Hook‐shaped enterolith and secondary cachexia in a free‐living grey nurse shark (Carcharias taurus, Rafinesque 1810)

Abstract

The carcass of a critically endangered, juvenile female grey nurse shark (Carcharias taurus, Rafinesque 1810) was recovered from a south‐eastern Australian beach and subjected to necropsy. The 1.98‐m‐long shark exhibited advanced cachexia with its total weight (19.0 kg) and liver weight (0.37 kg) reduced by 60% and 89%, respectively, compared with a healthy individual of the same length. Marked tissue decomposition was evident preventing histopathology and identification of a definitive cause of death. At necropsy, the abdominal organs were abnormally displaced and showed marked reductions in size compared with a healthy individual of the same size. Importantly, a hook‐shaped enterolith (HSE), with a rough surface and cream in colour, was found within the spiral valve of the intestine and is to the authors’ knowledge, the first description of such in any marine animal. X‐ray diffractometry showed that the HSE comprised the minerals monohydrocalcite (Ca[CO₃].H₂O; ~70 wt%) and struvite (Mg [NH4] [PO4]. [H2O]6; ~30 wt%). A CT scan showed concentric lamellate concretions around a 7/o offset J‐hook that formed the nidus of the HSE. Nylon fishing line attached to the hook exited the HSE and was evident in the abdominal cavity through a perforation in the intestinal wall where the posterior intestinal artery merges. The most parsimonious reconstruction of events leading to enterolithiasis and secondary cachexia in this shark was the consumption of a hooked fish and subsequent hook migration causing perforations of the cardiac stomach wall followed by the thin, muscular wall of the apposed, sub‐adjacent intestine.

Source, fate and management of recreational fishing marine debris

“…Similarly, external injuries such as puncture wounds from hooks can impact an organisms' ability to move or feed. Marine debris can also be confused with prey species and ingested by marine wildlife, causing a physical blockage in digestive systems and lead to internal injuries and ultimately starvation (Valente et al, 2007;Pedà et al, 2016;Jovanović, 2017;Otway et al, 2021). Smaller debris may also be consumed unintentionally and the presence of such debris in marine organisms is ubiquitous and concerning.…”

“…Such hooking can also cause severe internal injuries. A recent case study on a carcass of this species documented ingestion of a J-hook that had perforated the intestinal wall, leading to cachexia, chronic bacterial infection and enterolithiasis (Otway et al, 2021). Ultimately it was the retention of this hook that led to the shark's death (Otway et al, 2021).…”

“…A recent case study on a carcass of this species documented ingestion of a J-hook that had perforated the intestinal wall, leading to cachexia, chronic bacterial infection and enterolithiasis (Otway et al, 2021). Ultimately it was the retention of this hook that led to the shark's death (Otway et al, 2021). The interaction between retained fishing gear and the greynurse shark is considered to be a key hindrance to the recovery of these populations (Bansemer and Bennett, 2010).…”

Single large enterolith in a cat with chronic inflammatory enteropathy

“…Most recently, a large enterolith was diagnosed in an aged labrador retriever 9 . There have been occasional reports of enteroliths in exotic species, including one of a hook‐shaped enterolith in a juvenile female grey nurse shark ( Carcharias taurus ) recovered from a south‐eastern Australian beach 10 …”

“…9 There have been occasional reports of enteroliths in exotic species, including one of a hook-shaped enterolith in a juvenile female grey nurse shark (Carcharias taurus) recovered from a south-eastern Australian beach. 10 The prevalence of enterolithiasis in people is reported to range from 0.3% to 10%, with a higher percentage in patients with Crohn's disease or Meckel's diverticulum. 1 Primary enterolithiasis has been shown to form in regions of gastrointestinal stasis or poor motility.…”