Common problems encountered when scanning museum fishes.

<p>Specimens were prepared for imaging and scanned as described in the Methods. Specific details for each species can be found in the DFL. (A) 3T horizontal image slice (937 µm³ resolution) of an oarfish, <i>Regalecus glesne</i> (SIO 96-82; SL 730 cm) demonstrating the effects of delaying soft tissue preservation. Arrows indicate tissues with significant decomposition. (B) 3T horizontal image slice (1.1 mm³ resolution) of a megamouth shark, <i>Megachasma pelagios</i> (SIO 07-53; standard length (SL) 215 cm) with significant tissue damage (arrows) from repeated freezing and thawing prior to fixation, resulting in poor tissue MRI signal and contrast. The asterisk indicates mechanical damage to the jaw. (C) 3T sagittal image slice (761 µm³ resolution) of a coelacanth, <i>Latimeria chalumnae</i> (SIO 75-347; SL 950 mm) demonstrating poor MRI results from being frozen and thawed prior to fixation and from extensive handling including dissection. (D) 7T sagittal slice (100 µm³ resolution) of a triplespot blenny, <i>Crossosalarias macrospilus</i> (SIO 02-3; SL 73 mm) exhibiting poor imaging results caused by exposure to alcohol without prior formalin fixation. (E) 3T sagittal slice (586 µm³ resolution) of a spiny dogfish, <i>Squalus acanthias</i> (SIO 08-138; SL 740 mm) showing the presence of inorganic particles in the inner ear causing a prominent magnetic susceptibility artefact. (F) 7T sagittal slice (100 µm³ resolution) of a California killifish, <i>Fundulus parvipinnis</i> (SIO 09-224; SL 68 mm) exhibiting a prominent magnetic susceptibility artefact caused by gases trapped in its gut. (G) 7T sagittal and horizontal slices (60 µm³ resolution) of a benttooth bristlemouth, <i>Cyclothone acclinidens</i> (SIO 07-166; SL 53 mm) exhibiting very poor image contrast caused by its extreme low body mass leading to an insufficient signal loading of the RF coil. (H) 7T sagittal and horizontal slices (100 µm³ resolution) of a glass catfish, <i>Kryptopterus bicirrhis</i> (SIO Uncat; SL 45 mm) showing problems with slice plane misalignment associated with scanning very flat or thin-bodied fishes. (I) 3T sagittal and horizontal slices (586 µm³ resolution) of a shortfin mako, <i>Isurus oxyrinchus</i> (SIO 55-85; SL 875 mm) showing slice plane misalignment problems associated with scanning large and/or elongate specimens requiring sequential repositioning of the coil to scan their full length. (I) 7T sagittal and horizontal slices (100 µm³ resolution) of a Pacific hagfish, <i>Eptatretus stoutii</i> (SIO 87-125; SL 145 mm) illustrating slice plane misalignment problems associated with scanning specimens preserved with body positions that cannot be straightened, preventing acquisition of bilaterally symmetrical slices in every plane.