Shell length measurements (in mm) was done measuring the curvilinear shell length (i.e. the longest distance from the apex to the anterior edge of the shell along the dorsal side) for Lepetodrilus species and the maximal antero-posterior shell length for S. tollmanni. Measurements were conducted with the Leica Application Suite software linked to a Leica MC 170 HD camera mounted on a Leica M125 stereoscopic microscope for Lepetodrilus species, and through the ZEN pro 3.2 software connected to a ZEISS AxioCam 208 Color camera mounted on a ZEISS SteREO Discovery.V20 stereoscopic microscope for Shinkailepas tollmanni. Post-larval and juvenile shells of S. tollmanni were photographed under an Olympus SX16 microscope linked by an Infinity 1 Camera to the Infinity capture software and measured using ImageJ.

For oocyte size measurements (in µm), photographs of histological sections were taken using the Leica Application Suite AF software connected to a Leica DFC 450C camera on a Leica DMI6000 B inverted videomicroscope. Oocytes were then measured and counted using the ImageJ software.  For measurments, maximum and minimum Feret’s diameter were used to calculate the area of an ellipse to infer the area-equivalent diameter which is the √(4*area/π). Two development stages were measured: the vitellogenic stage (vo) which represents mature oocytes, and the previtellogenic stage (pvo) considered as non-mature. Some oogonia were also measured (oo).