Ecological mechanisms driving the anti-predator defense response in Crucian carp (Carassius carassius): Variation in morphology, resource use, and life-history strategies along a gradient of predation risk

© Ilaria de Meo (2021). Faculty of Applied Ecology, Agricultural Sciences and Biotechnology, Inland Norway University of Applied Sciences (INN), Department of Forestry and Wildlife Management, Evenstad, NorwayPredation is one of the main structuring forces of freshwater communities, influencing population dynamics, phenotypic variation, resource use, and life-history traits within and among prey populations. In order to counteract predation risk, prey organisms may display several anti-predator morphological and behavioral adaptations. The crucian carp (Carassius carassius) represents a classic example of predator-induced morphological defense, as it develops a deep body to decrease vulnerability to predation. Very few studies, however, have explored the ecological drivers underlying morphological variation observed among crucian carp populations in the wild. This PhD thesis aimed at revealing the effects of predation risk on morphology, resource use, and life-history traits of crucian carp along a natural gradient of predation risk. The study was performed in fifteen small lakes from southern Norway, which presented no predators or increasingly efficient gape-limited predators: brown trout, perch, or pike. The results show that crucian carp is provided with a fine-tuned morphological defense response against gape-limited predators. Progressively efficient predators determined an increase in crucian carp relative body depth and size, a decrease in population density, rapid growth at young age, larger lifespans, and higher reproductive effort. Predation pressure likely reduced fish abundance, relaxing intraspecific resource competition and favoring individual growth of survivors. High-predation lakes also corresponded to productive systems with high food availability and complex vegetated littoral habitats. Reduced intraspecific competition, larger food availability, and increased habitat complexity associated with predation risk favored energy allocation to both growth and reproduction. Plastic feeding habits and a shift to more energetically rewarding prey with increasing body size may also have supported this energy allocation. Thus, the expression of the defense response in crucian carp was likely a result of the synergistic effects of predation risk and favorable environmental conditions.Sammendrag: Predasjon er en av de viktigste kreftene som strukturerer økosystemene i ferskvann, gjennom sin effekt på populasjonsdynamikk, fenotypisk variasjon, ressursbruk, og livshistorietrekk mellom og innen populasjonene av byttedyr. For å redusere risikoen for å bli spist kan byttedyrene utvise mange ulike antipredator-strategier, som for eksempel morfologiske og atferdsmessige tilpasninger. Utviklingen av en høy kroppsform hos karuss (Carassius carassius) er et klassisk eksempel på en predatorindusert morfologisk tilpasning (forsvar mot predasjon) for å unngå å bli spist av rovfisk. Det er imidlertid få studier som har undersøkt hvilke økologiske drivere som ligger bak den morfologiske variasjonen vi finner mellom ulike karusspopulasjoner i naturen. Denne PhD-avhandlingen har hatt som mål å finne ut hvordan predasjonsrisiko langs en naturlig gradient påvirker karussens morfologi, ressursbruk og livshistorietrekk. Studien ble gjennomført i femten små karussvann i Østlandsområdet, som varierte fra ikke å ha predatorer til stede til å ha predatorer med en økende grad av effektivitet (basert på størrelsen til fiskens gap): brun ørret (Salmo trutta), abbor (Perca fluviatilis) og gjedde (Esox lucius). Resultatene viser at karuss har en fininnstilt morfologisk forsvarsrespons mot rovfisk, som henger sammen med størrelsen på gapet til predatoren. Med økende effektivitet (gap) hos predatoren økte karussen i størrelse og relativ kroppshøyde, populasjonstettheten sank, veksten ble raskere i ung alder, livslengden økte og den reproduktive innsatsen økte. Det ser ut som om predasjonspress reduserer forekomsten av karuss, letter den intraspesifikke konkurransen om ressurser og favoriserer den individuelle veksten hos de som overlever. De vannene som hadde den høyeste graden av predasjon var også de mest produktive med høy tilgang på føde og med komplekse habitater i form av omfattende strandvegetasjon. Predasjonsrisiko ga redusert intraspesifikk konkurranse, mer tilgjengelig føde og økende habitatkompleksitet. Dette førte til mer energi til både vekst og reproduksjon. Varierende fødehabitat og et skifte til mer energirik føde som følge av økende kroppsstørrelse kan også ha bidratt til denne omfordelingen av energi. Det er altså sannsynlig at karussens forsvarsrespons er et resultat av synergi mellom effekten av predasjonsrisiko og fordelaktige miljøbetingelser.publishedVersio

Spatio-temporal distribution of pufferfish (Tetraodontidae) along the Turkish coast of the Mediterranean Sea

Pufferfish represent a serious threat to the marine ecosystem in the Mediterranean Sea. To better understand the population dynamics of pufferfish and their relation with ecological parameters, six pufferfish species were studied in two fishing and one non-fishing zone in one of the most oligotrophic regions of the Mediterranean Sea during 2014 and 2015, including different habitats of vegetated and non-vegetated and seasons. The results provide information on pufferfish ecological status compared with more eutrophic zones in which these species could potentially worsen their impact. Four species were common in the study area and two were rare. The dominant species was Lagocephalus suezensis, reaching abundances of 11,000 ind/km2 at 25 m in October, followed by Lagocephalus sceleratus, Lagocephalus guentheri, and Torquigener flavimaculosus. The rarest species, Tylerius spinosissimus and Sphoeroides pachygaster, reached higher abundance and biomass in October and February than the other sampling months. The riverine and meadow habitats played a crucial role for nursing and reproduction in the population dynamics of Lagocephalus species, while T. flavimaculosus was absent in these areas. Sex ratios changed depending on season and location. The occurrence of larger individuals of Lagocephalus spp. and T. flavimaculosus at greater depths evidenced an ontogenetic migration. Overall, length-weight (L-W) relationships indicate isometric growth for each of the species studied. Pufferfish populations were primarily a function of habitat and depth of seafloor and secondarily with water productivity

Length-weight relationships of 107 osseous and 9 cartilaginous fish species on a shelf-break zone of the eastern Mediterranean Sea

Overall and spatiotemporal total length-weight relationships (LWR) were studied for the 116 fish composing of 107 osseous and 9 cartilaginous fish species collected by otter trawl in the shelf and upper slope of Gulf of Antalya in 2014-2015. Of the 89 abundant bony species, 38 species had isometric growth, 24 species positive allometry, and 27 species negative allometry. Growth type was significantly affected with the sample size. LWRs of osseous fish species which had their body condition factor CF ≤ 1 were significantly differentiated by factors region, season and depth, but none was for the fish having CF ≥ 1. The factorial differences were found in relation with the CF. The b values for the osseous fish decreased slightly with bottom depth from lower shelf to middle shelf. The highest b values occurred for the ubiquitous fish on the entire shelf while the a values increased. At greater depths, the b values shifted the allometry from the isometry to the negative allometry. Average b value of osseous fish was 2.962 ± 0.048 (isometric), and median was 2.992. LWRs of body widthweight of batoid fish showed a b value ≤ 3. Sexual dimorphism in the LWR occurred for 10 species.publishedVersio

The role of predation risk in structuring life-history traits of crucian carp (Carassius carassius) in a series of small boreal lakes

Predation is a major evolutionary force determining life-history traits in prey by directand indirect mechanisms. This study focuses on life-history trait variation in cruciancarp (Carassius carassius), a species well known for developing a deep body as aninducible morphological defence against predation risk. Here, the authors tested vari-ation in growth and reproductive traits in 15 crucian carp populations in lakes along apredation risk gradient represented by increasingly efficient predator communities.Lakes were located in south-eastern Norway and were sampled in summer 2018 and2019. The authors expected crucian carp to attain higher growth rate, larger size, andlater age at maturity with increasing predation risk. In the absence of predators, theyexpected high adult mortality, early maturity and increased reproductive effortcaused by strong intraspecific competition. They found that the life-history traits ofcrucian carp were clearly related to the presence of piscivores: with increasing preda-tion risk, fish grew in body length and depth and attained larger asymptotic lengthand size at maturity. This growth was evident at young age, especially in productivelakes with pike, and it suggests that fish quickly outgrew the predation window byreaching a size refuge. Contrary to the authors’predictions, populations had similarage at maturity. High-predation lakes also presented low density of crucian carp. Thissuggests that fish from predator lakes may experience high levels of resource avail-ability due to reduced intraspecific competition. Predation regulated life-history traitsin crucian carp populations, where larger size, higher longevity and size at maturitywere observed in lakes with large gaped predators.publishedVersio

Predator community and resource use jointly modulate the inducible defense response in body height of crucian carp

Phenotypic plasticity can be expressed as changes in body shape in response to environmental variability. Crucian carp (Carassius carassius), a widespread cyprinid, displays remarkable plasticity in body morphology and increases body depth when exposed to cues from predators, suggesting the triggering of an antipredator defense mechanism. However, these morphological changes could also be related to resource use and foraging behavior, as an indirect effect of predator presence. In order to de-termine whether phenotypic plasticity in crucian carp is driven by a direct or indirect response to predation threat, we compared twelve fish communities inhabiting small lakes in southeast Norway grouped by four categories of predation regimes: no predator fish, or brown trout (Salmo trutta), perch (Perca fluviatilis), or pike (Esox lucius) as main piscivores. We predicted the body shape of crucian carp to be associated with the species composition of predator communities and that the presence of efficient piscivores would result in a deeper body shape. We use stable isotope analyses to test whether this variation in body shape was related to a shift in individual resource use- that is, littoral rather than pelagic resource use would favor the development of a specific body shape- or other environmental characteristics. The results showed that increasingly efficient predator communities induced progressively deeper body shape, larger body size, and lower population densities. Predator maximum gape size and individual trophic position were the best variables explaining crucian carp variation in body depth among predation categories, while littoral resource use did not have a clear effect. The gradient in predation pressure also corresponded to a shift in lake productivity. These results indicate that crucian carp have a fine-tuned morpho-logical defense mechanism against predation risk, triggered by the combined effect of predator presence and resource availabilitypublishedVersio

Resource use of crucian carp along a lake productivity gradient is related to body size, predation risk, and resource competition

Generalist fish species can feed on a wide resource spectrum and across trophic levels depending on resource availability and trophic interactions. Crucian carp (Carassius carassius) represents a good candidate species to investigate variation in the trophic ecology of generalist fish as it can be found in highly variable fish communities and its resource use is well documented. In this study, we explored the trophic ecology of crucian carp at the individual and population levels using stable isotope and gut content analysis. We tested if trophic resource use varied according to lake productivity, predation risk, intra- and interspecific competition, or individual fish size. We found that crucian carp resource preference was highly variable among and within lakes. In predator-free lakes, small crucian carp occurred in high densities, showed increased interindividual specialisation, and relied mainly on pelagic zooplankton. In presence of predators, large crucian carp occurred in low densities and included greater proportions of benthic macroinvertebrates in their diet. This shift in resource use was further favoured in productive, shallow lakes where littoral prey were probably abundant. Resource partitioning was an important factor determining crucian carp niche use, as fish had higher trophic position in absence of other cyprinids. Crucian carp showed highly dynamic resource use and food preferences in response to variable environmental conditions. Overlooking complex diet preferences of generalist fish may lead to an oversimplification of freshwater community dynamics.Peer reviewe

Resource use of crucian carp along a lake productivity gradient is related to body size, predation risk, and resource competition

Generalist fish species can feed on a wide resource spectrum and across trophic levels depending on resource availability and trophic interactions. Crucian carp (Carassius carassius) represents a good candidate species to investigate variation in the trophic ecology of generalist fish as it can be found in highly variable fish communities and its resource use is well documented. In this study, we explored the trophic ecology of crucian carp at the individual and population levels using stable isotope and gut content analysis. We tested if trophic resource use varied according to lake productivity, predation risk, intra- and interspecific competition, or individual fish size. We found that crucian carp resource preference was highly variable among and within lakes. In predator-free lakes, small crucian carp occurred in high densities, showed increased interindividual specialisation, and relied mainly on pelagic zooplankton. In presence of predators, large crucian carp occurred in low densities and included greater proportions of benthic macroinvertebrates in their diet. This shift in resource use was further favoured in productive, shallow lakes where littoral prey was probably abundant. Resource partitioning was an important factor determining crucian carp niche use, as fish had higher trophic position in absence of other cyprinids. Crucian carp showed highly dynamic resource use and food preferences in response to variable environmental conditions. Overlooking complex diet preferences of generalist fish may lead to an oversimplification of freshwater community dynamics.publishedVersio

Progression independent of relapse activity in relapsing multiple sclerosis: impact and relationship with secondary progression

Objectives: We investigated the occurrence and relative contribution of relapse-associated worsening (RAW) and progression independent of relapse activity (PIRA) to confirmed disability accrual (CDA) and transition to secondary progression (SP) in relapsing multiple sclerosis (MS). Methods: Relapsing-onset MS patients with follow-up > / = 5 years (16,130) were extracted from the Italian MS Registry. CDA was a 6-month confirmed increase in Expanded Disability Status Scale (EDSS) score. Sustained disability accumulation (SDA) was a CDA with no EDSS improvement in all subsequent visits. Predictors of PIRA and RAW and the association between final EDSS score and type of CDA were assessed using logistic multivariable regression and multivariable ordinal regression models, respectively. Results: Over 11.8 ± 5.4 years, 16,731 CDA events occurred in 8998 (55.8%) patients. PIRA (12,175) accounted for 72.3% of CDA. SDA occurred in 8912 (73.2%) PIRA and 2583 (56.7%) RAW (p < 0.001). 4453 (27.6%) patients transitioned to SPMS, 4010 (73.2%) out of 5476 patients with sustained PIRA and 443 (24.8%) out of 1790 patients with non-sustained PIRA. In the multivariable ordinal regression analysis, higher final EDSS score was associated with PIRA (estimated coefficient 0.349, 95% CI 0.120-0.577, p = 0.003). Discussion: In this real-world relapsing-onset MS cohort, PIRA was the main driver of disability accumulation and was associated with higher disability in the long term. Sustained PIRA was linked to transition to SP and could represent a more accurate PIRA definition and a criterion to mark the putative onset of the progressive phase

Parathyroid Retrospective Analysis of Neoplasms Incidence (pTRANI Study): An Italian Multicenter Study on Parathyroid Carcinoma and Atypical Parathyroid Tumour

Background: Parathyroid cancer (PC) is a rare sporadic or hereditary malignancy whose histologic features were redefined with the 2022 WHO classification. A total of 24 Italian institutions designed this multicenter study to specify PC incidence, describe its clinical, functional, and imaging characteristics and improve its differentiation from the atypical parathyroid tumour (APT). Methods: All relevant information was collected about PC and APT patients treated between 2009 and 2021. Results: Among 8361 parathyroidectomies, 351 patients (mean age 59.0 ± 14.5; F = 210, 59.8%) were divided into the APT (n = 226, 2.8%) and PC group (n = 125, 1.5%). PC showed significantly higher rates (p < 0.05) of bone involvement, abdominal, and neurological symptoms than APT (48.8% vs. 35.0%, 17.6% vs. 7.1%, 13.6% vs. 5.3%, respectively). Ultrasound (US) diameter >3 cm (30.9% vs. 19.3%, p = 0.049) was significantly more common in the PC. A significantly higher frequency of local recurrences was observed in the PC (8.0% vs. 2.7%, p = 0.022). Mortality due to consequences of cancer or uncontrolled hyperparathyroidism was 3.3%. Conclusions: Symptomatic hyperparathyroidism, high PTH and albumin-corrected serum calcium values, and a US diameter >3 cm may be considered features differentiating PC from APT. 2022 WHO criteria did not impact the diagnosis

Prescription appropriateness of anti-diabetes drugs in elderly patients hospitalized in a clinical setting: evidence from the REPOSI Register

Diabetes is an increasing global health burden with the highest prevalence (24.0%) observed in elderly people. Older diabetic adults have a greater risk of hospitalization and several geriatric syndromes than older nondiabetic adults. For these conditions, special care is required in prescribing therapies including anti- diabetes drugs. Aim of this study was to evaluate the appropriateness and the adherence to safety recommendations in the prescriptions of glucose-lowering drugs in hospitalized elderly patients with diabetes. Data for this cross-sectional study were obtained from the REgistro POliterapie-Società Italiana Medicina Interna (REPOSI) that collected clinical information on patients aged ≥ 65 years acutely admitted to Italian internal medicine and geriatric non-intensive care units (ICU) from 2010 up to 2019. Prescription appropriateness was assessed according to the 2019 AGS Beers Criteria and anti-diabetes drug data sheets.Among 5349 patients, 1624 (30.3%) had diagnosis of type 2 diabetes. At admission, 37.7% of diabetic patients received treatment with metformin, 37.3% insulin therapy, 16.4% sulfonylureas, and 11.4% glinides. Surprisingly, only 3.1% of diabetic patients were treated with new classes of anti- diabetes drugs. According to prescription criteria, at admission 15.4% of patients treated with metformin and 2.6% with sulfonylureas received inappropriately these treatments. At discharge, the inappropriateness of metformin therapy decreased (10.2%, P < 0.0001). According to Beers criteria, the inappropriate prescriptions of sulfonylureas raised to 29% both at admission and at discharge. This study shows a poor adherence to current guidelines on diabetes management in hospitalized elderly people with a high prevalence of inappropriate use of sulfonylureas according to the Beers criteria