Assessing the metabolic and physiological costs of oviparity in the epaulette shark (Hemiscyllium ocellatum)

Full description

Background:Reproduction in chondrichthyan fishes (sharks, rays, skates, and chimaeras) is generally assumed to be a long-term, energetically costly process due to their slow generation times. However, the metabolic costs of reproduction remain poorly understood, largely due to a lack of direct, non-lethal measurements. This study provides the first direct assessment of metabolic and physiological changes during oviparous reproduction in female epaulette sharks (Hemiscyllium ocellatum), offering new insight into reproductive energetics in chondrichthyans.

Methods:We tracked oxygen uptake rates (a proxy for metabolic rate) in five mature female epaulette sharks across a 19-day reproductive cycle, capturing data before, during, and after egg case encapsulation and oviposition. Reproductive hormones (testosterone, 17β-estradiol, progesterone) and hematological parameters (hematocrit, hemoglobin concentration) were also measured. Sharks were housed individually in temperature-controlled tanks and monitored for reproductive activity via daily palpation. Respirometry trials were conducted using intermittent-flow static chambers, and blood samples were collected post-trial for hematological and hormonal analyses. Hormones were quantified via radioimmunoassay, and metabolic rates were calculated using the RespiroRS package in R.

Data Contents:

• Oxygen uptake measurements across reproductive phases
• Hematological parameters per individual and timepoint
• Hormone concentrations (T, E2, P4) with assay metadata

Software/equipment used to create/collect the data: Oxygen uptake rates in the study were measured using a OXROB3 fiber optic probe inserted approximately 5 cm into the chamber proper via the overflow outlet connected to a Firesting Optical Oxygen Meter (Pyroscience GmbH, Aachen, Germany).

Software/equipment used to manipulate/analyse the data: All statistical analyses were conducted in R (version 4.5.1, R Core Development Team, 2025).