Do community changes persist after irruptive population dynamics? A case study from an invasive species boom and bust.

Irruptive or boom-and-bust population dynamics, also known as 'outbreaks', are an important phenomenon that has been noted in biological invasions at least since Charles Elton's classic book was published in 1958. Community-level consequences of irruptive dynamics are poorly documented and invasive species provide excellent systems for their study. African Jewelfish (Rubricatochromis letourneuxi, "jewelfish") are omnivores that demonstrate opportunistic carnivory, first reported in Florida in the 1960s and in Everglades National Park (ENP) in 2000. Twelve years after invasion in ENP, jewelfish underwent a 25-fold increase in density in one year. By 2016, jewelfish represented 25-50% of fish biomass. Using a 43-year fish community dataset at two sites (1978-2021), and a 25-year dataset of fish and invertebrate communities from the same drainage (1996-2021), with additional spatial coverage, we quantified differences in fish and invertebrate communities during different phases of invasion. During jewelfish boom, abundant, native cyprinodontiform fishes decreased in density and drove changes in community structure as measured by similarity of relativized abundance. Density of two species declined by > 70%, while four declined by 50-62%. Following the jewelfish bust, some species recovered to pre-boom densities while others did not. Diversity of recovery times produced altered community structure that lagged for at least four years after the jewelfish population declined. Community structure is an index of ecological functions such as resilience, productivity, and species interaction webs; therefore, these results demonstrate that irruptive population dynamics can alter ecological functions of ecosystems mediated by community structure for years following that population's decline.

Horner Syndrome With Ipsilateral Wing Paresis in a Wild, Juvenile Yellow-Tailed Black Cockatoo (Calyptorhynchus funereus).

A juvenile yellow-tailed black cockatoo (Calyptorhynchus funereus) was presented with paresis of the right wing, ptosis, and miosis of the right eye; feather erection of the right side of the head and neck; and a penetrating injury over the right pectoral muscle. Temporary reversal of ptosis, miosis, and feather erection after administration of phenylephrine drops confirmed a diagnosis of Horner syndrome. Computed tomographic imaging revealed a fractured rib, traumatic lung lesions, and subcutaneous emphysema. The right-sided Horner syndrome and wing paresis were attributed to a sympathetic nerve trauma of the eye and feathers and to the brachial plexus, respectively. This report describes the diagnosis and resolution of ptosis and miosis within 8 weeks and recovery of feather symmetry and wing function within 11 weeks of the cockatoo's initial presentation with a conservative-management treatment plan.

A rare case of isolated traumatic avulsion of the pes anserinus tendon.

Complete rupture of the conjoint pes anserinus tendon is rare, and isolated rupture without injury to associated structures has not been previously reported in the literature. A case of complete isolated rupture of the pes anserinus tendon is described in a young, healthy male. The non-specific nature of the presentation and rarity of the condition makes diagnosis from history and examination alone challenging. Magnetic resonance imaging was critical in making the correct diagnosis and excluding other potential-associated injuries with the diagnosis confirmed intraoperatively. The patient underwent surgical repair and rehabilitation and made significant progress. The diagnosis may be overlooked on a routine knee MRI, particularly in the absence of other associated injuries. An untreated injury may result in a poor outcome for the patient, with chronic pain and reduced function. Hence it is important to consider it in traumatic injuries to the region, with a view for an extended scan to visualise the full extent of the pes tendons to their insertion, particularly when there is high fluid signal in the popliteal fossa along the semitendinosus.

Complete tibial insertion of the biceps femoris tendon: an MRI-based study to assess the prevalence of this variant.

PURPOSE: To quantify the prevalence of complete tibial insertion of the biceps femoris tendon in patients presenting for knee MRI scans. METHODS: Knee MRI scans over a 4-year period (2014-2018) were accessed at a tertiary referral centre and community-based private practice. A total of 433 scans were reviewed. 30 scans were excluded from the study due to repeat imaging or incomplete coverage of the biceps femoris tendon insertion. Appearances of the distal biceps tendon bony insertion were scrutinized on the remaining 403 scans. Each biceps femoris tendon insertion was classified into one of the four categories-complete fibular insertion, predominant fibular insertion, predominant tibial insertion and complete tibial insertion. RESULTS: Out of the final 403 scans included in the study, five cases of complete tibial insertion of the biceps femoris tendon were identified (just over 1% of the total population). 42 cases were identified as having predominant tibial insertion (10% of the total population). 113 cases had predominantly fibular insertion and 243 cases had complete fibular insertion. CONCLUSION: Complete anomalous insertion of the biceps femoris tendon on the anterolateral tibia is an uncommon entity. Such an attachment is found in approximately 1% of patients presenting for MRI evaluation of the knee.

Removing opportunities to calculate improves students' performance on subsequent word problems.

BACKGROUND: In two studies we investigated whether removing opportunities to calculate could improve students' subsequent ability to solve similar word problems. Students were first asked to write explanations for three word-problems that they thought would help another student understand the problems. Half of the participants explained typical word problems (i.e., problems with enough information to make calculating an answer possible), while the other half explained the same problems with numbers removed, making calculating an answer impossible. We hypothesized that removing opportunities to calculate would induce students to think relationally about the word problems, which would result in higher levels of performance on subsequent transfer problems. RESULTS: In both studies, participants who explained the non-calculable problems performed significantly better on the transfer test than participants who explained the typical (i.e., calculable) problems. This was so in spite of the manipulation not fully suppressing students' desire to calculate. Many students in the non-calculable group explicitly stated that they needed numbers in order to answer the question or made up numbers with which to calculate. There was a significant, positive relationship between the frequency with which students made up numbers and their self-reported mathematics anxiety. CONCLUSIONS: We hypothesized that the mechanism at play was a reduction in instrumental thinking (and an increase in relational thinking). Interventions designed to help students remediate prior mathematical failure should perhaps focus less on the specific skills students are lacking, and more on the dispositions they bring to the task of "doing mathematics."

Exploring the practicing-connections hypothesis: using gesture to support coordination of ideas in understanding a complex statistical concept.

In this article, we begin to lay out a framework and approach for studying how students come to understand complex concepts in rich domains. Grounded in theories of embodied cognition, we advance the view that understanding of complex concepts requires students to practice, over time, the coordination of multiple concepts, and the connection of this system of concepts to situations in the world. Specifically, we explore the role that a teacher's gesture might play in supporting students' coordination of two concepts central to understanding in the domain of statistics: mean and standard deviation. In Study 1 we show that university students who have just taken a statistics course nevertheless have difficulty taking both mean and standard deviation into account when thinking about a statistical scenario. In Study 2 we show that presenting the same scenario with an accompanying gesture to represent variation significantly impacts students' interpretation of the scenario. Finally, in Study 3 we present evidence that instructional videos on the internet fail to leverage gesture as a means of facilitating understanding of complex concepts. Taken together, these studies illustrate an approach to translating current theories of cognition into principles that can guide instructional design.

Intravenous lobular capillary haemangioma (pyogenic granuloma): A case report and a review of imaging findings as reported in the literature.

INTRODUCTION: Intravenous lobular capillary haemangioma (IVLCH) is a rare benign lesion with minimal published reports containing a description of its appearance at medical imaging. We present the ultrasound and MRI images of a histologically proven IVLCH and provide the first review of the imaging findings reported in the literature. METHODS: The imaging findings of a case of IVLCH are presented. A PubMed search of English language articles was performed from 1966 to October 2016, and all relevant papers were reviewed. Imaging findings from those papers are summarised. RESULTS: Key features on ultrasound are of a well-defined, usually hypoechoic, mass which is highly vascular. The host vein is usually apparent. MRI imaging usually shows T1 signal isointense to muscle and variable T2 signal, either isointense or of high signal relative to the vein. The lesions enhance with gadolinium. CONCLUSION: Intravenous lobular capillary haemangioma has distinctive ultrasound but less consistent MRI features although radiological diagnosis should usually be possible. Review of reported cases shows that a previously described gender bias is incorrect.

Ring finger lumbrical origin strain: a case series with imaging findings.

Lumbrical strain is a relatively unknown hand injury. We report four cases of lumbrical origin strain involving the ring finger flexor tendons. Three patients sustained the injury during rock climbing and one while working with a jackhammer. In all cases, circumferential fluid around the flexor tendons of the ring finger was demonstrated on MRI and/or ultrasound at the distal palmar level at the "bare area," which is normally devoid of a synovial sheath. There is a paucity of information in the literature regarding this injury and its specific imaging features. Lack of awareness of this injury renders accurate diagnosis difficult.

Differential patterns of inputs create functional zones in central nucleus of inferior colliculus.

Distinct pathways carry monaural and binaural information from the lower auditory brainstem to the central nucleus of the inferior colliculus (ICC). Previous anatomical and physiological studies suggest that differential ascending inputs to regions of the ICC create functionally distinct zones. Here, we provide direct evidence of this relationship by combining recordings of single unit responses to sound in the ICC with focal, iontophoretic injections of the retrograde tracer Fluoro-Gold at the physiologically characterized sites. Three main patterns of anatomical inputs were observed. One pattern was identified by inputs from the cochlear nucleus and ventral nucleus of the lateral lemniscus in isolation, and these injection sites were correlated with monaural responses. The second pattern had inputs only from the ipsilateral medial and lateral superior olive, and these sites were correlated with interaural time difference (ITD)-sensitive responses to low frequency (<500 Hz). A third pattern had inputs from a variety of olivary and lemniscal sources, notably the contralateral lateral superior olive and dorsal nucleus of the lateral lemniscus. These were correlated with high-frequency ITD sensitivity to complex acoustic stimuli. These data support the notion of anatomical regions formed by specific patterns of anatomical inputs to the ICC. Such synaptic domains may represent functional zones in ICC.

Disturbance frequency and community structure in a twenty-five year intervention study.

Models of community regulation commonly incorporate gradients of disturbance inversely related to the role of biotic interactions in regulating intermediate trophic levels. Higher trophic-level organisms are predicted to be more strongly limited by intermediate levels of disturbance than are the organisms they consume. We used a manipulation of the frequency of hydrological disturbance in an intervention analysis to examine its effects on small-fish communities in the Everglades, USA. From 1978 to 2002, we monitored fishes at one long-hydroperiod (average 350 days) and at one short-hydroperiod (average 259 days; monitoring started here in 1985) site. At a third site, managers intervened in 1985 to diminish the frequency and duration of marsh drying. By the late 1990s, the successional dynamics of density and relative abundance at the intervention site converged on those of the long-hydroperiod site. Community change was manifested over 3 to 5 years following a dry-down if a site remained inundated; the number of days since the most recent drying event and length of the preceding dry period were useful for predicting population dynamics. Community dissimilarity was positively correlated with the time since last dry. Community dynamics resulted from change in the relative abundance of three groups of species linked by life-history responses to drought. Drought frequency and intensity covaried in response to hydrological manipulation at the landscape scale; community-level successional dynamics converged on a relatively small range of species compositions when drought return-time extended beyond 4 years. The density of small fishes increased with diminution of drought frequency, consistent with disturbance-limited community structure; less-frequent drying than experienced in this study (i.e., longer return times) yields predator-dominated regulation of small-fish communities in some parts of the Everglades.

Organization of binaural excitatory and inhibitory inputs to the inferior colliculus from the superior olive.

The major excitatory, binaural inputs to the central nucleus of the inferior colliculus (ICC) are from two groups of neurons with different functions-the ipsilateral medial superior olive (MSO) and the contralateral lateral superior olive (LSO). A major inhibitory, binaural input emerges from glycinergic neurons in the ipsilateral LSO. To determine whether these inputs converge on the same postsynaptic targets in the ICC, two different anterograde tracers were injected in tonotopically matched areas of the MSO and the LSO on the opposite side in the same animal. The main findings were that the boutons from MSO axons terminated primarily in the central and caudal parts of the ICC laminae but that contralateral LSO terminals were concentrated more rostrally and on the ventral margins of the MSO inputs. In contrast, the ipsilateral LSO projection converged with the MSO inputs and was denser than the contralateral LSO projection. Consistent with this finding, retrograde transport experiments showed that the very low-frequency areas of the ICC with dense MSO inputs also received inputs from greater numbers of ipsilateral LSO neurons than from contralateral LSO neurons. The results suggest that different binaural pathways through the low-frequency ICC may be formed by the segregation of excitatory inputs to ICC from the MSO and the contralateral LSO. At the same time, the ipsilateral LSO is a major inhibitory influence in the target region of the MSO. These data support the concept that each frequency-band lamina in the ICC may comprise several functional modules with different combinations of inputs.

Topography of interaural temporal disparity coding in projections of medial superior olive to inferior colliculus.

Neurons in the medial superior olive encode interaural temporal disparity, and their receptive fields indicate the location of a sound source in the azimuthal plane. It is often assumed that the projections of these neurons transmit the receptive field information about azimuth from point to point, much like the projections of the retina to the brain transmit the position of a visual stimulus. Yet this assumption has never been verified. Here, we use physiological and anatomical methods to examine the projections of the medial superior olive to the inferior colliculus for evidence of a spatial topography that would support transmission of azimuthal receptive fields. The results show that this projection does not follow a simple point-to-point topographical map of receptive field location. Thus, the representation of sound location along the azimuth in the inferior colliculus most likely relies on a complex, nonlinear map.

Separating the effects of intra- and interspecific age-structured interactions in an experimental fish assemblage.

We documented patterns of age-structured biotic interactions in four mesocosm experiments with an assemblage of three species of co-occurring fishes from the Florida Everglades, the eastern mosquitofish (Gambusia holbrooki), sailfin molly (Poecilia latipinna), and bluefin killifish (Lucania goodei). These species were chosen based on their high abundance and overlapping diets. Juvenile mosquitofish and sailfin mollies, at a range of densities matching field estimates, were maintained in the presence of adult mosquitofish, sailfin mollies, and bluefin killifish to test for effects of competition and predation on juvenile survival and growth. The mesocosms held 1,200 l of water and all conditions were set to simulate those in Shark River Slough, Everglades National Park (ENP), USA. We placed floating mats of periphyton and bladderwort in each tank in standard volumes that matched field values to provide cover and to introduce invertebrate prey. Of 15 possible intra- and interspecific age-structured interactions, we found 7 to be present at the densities of these fish found in Shark River Slough marshes. Predation by adult mosquitofish on juvenile fish, including conspecifics, was the strongest effect observed. We also observed growth limitation in mosquitofish and sailfin molly juveniles from intra- and interspecific competition. When maintained at high densities, juvenile mosquitofish changed their diets to include more cladocerans and fewer chironomid larvae relative to low densities. We estimated size-specific gape limitation by adult mosquitofish when consuming juvenile mosquitofish and sailfin mollies. At high field densities, intraspecific competition might prolong the time period when juveniles are vulnerable to predation by adult mosquitofish. These results suggest that path analysis, or other techniques used to document food-web interactions, must include age-specific roles of these fishes.