Histologic Observations of Dermal Wound Healing in a Free-Ranging Blacktip Shark from the Southeastern U.S. Atlantic Coast: A Case Report

The costs and healing rates of minor injuries in neonatal reef sharks

Elasmobranch fishes (i.e., sharks, skates, and rays) exhibit remarkable wound-healing capabilities and consistently maintain a high capacity for tissue regeneration throughout their lives. This high capacity for wound healing may be particularly important for neonatal elasmobranchs that are still developing their immune system. However, little is known about the costs associated with wound healing and the potential influence of environmental variables or life history. In this study, we explore (1) the impact of minor, external injuries on the growth and body condition of neonatal blacktip reef (Carcharhinus melanopterus) and sicklefin lemon (Negaprion acutidens) sharks using a long-term fisheries-independent dataset from Moorea, French Polynesia, (2) the influence of ambient temperature on healing rates in neonatal blacktip reef sharks at two experimental temperatures (25°C and 29°C), and (3) variations in umbilical wound-healing rates between blacktip reef and sicklefin lemon sharks using an additional long-term dataset from St. Joseph Atoll, Seychelles. We found no impact of minor, external injuries on growth and body condition in neonatal blacktip reef and sicklefin lemon sharks, accelerated umbilical wound healing in neonatal blacktip reef sharks exposed to elevated ambient temperatures, and distinct umbilical wound-healing rates between neonatal blacktip reef and sicklefin lemon sharks. Enhancing our understanding of sharks' healing capabilities and the influence of environmental factors on this process is crucial for informing handling practices aimed at improving post-release survival rates of captured sharks under current and future oceanic conditions.

Pathological study of a traumatic anthropogenic injury in the skeleton of a spiny butterfly ray (Gymnura altavela)

Introduction

External injuries in elasmobranchs are frequent findings, either due to inter- or intraspecific interactions or as a result of interaction with human activities. However, the resilience of these species to traumatic injury remains poorly understood. This work provides an insight into the clinical presentation, diagnostic imaging, and pathological features of a severe traumatic injury to the cartilaginous skeleton of a spiny butterfly ray (Gymnura altavela).

Methods

An adult female was found lethargic in the bottom of the coast of Gran Canaria, with an external incised-contused traumatic lesion of 2 cm diameter in the scapulocoracoid cartilage. It was captured and transferred to the Poema del Mar Aquarium for its clinical evaluation and treatment. Despite these efforts, the animal eventually died and was transfer to the Institute of Animal Health and Food Safety (IUSA) for its pathological diagnosis, including a Computed Tomography (CT) study and necropsy.

Results

The animal presented a marked reduction in hematocrit and hepatosomatic index due a chronic debilitation process. The CT scan revealed a destructive lesion with irregular margins at the level of the right scapulocoracoid cartilage. The main pathological findings were the disorganization of the tesserae layer, appearing as whitish square to rectangular geometric pieces separated from the cartilaginous core. Histologically, these pieces of tesserae were separated from the unmineralized cartilage core and displaced from the adjacent perichondrium, where inflammatory cells infiltrate. Edema and hemorrhages were also observed.

Conclusions

This study reports the first comprehensive description of skeleton trauma in a spiny butterfly ray, including the clinical presentation, diagnostic imaging and the anatomopathological features.

Effect of photobiomodulation therapy as a multimodal approach to treatment of dermal abrasions in cownose rays (Rhinoptera bonasus)

Photobiomodulation therapy (PBMT) has become increasingly utilized in the zoo and aquarium fields to treat ailments in various species; however, its use in teleosts and elasmobranchs is relatively underrepresented in the literature. This study examined the efficacy of PBMT as an adjunct treatment to reduce the healing time of dermal abrasions in cownose rays (Rhinoptera bonasus). Ten cownose rays were included in this study and separated into control (n = 5) and treatment groups (n = 5). Animals in both treatment and control groups received intramuscular injections of enrofloxacin every 72 h to provide broad-spectrum antibiotic coverage. Cownose rays in the treatment group additionally received PBMT using the Companion® CTC-12 unit using the large, noncontact head. Control group rays were subjected to identical handling without the use of PBMT. A total of 196 Joules were delivered at a power of 2 W based on a dose of 5 J/cm2 at each session. Observational analysis revealed a lack of appreciable difference in healing time between the treatment and control groups in the aforementioned settings; however, it is recommended that PBMT protocols should be re-evaluated if there is little to no response in healing after three to four sessions. PBMT use on acute superficial dermal abrasions in cownose rays was well-tolerated in this study and may have utility in a multimodal treatment approach to wound healing. This study also produced a wound scoring metric based on photographs captured at each treatment. Future studies should utilize increased fluence (J/cm2) and irradiance (W/cm2) and incorporate synchronous histological analysis and increased sample size.

The salamander blastema within the broader context of metazoan regeneration

Throughout the animal kingdom regenerative ability varies greatly from species to species, and even tissue to tissue within the same organism. The sheer diversity of structures and mechanisms renders a thorough comparison of molecular processes truly daunting. Are "blastemas" found in organisms as distantly related as planarians and axolotls derived from the same ancestral process, or did they arise convergently and independently? Is a mouse digit tip blastema orthologous to a salamander limb blastema? In other fields, the thorough characterization of a reference model has greatly facilitated these comparisons. For example, the amphibian Spemann-Mangold organizer has served as an amazingly useful comparative template within the field of developmental biology, allowing researchers to draw analogies between distantly related species, and developmental processes which are superficially quite different. The salamander limb blastema may serve as the best starting point for a comparative analysis of regeneration, as it has been characterized by over 200 years of research and is supported by a growing arsenal of molecular tools. The anatomical and evolutionary closeness of the salamander and human limb also add value from a translational and therapeutic standpoint. Tracing the evolutionary origins of the salamander blastema, and its relatedness to other regenerative processes throughout the animal kingdom, will both enhance our basic biological understanding of regeneration and inform our selection of regenerative model systems.

Pathology associated with Tripaphylus Richiardi, 1878 infection (Copepoda: Sphyriidae) in wild-caught Australian blackspot sharks, Carcharhinus coatesi (Whitley, 1939), off northern Australia

Female specimens of the newly described mesoparasitic copepod Tripaphylus squidwardi (Sphyriidae), collected from the Australian blackspot shark, Carcharhinus coatesi, off northern Australia were examined histologically. The ‘encapsulated’ head of the copepod was found in the ventral musculature of the throat of the shark. The head of the copepod was surrounded by a tissue capsule of unknown origin. There were signs of chronic inflammation associated with the infection, although there appeared to be no effect on the health of the shark.