Male Burrows Research Articles

Challenging monogamy in a spider with nontraditional sexual behavior

Each species and sex can develop different reproductive strategies to optimize their fitness while assigning reproductive effort. Allocosasenex is a sex-role reversed spider whose males construct long burrows in the sand. They wait for wandering females to approach, assess their sexual partners and donate their constructions to females after copulation. Females stay in the burrow and lay their egg-sac. When offspring are ready for dispersion, females leave the burrow and gain access to new mating opportunities. Males are choosy during mate courtship, preferring to mate with virgin females over copulated ones, which can even be cannibalized if males reject them. This situation turns new mating opportunities dangerous for copulated females. We wondered whether a copulated female inside the previous mate's burrow responds to courtship from a new male and if this new male can copulate, avoiding burrow construction costs. We also explored whether courtship and copulation behaviors during the first sexual encounter affected the probability of occurrence of a second copulation. For that purposes we exposed copulated females inside male burrows to new males (non-donor males). Males could locate and court females inside the previous male's burrow, and females accepted a second copulation. Hence, A.senex females are not monogamous as was expected but increase their reproductive success by copulating with non-donor males. Also, males can develop opportunistic tactics, suggesting a more dynamic mating system for this sex-role reversed spider than assumed.

Mating behavior of the Iranian fiddler crab Austruca iranica Pretzmann, 1971 (Decapoda: Brachyura: Ocypodidae), with an emphasis on the mate choice of burrow-mating females

Abstract Fiddler crabs exhibit two modes of mating: burrow and surface mating. In burrow mating, males wave and attract mate-searching females for mating inside their burrows, whereas in surface mating males search for and mate with females on the surface. We studied the reproductive behavior of Austruca iranica (Pretzmann, 1971), an Indo-West Pacific species, specifically female-mate choice with regard to the size of both male individuals and their burrows. We also compared the size of male and female burrows in the population. Austruca iranica performed both surface and burrow mating despite the different size of the burrow of the two sexes, within the semi-lunar tide cycles at the study site. There was strong size-assortative mating in burrow mating. Burrow-mating females generally chose larger males and wider burrows and even though chosen and rejected males were not different in burrow length, females sampled males with longer than average burrows. Surface-mating females also possessed burrows that were longer than those of the females in the population and this may have enabled them to mate on the surface and breed alone. Regardless of its similarities to some species that only perform burrow mating; the ecology of A. iranica has made it possible for this species to mate on the surface as well as in male-defended burrows. The choice of large males by burrow mating females may provide benefits to females from both the large male itself (e.g., protection) and his wider burrow (e.g., better incubation temperature).

Burrow characteristics and temporal variation in burrow temperature of the fiddler crab Tubuca rosea (Tweedie, 1937) (Brachyura, Ocypodidae) in southern Thailand

Abstract This study investigates the burrow temperature of large-sized male and female Tubuca rosea (Tweedie, 1937) crabs as well as the soil temperature near their burrows during the day and night. Burrow and soil temperatures were measured using temperature sensors and burrow characteristics were recorded. Both sexes built I- and J-shaped burrows. Female burrows were longer and deeper than male burrows, since female burrows act as breeding burrows in this species. J-shaped burrows were longer and slightly deeper than I-shaped ones. During the day, the burrow temperature was lower than the soil temperature; however, during the night, the opposite result was observed. The burrow length/depth was negatively correlated with the burrow temperature during the day, but these correlations were positive during the night. This study shows that the burrow characteristics of T. rosea modulate the inside temperature of the burrows, maintaining a suitable temperature for the crabs.

Amazon freshwater crab Dilocarcinus pagei (Decapoda: Trichodactylidae): a view about burrow construction behavior

Crabs use burrows to prevent predation, environmental interference and shelter. The present study investigated the excavation behavior of the trichodactylid crab Dilocarcinus pagei, considering the biometric aspects of the burrows, the excavation time, the amount of bioturbation and the excavation behavior of the two sexes. The burrows of males had a mean diameter larger than the females, although the depth was similar for both sexes. Females had higher bioturbation than males, and showed enlargement in a camera format at the bottom, even closing the entrance of the burrows with a "plug" after their construction. Both the camera and the presence of the "plug" in the burrows of the females may be associated with reproduction. The presence of pellets observed at the entrance of burrows is associated with the cleaning of the pereiopods by crabs after the excavation. The sequence of behaviors for the construction of the burrows is described in detail, contributing to the knowledge about the biology and ecology of freshwater crabs of the Amazon.

Previous experience and substrate matter: Plasticity in burrow digging in a South American wolf spider

Burrowing behavior can be affected by substrate conditions such as percentages of minerals, organic substances, granulometry, and biotic factors like densities of burrowing individuals, potential prey, and predators. Allocosa senex is a wolf spider that inhabits sandy areas next to rivers, lakes, and sandy coasts of the Atlantic Ocean in Argentina, Brazil, and Uruguay. This species shows reversal in sexual size dimorphism and sex roles, meaning that females are the smaller, more mobile and courting sex. Though all individuals dig burrows, the burrows of males are longer, and these are the sites where mating and oviposition occurs. The geographical distribution of this species includes coastal areas that differ in substrate granulometry, which could affect the characteristics of the burrows. Our objective was to test the occurrence of digging plasticity in A. senex in response to consecutive digging events and after sequential exposures to substrates with different granulometry. Males tended to enlarge their burrows after repeated digging events. Burrows were shorter on the fine substrate, and individuals showed greater weight loss after digging there. This could suggest that making a burrow in fine substrate is more energetically demanding than in coarse substrate. Individuals of A. senex are able to adapt their digging behavior according to substrate characteristics in order to maximize their fitness.

Sexual dimorphism in the spinning apparatus ofAllocosa senex(Araneae: Lycosidae), a wolf spider with a reversal in typical sex roles

Allocosa senex (Mello-Leitão, 1945) is a sex role-reversed wolf spider that inhabits sandy water-margin environments of southern South America. Males are larger than females and dig deeper burrows. Females are the courting sex and they prefer to mate with males that build deep burrows, suggesting high selective pressures on male digging behavior. Our aim was to investigate the external morphology and histological constitution of the spinning apparatus of males, females and juveniles of A. senex. Our results showed that A. senex adult males possess more piriform glands and spigots than adult females and juveniles. These glands produce silk for attachment discs that are crucial for the stability of the burrows. The differences according to the sex could be related to females' and males' digging strategies and strong selection on male burrow length in this species.

Surface mating influences chimney/burrow characteristics of Uca rosea (Tweedie, 1937) (Brachyura, Ocypodidae) in southern Thailand

We investigated how surface mating affects the characteristics of chimneys (diameter, height, and thickness) and burrows (total length, horizontal length, total depth, volume and shapes) in Uca rosea (Tweedie, 1937). In U. rosea, surface mating is the main mating mode, and females incubate eggs inside their own burrows. We investigated 73 randomly selected burrows with chimneys (36 females, and 37 males). We observed that chimney and burrow characteristics, except for burrow/chimney diameter, were greater in females than in similar-sized males. The burrows were I- and J-shaped, with a higher number of J-shaped burrows in females and a higher number of I-shaped burrows in males. J-shaped burrows were longer and deeper, had greater volumes, and had higher and thicker chimneys, than I-shaped burrows. Chimney characteristics were positively correlated with burrow characteristics. Our results indicate that U. rosea female burrows are used for breeding, and male burrows are used for temporary stays.

Claw regeneration, waving display and burrow characteristics of Austruca perplexa (H. Milne Edwards, 1852) (Brachyura, Ocypodidae) from southern Thailand

Abstract We studied the effects of claw regeneration on male waving rate and burrow characteristics (i.e., important mate choice criteria) by examining the waving rates and burrow characteristics (diameter, total and horizontal lengths, depth, volume, maximum width, entry and burrow angles, and presence and location of chambers) of large-sized original-clawed males (OCMs) and regenerated-clawed males (RCMs) of Austruca perplexa (H. Milne Edwards, 1852). Female burrows were also examined. The results showed that female burrows were smaller than male burrows, with no chamber and, thus, female burrows are not used for breeding; however, 80% of RCM burrows, and 65% of OCM burrows, had chambers. Other characteristics were not different between RCM and OCM burrows, except for maximum width, which was larger in RCM burrows. The waving rates of OCMs and RCMs were not different. Our results indicate that claw regeneration do not have detrimental effects on male waving rate and burrow characteristics.

Construction of earthen structure as a sexual signals in the fiddler crabs

We studied the reproductive behavior and the construction of an earthen structure in the four species of fiddler crab with reference to their habitat. Males of the Uca sindensis and U. iranica inhibit on open mudflats, construct the pillar and semidome structures at or near to the burrows openings. These structures perform the function to attract females, who wandering on the surface between male burrows for mating as well as provide protection or hiding object against the avian predator to mates. There were no earthen structures were observed in U. urvillie and U. annulipes , which inhibit among the vegetation. The well-marked intersexual different arrangement of mudballs was observed in U. annulipes . The earthen structures (pillar and semidome) and mudballs arrangements help courting females to assess the quality of mate as well as internal conditions of the burrow.

Thermal constraints on microhabitat selection and mating opportunities

Hot tropical environments constrain ectotherm mating opportunities when mate selection occurs on the surface. Thus, microhabitats and refugia can become a qualitative trait in mate selection. In fiddler crabs, the enlarged claw of males can act as a heat sink, which becomes advantageous when surface temperatures reach 50 °C during the day and crabs are actively seeking to mate. Uca mjoebergi females prefer male burrows found in the shade; therefore, we investigated the thermal constraints imposed on males and females in shaded and unshaded habitats. Crab surface activity decreased and body temperature increased as the day progressed, with more crabs active in shaded than sunny microhabitats. Body temperature was lower in male crabs found in burrows relative to crabs on the surface. Male claw size explained 10% of body temperature. Our results add further support to the hypothesis that thermal constraints imposed on males can be overcome by the large claw acting as a heat sink and the burrow acting as a refuge from heat. Classic sexually selected traits, including ornaments and behaviours, can have a secondary purpose in thermoregulation.

Burrow ornamentation in the fiddler crab (Uca leptodactyla): female mate choice and male–male competition

Non-biological ornamentation is found in the nests and burrows of different kinds of animals. We evaluated here whether sand hoods constructed by male fiddler crabs (Uca leptodactyla) are one of the signals used by males to attract females during courtship. We observed females when they were walking among the males, and we quantified the proportion of females that visited male burrows with and without ornamentation and the choice to stay in a male’s burrow. Females visited more burrows with hoods than burrows without hoods, and they chose significantly more builder males. Male investment in ornamentation nevertheless decreased when the proportion of females increased in the area. Male investment was not correlated with the proportion of non-builder males nearby, but was positively correlated with overall density. The density sex ratio, however, was more male-biased in high-density than in low-density areas suggesting that even if building attracts females, the function could be related to male competition for mates.

Male mating success in a fiddler crab: a lesson in sample sizes

Autotomy and regrowth of a body part occurs in many animal species. It is costly to regrow the limb and there are often additional long-term costs in, for example, limb strength, foraging efficiency and even mating success. In the fiddler crab Uca mjoebergi, 7 % of males have autotomized and regrown their large claw at some point in their lives. Previous work has shown that there is a great disadvantage to having a regenerated claw. While these males are able to attract mate-searching females to visit them, none of the 84 males observed to have mated in previously collected data had regenerated claws. Since females’ final mate choice is based on burrow structure, it was assumed that males with regenerated claws had poorer burrows. Here we show that, by finding only three cases of a female mating with a regenerated claw male, that there is, in fact, no mating disadvantage to having a regenerated claw. We also show that the burrows of males with regenerated claws are no different than those of orginal-clawed males. This is a very clear reminder that sample size matters, especially when dealing with rare events.

Characterisation of burrow architecture under natural conditions in the sand-dwelling wolf spider Allocosa brasiliensis

Allocosa brasiliensis (Petrunkevitch, 1910) is a wolf spider that constructs silk-lined burrows along the coastal sand dunes of Argentina, Brazil and Uruguay. This species shows a reversal in typical sex roles and sexual size dimorphism expected for spiders. Females are the smaller and mobile sex, which initiates courtship at the male burrow entrance. Mating occurs in the male burrow, and when it ends, the male leaves and the female stays inside. Females prefer to mate with those males showing longest burrows, so burrow dimensions would be under strong sexual selection pressures. Previous studies in the laboratory indicated that male burrows are longer than those of virgin females, which were described as simple silk capsules. Preliminary observations suggested that juvenile burrows presented differences from those of adults; however, detailed observations of A. brasilienisis burrow characteristics at the field were lacking. The aim of this study was to characterise the burrows of adults and juveniles of A. brasiliensis under natural conditions. We recorded the dimensions of burrows inhabited by males, females and juveniles (n = 30 for each category) and created beeswax moulds that reflected burrow shape. Juveniles inhabited tubular burrows with two branches and two openings; on the contrary, adults were found in tubular burrows with a single entry. Males and females inhabited burrows of similar length and width, but those of juveniles were shorter and narrower. We discuss the results and their possible functional explanations according to the selective pressures expected for each developmental stage and sex.

Constraints imposed by the major cheliped on burrow construction in the male fiddler crab, Uca annulipes (H. Milne Edwards, 1837)

The burrows excavated by male Uca annulipes at a lagoonal shore on Pulau Hantu Besar, an offshore island of Singapore, are generally less acutely bent, i.e., have significantly smaller mid-angles, than the burrows of females. In an ex situ study, burrows dug by males with the major cheliped removed, and by males with intact major cheliped, were cast with wax. Seven non-angular burrow morphological parameters (burrow diameter, total burrow depth, burrow neck height, curved burrow length, horizontal length, chamber diameter and burrow volume) and two angular variables (mid-angle and ground-angle) were compared to determine if sexual dimorphism in burrow curvature was due to the effect of the major cheliped on burrow excavation. A similar experiment using females with two intact chelipeds and one cheliped removed was conducted to determine if male crabs without the major cheliped dug burrows with dimensions similar to those of females with one cheliped removed. Mean mid-angle of burrows (± SE) was 24.9 ± 1.3° and 16.0 ± 1.0° for males whose major chelipeds were removed and with major intact chelipeds, respectively. Of all the burrow morphological parameters, only the mean mid-angle differed significantly between the two groups of crabs. Female crabs (with and without cheliped removal) did not excavate significantly different-shaped burrows (mid-angles: 20.7 ± 2.1° and 18.2 ± 1.5°, respectively) suggesting that removal of cheliped did not affect burrow architecture. The curvature of the burrows of males that had the major cheliped removed was not significantly different from those of females with one cheliped removed (mid-angles: 24.9 ± 1.3° and 20.7 ± 2.1°, respectively). Results of the study showed that the major cheliped in a male U. annulipes is most likely to be responsible for the sexual dimorphism in curvature of the burrows.

Effects of population density on female and male burrow characteristics in the fiddler crab, Uca bengali Crane, 1975

We examined the effects of population density on body size and burrow characteristics ofUca bengaliCrane, 1975. We predicted that (1) males in high-density areas (HD) should be larger in size and build higher quality burrows than males in low-density areas (LD), and (2) HD females should be larger in size, but build lower quality burrows than LD females, as HD females can find higher numbers of good quality male burrows around them for breeding and egg incubation. Our results showed that males and females in HD were larger in size than those in LD. Since HD males were larger in size, they built higher quality burrows than males in LD. On the other hand, even though LD females were smaller in size than HD ones, they built higher quality burrows than HD females. Our results thus indicate that density effects both body size and burrow characteristics.

Habitat-related differences in the pre-copulatory guarding and copulation behavior of Neohelice granulata (Brachyura, Grapsoidea, Varunidae)

Mating behavior strategies of brachyuran crabs are flexible depending on the habitat and social context. We evaluate pre-copulatory guarding in Neohelice granulata and describe the unusual copulatory behavior. Laboratory experiments were conducted to test whether factors such as male size, presence of burrows, a male-biased operational sex ratio (OSR) and female mating history affect the copulation duration in two different study areas. Females initiated a searching behavior approximately 20–26h before they became receptive by assessing large male burrows and displaying a courtship behavior (“flirting”) in its entrance. Once the female entered inside the male burrow, pre-copulatory guarding was observed until the female became receptive and successful copulation occurred immediately after. This species shows some very unusual copulatory behavior involving eyestalk grasping not seen in any other varunid crab. The copulation duration was independent of male size and the presence of burrows, although it was dependent on the study area, the OSR and the female mating history. Thus, copulation duration is a flexible character in this species which varies with habitat and biological factors such as mating history and sex ratio.

Seasonal Effects on Digging Activity and Burrow Architecture in the Cape Dune Mole-Rat,Bathyergus suillus(Rodentia: Bathyergidae)

Most polygynous male mammals exhibit little or no parental care or involvement raising young. Instead, they invest indirectly in their own morphological and physiological attributes which enhance their chance of reproduction. Such secondary morphological sex traits may contribute to differences in the burrow architecture of fossorial mammals, such as the Cape dune mole-rat, Bathyergus suillus. Indeed, little is known about the seasonal changes in burrow architecture or differences in burrow configuration may differ between the sexes of subterranean African mole-rats (Bathyergidae). We excavated burrow systems of male and female B. suillus during the summer and the winter to investigate whether male burrow architecture reflected putative mate-seeking behaviour. We consider burrow geometry in response to mating strategies. Male burrow systems explored the environment more efficiently than females. This is presumably because of the increase in associated energetic costs of being a large male. Males produce more mounds indicating territorial behaviour even when it is energetically costly to dispose of soil onto the surface when the soil is less friable during the summer. Overall tunnel dimensions did not differ between the sexes. It appears that a change in season does not affect the geometry of the burrow system or tunnel dimensions in a climatically buffered environment.

Amylin blunts hyperphagia and reduces weight and fat gain during recovery in socially stressed rats.

During recovery from social stress in a visible burrow system (VBS), during which a dominance hierarchy is formed among the males, rats display hyperphagia and gain weight preferentially as visceral adipose tissue. By proportionally increasing visceral adiposity, social stress may contribute to the establishment of metabolic disorder. Amylin was administered to rats fed ad libitum during recovery from VBS stress in an attempt to prevent hyperphagia and the resultant gain in body weight and fat mass. Amylin treatment reduced food intake, weight gain, and accumulation of fat mass in male burrow rats, but not in male controls that spent time housed with a single female rather than in the VBS. Amylin did not alter neuropeptide Y (NPY), agouti-related peptide (AgRP), or proopiomelanocortin (POMC) mRNA expression in the arcuate nucleus of the hypothalamus as measured at the end of the recovery period, nor did it affect plasma corticosterone or leptin. Amylin exerted most of its effect on food intake during the first few days of recovery, possibly through antagonism of NPY and/or increasing leptin sensitivity. The potential for chronic social stress to contribute to metabolic disorder is diminished by amylin treatment, though the neuroendocrine mechanisms behind this effect remain elusive.

Seasonal effects on digging activity and burrow architecture in the Cape dune mole-rat, Bathyergus suillus (Rodentia: Bathyergidae)

Most polygynous male mammals exhibit little or no parental care or involvement raising young. Instead, they invest indirectly in their own morphological and physiological attributes which enhance their chance of reproduction. Such secondary morphological sex traits may contribute to differences in the burrow architecture of fossorial mammals, such as the Cape dune mole-rat, Bathyergus suillus. Indeed, little is known about the seasonal changes in burrow architecture or differences in burrow configuration may differ between the sexes of subterranean African mole-rats (Bathyergidae). We excavated burrow systems of male and female B. suillus during the summer and the winter to investigate whether male burrow architecture reflected putative mate-seeking behaviour. We consider burrow geometry in response to mating strategies. Male burrow systems explored the environment more efficiently than females. This is presumably because of the increase in associated energetic costs of being a large male. Males produce more mounds indicating territorial behaviour even when it is energetically costly to dispose of soil onto the surface when the soil is less friable during the summer. Overall tunnel dimensions did not differ between the sexes. It appears that a change in season does not affect the geometry of the burrow system or tunnel dimensions in a climatically buffered environment.

Male mate choice in Allocosa alticeps (Araneae: Lycosidae), a sand-dwelling spider with sex role reversal

Abstract When males have high reproductive investment and female quality is variable, male assessment of sexual partners is expected. Allocosa alticeps (Mello-Leitao 1944) is a nocturnal wolf spider that shows a reversal in the sex roles and sexual size dimorphism usual in spiders. Females are the smaller, mobile sex, and they initiate courtship. Males construct burrows that serve as mating refuges and nests for female oviposition and cocoon care. In sex role reversed systems, male mate assessment is expected. Our objective was to test the occurrence of sequential male mate assessment based on female reproductive status and/or body characteristics in A. alticeps, discussing the results under sex role reversal hypotheses. We exposed males consecutively to virgin females and mated females and then recorded both courtship performance and mating occurrences relative to individuals' body characteristics. Virgin and mated females detected and entered male burrows in all the cases, and they were courted by males...