227

Geomagnetic Field Effects on Living Systems

 

Keller et al. (2021) further showed that the use of a magnetic map to derive positional information may

help explain aspects of the genetic structure of bonnethead populations in the northwest Atlantic and

this ability may contribute to population-level processes (Escatel-Luna et al., 2015; Fields et al., 2016;

Gonzalez et al., 2019; Díaz-Jaimes et al., 2020). Tere is other information useful for movements, such as

ocean currents and tides, but Keller et al. (2021) insisted that the MF is more stable than other informa­

tion, so it is likely to be more useful for navigation. Tese fndings complement recent research that has

shown elasmobranchs likely have a polarity compass (Newton and Kajiura, 2020a). Te combination of

magnetic map and compass senses would likely be highly adaptive and allow the evolution of complex

movement patterns that are a hallmark of elasmobranch life histories (Keller et al., 2021). Teir results

are signifcant because for 50 years researchers have highlighted the importance of determining whether

sharks and rays use the GMF to aid in orientation and navigation. Multiple species of elasmobranchs

have been shown capable of detecting various components of the MF (Kalmijn, 1981, 1982; Molteno and

Kennedy, 2009; Anderson et al., 2017; Newton and Kajiura, 2017, 2020a), and this research provides eco­

logic context for how these abilities may be used (Keller et al., 2021).

Recently, in the case of the birds, Nimpf et al. (2019) suggested that a putative mechanism of mag­

netoreception by EM induction in the pigeon inner ear. Nimpf et al. (2019) reported the presence of a

splice isoform of a voltage-gated calcium channel (CaV1.3) in the pigeon inner ear that has been shown

to mediate electroreception in skates and sharks (Bellono et al., 2018). Nimpf et al. (2019) proposed that

pigeons detect MFs by EM induction within the semicircular canals that are dependent on the presence

of apically located voltage-gated cation channels in a population of electrosensory hair cells.

It is suggested that the ampullae of Lorenzini in shark and highly sensitive electrosensory system to

detect MF-induced EFs may not be the sole sensory receptor structures used to perceive MF stimuli, and

that an EM induction-based magnetoreceptor structure capable of perceiving changes in MF intensity

may be located in the nasal olfactory capsules of sharks as putative magnetoreceptor structures (Anderson

et al., 2017). Tese elasmobranchs are one of the more electrosensitive species, and generally, they are pri­

marily responsive to both DC and AC low-intensity EFs between 0.02 and 100 μV/cm and frequencies of

0–15 Hz (Sisneros and Tricas, 2002; Bedore and Kajiura, 2013). Anderson et al. (2017) behaviorally con­

ditioned sandbar sharks (Carcharhinus plumbeus) to respond to weak magnetic stimuli (> 0.03 μT) that

generated electrical artifacts of 73 nV/cm. Moreover, sharks and stingrays are well known for their sensi­

tivity to EM felds (EMFs) themselves (Kalmijn, 1981, 1982; Newton and Kajiura 2017, 2020a,b; Anderson

et al., 2017). Terefore, as a future study, Newton and Kajiura (2020b) proposed that if chondrichthyans

do use their electroreceptors to detect, encode, and perceive magnetic stimuli, the next step is to uncover

how these fshes might distinguish between natural geomagnetic and bioelectric cues.

As a research experiment conducted to examine the efect on the MF generated by the high-voltage

transmission line, the conclusion that the efect could not be detected has been reported. One example is

a preliminary study of a project of hydrokinetic (HK) technologies that use the rapids of the Mississippi

River to generate 8,000 MW of electricity, led by the US Federal Energy Regulatory Commission (Cada

et al., 2011, 2012). Laboratory experiments conducted in the fscal year 2010 found no evidence that three

common freshwater taxa, i.e., the snail (Elimia clavaeformis), the clam (Corbicula fuminea), and the

fathead minnow (Pimephales promelas) were either attracted to or repelled by an SMF (~36 mT at the

strongest point) (Cada et al., 2011). Similarly, further experiments in the fscal year 2011 with juvenile

sunfsh (Lepomis spp.), channel catfsh (Ictalurus punctatus), and striped bass (Morone saxatilis) did not

detect a signifcant change in position relative to controls (Cada et al., 2012). Tese results suggested that

the predicted 60 Hz EMF (~166 mT at the strongest point) that may be created by a single submerged

DC transmission cable from a hydrokinetic project would not seriously afect the behavior of common

freshwater species (Cada et al., 2012). Te variable EMF associated with AC currents caused little or

no behavioral efects in American paddlefsh (Polyodon spathula) that is known to be highly sensitive

to EFs (Cada et al., 2012). However, another fsh of known EMF sensitivity, lake sturgeons (Acipenser

fulvescens) displayed temporarily altered swimming behavior when exposed to variable MFs (Cada

et al., 2012). Other than the brief reactions by sturgeon to the variable felds reported here, no long-term