Smooth Fan Research Articles

Impact of substrate particle size on the digging behavior of the juveniles of the smooth fan lobster Ibacus novemdentatus Gibbes, 1850 (Decapoda: Pleocymeta: Scyllaridae)

Abstract Aquaculture techniques for fan lobsters are still in an early stage of development due to the limited knowledge on their early-benthic stages. As the lobsters are diggers and thus the substrate influences their survival and growth, the physical characteristics of such substrates are a crucial environmental factor in an aquaculture setting. The appropriate size ranges of the substrate particles are nevertheless unknown. We studied the digging behavior of the juvenile of the smooth fan lobster, Ibacus novemdentatusGibbes, 1850, and examined its ability to dig into sand of different particle sizes to determine the optimal substrate conditions. Digging was completed by 100% of the juveniles in fine sand, 85.7% in medium-size sand, 25.7% in medium-coarse sand, and none in coarse sand. Juvenile digging involves three stages: searching for a location to dig, inserting the tail fan, and submerging into the sediment. The median length of time from the beginning of the experiment to the commencement of tail insertion in juveniles that completed digging did not differ significantly (P = 0.97) with the particle size. Juveniles placed on the substrate with medium-size and medium-coarse sand took significantly longer (P < 0.01) from the start of tail insertion to the complete submersion than those on fine sand. Considering the success rates of digging and the time required to complete digging, fine sand was the most appropriate substrate among the tested particle-size ranges. The juveniles that failed to complete the digging repeated a digging position and attempted to insert their tail fan into the sand without submerging. These juveniles took a significantly longer time (P < 0.05) to attempt to insert their tail fan than the juveniles that successfully completed digging, suggesting that juveniles placed on inappropriate substrates may spend more energy on digging and become more stressed.

Smooth fans that are endpoint rigid

Let X be a smooth fan and denote its set of endpoints by E(X). Let E be one of the following spaces: the natural numbers, the irrational numbers, or the product of the Cantor set with the natural numbers. We prove that there is a smooth fan X such that E(X) is homeomorphic to E and for every homeomorphism h : X → X , the restriction of h to E(X) is the identity. On the other hand, we also prove that if X is any smooth fan such that E(X) is homeomorphic to complete Erdős space, then X is necessarily homeomorphic to the Lelek fan; this adds to a 1989 result by Włodzimierz Charatonik.

A dichotomy for spaces near dimension zero

We prove that the classes of weakly 1-dimensional and almost 0-dimensional spaces are disjoint. The result has applications to hereditarily locally connected spaces, R-trees, and endpoints of smooth fans.

Cycles, cocycles, and duality on tropical manifolds

We prove a Poincar\'e duality for the Chow rings of smooth fans whose support are tropical linear spaces. As a consequence, we show that cycles and cocycles on tropical manifolds are Poincar\'e dual to each other. This allows us to define pull-backs of tropical cycles along arbitrary morphisms with smooth target.

Strong factorization and the braid arrangement fan

We establish strong factorization for pairs of smooth fans which are refined by the braid arrangement fan. Our method uses a correspondence between cones and preposets.

Nonlinear Behavior of High-Intensity Ultrasound Propagation in an Ideal Fluid

In this paper, nonlinearity associated with intense ultrasound is studied by using the one-dimensional motion of nonlinear shock wave in an ideal fluid. In nonlinear acoustics, the wave speed of different segments of a waveform is different, which causes distortion in the waveform and can result in the formation of a shock (discontinuity). Acoustic pressure of high-intensity waves causes particles in the ideal fluid to vibrate forward and backward, and this disturbance is of relatively large magnitude due to high-intensities, which leads to nonlinearity in the waveform. In this research, this vibration of fluid due to the intense ultrasonic wave is modeled as a fluid pushed by one complete cycle of piston. In a piston cycle, as it moves forward, it causes fluid particles to compress, which may lead to the formation of a shock (discontinuity). Then as the piston retracts, a forward-moving rarefaction, a smooth fan zone of continuously changing pressure, density, and velocity is generated. When the piston stops at the end of the cycle, another shock is sent forward into the medium. The variation in wave speed over the entire waveform is calculated by solving a Riemann problem. This study examined the interaction of shocks with a rarefaction. The flow field resulting from these interactions shows that the shock waves are attenuated to a Mach wave, and the pressure distribution within the flow field shows the initial wave is dissipated. The developed theory is applied to waves generated by 20 KHz, 500 KHz, and 2 MHz transducers with 50, 150, 500, and 1500 W power levels to explore the effect of frequency and power on the generation and decay of shock waves. This work enhances the understanding of the interactions of high-intensity ultrasonic waves with fluids.

Smooth fan lobster Ibacus novemdentatus in the southwestern Indian Ocean: an overlooked fisheries resource?

Bottom-trawl data collected by the RV Dr Fridtjof Nansen off Mozambique (in 1990, 2007 and 2018) and off eastern South Africa (in 2018) were analysed to investigate the distribution, abundance and size composition of the smooth fan lobster Ibacus novemdentatus as a potential fisheries resource. The lobsters occurred shallower (depth 53–297 m) than traditional deep-water trawl grounds, were concentrated in ‘hotspots’ at the seaward edges of sand/mud banks at the Thukela Bank, Delagoa Bight and Sofala Bank, and exhibited segregated juvenile and adult populations. Three other high-value lobster species and several marketable teleost species occurred in trawl nets where I. novemdentatus was present. Further exploration by trawling should be considered to better define hotspots of adults of this species and to investigate the contribution that I. novemdentatus could make to mixed-species commercial catches.

Homogeneity degree of fans

The homogeneity degree of a topological space X is the number of orbits of the action of the homeomorphism group of X on X. We initiate a study of dendroids of small homogeneity degree, beginning with fans. We classify all smooth fans of homogeneity degree 3, and discuss non-smooth fans and prove some results on degree 4.

Projective wonderful models for toric arrangements

In this paper we illustrate an algorithmic procedure which allows to build projective wonderful models for the complement of a toric arrangement in a n-dimensional algebraic torus T. The main step of the construction, inspired by [9], is a combinatorial algorithm that produces a toric variety by subdividing in a suitable way a given smooth fan.

The Lelek fan and the Poulsen simplex as Fra\xefss\xe9 limits

We describe the Lelek fan, a smooth fan whose set of end-points is dense, and the Poulsen simplex, a Choquet simplex whose set of extreme points is dense, as Fraïssé limits in certain natural categories of embeddings and projections. As an application we give a short proof of their uniqueness, universality, and almost homogeneity. We further show that for every two countable dense subsets of end-points of the Lelek fan there exists an auto-homeomorphism of the fan mapping one set onto the other. This improves a result of Kawamura, Oversteegen, and Tymchatyn from 1996.

Grooming behavior by elongated third maxillipeds of phyllosoma larvae of the smooth fan lobster riding on jellyfishes

Animals groom their body surface to prevent or remove parasites and non-biological fouling that can negatively impact their mobility, appearance, and health. The jellyfish riders, phyllosoma larvae of the smooth fan lobster Ibacus novemdentatus Gibbes which spend their planktonic larval period riding on and eating live jellyfish, have a characteristic body shape, a leaf-like flat body without gills and a pair of elongated third maxillipeds. Although the third maxillipeds lack exopods and are very long compared with that of other types of decapod crustacean adults and larvae, their function is not known. In the present study, we hypothesized that the elongated third maxillipeds of I. novemdentatus phyllosoma larvae constitute a grooming organ specialized to remove fouling from their body surface and/or an organ to manipulate their food, and tested the hypothesis through morphological and behavioral experiments. Our morphological observations show that the third maxillipeds are longer than the larva's body and that the tip of the maxillipeds has a comb-like structure. Our behavioral experiments show that the larvae spent about 50% of their time grooming with their third maxillipeds but did not use these maxillipeds to manipulate jellyfish for eating. The maxillipeds removed an experimentally-applied foulant from most of their body parts, suggesting that this artificial foulant stimulated grooming on that location. Thus, the grooming has characteristics of both programmed and stimulus-driven behaviors. Inhibition of this behavior enhanced growth of microbes on the body surface of that phyllosoma fed with jellyfish. Glycine was identified as major free amino acid in jellyfish tissue using amino acid analysis and as a major metabolite by nuclear magnetic resonance (NMR) spectroscopy. Glycine induced appetitive and grooming behaviors in the larvae. Thus, we conclude that the phyllosoma larvae use the elongated third maxillipeds for cleaning their entire body surface and that the maxillipeds are functionally specialized for this cleaning behavior. This frequent whole body cleaning behavior with specialized appendages might be adaptive to their lifestyle of riding on jellyfish, where they are exposed to large amounts of mucus released from the jellyfish which could otherwise cause growth of microbes on their body surface.

Rigidity of symmetric products

Given a metric continuum X, we consider the following hyperspaces of X: 2X, Cn(X) and Fn(X) (n∈N). Let F1(X)={{x}:x∈X}. A hyperspace K(X) of X is said to be rigid provided that for every homeomorphism h:K(X)→K(X) we have that h(F1(X))=F1(X). In this paper we study under which conditions a continuum X has a rigid hyperspace Fn(X).Among others, we consider families of continua such as, dendroids, Peano continua, indecomposable arc continua (all their proper nondegenerate subcontinua are arcs), hereditarily indecomposable continua and smooth fans.

Choniomyzon inflatus n. sp. (Crustacea: Copepoda: Nicothoidae) associated with Ibacus novemdentatus (Crustacea: Decapoda: Scyllaridae) from Japanese waters

A new species of parasitic copepod, Choniomyzon inflatus n. sp., is described based on specimens collected from the external egg masses of the smooth fan lobster Ibacus novemdentatus Gibbes captured in the North Pacific Ocean off Ainan, Ehime Prefecture, western Japan. The new species differs from its congeners in having a globular to ovoid prosome, in bearing asymmetrically arranged denticles at a rounded apex of both the terminal segment of the antenna and the maxilliped, and in lacking serrate lobes on the basis of legs 1 and 2. The species is similar in size and shape to the host's eggs, which may be interpreted as egg mimicry. The new species is the first member of Choniomyzon Pillai, 1962 from subtropical regions.

Making Holes in the Hyperspace of Subcontinua of Some Continua

Let be a metric continuum. Let , is said to make a hole in , if is not unico-herent. In this paper, we characterize elements such that makes a hole in , where is either a smooth fan or an Elsa continuum.

The space of selections of smooth fans

In this paper we show that the space of selections of a smooth fan is a complete separable absolute retract. Then, we show that it is homeomorphic to the Hilbert space l 2 .

Sediment Transport Monitoring and Short Term Modeling in the Okavango Delta, Botswana

The Okavango Delta of northern Botswana comprises large wetlands that spread over an alluvial fan of 150 km in length. Only part of the fan is covered with wetlands but the repeated shifting of the zones prone to inundation has led to a regular distribution of sediments and eventually to the formation of a smooth fan surface. We conducted repeated solute and bedload transport measurements at the inlet and within the wetlands proper to quantify sediment input and channel aggradation rates. The relationship between flow velocity and bedload transport was used to simulate channel erosion and aggradation, and a bedload transport component was built into a numerical hydrological model of the Okavango Delta. The model was used to assess the impact of a hypothetical dam in the upstream of the wetlands on channel bed elevations and the distribution of flooded areas. Our results suggest that the contribution of solute inputs to the overall sediment accumulation of the fan has been overestimated relative to bedload inputs. The numerical simulations reveal that a dam would have an impact on channel elevations only in its immediate downstream, but an impact on the distribution of flooding would be felt over the entire wetland system.

Hodge spaces of real toric varieties

We define the ℤ2 Hodge spacesH pq (Σ) of a rational fan Σ. If Σ is the normal fan of a reflexive polytope Δ then we use polyhedral duality to compute the Σ2 Hodge Spaces of Σ. In particular, if the cones of dimension at most e in the face fan Σ* of Δ are smooth then we computeH pq (Σ) forp <e − 1. If Σ* is a smooth fan then we completely determine the spacesH pq (Σ) and we showX Σ is maximal, meaning that the sum of the ℤ2 Betti numbers ofX Σ(ℝ) is equal to the sum of the ℤ2 Betti numbers ofX Σ(ℂ).

Open selections on smooth fans

Given a dendroid X, an open selection is an open map s : C ( X ) → X such that s ( A ) ∈ A for every A ∈ C ( X ) . We show that a smooth fan X admits an open selection if and only if X is locally connected.

On the fundamental group of real toric varieties

LetX (Δ) be the real toric variety associated to a smooth fan Δ. The main purpose of this article is: (i) to determine the fundamental group and the universal cover ofX (Δ), (ii) to give necessary and sufficient conditions on Δ under which π1(X(Δ)) is abelian, (iii) to give necessary and sufficient conditions on Δ under whichX(Δ) is aspherical, and when Δ is complete, (iv) to give necessary and sufficient conditions forC Δ to be aK (π, 1) space whereC Δ is the complement of a real subspace arrangement associated to Δ.

Non-metric Rim-metrizable continua and unique hyperspace

A class Λ of continua is said to be C-determined provided that if X, Y _ Λ and C(X) ≈ C(Y), then X ≈ Y. A continuum X has unique hyperspace provided that if Y is a continuum and C(X) ≈ C(Y), then X ≈ Y. In the realm of metric continua the following classes of continua are known to have unique hyperspace: hereditarily indecomposable continua, smooth fans (in the class of fans) and indecomposable continua whose proper and non-degenerate subcontinua are arcs. We prove that these classes have unique hyperspace in the realm of rim-metrizable non-metric continua. .