Feeding Biology Research Articles

Still waters and deep: Habitat characteristics, density and distribution of a lake-dwelling population of the freshwater pearl mussel Margaritifera margaritifera

The freshwater pearl mussel, Margaritifera margaritifera is widely considered to be confined to fast-flowing, near-pristine rivers, and is highly endangered throughout its Holartic range. Here we describe a large population of some 150–200,000 individuals of the freshwater pearl mussel living in an oligotrophic Irish lake.Employing underwater photographic techniques and snorkel diving, mussels were found in two separate locations in the lake. In the first location, 200 m from the shore, mussels were found at a maximum density of 43 m−2, in a largely random distribution in the sandy bed substrate of the lake, up to 9.5 m deep. In the second shoreline location, mussels were observed in dense aggregations up to 118 individuals m−2, in sandy pockets in between boulders and bedrock, in waters 1–2 m deep. In both locations, mussels were found associated with macrophytes – the charophyte Nitella sp. in the deeper location and the quillwort Isoetes lacustris in the shallower shoreline location. Juvenile mussels (>1.5 cm length) were observed lying exposed on the sediment surface in the shallow littoral location, indicating that recruitment occurs in this population, although no estimates of juvenile density were obtained.The discovery of a large population of lentic Margaritifera margaritifera has significant implications for the species’ conservation and indicates that there may be substantial lentic populations of the species elsewhere. The environmental envelope of the species is clearly much wider than thought and our discovery challenges assumptions about the fundamental feeding and reproductive biology of this endangered species.

Feeding biology of crown-of-thorns seastars across sites differing in Acropora availability

Crown-of-thorns seastars (COTS, Acanthaster spp.) are a major contributor to coral mortality across the Indo-Pacific and can cause extensive reef degradation. The diet preferences of COTS can influence coral community structure by predation on fast-growing genera such as Acropora and avoidance of rare coral genera. In non-outbreaking populations, this preference can increase species diversity. The feeding biology of Acanthaster cf. solaris was compared at two sites (Shark Alley and Second Lagoon) on One Tree Island reef, located in the southern Great Barrier Reef, to determine whether the availability of Acropora influences differences in COTS movement, feeding preference and feeding rates within the same reef system. Acanthaster cf. solaris were tracked daily for five days across both sites, with measurements of movement, feeding scars and coral composition recorded over this time. While Shark Alley and Second Lagoon have similar live coral cover (40 and 44 % respectively), Shark Alley has significantly lower Acropora availability than Second Lagoon (2 vs 32 %). The feeding rate of COTS was significantly different between Shark Alley and Second Lagoon (259.8 and 733.8 cm2 of coral per day, respectively), but did not differ between seastar size (25–40 cm and >40 cm). Acanthaster cf. solaris showed preference for Pocillopora, Seriatopora, Acropora and Isopora and an avoidance of Porites at both sites. The results suggest that for coral reef sites where Acropora is not dominant, COTS outbreaks may be less likely to initiate, with comparatively low feeding rates found in comparison to coral reefs where Acropora is dominant.

Morphology and feeding biology of larvae of the South African endemic water beetle genus Prosthetops Waterhouse, 1879 (Coleoptera: Hydraenidae)

The larvae of three species of the South African endemic water beetle genus Prosthetops Waterhouse, 1879 are described and illustrated for the first time. The second and third instar larvae of Prosthetops nitens (Péringuey, 1892), as well as third instar larva of P. megacephalus (Boheman, 1851) and P. wolfbergensis Bilton, 2013, are treated here. These three species share a combination of morphological and chaetotaxic characters that can be used for positive identification of larvae of this genus: head capsule with pores FC1 present, second antennomeres with two well-developed distal sensory appendages, maxillary seta Cdo1 very reduced, thoracic subprimary setae Dd’ absent, subprimary setae Dc’ minute and inserted on the boundary between pretergal and tergal areas, urogomphi moderately separated at the base, anal lobe with well-developed dorsal, lateral and ventral plates, and a lack of anal hooks. Some insights on the gut-contents of the larva of P. wolfbergensis are offered and an unusual urogomphal malformation observed in a larva of P. nitens is also described and illustrated. These are the first described larvae of the subfamily Prosthetopinae, and their morphology is compared to that of other known hydraenid larvae.

Radula formation and development in Limapontia senestra (Quatrefages, 1844) (Heterobranchia, Gastropoda) from the White Sea

Sacoglossa is a monophyletic group of small suctorial herbivorous Нeterobranchia. Due to the biology of feeding, most sacoglossans (except Cylindrobulla) have a distinctive feeding apparatus, which includes a sucking muscular organ as well as a sacoglossan-type radula with one tooth in a transverse row, which pierces algal cells. Although there is obvious interest in the radular morphology and developmental modes of Sacoglossa, as these characters may provide some insight into the evolutionary history and phylogenetic relationships of Sacoglossa, data on radula formation and morphogenesis in this group are sparse. This paper presents original data on the direct development, formation, and morphogenesis of the radula of Limapontia senestra (Quatrefages, 1844) from the White Sea. Based on the data obtained, we describe the development and formation of the radula. They fit into the general pattern of heterochrony in the radula anlage, characteristic of all gastropods. The small number of odontoblasts in the formation of the adult radula of L. senestra is a distinctive feature of the radula of Heterobranchia.

A new species of Caloptilia (Lepidoptera: Gracillariidae) from Japan and Korea

A new species of Caloptilia, C. rhynchosiae n. sp. is described, based on 16 specimens from Japan and Korea. The species is characterized by the presence of the saccular process in the male genitalia. A fabaceous vine, Rhynchosia tomentosa (L.) Hook. & Arn. is reported as the larval host of C. rhynchosiae n. sp. Larval feeding preference, biology and pupation process are described for the species. The species turned out to be host-specific. Two sets of COI barcodes were generated for C. rhynchosiae n. sp. The genetic distances of COI barcodes between the new species and other congeners in the public databases are compared. The conclusion was made that C. rhynchosiae n. sp. was misidentified as C. soyella in the BOLD and GenBank DNA barcode depositories.

Insights into reproductive dynamics and feeding biology of Sphyraena putnamae Jordan and Seale, 1905 exploited in the Indian EEZ

The sawtooth barracuda Sphyraena putnamae, widely distributed in the Indo-Pacific region, isone of the commercially important barracuda species exploited by trawls in the Indian EEZ.The present study examined 2,135 S. putnamae collected during 2014-2020 from differentfish landing centres along the Indian coast, to elucidate their reproductive and feedingbehaviour. The fork length of sampled females and males varied from 12.5 to 130.9 cm and16.5 to 90.0 cm respectively. Negative allometric growth was observed with a significantdifference (p<0.05) between the sexes. The observed sex ratio (Female:Male) was 1.23:1,indicating the dominance of females. Size at sexual maturity for females and males wereestimated at 55.3 and 45.4 cm fork length respectively. The higher proportion of spawningcapable individuals and higher gonadosomatic index (GSI) values in females observedduring March to May and November-December revealed the bimodal and protractedspawning nature of this species. Absolute fecundity increased with fork length and weightand varied from 70,080 to 10,18,068 oocytes with an average of 3,16,568 oocytes. Thestomach vacuity index of females and males was 49.09 and 47.92% respectively. Fifty-nineprey items were identified in the diet, with a predominance of fishes confirming S. putnamaehas a piscivorous feeding behaviour. Keywords:Management, Protracted spawners, Piscivore,Sawtooth barracuda, Sex ratio

Changes in saliva protein profile throughout Rhipicephalus microplus blood feeding

BackgroundWhen feeding on a vertebrate host, ticks secrete saliva, which is a complex mixture of proteins, lipids, and other molecules. Tick saliva assists the vector in modulating host hemostasis, immunity, and tissue repair mechanisms. While helping the vector to feed, its saliva modifies the site where pathogens are inoculated and often facilitates the infection process. The objective of this study is to uncover the variation in protein composition of Rhipicephalus microplus saliva during blood feeding.MethodsTicks were fed on calves, and adult females were collected, weighed, and divided in nine weight groups, representing the slow and rapid feeding phases of blood feeding. Tick saliva was collected, and mass spectrometry analyses were used to identify differentially secreted proteins. Bioinformatic tools were employed to predict the structural and functional features of the salivary proteins. Reciprocal best hit analyses were used to identify conserved families of salivary proteins secreted by other tick species.ResultsChanges in the protein secretion profiles of R. microplus adult female saliva during the blood feeding were observed, characterizing the phenomenon known as “sialome switching.” This observation validates the idea that the switch in protein expression may serve as a mechanism for evading host responses against tick feeding. Cattle tick saliva is predominantly rich in heme-binding proteins, secreted conserved proteins, lipocalins, and protease inhibitors, many of which are conserved and present in the saliva of other tick species. Additionally, another remarkable observation was the identification of host-derived proteins as a component of tick saliva.ConclusionsOverall, this study brings new insights to understanding the dynamics of the proteomic profile of tick saliva, which is an important component of tick feeding biology. The results presented here, along with the disclosed sequences, contribute to our understanding of tick feeding biology and might aid in the identification of new targets for the development of novel anti-tick methods.Graphical

Discovery and characterization of the α-amylases cDNAs from Enchytraeus albidus shed light on the evolution of “Enchytraeus-Eisenia type” Amy homologs in Annelida

Although enchytraeids have gained popularity in scientific research, fundamental questions regarding their feeding ecology and biology remain largely unexplored. This study investigates α-amylases, major digestive enzymes responsible for hydrolyzing starch and similar polysaccharides into sugars, in Enchytraeus albidus. Genetic data related to α-amylases is currently lacking for the family Enchytraeidae but also for the entire Annelida. To detect and identify coding sequences of the expressed α-amylase genes in COI-monohaplotype culture (PL-A strain) of E. albidus, we used classical “gene fishing” and transcriptomic approaches. We also compared coding sequence variants of α-amylase retrieved from transcriptomic data related to freeze-tolerant strains. Our results reveal that E. albidus possesses two distinct α-amylase genes (Amy I and Amy II) that are homologs to earthworm Eisenia fetida Ef-Amy genes. Different strains of E. albidus possess distinctive alleles of α-amylases with unique SNP patterns specific to a particular strain. Unlike Amy II, Amy I seems to be a highly polymorphic and multicopy gene. The domain architecture of the putative Amy proteins was found the same as for classical animal α-amylases with ABC-domains. A characteristic feature of Amy II is the lack of GHGA motif in the flexible loop region, similarly to many insect amylases. We identified “Enchytraeus-Eisenia type” α-amylase homologs in other clitellates and polychaetes, indicating the ancestral origin of Amy I/II proteins in Annelida. This study provides the first insight into the endogenous non-proteolytic digestive enzyme genes in potworms, discusses the evolution of Amy α-amylases in Annelida, and explores phylogenetic implications.

A Study on the Feeding Biology of Soil Oribatid Mite Papillacarus (Papillacarus) elongatus (Acari, Lohmanniidae)

The feeding biology of lohmanniid mite Papillacarus (Papillacarus) elongatus Xavier, 2007 was investigated under laboratory conditions (relative humidity 80 ± 2 % and temperature 27 ± 2˚C) using appropriate feeding preference tests. Different microfungi and semi-degraded leaves were provided as food items. To validate feeding biology, the gut enzymes and structural morphology of mouth parts of P. (P.) elongatus were also examined. The results demonstrated that the P. (P.) elongatus are panphytophages, and could feed on both higher and lower plant elements. These alternative feeding guilds might enable these mites to coexist with other soil organisms; moreover, they can be directly involved in the biodegradation of leaf litter and indirectly influence the microbial activity in the soil ecosystem.

Ecological niche and life-history traits of redbelly tilapia (Coptodon zillii, Gervais 1848) in its native and introduced ranges

Redbelly tilapia (Coptodon zillii) is a member of a group of fishes in the Cichlidae family endemic to the northern half of Africa and the Middle East. In the literature, the name C. zillii is mostly associated with a negative impact on the ecosystem and biodiversity in the areas to which it was introduced. In its native range, it is not a much-appreciated fish species from both fisheries and aquaculture perspectives because of its small size and difficulty to catch when compared to Nile tilapia, Oreochromis niloticus. Although C. zillii has several desirable aquaculture traits such as feeding at lower trophic levels, high fecundity, saltwater and cold tolerance, the attempts to capitalize on this potential are lacking. Moreover, comprehensive studies that characterize its ecological niche in its native range and adaptive mechanisms of invasiveness in introduced areas are also limited. Notwithstanding, it is a species of invasion concern that requires continuous monitoring and implementation of mitigation actions in non-native regions. Compilation of information regarding the environmental requirements, feeding, and reproductive biology of C. zillii may serve as a starting ingredient for further research and management of its invasiveness, which is highly required in the face of freshwater ecosystem modifications as a result of climate change. This paper also addresses the current state and potential of C. zillii for utilization in capture fisheries and fish farming.

Microplastic burden in marine benthic invertebrates depends on species traits and feeding ecology within biogeographical provinces

The microplastic body burden of marine animals is often assumed to reflect levels of environmental contamination, yet variations in feeding ecology and regional trait expression could also affect a species’ risk of contaminant uptake. Here, we explore the global inventory of individual microplastic body burden for invertebrate species inhabiting marine sediments across 16 biogeographic provinces. We show that individual microplastic body burden in benthic invertebrates cannot be fully explained by absolute levels of microplastic contamination in the environment, because interspecific differences in behaviour and feeding ecology strongly determine microplastic uptake. Our analyses also indicate a degree of species-specific particle selectivity; likely associated with feeding biology. Highest microplastic burden occurs in the Yellow and Mediterranean Seas and, contrary to expectation, amongst omnivores, predators, and deposit feeders rather than suspension feeding species. Our findings highlight the inadequacy of microplastic uptake risk assessments based on inventories of environmental contamination alone, and the need to understand how species behaviour and trait expression covary with microplastic contamination.

Reproductive Parameters and Host Specificity of Eurytoma erythrinae (Hymenoptera: Eurytomidae), a Biological Control Agent of the Erythrina Gall Wasp, Quadrastichus erythrinae (Hymenoptera: Eulophidae).

Eurytoma erythrinae Gates & Delvare (Hymenoptera: Eurytomidae) is an important biological control agent of the erythrina gall wasp (EGW), Quadrastichus erythrinae Kim (Hymenoptera: Eulophidae), an invasive species likely originating in eastern Africa that is a threat to Erythrina trees in Hawaii and worldwide. Thousands of Erythrina trees in Hawaii have succumbed to EGW since 2005 and died within a few years of infestation. The endemic wiliwili tree, Erythrina sandwicensis, an important component of Hawaii's dry forests and one of few deciduous native trees, were severely impacted by this wasp. Early during the invasion by EGW it became evident that the endemic species may be driven to extinction, and exploration programs for natural enemies of the EGW started in December 2005. East Africa was selected as the starting point for natural enemy exploration owing to high native Erythina species richness. Several gall formers were found in Tanzania and a putative color variant type of Q. erythrinae was detected in association with three ectoparasitoids. During January 2006, the dominant parasitoid of this gall former was introduced to Hawaii and described as the new species, E. erythrinae. It was found in Ghana and South Africa attacking other gall wasp species on Erythrina. Eurytoma erythrinae was a voracious ectoparasitoid feeding as a predator on 1-5 adjacent EGW immatures to complete its development. Host specificity studies that included seven nontarget gall-forming species showed no evidence of attraction or parasitism by this parasitoid. Mean ± SEM longevity of host-deprived females (40.4 ± 2.2 days) was significantly higher than males (20.5 ± 1.1 days). Host feeding enhanced longevity of ovipositing females (51.3 ± 1.5 days). Female E. erythrinae is synovigenic, with high egg-maturation rate. Peak fecundity (105-239 offspring/female), host feeding biology, short life cycle (18.4 ± 0.1 days), and synchronization with the host were additional desirable attributes of this species. The parasitoid was approved for field release in Hawaii in November 2008. A total of 3998 wasps were distributed on six Hawaiian Islands, with establishment in less than a year. Impacts on high density infestations of EGW were sufficient to prevent tree deaths. Limited rates of parasitism on low-density galled leaves, flowers, and seedpods necessitated the consideration for releasing a second parasitoid, Aprostocetus nitens Prinsloo & Kelly (Hymenoptera: Eulophidae). We report on the reproductive characteristics and host specificity of E. erythinae that could be of importance for classical biocontrol programs in areas with an EGW problem.

How will climate change affect the feeding biology of Collembola?

Collembolans are one of the most diverse and abundant group of soil invertebrates. Recent studies have shown anthropogenic climate warming to alter Collembola diversity and density in warm-dry (more detrimental effects) and warm-wet (lesser detrimental effects) conditions. Besides the direct influence of abiotic stressors, shifts in food availability could help understand variable collembolan responses to climate warming. Collembolan diet is generally formed by two main groups of soil fungi: saprotrophic and mycorrhizal fungi, which occupy different spatial niches in the soil, and are simultaneously affected by climate warming and drought. These fungal responses to climate change alter food availability for Collembola, inducing shifts in their dietary composition. Collembolans preferentially consume saprotrophic fungi, regardless of their spatial niche. However, those inhabiting deeper soil layers occasionally feed on mycorrhizal fungi and rely more frequently on such diets when other food sources become scarce. We suggest that climate change-driven scarcity of saprotrophic fungal diets in soils would make collembolans depend more on mycorrhizal fungal diets. We then discuss how such dietary shifts are driven by distinct mechanisms in warm-dry and warm-wet soil conditions. We finally call for the use of emerging techniques (e.g., stable isotope analysis, molecular gut content) to quantify the diets of Collembola more accurately under different climate change scenarios, which will help us shed more insights on how warming and precipitation variability are going to alter Collembola-fungal trophic interactions in a changing world.

Biological observations of Salmostoma novacula fishery of a protected reservoir in India

Feeding and breeding biology of a prominent indigenous fishery of Peechi Reservoir(protected reservoir) was assessed using 300 specimens in this study. Catch compositionstudies identified Salmostoma sp. as the major species contributing to the reservoir fishery.With the help of mitochondrial CO1 gene, the species was identified as Salmostomanovacula. The feeding biology of the fishes was studied using index of preponderance(IOP), gastro-somatic index (GaSI) and relative gut length (RGL). IOP of S. novacula revealedthat zooplankton dominated the gut of the species to the tune of nearly 70.82%. The meanRGL and GaSI of S. novacula was estimated at 1.42 (1.42±0.25) and 4.22 respectively. Theindices used for reproductive study were size at first maturity, sex ratio, gonado-somaticindices and fecundity. The size at first maturity for S. novacula was found to be 13.0 cm. Thesex ratio and relative fecundity were estimated at 1.2:1.0 and 8500-8833 nos. per gram bodyweight of fish. The study indicated that the fishes mature during March to August and exhibitspawning activity in September. The paper emphasises a need for enforcing minimum legalsize and restricted monsoon fishing for sustained fisheries in this reservoir. Keywords:CO1 gene, Feeding biology, Fisheries management,Reproductive biology, Salmostoma novacula

Feeding dynamics and reproductive biology of the obtuse barracuda Sphyraena obtusata (Cuvier, 1829) from Ratnagiri, central west coast of India

The obtuse barracuda Sphyraena obtusata (Cuvier, 1829) is a commercially important foodfish belonging to the family Sphyraenidae and landed mostly as trawl bycatch along Ratnagiri.Investigations were carried out on the species with respect to the length-weight relationship,condition factor, morphometrics, feeding and reproductive biology. The length-weightrelationship showed positive allometric growth in males, females and pooled individuals. Allmorphometric measurements showed a high degree of correlation with total length. The gutcontent analysis revealed S. obtusata to be a carnivore fish feeding mainly on fish juveniles,fish scales, crustaceans and cephalopod appendages. The male:female sex ratio was foundto be 1:0.90. Gonado-somatic index (GSI), maturity and ova diameter studies indicated thatS. obtusata has a prolonged spawning season with individuals spawning twice in a season.Absolute fecundity ranged from 68355 to 310615 eggs with an average of 137783 eggs. Themean length at sexual maturity for females was found to be 22.92 cm. Keywords:Carnivorous fish, Fish biology, Life history,Trophodynamics, Tropical fisheries

Biology of Length-weight and Feeding in Juveniles and Adults of Air-breathing Perch <i>Anabas testudineus</i> (BLOCH)

The biology of feeding and growth pertaining to seasonal variations in diet composition, length-weight relationship and condition factor of Anabas testudineus was studied for a period of one year in two size group fishes (Group I: juveniles of <100 mm and Group II: adults of >100 mm). The length-weight relationship of the fish for Group I was W=0.00849 L3.2168 and for Group II was W=0.00877 L3.1502. The relative condition factor fluctuated from 1.032 to 1.372 indicating a significant variation (p < 0.05) in two size groups. The feeding intensity was maximum during October to December. Diet composition indicated the highest occurrence of insects followed by crustaceans and decayed organic matter. It also showed variations in different size group of fishes.

ATP-sensitive inward rectifier potassium channels regulate secretion of pro-feeding salivary proteins in the lone star tick (Amblyomma americanum)

Understanding the physiological and molecular regulation of tick feeding is necessary for developing intervention strategies to curb disease transmission by ticks. Pharmacological activation of ATP-gated inward rectifier potassium (KATP) channels reduced fluid secretion from isolated salivary gland and blood feeding in the lone star tick, Amblyomma americanum, yet the temporal expression pattern of KATP channel proteins remained unknown. KATP channels were highly expressed in type II and III acini in off-host stage and early feeding phase ticks, yet expression was reduced in later stages of feeding. We next assessed KATP channel regulation of the secreted proteome of tick saliva. LC-MS/MS analysis identified 40 differentially secreted tick saliva proteins after exposure to KATP activators or inhibitors. Secretion of previously validated tick saliva proteins that promote tick feeding, AV422, AAS27, and AAS41 were significantly reduced by upwards of 8 log units in ticks exposed to KATP channel activators when compared to untreated ticks. Importantly, activation of KATP channels inhibited tick feeding and vice versa for KATP channel inhibitors. Data indicate KATP channels regulate tick feeding biology by controlling secretion of pro-feeding proteins that are essential during early feeding phases, which provides insights into physiological and molecular regulation of tick feeding behavior.

Identification of potential breeding ground of flathead grey mullet, Mugil cephalus (Linnaeus, 1758), along the Mumbai coast, India, for ecological monitoring and conservation strategies.

Identifying the breeding grounds of fishes is crucial for the sustainable management of fisheries resources. The present study is aimed at identifying the potential breeding ground of Mugil cephalus along the estuary of the North Mumbai coast. A total of 1197 specimens of M. cephalus, including 546 eggs, 271 larvae, 235 juveniles, and 235 adults, were collected from four sampling stations in the Karanja estuary between January to October 2022. Water quality parameters, plankton dynamics in the estuary, and the reproductive and feeding biology of M. cephalus were also examined. The eggs, larvae, juveniles, and adults were identified using traditional morpho-meristic and DNA barcoding techniques. The results revealed a potential spawning ground of M. cephalus in the Karanja estuary. The results of reproductive biology also confirmed the occurrence of matured fishes during May-July. The abundance of eggs and larvae at the estuary's mouth and the presence of juveniles and mature individuals of M. cephalus dominantly in the Karanja estuary from May to July infer the presence of a spawning site. It is also recorded that M. cephalus spawn in higher salinity (35 ppt) and seawater temperature (33 °C) where the hatching of offspring takes place successfully. This study emphasizes the significance of DNA barcoding in guiding routine monitoring surveys and demonstrates its usefulness when combined with these techniques in identifying fish spawning grounds. The study findings will serve as baseline information to develop effective conservation and management strategies and protect the ideal spawning stock.

A Comprehensive Review on Feeding and Breeding Biology of Freshwater Garfish, Xenentodon cancila (Hamilton, 1822) for Captive Culture

A Comprehensive Review on Feeding and Breeding Biology of Freshwater Garfish, Xenentodon cancila (Hamilton, 1822) for Captive Culture

A Comprehensive Review on Feeding and Reproductive Biology of Amblypharygodon mola

A Comprehensive Review on Feeding and Reproductive Biology of Amblypharygodon mola