Development of Hybrid Film Based on Carboxymethyl Chitosan-Gum Arabic Incorporated Citric Acid and Polyphenols from Cinnamomum camphora Seeds for Active Food Packaging

Journal of Polymers and the Environment - In this study, carboxymethyl chitosan with gum Arabic (CG) based novel functional films containing Cinnamomum camphora seeds extract (CCSE) at varying...     

Characterisation of cysteine proteinase activities in the digestive tract of juvenile <Emphasis Type="Italic">Paragnathia formica</Emphasis> isopods,ectoparasites of estuarine fish

Juveniles of Paragnathia formica Hesse (Isopoda; Gnathiidae) are haematophagous ectoparasites, feeding on fish blood which supplies the nutrients for their development through growth and moulting, and the subsequent survival and reproduction of the free-living adults. Little is known of the mechanisms of digestion in juvenile gnathiids, and biochemical studies on the digestive tract of these interesting estuarine isopods have not been undertaken previously. Here, functionally active cathepsin-like cysteine proteinases are identified in the digestive system of juvenile praniza (fed) and zuphea (unfed) forms. The physiological pH of the digestive tract and the optimum proteolytic activities detected in praniza 3 homogenates using the cathepsin B/L, cathepsin B, and cathepsin H fluorogenic substrates, N-Carbobenzoxy-Phe-Arg-4-methoxy-2-naphthylamine (Z-phe-arg-MNA), N-Carbobenzoxy-Arg-Arg-4-methoxy-2-naphthylamine (Z-arg-arg-MNA) and Arg-4-methoxy-2-naphthylamine (H-arg-MNA), respectively, are in the acidic range (pH 5.8–6.7). Inhibition profiles against Z-phe-arg-MNA and Z-arg-arg-MNA using the cathepsin B inactivator urea, and cysteine proteinase inhibitors, support the presence of cathepsin L- and B-like enzymes. These proteolytic activities are 10–50 times higher in homogenates of praniza 3 compared with zuphea 3 forms. Histochemistry of praniza 3 sections reveals that the predominant enzyme activity towards Z-phe-arg-MNA is limited to the digestive glands during early and mid stages of digestion; later, this activity appears in the lining of the anterior hindgut. Moreover, activity towards Z-arg-arg-MNA is generally restricted to the digestive glands, and only occasionally present in the anterior hindgut. In conclusion, the digestive glands are the main site of cathepsin-like cysteine proteinase activities in P. formica juveniles; these enzymes appear to be important to the digestion of host fish blood enabling development through to the free-living adult.     

Thermal dependency of burrowing in three species within the bivalve genus <Emphasis Type="Italic">Laternula</Emphasis>: a latitudinal comparison

The upper thermal limits for burrowing and survival were compared with micro-habitat temperature for anomalodesmatan clams: Laternula elliptica (Antarctica, 67°S); Laternula recta, (temperate Australia, 38°S) and Laternula truncata (tropical Singapore, 1°N). Lethal limits (LT₅₀) were higher than burrowing limits (BT₅₀) in L. elliptica (7.5–9.0 and 2.2°C) and L. recta (winter, 32.8–36.8 and 31.1–32.8°C) but the same range for L. truncata (33.0–35.0 and 33.4–34.9°C). L. elliptica and L. truncata had a BT₅₀ 0.4 and 2.4–3.9°C, respectively, above their maximum experienced temperature. L. recta, which experience solar heating during midday low tides, had a BT₅₀ 0.7–2.4°C below and a range for LT₅₀ that spanned their predicted environmental maximum (33.5°C). L. recta showed no seasonal difference in LT₅₀ or BT₅₀. Our single genus comparisons contrast with macrophysiological studies showing that temperate species cope better with elevated temperatures. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Underwater and above-water search patterns of an Arctic seabird: reduced searching at small spatiotemporal scales

How predators vary search patterns in response to prey predictability is poorly known. For example, marine invertebrates may be predictable but of low energy value, while fish may be of higher energy value but unpredictable at large (pelagic schools) or small (solitary benthics) spatial scales. We investigated the search patterns of the thick-billed murre (Uria lomvia), an Arctic seabird feeding on invertebrates, pelagic fish, or benthic fish. Foraging ranges at the Coats Island colony are generally smaller (<240 min per trip) than at larger colonies, and many birds specialize in foraging tactics and diet. Underwater search times for benthic fish were higher than for pelagic fish or invertebrates while above-water search times for pelagic fish were higher than for benthic fish or invertebrates. There were few stops during trips. Total trip time, flying time, number of flights, and number of dives were intercorrelated and increased with prey energy content, suggesting that longer trips involved fewer prey encounters due to selection of higher-quality, but rarer, prey items. Flight times were not Lévy-distributed and seabirds may have used area-restricted searches. The high degree of specialization, apparent absence of information center effects, and reduced above-water searching times may be linked to the relatively small colony size and the resulting short commuting distances to feeding areas, leading to greater prey predictability. We concluded that prey predictability over various scales affected predator search patterns.     

The influence of successional processes and disturbance on the structure of Tsuga canadensis forests

Old-growth forests are valuable sources of ecological, conservation, and management information, yet these ecosystems have received little study in New England, due in large part to their regional scarcity. To increase our understanding of the structures and processes common in these rare forests, we studied the abundance of downed coarse woody debris (CWD) and snags and live-tree size-class distributions in 16 old-growth hemlock forests in western Massachusetts. Old-growth stands were compared with eight adjacent second-growth hemlock forests to gain a better understanding of the structural differences between these two classes of forests resulting from contrasting histories. In addition, we used stand-level dendroecological reconstructions to investigate the linkages between disturbance history and old-growth forest structure using an information-theoretic model selection framework. Old-growth stands exhibit a much higher degree of structural complexity than second-growth forests. In particular, old-growth stands had larger overstory trees and greater volumes of downed coarse woody debris (135.2 vs. 33.2 m3/ha) and snags (21.2 vs. 10.7 m3/ha). Second-growth stands were characterized by either skewed unimodal or reverse-J shaped diameter distributions, while old-growth forests contained bell-shaped, skewed unimodal, rotated sigmoid, and reverse J-shaped distributions. The variation in structural attributes among old-growth stands, particularly the abundance of downed CWD, was closely related to disturbance history. In particular, old-growth stands experiencing moderate levels of canopy disturbance during the last century (1930s and 1980s) had greater accumulations of CWD, highlighting the importance of gap-scale disturbances in shaping the long-term development and structural characteristics of old-growth forests. These findings are important for the development of natural disturbance-based silvicultural systems that may be used to restore important forest characteristics lacking in New England second-growth stands by integrating structural legacies of disturbance (e.g., downed CWD) and resultant tree-size distribution patterns. This silvicultural approach would emulate the often episodic nature of CWD recruitment within old-growth forests.     

Density dependence vs. independence, and irregular population dynamics of a swallow-wort fruit fly

Although most long-term studies of consumer-resource (e.g., predator-prey) interactions select species showing cyclic population dynamics, strong consumer-resource interactions can also produce irregular, noncyclic dynamics. Here, we present a case in which a seed predator, the tephritid fruit fly Euphranta connexa, shows fluctuations in density of more than two orders of magnitude over a 22-year period. To explain these fluctuations, we analyzed a stage-specific data set to quantify the density-dependent and density-independent components of larval survivorship and realized fecundity. Both larval survivorship and realized fecundity were strongly density dependent. Larval survivorship dropped from 0.62 at low larval density to 0.081 at high larval density, whereas fecundity dropped from 84.3 to 0.32 eggs per individual, more than a 100-fold decrease. We divided density-independent variation in E. connexa population dynamics into components for variability in (1) larval survivorship, (2) realized fecundity, and (3) annual fruit abundance. Of these components, 96% of the density-independent variance in per capita population growth rates was caused by fluctuations in fruit abundance. This highlights the importance of the strong consumer-resource interactions in driving fluctuations in E. connexa abundance. It also demonstrates that E. connexa dynamics are remarkably simple, and aside from the 4% of unexplained variance in per capita population growth rates, our understanding of E. connexa dynamics is remarkably complete.     

Conservation resource allocation,small population resiliency,and the fallacy of conservation triage

Some conservation prioritization methods are based on the assumption that conservation needs overwhelm current resources and not all species can be conserved; therefore, a conservation triage scheme (i.e., when the system is overwhelmed, species should be divided into three groups based on likelihood of survival, and efforts should be focused on those species in the group with the best survival prospects and reduced or denied to those in the group with no survival prospects and to those in the group not needing special efforts for their conservation) is necessary to guide resource allocation. We argue that this decision-making strategy is not appropriate because resources are not as limited as often assumed, and it is not evident that there are species that cannot be conserved. Small population size alone, for example, does not doom a species to extinction; plants, reptiles, birds, and mammals offer examples. Although resources dedicated to conserving all threatened species are insufficient at present, the world's economic resources are vast, and greater resources could be dedicated toward species conservation. The political framework for species conservation has improved, with initiatives such as the UN Sustainable Development Goals and other international agreements, funding mechanisms such as The Global Environment Facility, and the rise of many nongovernmental organizations with nimble, rapid-response small grants programs. For a prioritization system to allow no extinctions, zero extinctions must be an explicit goal of the system. Extinction is not inevitable, and should not be acceptable. A goal of no human-induced extinctions is imperative given the irreversibility of species loss.     

Genetic Introgression of Endemic Taxa by Non-natives: A Case Study with Leon Springs Pupfish and Sheepshead Minnow

Genetic studies of a pupfish (Cyprinodon bovinus) endemic to a small, spring-fed system in west Texas illustrate the potential for small introductions of non-native species to cause large-scale genetic changes through hybridization and genetic introgression. We performed a genetic survey (allozymes and RFLP analysis of mtDNA) of four samples of C. bovinus representing all wild populations of the species and a captive population maintained since 1976 at Dexter, New Mexico. The results indicate genetic introgression of the entire wild population by sheepshead minnow (C. variegatus), a coastal species with a history of introductions in west Texas. Frequencies of foreign genetic elements averaged across four diagnostic allozyme loci and mtDNA varied from 6.1 to 15.1%. The captive population appears free of foreign genetic material. Comparisons with past studies of C. bovinus indicate the present situation is largely due to a recent introduction of C. variegatus, not to an introduction in the mid-1970s; however, residual effects from the earlier introduction cannot be completely discounted. Genetic analysis indicates that the source of introduced C. variegatus in Diamond Y Draw is the nearest known population, an introduced stock in Lake Balmorhea approximately 90 km away. The results demonstrate the value of maintaining imperiled species in captivity. Captive C. bovinus provide an opportunity to restore the genetic integrity of wild populations.     

Forest Management Patterns in the Floodplain of the Amazon Estuary

In the Amazon basin, few studies have focused on environmentally sound land-use alternatives that are linked to markets. This paper analyzes land uses carried out by traditional inhabitants ( ribeirinhos ) on three islands in the Amazon estuary. Management of the native floodplain forest is the most extensive form of land use on these islands. Such management varies in response to local economic and ecological conditions but invariably targets key nontimber forest resources destined for local markets, requires minimal input of labor and capital, and maintains a considerable stock of biotic resources. While restricted to a specific forest type, this form of land use is associated with relatively high population densities and, if supported by appropriate development policies, could provide an environmentally sound land-use alternative for hundreds of thousands of rural inhabitants of Amazonia.