Abstracts
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LIST OF MEETING ABSTRACTS
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Oral Presentations
Day: 2, Session: 3, Talk: 1
KEY NOTE: Natural Born Killers: The Oomycetes as Important Pathogens of Animals
Gordon Beakes
The oomycete “fungi” belong to the Straminipile/Alveolate/Rhizaria superkingdom and are closely related to the golden-brown algae. They used to be thought of as predominantly freshwater saprotrophs or parasites of plants. Over past two decades molecular phylogeny has radically altered the way we view the oomycetes. There are a number of early diverging, non oogamously reproducing, clades that contain mostly marine parasites of nematodes, crustaceans and seaweeds, many of which have extra-ordinarily elaborate infection structures. The Haliphthorales are important pathogens of crustaceans, that can result in significant losses in marine aquaculture systems. The major divergence in the oomycete lineage came with the splitting off of the Peronosporalean and Saprolegnialean lines. The former are largely terrestrial, often soil born or plant pathogens and are characterised by their periplasmic oogenesis (which requires exogenous sterols) and often vesiculate discharge of zoospores. The latter, encompass most of the familiar water mould genera, and include the basal Leptomitales and the more familiar Saprolegniales, that contain general such as Aphanomyces, Achlya and Saprolegnia. The Aphanomyces clade is particularly interesting as it encompasses clades that are predominantly animal pathogens (including A. astaci), plant pathogens and saprotrophs. It also includes several genera that parasitize invertebrates such as rotifers (Aquastella) and nematodes (Sommerstorrfia). The evolutionary equivalent in the Peronosporalean lineage appears to be the Pythiaceous clades that include pathogens of nematodes (Lagenidium, Myzocytiopsis), crustaceans (Salilagenidium) and vertebrates (Paralagenidium, as well as the more familiar saprotrophs and plant pathogens (Pythium spp.). The overall evolutionary significance of these findings will be discussed.
Day: 4, Session: 1, Talk: 3
Low Local Crayfish Diversity and High Species Turnover in Lowland Streams may be Influenced by a Few Widely Distributed Crayfish Species
William R. Budnick, Harlan AR, Pasco TF, Kelso WE and Kaller MD
Crayfish are a numerous and diverse group of decapods that occupy multiple niches in lowland streams. However, the diversity of Louisiana crayfishes (~39 species) is poorly understood and is based on sporadic and voluntary reporting. Thus, average local diversity (a-diversity) and compositional turnover among localities (ß-diversity) have never been rigorously quantified or mapped. Herein, we quantify crayfish diversity using diversity indices, multiplicative hierarchical diversity partitioning, and variance in community composition among localities. Our data source from 59 wadeable streams in Central Louisiana sampled during summer 2013 and 2014 and span an area of approximately 24,000 km2 (~15% of state area), 5 major river drainages and 14 watersheds. Average a-diversity among all sites was characterized by low richness (typically 2-3 species) and extreme unevenness. Average a-diversity was typically lower than expected by random chance at drainage and watershed scales, whereas ß-diversity was typically greater than expected at both scales. Species turnover was the predominant beta diversity pattern at all spatial scales, but species loss (nestedness) increased relative to turnover at drainage and watershed scales. Finally, most variance in community composition resulted from variation in relative abundances of Procambarus clarkii,, Procambarus (Pennides) species, Orconectes lancifer, and Cambarellus puer. Our results suggest distributions and relative abundances of P. clarkii, O. lancifer and Procambarus (Pennides) species may play a deterministic role through competition and dispersal in diversity structuring of our study area. Future research will examine whether suppressed local diversity and enhanced turnover is a general feature of crayfish assemblages among lowland stream ecosystems.
Day: 5, Session: 3, Talk: 3
Effects of Flood-control Impoundments on Community Assemblages of Stream Crayfish
Zanethia C. Barnett
Over half of the world’s rivers have seen changes in the magnitude and timing of flows due to water regulation and increased water usage, affecting the diversity and abundance of stream organisms. I tested whether flood-control impoundments altered crayfish assemblage up and downstream of impoundments in two impounded creeks (Little Bear and Cedar creeks) and one unimpounded creek (Rock Creek) northern Alabama, USA. Crayfish and fish were sampled and physiochemical variables were measured at 6 - 8 sites along each creek in 2015. Crayfish abundance and diversity (species richness) differed between impounded and unimpounded creeks, as well as up and downstream of impoundments. Catch-per-unit-effort (CPUE) of Orconectes validus was higher in Rock Creek than impounded creeks in both the spring and fall. Upstream of impoundments also showed higher CPUE of Orconectes erichsonianus than sites downstream. In Rock Creek, crayfish diversity at the site furthest downstream was significantly greater than at the three furthest upstream sites. There was no difference in the diversity at similar distances up and downstream of impounded creeks, except the furthest up and downstream sites in Little Bear Creek (p<0.05), with diversity being greater downstream. Fish predators of crayfish were significantly greater in impounded than unimpounded creeks. Water temperatures and percent dissolved oxygen were higher in impounded than unimpounded creeks. Turbidity was higher downstream than upstream of impoundments. Crayfish diversity and abundance in thousands of stream kilometers are being affected by dams, which will influence freshwater and riparian ecosystems by impacting the important functions that crayfish provide.
Poster Presentations
POSTER 5
Mate Choice in Spiny-cheek Crayfish (Orconectes limosus, Rafinesque 1817): Females Prefer Males from the Same Population, Males not
Kubec J, Kouba A, Kozák P and Buřič M
Investigating of different effects on mate choice belong to major principles in behavioural and ecological studies. The mate choice is often based on recognition of conspecifics and social experiences (e.g. hierarchy, aggression or fighting), which play important roles in decision-making. In crayfish, it is known that females, which have large energy cost, are more choosy than males. We analysed mate selection of the spiny-cheek crayfish (Orconectes limosus) in the laboratory conditions. Our objective was to explore the effect of different origin of individuals (three geographically separated populations) on preference in mate choice. Both sexes were divided into triad groups (male with a familiar and unfamiliar female; female with a familiar and unfamiliar male). Our results suggest that spiny-cheek crayfish females choose mates from the familiar population, whereas males do not exhibit any specific preference between conspecifics from all. Our study offers information around reproductive behaviour that previous experience enables invertebrate females to easier decision making. While the males confirmed hypothesis about lesser selectivity. This study has the potential for future research on the largely overlooked field of mate choice in invertebrates.
POSTER 8
Fine Structure of the Spermatozoon in Three Species of (Arthropoda: Crustacea: Decapoda) Cambarus robustus, Orconectes propinquus and Orconectes rusticus: A Comparative Biometrical Study
Yazicioglu B, Hamr P, Kozák P, Kouba A and Niksirat H
The ultrastructure of spermatozoa in three species of cambarid crayfish, including Cambarus robustus, Orconectes propinquus, and Orconectes rusticus were studied and compared with eight previously studied species from different crayfish families using morphological features and biometrical data. The ultrastructure of spermatozoa show a generally conserved pattern including an acrosome and nucleus in the anterior and posterior parts of the cell, respectively, radial arms that wrap around the nucleus, and the whole cell is enclosed by an extracellular capsule. The most outstanding morphological feature in spermatozoa of three studied cambarid crayfish is the crest-like protrusions in the anterior part of the acrosome that can be used as one of the features for distinguishing the members of this family. Results of biometrical data reveal that acrosome size in the representatives of Parastacidae are the smallest, while representatives of Astacidae show the biggest acrosome. The acrosome size in species belonging to Cambaridae occupy an intermediate position between the two other families of freshwater crayfish. In conclusion, a combination of morphological features and biometrical data of spermatozoa can provide an effective tool to distinguish different species of the freshwater crayfish.
POSTER 25
Photoperiod Affects Light/Dark Preference and Exploratory Behaviour in Noble Crayfish (Astacus astacus)
Abeel T, Platteaux I, Roelant E, Adriaen J and Vervaecke H
Artificial day-night cycles are known to affect crayfish growth, behaviour and physiological stress levels in aquaculture. Based on the protocol by Fossat et al. (2015), who validated decreased exploratory behaviour and raised photophobia as stress-induced anxiety-like behaviours in Procambarus clarkii, we evaluated the effect of different photoperiods on noble crayfish activity and light/dark preference in an aquatic plus maze. We kept 135 two-summer-old crayfish in a recirculating aquaculture system and exposed them to five different photoperiods: hours light/dark (L:D) 0:24, 8:16, 12:12, 16:8 and 24:0. All animals had access to brushes and PVC pipes as shelters. After 144 days, the crayfish were submitted to the plus maze test. During a ten minute period, each individual’s location was scored every five seconds. Exploratory behaviour was assessed by quantifying the number of movements between different locations in the maze. Light/dark preference was determined by the time spent in the dark or lit arms. A linear mixed model for the different outcomes was fitted using tank as a random intercept and treatment as a fixed effect. Crayfish kept in 24L showed a higher amount of movements (43.6±4.3 mean±stdev) than individuals from all other treatments (ranging from 30.9±2.4 in L16:D8 down to 23.3±3.3 in L12:D12, p=0.0004). They also spent more time in the lit arms of the maze (43.40±1.74%) than animals from the 24D treatment (25.07±4.22%) (p=0.040). These results show that continuous light stimulates exploratory behaviour and continuous darkness causes more neophobia towards lit areas.
Oral Presentations from IAA21
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Poster Presentations
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General Assembly
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