scholarly journals Physiological variation as a mechanism for developmental caste-biasing in a facultatively eusocial sweat bee

2011 ◽  
Vol 279 (1732) ◽  
pp. 1437-1446 ◽  
Author(s):  
Karen M. Kapheim ◽  
Adam R. Smith ◽  
Kate E. Ihle ◽  
Gro V. Amdam ◽  
Peter Nonacs ◽  
...  
Keyword(s):  
Body Size ◽  
Division Of Labour ◽  
Ovary Development ◽  
Maternal Behaviour ◽  
Sweat Bee ◽  
Physiological Variation ◽  
Eusocial Insects ◽  
Caste Evolution ◽  
Social Caste ◽  
Reproductive Females

Social castes of eusocial insects may have arisen through an evolutionary modification of an ancestral reproductive ground plan, such that some adults emerge from development physiologically primed to specialize on reproduction (queens) and others on maternal care expressed as allo-maternal behaviour (workers). This hypothesis predicts that variation in reproductive physiology should emerge from ontogeny and underlie division of labour. To test these predictions, we identified physiological links to division of labour in a facultatively eusocial sweat bee, Megalopta genalis . Queens are larger, have larger ovaries and have higher vitellogenin titres than workers. We then compared queens and workers with their solitary counterparts—solitary reproductive females and dispersing nest foundresses—to investigate physiological variation as a factor in caste evolution. Within dyads, body size and ovary development were the best predictors of behavioural class. Queens and dispersers are larger, with larger ovaries than their solitary counterparts. Finally, we raised bees in social isolation to investigate the influence of ontogeny on physiological variation. Body size and ovary development among isolated females were highly variable, and linked to differences in vitellogenin titres. As these are key physiological predictors of social caste, our results provide evidence for developmental caste-biasing in a facultatively eusocial bee.

scholarly journals Polymorphism and division of labour in a socially complex ant: neuromodulation of aggression in the Australian weaver ant, Oecophylla smaragdina

2015 ◽  
Vol 282 (1811) ◽  
pp. 20150704 ◽  
Author(s):  
J. Frances Kamhi ◽  
Kelley Nunn ◽  
Simon K. A. Robson ◽  
James F. A. Traniello
Keyword(s):  
Social Systems ◽  
Division Of Labour ◽  
Oecophylla Smaragdina ◽  
Minor Worker ◽  
Task Specialization ◽  
Territorial Defence ◽  
Weaver Ant ◽  
Eusocial Insects ◽  
Worker Size ◽  
Pharmacological Manipulations

Complex social structure in eusocial insects can involve worker morphological and behavioural differentiation. Neuroanatomical variation may underscore worker division of labour, but the regulatory mechanisms of size-based task specialization in polymorphic species are unknown. The Australian weaver ant, Oecophylla smaragdina , exhibits worker polyphenism: larger major workers aggressively defend arboreal territories, whereas smaller minors nurse brood. Here, we demonstrate that octopamine (OA) modulates worker size-related aggression in O. smaragdina . We found that the brains of majors had significantly higher titres of OA than those of minors and that OA was positively and specifically correlated with the frequency of aggressive responses to non-nestmates, a key component of territorial defence. Pharmacological manipulations that effectively switched OA action in major and minor worker brains reversed levels of aggression characteristic of each worker size class. Results suggest that altering OA action is sufficient to produce differences in aggression characteristic of size-related social roles. Neuromodulators therefore may generate variation in responsiveness to task-related stimuli associated with worker size differentiation and collateral behavioural specializations, a significant component of division of labour in complex social systems.

scholarly journals Body Size Differences between Foraging and Intranidal Workers of the Monomorphic Ant Lasius niger

Insects ◽  
2020 ◽  
Vol 11 (7) ◽  
pp. 433
Author(s):  
Mateusz Okrutniak ◽  
Bartosz Rom ◽  
Filip Turza ◽  
Irena M. Grześ
Keyword(s):  
Body Size ◽  
Field Experiment ◽  
Important Determinant ◽  
Size Variation ◽  
Division Of Labour ◽  
The Body ◽  
Food Type ◽  
Lasius Niger ◽  
Worker Size ◽  
Body Sizes

The association between the division of labour and worker body size of ants is typical for species that maintain physical castes. Some studies showed that this phenomenon can be also observed in the absence of distinct morphological subcastes among workers. However, the general and consistent patterns in the size-based division of labour in monomorphic ants are largely unidentified. In this study, we performed a field experiment to investigate the link between worker body size and the division of labour of the ant Lasius niger (Linnaeus, 1758), which displays limited worker size variation. We demonstrated that the body size of workers exploring tuna baits is slightly but significantly smaller than the size of workers located in the upper parts of the nest. Comparing the present results with existing studies, large workers do not seem to be dedicated to work outside the nest. We suggest that monomorphic workers of certain body sizes are flexible in the choice of task they perform, and food type may be the important determinant of this choice.

Reproductive patterns of European pond turtles differ between sites: a small scale scenario

2015 ◽  
Vol 36 (4) ◽  
pp. 339-349
Author(s):  
Marco A.L. Zuffi ◽  
Elena Foschi
Keyword(s):  
Body Size ◽  
Egg Production ◽  
Shell Height ◽  
The Body ◽  
Small Scale ◽  
Central Mediterranean ◽  
Population Structures ◽  
Body Sizes ◽  
Reproductive Females ◽  
Similar Body

From 1996 to 2002, we studied the body size, measures of reproductive strategy (relative clutch mass and delayed reproduction at sexual maturity), and reproductive output (clutch frequency and annual egg production) of female European Pond turtles,Emys orbicularis, at two sites separated by 12 km in central Mediterranean Tuscany (San Rossore and Camp Darby, central northern Italy). Females did not reproduce at the first appearance of external sexual characters, but reproduced at larger sizes, probably as older turtles. Among years, reproductive females were more common than were non-reproductive females, yet both groups had similar body sizes. Body size (carapace length and width, plastron length and width, shell height and body mass) varied between localities and among years. Body size differed between reproductive and non reproductive females in Camp Darby, but not in San Rossore females. Shell volume did not vary among years, nor between localities, nor between reproductive status. Reproductive females had higher body condition indices (BCI) than did non-reproductive females, while BCI did not differ between females laying one clutch and females laying multiple clutches. Clutch size did not vary among years. One clutch per year was much more frequent than multiple clutches, and multiple clutches were more frequent in Camp Darby than in San Rossore females, likely due to differences in population structures between sites.

scholarly journals The effect of age on non-reproductive division of labour in the tropical primitively eusocial wasp, Ropalidia cyathiformis

2020 ◽  
Vol 64 (4-5-6) ◽  
pp. 267-273
Author(s):  
Sruthi Unnikrishnan ◽  
Raghavendra Gadagkar
Keyword(s):  
Division Of Labour ◽  
Age Polyethism ◽  
Relative Age ◽  
Eusocial Insects ◽  
Primitively Eusocial Wasp ◽  
Eusocial Wasp ◽  
Reproductive Division Of Labour ◽  
Absolute Age ◽  
Reproductive Division ◽  
Primitively Eusocial

Division of labour among workers (non-reproductive division of labour), a characteristic feature of eusocial insects enables the efficient functioning of their colonies. In many advanced insect societies division of labour is based on age (age polyethism). Primitively eusocial insects however are believed to have a weak age polyethism. Here we investigated the role of age in non-reproductive division of labour in the tropical primitively eusocial wasp, Ropalidia cyathiformis and compared it with that in Ropalidia marginata, a congeneric species that exhibits relatively strong age polyethism. Age had a significant effect on the first performance of the four tasks studied; tasks were initiated in the sequence feed larva, build, bring food and bring building material. We measured task performance as the absolute frequency of tasks performed (FTP) and the probability of performing a task relative to other tasks (PTP) and age as absolute age in days since eclosion as well as relative age compared to nestmates. FTP varied significantly with both absolute and relative age, although absolute age explained more variance. PTP varied significantly with absolute age but not always with relative age. This is contrary to R. marginata, where more variation is explained by relative age than by absolute age. There was no trade-off between intranidal and extranidal tasks in R. cyathiformis unlike in R. marginata where the frequency of intranidal tasks decreased and that of extranidal tasks increased with age. We conclude that age polyethism is weak and less flexible in R. cyathiformis compared to that in R. marginata.

scholarly journals Honeybees possess a structurally diverse and functionally redundant set of queen pheromones

2019 ◽  
Vol 286 (1905) ◽  
pp. 20190517 ◽  
Author(s):  
Sarah A. Princen ◽  
Ricardo Caliari Oliveira ◽  
Ulrich R. Ernst ◽  
Jocelyn G. Millar ◽  
Jelle S. van Zweden ◽  
...  
Keyword(s):  
Division Of Labour ◽  
Ovary Development ◽  
Mandibular Glands ◽  
Queen Mandibular Pheromone ◽  
Queen Pheromones ◽  
Honeybee Queen ◽  
Queen Signal ◽  
Insect Societies ◽  
Reproductive Division Of Labour ◽  
Reproductive Division

Queen pheromones, which signal the presence of a fertile queen and induce workers to remain sterile, play a key role in regulating reproductive division of labour in insect societies. In the honeybee, volatiles produced by the queen's mandibular glands have been argued to act as the primary sterility-inducing pheromones. This contrasts with evidence from other groups of social insects, where specific queen-characteristic hydrocarbons present on the cuticle act as conserved queen signals. This led us to hypothesize that honeybee queens might also employ cuticular pheromones to stop workers from reproducing. Here, we support this hypothesis with the results of bioassays with synthetic blends of queen-characteristic alkenes, esters and carboxylic acids. We show that all these compound classes suppress worker ovary development, and that one of the blends of esters that we used was as effective as the queen mandibular pheromone (QMP) mix. Furthermore, we demonstrate that the two main QMP compounds 9-ODA and 9-HDA tested individually were as effective as the blend of all four major QMP compounds, suggesting considerable signal redundancy. Possible adaptive reasons for the observed complexity of the honeybee queen signal mix are discussed.

Body size, demography and foraging in a socially plastic sweat bee: a common garden experiment

2012 ◽  
Vol 66 (5) ◽  
pp. 743-756 ◽  
Author(s):  
Jeremy Field ◽  
Robert Paxton ◽  
Antonella Soro ◽  
Paul Craze ◽  
Catherine Bridge
Keyword(s):  
Body Size ◽  
Common Garden ◽  
Sweat Bee ◽  
Common Garden Experiment

Naked mole-rats (Heterocephalus glaber) do not specialise on cooperative tasks

2021 ◽  
Author(s):  
Susanne Siegmann ◽  
Romana Feitsch ◽  
Daniel W Hart ◽  
Nigel C Bennett ◽  
Dustin J Penn ◽  
...  
Keyword(s):  
Body Mass ◽  
Division Of Labour ◽  
Behavioural Plasticity ◽  
Specific Work ◽  
Heterocephalus Glaber ◽  
Eusocial Insects ◽  
Cooperative Tasks ◽  
Trade Offs ◽  
Mole Rat ◽  
Work Tasks

It has been proposed that naked mole-rat (Heterocephalus glaber) societies resemble those of eusocial insects by showing a division of labour among non-breeding individuals. Earlier studies suggested that non-breeders belong to distinct castes that specialise permanently or temporarily on specific cooperative tasks. In contrast, recent research on naked mole-rats has shown that behavioural phenotypes are continuously distributed across non-breeders and that mole-rats exhibit considerable behavioural plasticity suggesting that individuals may not specialise permanently on work tasks. However, it is currently unclear whether individuals specialise temporarily and whether there is a sex bias in cooperative behaviour among non-breeders. Here we show that non-breeding individuals vary in overall cooperative investment, but do not specialise on specific work tasks. Within individuals, investment into specific cooperative tasks such as nest building, food carrying and burrowing are positively correlated, and there is no evidence that individuals show trade-offs between these cooperative behaviours. Non-breeding males and females do not differ in their investment in cooperative behaviours and show broadly similar age and body mass related differences in cooperative behaviours. Our results suggest that non-breeding naked mole-rats vary in their overall contribution to cooperative behaviours and that some of this variation may be explained by differences in age and body mass. Our data provide no evidence for temporary specialisation, as found among some eusocial insects, and suggests that the behavioural organisation of naked mole-rats resembles that of other cooperatively breeding vertebrates more than that of eusocial insect species.

Carriers and cutters: size-dependent caste polyethism in the tropical fire ant (Solenopsis geminata)

2019 ◽  
Vol 110 (3) ◽  
pp. 388-396
Author(s):  
Ming-Chung Chiu ◽  
Wen-Jer Wu ◽  
Li-Chuan Lai
Keyword(s):  
Gaussian Mixture ◽  
Division Of Labour ◽  
Fire Ant ◽  
Life History Trait ◽  
Head Width ◽  
Large Prey ◽  
Task Partitioning ◽  
Solenopsis Geminata ◽  
Eusocial Insects ◽  
Large Worker

AbstractBody size is an important life-history trait in eusocial insects which plays a key role in colony fitness. The division of labour, represented by caste polyethism, correlates with divergent morphological traits. Size polymorphism has been noted in the tropical fire ant, Solenopsis geminata; however, little is known regarding the differences in the size distributions of workers performing foraging tasks. In the present study, task partitioning was observed in the foraging activities of S. geminata. Two subgroups among foraging workers of S. geminata were discovered using the Gaussian mixture model: a large worker group (head width ≥ 0.924 mm) and a small worker group (head width < 0.924 mm). The foraging worker population comprised two distinct groups – 25.64% were large workers and 74.36% were small workers. Larger workers delivered heavier seeds faster than smaller workers, but this difference became less apparent when lighter seeds were being carried. When large prey such as crickets was encountered during foraging, S. geminata partitioned their tasks into cutting and transportation. The large workers were observed to cut cricket prey into fragments with their longer mandibles, and the small workers then transported these fragments back to the nest. These results present evidence of task partitioning among tropical fire ants, with different tasks being performed by ants of different castes.

Variation in mating pattern in a population of the Andean frog Hyla labialis

2001 ◽  
Vol 22 (2) ◽  
pp. 199-207 ◽  
Author(s):  
Horst Lüddecke
Keyword(s):  
Body Size ◽  
Mate Choice ◽  
Female Mate Choice ◽  
Male Competition ◽  
The Body ◽  
Size Difference ◽  
Mating Pattern ◽  
Colombian Andes ◽  
Reproductive Females ◽  
Breeding Seasons

AbstractUnmated frogs and mated pairs from a population of individually marked Hyla labialis were captured, measured and released over four consecutive years in a highland valley of the Colombian Andes. Across eight prolonged breeding seasons, three times more males than females were captured. On average, females were significantly larger than males. Although the largest reproductive males were larger than the smallest reproductive females, amplexing males were always smaller than the females they clasped. Larger males had no mating advantage, because the body size distribution of males was the same for mated and unmated males, and the average snout-vent length of mated males was similar to that of unmated males. There was no indication of larger males taking over clasped females during male-male competition, because there was no size difference between males clasping gravid, spawning and spent females. Significantly size-assortative matings occurred on days when male availability per female was moderately high, but not when it was low, suggesting that female mate choice is relatively more important than male-male competition in shaping mating pattern.

The link between sexual dimorphism, activity budgets, and group cohesion: the case of the plains zebra (Equus burchelli)

2002 ◽  
Vol 80 (8) ◽  
pp. 1437-1441 ◽  
Author(s):  
P Neuhaus ◽  
K E Ruckstuhl
Keyword(s):  
Body Size ◽  
Reproductive Status ◽  
Sexually Dimorphic ◽  
Time Budgets ◽  
Activity Budgets ◽  
Equus Burchelli ◽  
Lactating Females ◽  
Males And Females ◽  
Reproductive Females ◽  
Dimorphic Species

Animals that differ in reproductive status and body size have different needs in terms of foraging and resting. In most social ungulates this leads to sexual segregation, probably because of incompatibilities between the activity budgets of males and females. Since most studies on behavioural differences between the sexes have been done on sexually dimorphic species, we decided to look at a system in which males and females are similar in body size. We studied time budgets, synchrony of behaviour, and bite rates of plains zebras (Equus burchelli) to evaluate the factors that enable these extremely social ungulates to stay in stable mixed-sex family groups throughout the year. As we predicted, time budgets were similar among males, lactating females, pregnant females, and non-reproductive females. Furthermore, we observed close synchronization of behaviours between females that differed in reproductive status and males. Lactating females, however, did take more bites per minute when foraging than either pregnant or non-reproducing females or males. We assume that the higher bite rates of lactating females were due to the extra costs of producing milk for their foal. We concluded that the special harem mating system, and for females the year-round possibility of conceiving, force the animals to synchronize their time budgets, which might be a major reason for the lack of difference in body size between males and females.

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