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Donald L. Mykles - One of the best experts on this subject based on the ideXlab platform.

  • Characterization of G-protein coupled receptors from the blackback land crab Gecarcinus lateralis Y organ transcriptome over the molt cycle.
    BMC Genomics, 2019
    Co-Authors: Nhut Minh Tran, Donald L. Mykles, Abigail Elizur, Tomer Ventura
    Abstract:

    Background: G-protein coupled receptors (GPCRs) are ancient, ubiquitous, constitute the largest family of transducing cell surface proteins, and are integral to cell communication via an array of ligands/neuropeptides. Molt inhibiting hormone (MIH) is a key neuropeptide that controls growth and reproduction in crustaceans by regulating the molt cycle. It inhibits ecdysone biosynthesis by a pair of endocrine glands (Y-organs; YOs) through binding a yet uncharacterized GPCR, which triggers a signalling cascade, leading to inhibition of the ecdysis sequence. When MIH release stops, ecdysone is synthesized and released to the hemolymph. A peak in ecdysone titer is followed by a molting event. A transcriptome of the blackback land crab Gecarcinus lateralis YOs across molt was utilized in this study to curate the list of GPCRs and their expression in order to better assess which GPCRs are involved in the molt process. Results: Ninety-nine G. lateralis putative GPCRs were obtained by screening the YO transcriptome against the Pfam database. Phylogenetic analysis classified 49 as class A (Rhodopsin-like receptor), 35 as class B (Secretin receptor), and 9 as class C (metabotropic glutamate). Further phylogenetic analysis of class A GPCRs identified neuropeptide GPCRs, including those for Allatostatin A, Allatostatin B, Bursicon, CCHamide, FMRFamide, Proctolin, Corazonin, Relaxin, and the biogenic amine Serotonin. Three GPCRs clustered with recently identified putative CHH receptors (CHHRs), and differential expression over the molt cycle suggests that they are associated with ecdysteroidogenesis regulation. Two putative Corazonin receptors showed much higher expression in the YOs compared with all other GPCRs, suggesting an important role in molt regulation. Conclusions: Molting requires an orchestrated regulation of YO ecdysteroid synthesis by multiple neuropeptides. In this study, we curated a comprehensive list of GPCRs expressed in the YO and followed their expression across the molt cycle. Three putative CHH receptors were identified and could include an MIH receptor whose activation negatively regulates molting. Orthologs of receptors that were found to be involved in molt regulation in insects were also identified, including LGR3 and Corazonin receptor, the latter of which was expressed at much higher level than all other receptors, suggesting a key role in YO regulation.;

  • transcriptome analysis of the molting gland y organ from the blackback land crab gecarcinus lateralis
    Comparative Biochemistry and Physiology Part D: Genomics and Proteomics, 2016
    Co-Authors: Sunetra Das, Natalie L Pitts, Megan R Mudron, David S Durica, Donald L. Mykles
    Abstract:

    In decapod crustaceans, arthropod steroid hormones or ecdysteroids regulate molting. These hormones are synthesized and released from a pair of molting glands called the Y-organs (YO). Cyclic nucleotide, mTOR, and TGFβ/Smad signaling pathways mediate molt cycle-dependent phase transitions in the YO. To further identify the genes involved in the regulation of molting, a YO transcriptome was generated from three biological replicates of intermolt blackback land crab, Gecarcinus lateralis. Illumina sequencing of cDNA libraries generated 227,811,829 100-base pair (bp) paired-end reads; following trimming, 90% of the reads were used for further analyses. The trimmed reads were assembled de novo using Trinity software to generate 288,673 contigs with a mean length of 872 bp and a median length of 1842 bp. Redundancy among contig sequences was reduced by CD-HIT-EST, and the output constituted the baseline transcriptome database. Using Bowtie2, 92% to 93% of the reads were mapped back to the transcriptome. Individual contigs were annotated using BLAST, HMMER, TMHMM, SignalP, and Trinotate, resulting in assignments of 20% of the contigs. Functional and pathway annotations were carried out via gene ontology (GO) and KEGG orthology (KO) analyses; 58% and 44% of the contigs with BLASTx hits were assigned to GO and KO terms, respectively. The gene expression profile was similar to a crayfish YO transcriptome database, and the relative abundance of each contig was highly correlated among the three G. lateralis replicates. Signal transduction pathway orthologs were well represented, including those in the mTOR, TGFβ, cyclic nucleotide, MAP kinase, calcium, VEGF, phosphatidylinositol, ErbB, Wnt, Hedgehog, Jak-STAT, and Notch pathways.

  • rheb an activator of target of rapamycin in the blackback land crab gecarcinus lateralis cloning and effects of molting and unweighting on expression in skeletal muscle
    The Journal of Experimental Biology, 2012
    Co-Authors: Kyle S Maclea, Joseph A Covi, Brandon D Bader, Ernest S Chang, Ali M Abuhagr, Natalie L Pitts, Donald L. Mykles
    Abstract:

    SUMMARY Molt-induced claw muscle atrophy in decapod crustaceans facilitates exuviation and is coordinated by ecdysteroid hormones. There is a 4-fold reduction in mass accompanied by remodeling of the contractile apparatus, which is associated with an 11-fold increase in myofibrillar protein synthesis by the end of the premolt period. Loss of a walking limb or claw causes a loss of mass in the associated thoracic musculature; this unweighting atrophy occurs in intermolt and is ecdysteroid independent. Myostatin (Mstn) is a negative regulator of muscle growth in mammals; it suppresses protein synthesis, in part, by inhibiting the insulin/metazoan target of rapamycin (mTOR) signaling pathway. Signaling via mTOR activates translation by phosphorylating ribosomal S6 kinase (s6k) and 4E-binding protein 1. Rheb (Ras homolog enriched in brain), a GTP-binding protein, is a key activator of mTOR and is inhibited by Rheb-GTPase-activating protein (GAP). Akt protein kinase inactivates Rheb-GAP, thus slowing Rheb-GTPase activity and maintaining mTOR in the active state. We hypothesized that the large increase in global protein synthesis in claw muscle was due to regulation of mTOR activity by ecdysteroids, caused either directly or indirectly via Mstn. In the blackback land crab, Gecarcinus lateralis , a Mstn-like gene ( Gl-Mstn ) is downregulated as much as 17-fold in claw muscle during premolt and upregulated 3-fold in unweighted thoracic muscle during intermolt. Gl-Mstn expression in claw muscle is negatively correlated with hemolymph ecdysteroid level. Full-length cDNAs encoding Rheb orthologs from three crustacean species ( G. lateralis , Carcinus maenas and Homarus americanus ), as well as partial cDNAs encoding Akt ( Gl-Akt ), mTOR ( Gl-mTOR ) and s6k ( Gl-s6k ) from G. lateralis , were cloned. The effects of molting on insulin/mTOR signaling components were quantified in claw closer, weighted thoracic and unweighted thoracic muscles using quantitative polymerase chain reaction. Gl-Rheb mRNA levels increased 3.4-fold and 3.9-fold during premolt in claw muscles from animals induced to molt by eyestalk ablation (ESA) and multiple leg autotomy (MLA), respectively, and mRNA levels were positively correlated with hemolymph ecdysteroids. There was little or no effect of molting on Gl-Rheb expression in weighted thoracic muscle and no correlation of Gl-Rheb mRNA with ecdysteroid titer. There were significant changes in Gl-Akt , Gl-mTOR and Gl-s6k expression with molt stage. These changes were transient and were not correlated with hemolymph ecdysteroids. The two muscles differed in terms of the relationship between Gl-Rheb and Gl-Mstn expression. In thoracic muscle, Gl-Rheb mRNA was positively correlated with Gl-Mstn mRNA in both ESA and MLA animals. By contrast, Gl-Rheb mRNA in claw muscle was negatively correlated with Gl-Mstn mRNA in ESA animals, and no correlation was observed in MLA animals. Unweighting increased Gl-Rheb expression in thoracic muscle at all molt stages; the greatest difference (2.2-fold) was observed in intermolt animals. There was also a 1.3-fold increase in Gl-s6k mRNA level in unweighted thoracic muscle. These data indicate that the mTOR pathway is upregulated in atrophic muscles. Gl-Rheb , in particular, appears to play a role in the molt-induced increase in protein synthesis in the claw muscle.

  • cloning of a nitric oxide synthase from green shore crab carcinus maenas a comparative study of the effects of eyestalk ablation on expression in the molting glands y organs of c maenas and blackback land crab gecarcinus lateralis
    Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2011
    Co-Authors: Audrey A Mcdonald, Ernest S Chang, Donald L. Mykles
    Abstract:

    Molting in decapod crustaceans is regulated by ecdysteroids produced by a pair of Y-organs (YOs) located in the cephalothorax. YO ecdysteroidogenesis is suppressed by molt-inhibiting hormone (MIH), a neuropeptide produced in the X-organ of the eyestalk (ES) ganglia. MIH signaling may involve nitric oxide synthase (NOS) and NO-sensitive guanylyl cyclase (GC-I). A full-length cDNA encoding Carcinus maenas NOS (Cm-NOS; 3836 base pairs) of 1164 amino acid residues (estimated mass 131,833 Da) was cloned with 88% identity to Gecarcinus lateralis NOS (Gl-NOS). End-point reverse transcription-polymerase chain reaction (RT-PCR) showed that Cm-NOS was expressed at varying levels in the YO, testis, ovary, hepatopancreas, midgut, hindgut, heart, thoracic ganglion, and skeletal muscle and was not detected in the gill. Immunofluorescence microscopy showed localization of NOS and cGMP in the steroidogenic cells and the surrounding connective tissue layer of the C. maenas YO. ES ablation (ESA) induced molting in G. lateralis; hemolymph ecdysteroid titers increased during premolt and reached a peak of about 400 pg/μL at 20 days and 24 days post-ESA. By contrast, ESA did not induce molting in C. maenas; hemolymph ecdysteroid titers increased about 2-fold (53 to 121 pg/μL) by 3 days post-ESA and remained at that level at 7 days post-ESA. Real time PCR was used to quantify the effects of ESA on the expression of NOS in C. maenas and G. lateralis YOs. ESA caused 32-fold and 5-fold increases in Gl-NOS and Cm-NOS transcripts by 24 days and 7 days post-ESA, respectively, which were correlated with hemolymph ecdysteroid levels. In addition, GC-I catalytic subunit (Gl-GC-Iβ) mRNA level increased 7.4-fold by 24 days post-ESA, but there was no significant effect of ESA on membrane GC (Gl-GC-II) mRNA level. These data indicate that the YO up-regulates NO signaling components in response to withdrawal of ES neuropeptides.

  • molt cycle regulation of protein synthesis in skeletal muscle of the blackback land crab gecarcinus lateralis and the differential expression of a myostatin like factor during atrophy induced by molting or unweighting
    The Journal of Experimental Biology, 2010
    Co-Authors: Joseph A Covi, Brandon D Bader, Ernest S Chang, Donald L. Mykles
    Abstract:

    SUMMARY In decapod crustaceans, claw muscle undergoes atrophy in response to elevated ecdysteroids while thoracic muscle undergoes atrophy in response to unweighting. The signaling pathways that regulate muscle atrophy in crustaceans are largely unknown. Myostatin is a negative regulator of muscle growth in mammals, and a myostatin-like cDNA is preferentially expressed in muscle of the land crab, Gecarcinus lateralis (Gl-Mstn) . Contrary to prediction, levels of Gl-Mstn mRNA decreased dramatically in both the claw closer and weighted thoracic muscles when molting was induced by either eyestalk ablation (ESA) or multiple limb autotomy (MLA). However, the effect of molt induction was greater in the claw muscle. By late premolt, Gl-Mstn mRNA in the claw muscle decreased 81% and 94% in ESA and MLA animals, respectively, and was negatively correlated with ecdysteroids. Gl-Mstn mRNA in thoracic muscle decreased 68% and 82% in ESA and MLA animals, respectively, but was only weakly correlated with ecdysteroid. Claw and thoracic muscles also differed to varying extents in the expression of ecdysteroid receptor ( Gl-EcR and Gl-RXR ), elongation factor-2 ( Gl-EF-2 ), and calpain T ( Gl-CalpT ) in response to molt induction, but levels of the four transcripts were not correlated with ecdysteroid. The downregulation of Gl-Mstn expression in premolt claw muscle coincided with 11- and 13-fold increases in protein synthesis in the myofibrillar and soluble protein fractions, respectively. Furthermore, the rate of the increase in the synthesis of soluble proteins was greater than that of myofibrillar proteins during early premolt (1.4:1, soluble:myofibrillar), but the two were equivalent during late premolt. By contrast, Gl-Mstn mRNA increased 3-fold and Gl-CalpT mRNA decreased 40% in unweighted thoracic muscle; there was little or no effect on Gl-EF-2, Gl-EcR , and Gl-RXR mRNA levels. These data indicate that Gl-Mstn expression is negatively regulated by both ecdysteroids and load-bearing contractile activity. The downregulation of Gl-Mstn in claw muscle may induce the elevated protein turnover associated with remodeling of the contractile apparatus during molt-induced atrophy. The upregulation of Gl-Mstn in unweighted thoracic muscle suggests that this factor is also involved in disuse atrophy when hemolymph ecdysteroid levels are low.

Thangavel Rajagopal - One of the best experts on this subject based on the ideXlab platform.

  • detection of estrus in indian Blackbuck behavioural hormonal and urinary volatiles evaluation
    General and Comparative Endocrinology, 2013
    Co-Authors: Govindaraju Archunan, Thangavel Rajagopal
    Abstract:

    The determination of the reproductive status is one of the most important factors for effective wild life conservation and management, and effective use of assisted reproductive techniques like artificial insemination, in vitro fertilization/embryo transfer depends on the knowledge of the basic reproductive physiology. In this context the reproductive status of female Blackbucks (Antelope cervicapra L.) was assessed by behaviour and determination, sex steroid hormones in faeces and urinary volatile compounds. The male and female Blackbucks exhibited as many as 31 different reproductive/courtship behaviour patterns. Particularly, the males showed a more extensive repertoire: i.e. 23 behavioural patterns by territorial males, 11 by bachelor males and 4 by females. The behaviours such as, mounting, Flehmen, clockwise and anticlockwise movements were significantly higher in male Blackbuck when exposed to estrus. By contrast, such courtship behaviours were completely absent in male when exposed to diestrus. It clearly indicates that, the estrus female produces specific chemical cues (pheromone) through urine, which would involve in attracting the conspecifics. In addition, the average faecal oestrogen concentration was significantly higher (p<0.05) during the estrus faecal than the proestrus and diestrus periods. In contrast, the faecal progesterone concentration was significantly higher (p<0.05) during the diestrus faecal sample than that of proestrus and estrus faecal sample. Twenty-eight volatiles are identified, across the three reproductive phases (i.e. proestrus, estrus and diestrus) of sexually mature and prepubertal females. Amongst, the compounds 2-methyl-3-butyn-2-ol, 3,7-dimethylnonane, 3-phenyl-2-propen-1-ol and 2-hydroxybenzoic acid occurred only during estrus which may be considered as marker for detection of estrus which would ultimately help for artificial insemination in captive condition. The findings of the present study suggest that the non-invasive approaches like reproductive behaviours, faecal steroids and estrus-specific urinary volatiles could serve as good indicators for detection of estrus for Blackbuck.

  • diurnal variation in preorbital gland scent marking behaviour of captive male indian Blackbuck antelope cervicapra l and its territorial significance
    Biological Rhythm Research, 2011
    Co-Authors: Thangavel Rajagopal, Arulmani Manimozhi, Govindaraju Archunan
    Abstract:

    Scent marking is a common behaviour among mammals, which involves the deposition of a pheromone, intended to elicit a response from conspecifics. The present study is aimed to establish the diurnal profile of the distribution of scent marking behaviour and its influence of the marker. The frequency of preorbital gland scent marking behaviour was observed in territorial and non-territorial male Indian Blackbucks on 72 days, over a period of 18 weeks, starting data collection at 06.00 and continuing until the end of the photophase at about 16.00. An ANOVA with post hoc (DMRT) test was assessed to compare the frequency of preorbital gland scent marking at six 2-hour intervals using pooled data for territorial and non-territorial males. The result showed that the preorbital gland scent marking behaviour occurred significantly (P < 0.001) more often between 10:00–12:00 hrs and 16:00–18:00 hrs. It suggests that scent-marking behaviour in Indian Blackbuck has a preferential incidence at a particular time, and th...

  • impact of zoo visitors on the fecal cortisol levels and behavior of an endangered species indian Blackbuck antelope cervicapra l
    Journal of Applied Animal Welfare Science, 2011
    Co-Authors: Thangavel Rajagopal, Govindaraju Archunan, Mahadevan Sekar
    Abstract:

    This study investigated behavioral activities (resting, moving, aggressive, social, and reproductive behavior) and fecal cortisol levels in 8 individually identified adult male Blackbucks during periods of varying levels of zoo visitors (zero, low, high, and extremely high zoo visitor density). This study also elucidated whether zoo visitor density could disturb nonhuman animal welfare. This study analyzed fecal cortisol from the samples of Blackbuck by radioimmunoassay and found significant differences (p < .05) for time the animals devoted to moving, resting, aggressive, reproductive, and social behavior on days with high and extremely high levels of zoo visitors. The ANOVA with Duncan's Multiple Range Test test showed that the fecal cortisol concentration was higher (p < .05) during the extremely high (137.30 ± 5.88 ng/g dry feces) and high (113.51 ± 3.70 ng/g dry feces) levels of zoo visitor density. The results of the study suggest that zoo visitor density affected behavior and adrenocortical secretion in Indian Blackbuck, and this may indicate an animal welfare problem.

  • assessment of dominance hierarchy through urine scent marking and its chemical constituents in male Blackbuck antelope cervicapra a critically endangered species
    Behavioural Processes, 2010
    Co-Authors: Thangavel Rajagopal, Govindaraju Archunan, Pitchairaj Geraldine, Chellam Balasundaram
    Abstract:

    In ungulates the process of chemical communication by urinary scent marking has been directly related to reproductive dominance, territorial defense and proximity to resources. The differences in the frequency of urine marking and chemical composition of urine of males Antelope cervicapra before, during and after the dominance hierarchy period were assessed. The variations in the urine marking and its chemical profiles of dominant males (n=9), bachelors (n=5) and sub-adult males (n=5) were compared to find out how the dominance hierarchy influences the confined Blackbuck herd under semi-natural captive conditions. The frequency of urine marking is significantly higher (p<0.001) in dominant males. Twenty-eight major constituents were identified in the urine of dominant males (before, during and after the dominance hierarchy period), bachelor and sub-adult males. Among these, three specific compounds namely, 3-hexanone (I), 6-methyl-5-hepten-2-one (II) and 4-methyl-3-heptanone (III) were seen only in dominant males urine during the dominance hierarchy period. Based on the behavioural observation and the unique chemical constituents in the urine, it is concluded that the dominant male scent odor suppresses aggression, scent marking, scent production and territorial patrolling activities of subordinate males, through which the dominant male establish their hierarchy and attains success in reproduction.

Marcus Clauss - One of the best experts on this subject based on the ideXlab platform.

  • physical characteristics of forestomach contents from two nondomestic small ruminants the Blackbuck antilope cervicapra and the arabian sand gazelle gazella subgutturosa marica
    Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2021
    Co-Authors: Janine Hertaeg, Cathrine Sauer, Sven Hammer, Mads F Bertelsen, P Lund, M R Weisbjerg, Marcus Clauss
    Abstract:

    Rumen content stratification and the degree of dissociation of particle and fluid retention in the reticulorumen differ between 'moose-type' and 'cattle-type' ruminant species. These differences are not strictly linked to diet, except for a seeming limitation of 'moose-type' ruminants to a browsing niche. Nevertheless, these differences can be plausibly linked to other observed differences in ruminants, such as the intraruminal papillation pattern, or the size of the omasum. However, many of the corresponding measures are still only available for a restricted number of species. Here, we investigated the dry matter (i.e., the inverse of the moisture) concentration in forestomach contents of 10 Blackbuck (Antilope cervicapra) and 7 Arabian sand gazelle (Gazella subgutturosa marica), and quantified the rumen papillation pattern. The Blackbucks had distinct rumen contents stratification, with more moisture in ventral than in dorsal contents (difference 3.6% units, P < 0.001), whereas this difference was much less pronounced in the sand gazelles (0.6% units, P = 0.227). While reticulum contents were particularly moist in both species, omasum contents were particularly dry in sand gazelles, but did not differ in moisture from rumen contents in the Blackbuck. This species is an outlier among ruminants due to its extremely small omasum. The intraruminal papillation pattern did not differ between Blackbucks and sand gazelles and showed a surface enlargement factor (SEF) in the dorsal rumen of 27-28% of the SEF in the Atrium ruminis. Compared to data on digesta retention in the same species, the findings are in line with the overall concept of a high fluid throughput causing a distinct stratification of rumen contents and intraruminal papillation, and necessitating a large omasum for fluid re-absorption. However, the data also show that individual species may not correspond to all the assumptions of the concept, suggesting taxon-specific differences between species. Reasons for these differences cannot be linked to a dietary grass-browse spectrum, but may lie in evolutionary contingency.

  • Birth seasonality in captive bovids at Al Wabra Wildlife Preservation (AWWP), Qatar.
    2009
    Co-Authors: Y. P. Schuler, C Hammer, Marcus Clauss, Sven Hammer, Gudrun Wibbelt, P. Kretschmar, Heribert Hofer, S. Seet
    Abstract:

    Twenty six African and/or Asian bovid species kept at Al Wabra Wildlife Preservation, Qatar (latitude 25 °N, longitude 51 °E, altitude < 100m above sea level) were evaluated for their birth seasonality. A broad range of breeding patterns could be observed, from breeding throughout the whole year (e.g. Blackbuck, dorcas gazelle, idmi gazelle, Speke´s gazelle), to explicit seasonality (e.g. mouflon, nilgai, Nubian ibex, wild goat) in breeding patterns. In general, natural breeding patterns were preserved in captivity. In some species, deviations from patterns reported in the wild are evident, with longer birthing seasons in captivity, sometimes with calves being born the whole year round. This applies mainly for species where birthing correlates with the rainfall season in the wild (e.g. beira antelope, idmi gazelle). It can be speculated that when water, and subsequently food, is supplied constantly, breeding is no longer seasonally restricted, indicating that the respective species are mainly resource-controlled in their reproduction. In species in which reproductive seasonality is preserved in captivity, day length itself is speculated to trigger oestrus activity (e.g. wild goat, Nubian ibex).

Cathrine Sauer - One of the best experts on this subject based on the ideXlab platform.

  • physical characteristics of forestomach contents from two nondomestic small ruminants the Blackbuck antilope cervicapra and the arabian sand gazelle gazella subgutturosa marica
    Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2021
    Co-Authors: Janine Hertaeg, Cathrine Sauer, Sven Hammer, Mads F Bertelsen, P Lund, M R Weisbjerg, Marcus Clauss
    Abstract:

    Rumen content stratification and the degree of dissociation of particle and fluid retention in the reticulorumen differ between 'moose-type' and 'cattle-type' ruminant species. These differences are not strictly linked to diet, except for a seeming limitation of 'moose-type' ruminants to a browsing niche. Nevertheless, these differences can be plausibly linked to other observed differences in ruminants, such as the intraruminal papillation pattern, or the size of the omasum. However, many of the corresponding measures are still only available for a restricted number of species. Here, we investigated the dry matter (i.e., the inverse of the moisture) concentration in forestomach contents of 10 Blackbuck (Antilope cervicapra) and 7 Arabian sand gazelle (Gazella subgutturosa marica), and quantified the rumen papillation pattern. The Blackbucks had distinct rumen contents stratification, with more moisture in ventral than in dorsal contents (difference 3.6% units, P < 0.001), whereas this difference was much less pronounced in the sand gazelles (0.6% units, P = 0.227). While reticulum contents were particularly moist in both species, omasum contents were particularly dry in sand gazelles, but did not differ in moisture from rumen contents in the Blackbuck. This species is an outlier among ruminants due to its extremely small omasum. The intraruminal papillation pattern did not differ between Blackbucks and sand gazelles and showed a surface enlargement factor (SEF) in the dorsal rumen of 27-28% of the SEF in the Atrium ruminis. Compared to data on digesta retention in the same species, the findings are in line with the overall concept of a high fluid throughput causing a distinct stratification of rumen contents and intraruminal papillation, and necessitating a large omasum for fluid re-absorption. However, the data also show that individual species may not correspond to all the assumptions of the concept, suggesting taxon-specific differences between species. Reasons for these differences cannot be linked to a dietary grass-browse spectrum, but may lie in evolutionary contingency.

  • macroscopic digestive tract anatomy of two small antelopes the Blackbuck antilope cervicapra and the arabian sand gazelle gazella subgutturosa marica
    Anatomia Histologia Embryologia, 2016
    Co-Authors: Cathrine Sauer, Mads F Bertelsen, P Lund, M R Weisbjerg
    Abstract:

    The digestive tract anatomy of 14 Blackbucks (Antilope cervicapra) and seven Arabian sand gazelles (Gazella subgutturosa marica) was quantified by dimensions, area and weight. Data from the two small-sized antilopinae were evaluated against a larger comparative data set from other ruminants classified as having either a 'cattle-type' or 'moose-type' digestive system. The digestive anatomy of the Blackbuck resembled that of 'cattle-type' ruminants, which corresponds to their feeding ecology and previous studies of solute and particle retention time; however, a surprising exception was the remarkably small omasum in this species, which makes the Blackbuck stand out from the general rule of a relatively large omasum in grazing ruminants. Sand gazelles had morphological features that corresponded more to the 'moose type' or an intermediate position, although previous studies of solute and particle retention time had led to the expectation of a more 'cattle-type' anatomy. The results show that outliers to general morphological trends exist, that findings on physiology and anatomy do not always match completely and that differences in the digestive morphology among ruminant species are more difficult to demonstrate at the lower end of the body mass range.

Kavita Isvaran - One of the best experts on this subject based on the ideXlab platform.

  • Top ranked models from a model set comprising 27 models exploring variables affecting Blackbuck signs.
    2016
    Co-Authors: Yarlagadda Chaitanya Krishna, Ajith Kumar, Kavita Isvaran
    Abstract:

    Top ranked models from a model set comprising 27 models exploring variables affecting Blackbuck signs.

  • behavioural ecology of a grassland antelope the Blackbuck antilope cervicapra linking habitat ecology and behaviour
    2016
    Co-Authors: Yadvendradev V Jhala, Kavita Isvaran
    Abstract:

    The Blackbuck (Antelope cervicapra), a medium-sized antelope endemic to the Indian subcontinent, is found in diverse shortgrass and savanna habitats. It displays extreme sexual dimorphism and highly variable social and mating systems. The behavioural ecology, demography and nutritional physiology of the Blackbuck appear to be closely adapted to a stochastic low-resource environment and predation pressure. The chapter, based on extensive coverage of Blackbuck habitats across India and intensive long-term data from a typical Blackbuck habitat, elucidates these adaptations and explores links between habitat, ecology and behaviour. Blackbuck populations fluctuate mostly in response to catastrophic events, such as floods and droughts. They show high fecundity and a fast numerical response to predation and food availability. Combined predation on calves and adults by jackals, wolves and feral dogs can potentially regulate their population below nutritional carrying capacity. Predation by wolves and sex differences in mating strategies seem to shape the demographic structure of Blackbuck. Male Blackbuck have shorter life spans than females and males show a mortality peak in midlife corresponding to a peak in mate-competition. Blackbuck are primarily grazers and can survive on seasonally low-quality diets (crude protein <3 %) by catabolizing proteins, and reducing movement and forage intake during summer. Blackbuck respond to an arid environment by producing concentrated alkaline urine and dry feces. However, they need to drink when forage water content is below 30 %. Blackbuck social organisation is highly variable and appears to be strongly influenced by habitat. Group sizes increase with habitat openness and resource availability. A comparison of peninsular Indian ungulates reveals that Blackbuck in semi-arid grasslands show, by far, the largest group sizes. Blackbuck mating system similarly shows a close association with habitat. Like the large group sizes, the rare and spectacular lek mating system is associated with high local animal numbers and open grassland habitat. In most populations, local numbers are lower and resource-based mating territoriality is the dominant mating system. Taken together, the behaviour, nutritional ecology, breeding biology and demography of the Blackbuck are suggestive of an antelope highly specialised to the shortgrass semi-arid biome.

  • Antelope mating strategies facilitate invasion of grasslands by a woody weed
    Oikos, 2013
    Co-Authors: Shivani Jadeja, Soumya Prasad, Suhel Quader, Kavita Isvaran
    Abstract:

    Intra and interspecific variation in frugivore behaviour can have important consequences for seed dispersal outcomes. However, most information comes from among-species comparisons, and within-species variation is relatively poorly understood. We examined how large intraspecific differences in the behaviour of a native disperser, Blackbuck antelope Antilope cervicapra, influence dispersal of a woody invasive, Prosopis juliflora, in a grassland ecosystem. Blackbuck disperse P. juliflora seeds through their dung. In lekking Blackbuck populations, males defend clustered or dispersed mating territories. Territorial male movement is restricted, and within their territories males defecate on dung-piles. In contrast, mixed-sex herds range over large areas and do not create dung-piles. We expected territorial males to shape seed dispersal patterns, and seed deposition and seedling recruitment to be spatially localized. Territorial males had a disproportionately large influence on seed dispersal. Adult males removed twice as much fruit as females, and seed arrival was disproportionately high on territories. Also, because lek-territories are clustered, seed arrival was spatially highly concentrated. Seedling recruitment was also substantially higher on territories compared with random sites, indicating that the local concentration of seeds created by territorial males continued into high local recruitment of seedlings. Territorial male behaviour may, thus, result in a distinct spatial pattern of invasion of grasslands by the woody P. juliflora. An ex situ experiment showed no beneficial effect of dung and a negative effect of light on seed germination. We conclude that large intraspecific behavioural differences within frugivore populations can result in significant variation in their effectiveness as seed dispersers. Mating strategies in a disperser could shape seed dispersal, seedling recruitment and potentially plant distribution patterns. These mating strategies may aid in the spread of invasives, such as P. juliflora, which could, in turn, negatively influence the behaviour and ecology of native dispersers.

  • Intraspecific variation in group size in the Blackbuck antelope: the roles of habitat structure and forage at different spatial scales
    Oecologia, 2007
    Co-Authors: Kavita Isvaran
    Abstract:

    The main ecological factors that are hypothesized to explain the striking variation in the size of social groups among large herbivores are habitat structure, predation, and forage abundance and distribution; however, their relative roles in wild populations are not well understood. I combined analyses of ecological correlates of spatial variation in group size with analyses of individual behaviour in groups of different sizes to investigate factors maintaining variation in group size in an Indian antelope, the Blackbuck Antilope cervicapra. I measured group size, habitat structure, forage, and the occurrence of predators in ten Blackbuck populations, and, at a smaller spatial scale, within an intensively studied population. To examine the processes by which these ecological factors influence group size, I used behavioural observations and an experiment to estimate the shape of the relationship between group size and potential costs and benefits to individuals. Group size varied extensively both among and within populations. Analyses of spatial variation in group size suggested that both forage and habitat structure influence group size: large-scale, among-population variation in group size was primarily related to habitat structure, while small-scale, within-population variation was most closely related to forage abundance. Analyses of individual behaviour suggested that larger groups incur greater travel costs while foraging. However, individuals in larger groups appeared to experience greater benefits, namely the earlier detection of a "predator", a reduction in vigilance, and an increase in the time spent feeding. Overall, these findings suggest that individuals in groups experience a trade-off between predation-related benefits and costs arising from feeding competition. Habitat structure and forage likely influence the nature of this trade-off; thus, variation in these ecological factors may maintain variation in group size. The role of predation pressure and other factors in explaining the remaining variation needs further exploration.