb morphology is thought to have limited them to surface feeding. However, the evidence here that at least some forms were able to utilize benthic invertebrate prey indicates that, like modern sea turtles, protostegids probably exhibited a much broader range of feeding habits.

scholarly journals Prey preferences, consumption rates and predation effects of Asian shore crabs (Hemigrapsus takanoi) in comparison to native shore crabs (Carcinus maenas) in northwestern Europe

2021 ◽  
Vol 51 (5) ◽  
Author(s):  
Annika Cornelius ◽  
Katerina Wagner ◽  
Christian Buschbaum
Keyword(s):  
Feeding Behavior ◽  
Wadden Sea ◽  
Feeding Habits ◽  
Carcinus Maenas ◽  
Shore Crab ◽  
Crab Species ◽  
Blue Mussels ◽  
Pacific Oysters ◽  
Shore Crabs ◽  
Consumption Rates

AbstractThe Asian brush-clawed shore crab Hemigrapsus takanoi was introduced to the northern Wadden Sea (southeastern North Sea) in 2009 and now represents one of the most abundant brachyuran crab species. Abundance studies revealed an increase of mean crab densities on mixed reefs of native blue mussels (Mytilus edulis) and Pacific oysters (Magallana gigas) from 18 individuals m−2 in 2011 to 216 individuals m−2 in 2020. Despite its current high densities only little is known about the feeding habits of H. takanoi, its effects on prey populations and on the associated community in the newly invaded habitat. We summarize results of individual field and laboratory experiments that were conducted to assess feeding habits and consumption effects caused by Asian brush-clawed shore crabs and, additionally, compare the feeding ecology of H. takanoi with the one of the native shore crab Carcinus maenas. Field experiments manipulating crab densities revealed that both crab species affected the recruitment success of blue mussels, Pacific oysters and Australian barnacles (Austrominius modestus) with highest number of recruits at crab exclusion. However, endobenthic polychaetes within the reefs were differently affected. Only the native C. maenas caused a significant reduction in polychaete densities, whereas the introduced H. takanoi had no effect. Additional comparative laboratory studies revealed that single C. maenas consume more juvenile blue mussels than Asian brush-clawed shore crabs of the same size class. When offering amphipods as a mobile prey species, we found the same pattern with higher consumption rates by C. maenas than by H. takanoi. For Asian but not for native shore crabs, we detected a sex-dependent feeding behavior with male H. takanoi preferring blue mussels, while females consumed more amphipods. Considering mean crab densities and feeding behavior, our results suggest that despite lower consumption rates of single crabs, Asian brush-clawed shore crabs can cause stronger impacts on prey organisms than the native C. maenas, because H. takanoi exceeds their densities manifold. A strong impact of the invader on prey populations is supported by low amphipod occurrence at sites where H. takanoi density is high in the study area. Thus, the introduced Asian brush-clawed shore crab is an additional consumer with significant effects on the associated community of mixed reefs of mussels and oysters in the Wadden Sea.

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