Modes of transmission and evolution of life histories in zooparasitic nematodes

1986 ◽  
Vol 64 (7) ◽  
pp. 1375-1384 ◽  
Author(s):  
Martin L. Adamson
Keyword(s):  
Life Histories ◽  
Intestinal Microflora ◽  
Feeding Habits ◽  
Intermediate Hosts ◽  
Free Living ◽  
Modes Of Transmission ◽  
Transmission Modes ◽  
Evolution Of Life ◽  
Two Factors ◽  
Life History Patterns

A hypothetical phylogeny of life-history patterns in zooparasitic nematodes is presented. It is suggested that the course of evolution of life histories has been strongly influenced by conditions under which parasitism arose; two factors appear particularly important, namely the primitive mode of transmission and the feeding habits of the ancestral populations. Two transmission modes were available at the outset: active penetration (usually cutaneous) and passive oral contamination. Only groups that arose using the former mode developed tissue parasitism and heteroxeneity. With percutaneous transmission, nematodes were forced to respond and adapt to the tissue environment from the beginnings of parasitism, and the penetrating habit probably facilitated experimentation with intermediate hosts. The Enoplida and Tylenchia arose from stylet-bearing predaceous or plant-parasitic fluid feeders adapted to feed on tissues. Cutaneous penetration was probably the primitive transmission mode and these groups were tissue dwelling at the outset. Zooparasitic Rhabditia and Diplogasteria are derived from free-living particulate feeders and the earliest parasitic forms probably fed on the intestinal microflora of the host; tissue parasitism arose secondarily and only in lineages that primitively used penetrative transmission.

scholarly journals The life histories and population dynamics of monogenean gill parasites of Trachurus trachurus (L.)

1962 ◽  
Vol 42 (3) ◽  
pp. 587-600 ◽  
Author(s):  
J. Llewellyn
Keyword(s):  
Coastal Waters ◽  
Life Histories ◽  
Feeding Habits ◽  
Limiting Factor ◽  
Trachurus Trachurus ◽  
Free Living ◽  
Sea Bottom ◽  
Second Year ◽  
Post Spawning ◽  
Gill Parasites

Gastrocotyle trachuri and Pseudaxine trachuri infect young Trachurus trachurus at Plymouth as soon as the 3- or 4-month-old adolescent fishes descend to the sea bottom in October. The parasites normally mature in 3 or 4 months, but, exceptionally, in about 1 month, and the life-span is normally no longer than 1 year. Trachurus specimens at the beginning of their second year pick up a largely new infection of parasites.G. trachuri and P. trachuri are much less frequent on 2- and 3-year-old specimens of Trachurus and probably occur only very rarely on still older fishes, the limiting factor being not an age-immunity but a post-spawning migration of the host from the concentration of free-living infective stages of the parasites in coastal waters.The parasites have adapted themselves to a seasonal change in the feeding habits of Trachurus by ceasing to produce larvae in anticipation of the summer disappearance of scad from the sea bottom in pursuit of pelagic food-organisms.

A Primer of Life Histories

2021 ◽  
Author(s):  
Jeffrey A. Hutchings
Keyword(s):  
Life History ◽  
Life Histories ◽  
Life History Theory ◽  
Life History Traits ◽  
Reproductive Effort ◽  
Effective Means ◽  
Academic Experience ◽  
Sustainable Exploitation ◽  
Evolution Of Life ◽  
Opportune Time

Life histories describe how genotypes schedule their reproductive effort throughout life in response to factors that affect their survival and fecundity. Life histories are solutions that selection has produced to solve the problem of how to persist in a given environment. These solutions differ tremendously within and among species. Some organisms mature within months of attaining life, others within decades; some produce few, large offspring as opposed to numerous, small offspring; some reproduce many times throughout their lives while others die after reproducing just once. The exponential pace of life-history research provides an opportune time to engage and re-engage new generations of students and researchers on the fundamentals and applications of life-history theory. Chapters 1 through 4 describe the fundamentals of life-history theory. Chapters 5 through 8 focus on the evolution of life-history traits. Chapters 9 and 10 summarize how life-history theory and prediction has been applied within the contexts of conservation and sustainable exploitation. This primer offers an effective means of rendering the topic accessible to readers from a broad range of academic experience and research expertise.

scholarly journals Minimal transmission in an influenza A (H3N2) human challenge-transmission model within a controlled exposure environment

2019 ◽  
Author(s):  
Jonathan S. Nguyen-Van-Tam ◽  
Ben Killingley ◽  
Joanne Enstone ◽  
Michael Hewitt ◽  
Jovan Pantelic ◽  
...  
Keyword(s):  
Attack Rate ◽  
Influenza A ◽  
Transmission Model ◽  
Epidemiological Methods ◽  
Large Droplet ◽  
Transmitted Infection ◽  
Modes Of Transmission ◽  
Transmission Modes ◽  
Building Ventilation ◽  
Transmission Studies

AbstractUncertainty about the importance of influenza transmission by airborne droplet nuclei generates controversy for infection control. Human challenge-transmission studies have been supported as the most promising approach to fill this knowledge gap. Healthy, seronegative volunteer ‘Donors’ (n=52) were randomly selected for intranasal challenge with influenza A/Wisconsin/67/2005 (H3N2). ‘Recipients’ randomized to Intervention (IR, n=40) or Control (CR, n=35) groups were exposed to Donors for four days. IRs wore face shields and hand sanitized frequently to limit large droplet and contact transmission. One transmitted infection was confirmed by serology in a CR, yielding a secondary attack rate of 2.9% among CR, 0% in IR (p=0.47 for group difference), and 1.3% overall, significantly less than 16% (p<0.001) expected based on a proof-of-concept study secondary attack rate and considering that there were twice as many Donors and days of exposure. The main difference between these studies was mechanical building ventilation in the follow-on study, suggesting a possible role for aerosols.Author summaryUnderstanding the relative importance of influenza modes of transmission informs strategic use of preventive measures to reduce influenza risk in high-risk settings such as hospitals and is important for pandemic preparedness. Given the increasing evidence from epidemiological modelling, exhaled viral aerosol, and aerobiological survival studies supporting a role for airborne transmission and the potential benefit of respirators (and other precautions designed to prevent inhalation of aerosols) versus surgical masks (mainly effective for reducing exposure to large droplets) to protect healthcare workers, more studies are needed to evaluate the extent of risk posed airborne versus contact and large droplet spray transmission modes. New human challenge-transmission studies should be carefully designed to overcome limitations encountered in the current study. The low secondary attack rate reported herein also suggests that the current challenge-transmission model may no longer be a more promising approach to resolving questions about transmission modes than community-based studies employing environmental monitoring and newer, state-of-the-art deep sequencing-based molecular epidemiological methods.

scholarly journals Cormorant pellets as a tool for the knowledge of parasite-intermediate host associations and nematode diversity in the environment

2019 ◽  
Vol 56 (4) ◽  
pp. 296-302 ◽  
Author(s):  
L. Garbin ◽  
J. I. Diaz ◽  
A. Morgenthaler ◽  
A. Millones ◽  
L. Kuba ◽  
...  
Keyword(s):  
Prey Item ◽  
Feeding Habits ◽  
Paratenic Host ◽  
Intermediate Hosts ◽  
Good Tool ◽  
Larval Stages ◽  
Nematode Diversity ◽  
Bird Colonies ◽  
Prey Items ◽  
Host Associations

SummaryAnisakids are usually acquired through the diet. Cormorant pellets are useful to detect both parasite larval stages, and prey items which could act as intermediate hosts in the environment. The current study provides information about the feeding habits of both birds and mammals, and the diversity of parasites circulating in the environment. The objective of the study was to identify Anisakidae larvae and prey items in pellets from the Imperial shag Phalacrocorax atriceps and the Red-legged cormorant P. gaimardi, suggesting possible parasite–prey associations. A total of 92 P. atriceps’ and 82 P. gaimardi’s pellets were collected from both Punta León, and Isla Elena bird colonies, respectively, during the period from 2006 to 2010. Pellets were preserved in ethanol and hard prey item remnants, and nematode larvae were studied using standard techniques. Prey item occurrence, nematode prevalence, and mean intensity were calculated. A correspondence analysis was performed to evaluate the larvae-prey association. Contracaecum spp., Pseudoterranova spp,, Anisakis spp., Terranova spp., and Hysterothylacium spp. third-stage larvae (L3) were identifi ed in pellets. Pseudoterranova spp. and Anisakis spp. L3 predominated in the environment of Punta León, whereas Contracaecum spp. and Hysterothylacium spp. L3 predominated in the Puerto Deseado area. The highest larvae-prey association was that of Contracaecum spp. L3 with Engraulis anchoita, followed by with Odontestes sp. in P. atriceps’ pellets. Contracaecum spp. L3 were significantly related to both sprats, Sprattus fueguensis and Ramnogaster arcuatta, in P. gaimardi’s pellets. It was verifi ed that E. anchovy is the main gateway of Contracaecum spp. L3 in P. atriceps. Odonthestes sp. might act as an intermediate/paratenic host of Contracaecum spp. L3 in the area. Both sprats might play a role as intermediate/paratenic hosts of C. australe, being the main gateway into P. gaimardi in the area. Thus, pellet analysis can be postulated as a good tool for indicating parasite-host associations between anisakids, and the prey items which act as intermediate hosts.

How long do Tydeidae live?

Zoosymposia ◽  
2021 ◽  
Vol 20 ◽  
Author(s):  
LIANA JOHANN ◽  
GUILHERME LIBERATO DA SILVA
Keyword(s):  
Life History ◽  
Feeding Habits ◽  
Free Living ◽  
The Family ◽  
The World

The family Tydeidae consists of small, free-living, soft-bodied mites with a diversity of feeding habits, including phytophages, pollen feeders and even predators, but the majority are scavengers or fungivores. Approximately 330 species in 30 genera have been described from throughout the world, but only a few species (<1% of all species) have been studied for their life history. This review provides a survey of their life history with a focus on their lifespan.

Feeding ecology of free-living nematodes.

2021 ◽  
pp. 185-215
Author(s):  
Nabil Majdi ◽  
Tom Moens ◽  
Walter Traunspurger
Keyword(s):  
Feeding Ecology ◽  
Trophic Interactions ◽  
Feeding Habits ◽  
Food Sources ◽  
Environmental Constraints ◽  
Feeding Rates ◽  
Feeding Selectivity ◽  
Free Living ◽  
Aquatic Nematodes ◽  
Food Recognition

Abstract This chapter provides overview of the feeding habits and food sources of aquatic nematodes. The environmental constraints on feeding, food recognition, and feeding selectivity are also addressed, together with the complex, indirect trophic interactions between nematodes and their microbial prey. To raise awareness of the inherent methodological and/or interpretational problems in studies of nematode feeding ecology, the chapter ends with a brief look at the methods that have been adapted to quantify feeding rates in nematodes.

Sign in / Sign up

Export Citation Format

Share Document