Temperature-induced physiological stress and reproductive characteristics of the migratory seahorse Hippocampus erectus during a thermal stress simulation

Abstract

Inshore-offshore migration occurs frequently in seahorse species, either because of prey opportunities or because they are driven by reproduction, and variations in water temperature may dramatically change migratory seahorse behavior and physiology. The present study investigated the behavioral and physiological responses of the lined seahorse Hippocampus erectus under thermal stress and evaluated the potential effects of different temperatures on its reproduction. The results showed that the thermal tolerance of the seahorses was time dependent. Acute thermal stress (30°C, 2–10 h) increased the basal metabolic rate (breathing rate) and the expression of stress response genes (Hsp genes) significantly and further stimulated seahorse appetite. Chronic thermal treatment (30°C, 4 weeks) led to a persistently higher basal metabolic rate, higher stress response gene expression and higher mortality rates, indicating that the seahorses could not acclimate to chronic thermal stress and might experience massive mortality rates due to excessively high basal metabolic rates and stress damage. Additionally, no significant negative effects on gonad development or reproductive endocrine regulation genes were observed in response to chronic thermal stress, suggesting that seahorse reproductive behavior could adapt to higher-temperature conditions during migration and within seahorse breeding grounds. In conclusion, this simulation experiment indicates that temperature variations during inshore-offshore migration have no effect on reproduction, but promote significantly high basal metabolic rates and stress responses. Therefore, we suggest that the observed high tolerance of seahorse reproduction is in line with the inshore-offshore reproductive migration pattern of lined seahorses.This article has an associated First Person interview with the first author of the paper.

From gametogenesis to spawning: How climate‐driven warming affects teleost reproductive biology

“…However, there are exceptions where exposure to high temperatures had no apparent impact on circulating steroid levels, or the impacts on the endocrine system were inconsistent. In Hippocampus erectus Perry 1810, 1 month of chronic thermal stress at 30°C did not impair E2 and T plasma levels relative to other groups at 22°C and 26°C, even though mortality and basal metabolic rate increased (Qin et al ., 2018). Furthermore, in O. mykiss the impacts on steroid production were inconsistent between years, with the depression of circulating E2 present in some years and not others (Pankhurst et al ., 1996; Pankhurst & Thomas, 1998).…”

The Roles of the Kisspeptin System in the Reproductive Physiology of the Lined Seahorse (Hippocampus erectus), an Ovoviviparous Fish With Male Pregnancy

“…All experiments were performed according to the standard procedure in our lab (Zhang et al, 2016; Qin et al, 2018). In brief, total RNA was extracted using TRIzol reagent (Invitrogen, United States) according to the manufacturer’s protocol.…”

Mechanisms for Temperature Modulation of Feeding in Goldfish and Implications on Seasonal Changes in Feeding Behavior and Food Intake

“…In poikilotherms, especially in fish species, body functions including somatic growth ( 8 , 9 , 17 ), reproduction ( 18 , 19 ), metabolism ( 20 ), locomotor activity ( 21 ), stress responses ( 22 ), embryonic development ( 23 ), and immune functions ( 24 ) are known to be sensitive to temperature change. In fish models, circannual cycle in feeding pattern/food intake has been reported and can be associated with seasonal changes in water temperature and photoperiod ( 4 ).…”