Delineation of blacktip shark (Carcharhinus limbatus) nursery habitats in the north-western Gulf of Mexico.

Coevolution with predators leads to the use of low-risk habitats by many prey species, which promotes survival during early developmental phases. These nurseries are valued by conservation and management agencies because of their contributions to adult populations. However, the physical and geographic characteristics, like shallow depths and isolation from other marine habitats, that restrict access to predators and thereby reduce risk to juvenile animals can also limit scientific research. Consequently, many nursery habitats are still unidentified and understudied. Here we used gillnet monitoring from 1982 to 2018 to delineate blacktip shark (Carcharhinus limbatus) nurseries in the north-western Gulf of Mexico and elucidated their physical, environmental and biological characteristics. Nursery habitats within estuaries (<2% of spatial area) were proximate to the Gulf of Mexico and exhibited significantly lower variability in salinity than non-nurseries. However, relative abundances of predators and prey were not significant delineators of nursery habitats. As such, food and risk may not influence juvenile blacktip habitat use as expected. Alternatively, reduced osmoregulatory stress attributed to predictable environments likely provides advantageous conditions for blacktips to develop foraging and antipredator tactics, which is vital prior to the winter migration of juvenile sharks into the Gulf of Mexico.

Grow fast, die young: Does compensatory growth reduce survival of juvenile blacktip sharks (Carcharhinus limbatus) in the western Gulf of Mexico?

Effective conservation and management necessitate an understanding of the ecological mechanisms that shape species life histories in order to predict how variability in natural and anthropogenic impacts will alter growth rates, recruitment, and survival. Among these mechanisms, the interaction between parturition timing and prey availability frequently influences offspring success, particularly when postnatal care is absent. Here, we assess how parturition timing and nursery conditions, including prey abundance and environmental conditions, influence the growth and potential survival of blacktip sharks (Carcharhinus limbatus) in western Gulf of Mexico (GOM) estuaries over their first year. Catch data from long-term gillnet monitoring allowed for clear delineation of cohorts based on size frequency distribution plots, and showed that late parturition cohorts born in estuaries with fewer prey resources exhibited more rapid growth than early parturition cohorts that experienced more abundant prey. Compensatory behaviors that promoted accelerated growth led to reduced second year residency, likely due to reduced survival resultant from greater risk taking and potentially due to reduced site fidelity attributed to larger body size. Water temperatures influenced blacktip growth rates through physiological increases in metabolism and potential premigratory foraging cues associated with cooling temperatures. Gradual warming of the GOM (0.03°C year-1) was also correlated with earlier parturition across the study period (1982-2017), similar to other migratory species. Considering current trends in climate and associated phenological shifts in many animals, testing hypotheses assessing compensatory growth-risk trade-offs is important moving forward to predict changes in life histories and associated recruitment in concert with current and future conservation actions, like wildlife management.

New insights into the trophic ecology of blacktip sharks (Carcharhinus limbatus) from a subtropical estuary in the western Gulf of Mexico.

As environmental change persists, understanding resource use patterns is of value to predict the consequences of shifting trophic structures. While many sharks are opportunistic predators, some exhibit prey selectivity, putting them at higher risk compared to species with greater trophic plasticity. In the Gulf of Mexico (GOM), Clupeids and Sciaenids comprise 69% of blacktip shark (Carcharhinus limbatus) diets, which is consequential considering potential responses of these prey groups to disturbance and over harvesting. We assessed if blacktips exhibit selectivity for Clupeids and Sciaenids in the western GOM based on stomach contents from sharks in coastal Texas. Clupeids comprised <2% of diets, while striped mullet (Mugil cephalus) and red drum (Sciaenops ocellatus) comprised >70% of identifiable prey. Ontogenetic shifts from smaller (Clupeids, small Sciaenids) to larger, higher trophic level (Ariidae, Elasmobranchii) prey fits our understanding of foraging among coastal sharks, and suggests our regional understanding of blacktip trophic ecology may be limited by the sizes of sampled sharks. Observed increases in blacktip densities coupled with declines in prey (Mugilids, Sciaenids) is concerning if blacktips have limited diet plasticity. Yet GOM blacktips may be more generalized than previously thought, which is promising for conservation and management.

Climate-related factors cause changes in the diversity of fish and invertebrates in subtropical coast of the Gulf of Mexico.

Climate change impacts physical and chemical properties of the oceans, and these changes affect the ecology of marine organisms. One important ecological consequence of climate change is the distribution shift of marine species toward higher latitudes. Here, the prevalence of nearly 150 species of fish and invertebrates were investigated to find changes in their distributions over 35 years along a subtropical coast within the Gulf of Mexico. Our results show that 90 species increased their occupancy probability, while 33 decreased (remaining species neither increase or decrease), and the ranges of many species expanded. Using rarefaction analysis, which allows for the estimation of species diversity, we show that species diversity has increased across the coast of Texas. Climate-mediated environmental variables are related to the changes in the occupancy probability, suggesting the expansion of tropical species into the region is increasing diversity.

Diverse cyclic seed peptides in the Mexican zinnia (Zinnia haageana).

A new family of small plant peptides was recently described and found to be widespread throughout the Millereae and Heliantheae tribes of the sunflower family Asteraceae. These peptides originate from the post-translational processing of unusual seed-storage albumin genes, and have been termed PawS-derived peptides (PDPs). The prototypic family member is a 14-residue cyclic peptide with potent trypsin inhibitory activity named SunFlower Trypsin Inhibitor (SFTI-1). In this study we present the features of three new PDPs discovered in the seeds of the sunflower species Zinnia haageana by a combination of de novo transcriptomics and liquid chromatography-mass spectrometry. Two-dimensional solution NMR spectroscopy was used to elucidate their structural characteristics. All three Z. haageana peptides have well-defined folds with a head-to-tail cyclized peptide backbone and a single disulfide bond. Although two possess an anti-parallel ß-sheet structure, like SFTI-1, the Z. haageana peptide PDP-21 has a more irregular backbone structure. Despite structural similarities with SFTI-1, PDP-20 was not able to inhibit trypsin, thus the functional roles of these peptides is yet to be discovered. Defining the structural features of the small cyclic peptides found in the sunflower family will be useful for guiding the exploitation of these peptides as scaffolds for grafting and protein engineering applications.

Delayed Ureterectomy after Incomplete Nephroureterectomy for Upper Tract Urothelial Carcinoma: Pathologic Findings and Outcomes

Objectives To evaluate the pathologic findings and outcomes after distal ureterectomy for a retained ureteral segment following incomplete nephroureterectomy for urothelial carcinoma of the renal pelvis or ureter. Materials and Methods After IRB approval, an institutional database identified patients who underwent distal ureterectomy for a retained ureteral segment after assumed complete nephroureterectomy for urothelial carcinoma of the upper ureter or renal pelvis. Clinical and pathologic variables were analyzed. Results From January 1993 to July 2007, 12 patients were identified with median age at the time of ureterectomy of 60.5 years (41-85 years). Initial approach to surgery was open in 9 patients and laparoscopic in 3 patients. The median time from nephroureterectomy to distal ureterectomy was 23.5 months (range 2-66). At the time of initial surgery, pathologic stage was Ta, T1, T2, and T3 in 3,4,1, and 4 patients respectively. Initial pathology was urothelial carcinoma; grade 2 in 6 patients and grade 3 in six patients. Pathology from the subsequent surgery demonstrated urothelial carcinoma in the retained ureteral segment in 8 patients, dysplasia or atypia in 3 patients, and 1 patient with chronic inflammation. Local recurrence in 2 patients was present in a segment of ureter discontinuous with the bladder after laparoscopic nephroureterectomy. Three patients (25%), all with initial grade 3 renal pelvis lesions, developed metastatic disease. Conclusions Tumor recurrence in a retained ureteral segment after incomplete nephroureterectomy is a significant problem and may contribute to intravesical recurrence or metastatic disease. Complete, en bloc resection is imperative to minimize these risks. .

Delayed ureterectomy after incomplete nephroureterectomy for upper tract urothelial carcinoma: pathologic findings and outcomes.

OBJECTIVES: To evaluate the pathologic findings and outcomes after distal ureterectomy for a retained ureteral segment following incomplete nephroureterectomy for urothelial carcinoma of the renal pelvis or ureter. MATERIALS AND METHODS: After IRB approval, an institutional database identified patients who underwent distal ureterectomy for a retained ureteral segment after assumed complete nephroureterectomy for urothelial carcinoma of the upper ureter or renal pelvis. Clinical and pathologic variables were analyzed. RESULTS: From January 1993 to July 2007, 12 patients were identified with median age at the time of ureterectomy of 60.5 years (41-85 years). Initial approach to surgery was open in 9 patients and laparoscopic in 3 patients. The median time from nephroureterectomy to distal ureterectomy was 23.5 months (range 2-66). At the time of initial surgery, pathologic stage was Ta, T1, T2, and T3 in 3,4,1, and 4 patients respectively. Initial pathology was urothelial carcinoma; grade 2 in 6 patients and grade 3 in six patients. Pathology from the subsequent surgery demonstrated urothelial carcinoma in the retained ureteral segment in 8 patients, dysplasia or atypia in 3 patients, and 1 patient with chronic inflammation. Local recurrence in 2 patients was present in a segment of ureter discontinuous with the bladder after laparoscopic nephroureterectomy. Three patients (25%), all with initial grade 3 renal pelvis lesions, developed metastatic disease. CONCLUSIONS: Tumor recurrence in a retained ureteral segment after incomplete nephroureterectomy is a significant problem and may contribute to intravesical recurrence or metastatic disease. Complete, en bloc resection is imperative to minimize these risks.