Skates exhibit a variety of manifestations of sexual dimorphism. However, this phenomenon has been poorly documented in deepwater species. New data on the sexual dimorphism of five species of deepwater skates from the North Atlantic Ocean are presented:
Skates (Rajoidei) comprise an important component of shelf and continental slope benthic communities of the world’s oceans. They are major consumers of cephalopods, decapods, and fishes, often utilizing the same food resources as the apex predators, such as sea birds, marine mammals, and sharks [
Our comparative analysis of skate morphology was based on the measurement of 45–47 morphometric and 2–15 meristic characters, according to protocols used in recent years [
Furthermore, for our comparative analyses of
Because of the small number of deepwater skates available in ichthyological collections we had an opportunity to examine only 13 specimens of
Our results show that the greatest differences in male and female
Morphometrics and meristics of male and female Jensen’s ray Amblyraja jenseni from different areas of the North Atlantic (significant differences are given in bold, number of specimens examined are shown in parentheses, m = standard error).
Females (7) | Males (6) | |||||||||||
Character | Absolute | % TL | Absolute | % TL | ||||||||
Min | Max | Mean | Min | Max | Mean ± | Min | Max | Mean | Min | Max | Mean ± | |
TL, mm | 369.0 | 1065.0 | 686.6 | 223.0 | 1113.0 | 635.0 | ||||||
Disc width | 264.0 | 795.0 | 510.4 | 69.5 | 81.3 | 74.2 ± 1.51 | 156.5 | 837.0 | 466.4 | 70.2 | 75.5 | 73.3 ± 0.91 |
length | ||||||||||||
Snout length, preorbital | 61.2 | 157.0 | 103.3 | 14.0 | 16.6 | 15.2 ± 0.31 | 32.1 | 174.0 | 89.6 | 10.3 | 15.8 | 14.2 |
preoral | 54.9 | 135.0 | 92.9 | 11.6 | 16.3 | 13.6 ± 0.71 | 37.1 | 149.0 | 88.7 | 12.6 | 16.9 | 14.5 ± 0.65 |
prenasal | 38.7 | 80.3 | 65.0 | 7.5 | 10.6 | 9.7 ± 0.72 | 29.9 | 115.0 | 66.8 | 7.4 | 11.1 | 9.7 ± 0.81 |
Orbit, horizontal diameter | ||||||||||||
Interorbital width | 27.8 | 68.1 | 46.1 | 6.0 | 7.8 | 6.8 ± 0.26 | 13.8 | 77.2 | 47.4 | 6.2 | 11.1 | 7.5 ± 0.75 |
Spiracle length | 11.2 | 34.4 | 19.6 | 2.3 | 3.4 | 3.0 ± 0.16 | 5.6 | 37.3 | 20.4 | 2.5 | 3.8 | 3.1 ± 0.18 |
Interspiracular width | 40.8 | 110.0 | 75.8 | 10.3 | 12.0 | 11.1 ± 0.19 | 23.6 | 115.0 | 74.4 | 10.2 | 15.8 | 11.7 ± 0.85 |
Orbit + spiracle length | 20.9 | 56.3 | 42.2 | 5.3 | 6.9 | 6.2 ± 0.33 | 16.2 | 60.0 | 39.9 | 4.8 | 7.2 | 5.8 ± 0.41 |
D1, height | 6.0 | 42.0 | 17.3 | 1.5 | 4.9 | 2.3 ± 0.46 | 3.8 | 25.6 | 13.2 | 1.7 | 2.3 | 2.0 ± 0.10 |
base length | 17.8 | 47.0 | 30.7 | 4.3 | 5.4 | 4.7 ± 0.16 | 11.2 | 48.9 | 28.4 | 3.9 | 5.0 | 4.6 ± 0.16 |
D2, height | 5.6 | 28.0 | 14.4 | 1.3 | 3.3 | 2.0 ± 0.25 | 3.3 | 30.4 | 13.8 | 1.5 | 2.7 | 2.0 ± 0.18 |
base length | 19.7 | 44.6 | 32.3 | 4.2 | 5.8 | 5.0 ± 0.27 | 8.8 | 53.0 | 29.8 | 3.3 | 5.2 | 4.5 ± 0.29 |
Interdorsal space | 0.0 | 29.0 | 6.3 | 0.0 | 3.4 | 0.9 ± 0.44 | 0.0 | 3.1 | 1.3 | 0.0 | 1.1 | 0.4 ± 0.20 |
C, base length | 13.1 | 28.3 | 20.1 | 2.4 | 3.6 | 3.0 ± 0.28 | 10.9 | 25.0 | 18.0 | 2.2 | 4.0 | 2.7 ± 0.34 |
Tail, postdorsal length | 14.1 | 45.0 | 23.9 | 2.4 | 5.3 | 3.5 ± 0.49 | 8.7 | 30.0 | 18.1 | 2.2 | 5.5 | 3.3 ± 0.51 |
height at V-tips | ||||||||||||
width at V-tips | 11.4 | 30.3 | 21.1 | 2.7 | 3.6 | 3.1 ± 0.18 | 8.1 | 31.7 | 21.5 | 2.8 | 3.6 | 3.1 ± 0.14 |
height at D1 origin | 4.2 | 9.8 | 7.0 | 0.9 | 1.2 | 1.0 ± 0.06 | 3.0 | 11.0 | 7.2 | 0.8 | 1.3 | 1.0 ± 0.07 |
width at D1 origin | 4.9 | 13.5 | 8.5 | 0.9 | 1.6 | 1.3 ± 0.12 | 4.2 | 14.3 | 9.1 | 1.1 | 1.6 | 1.3 ± 0.08 |
lateral fold length | 143.0 | 337.0 | 243.0 | 31.6 | 38.8 | 36.4 ± 1.62 | 107.0 | 345.0 | 235.6 | 30.5 | 39.6 | 34.2 ± 1.81 |
Head length, ventrally | 105.3 | 281.0 | 205.3 | 26.4 | 33.3 | 30.4 ± 1.32 | 77.9 | 309.0 | 212.4 | 27.8 | 34.5 | 30.2 ± 1.22 |
Mouth width | 45.5 | 157.0 | 93.3 | 11.9 | 15.9 | 13.3 ± 0.58 | 27.9 | 150.0 | 84.7 | 12.3 | 14.5 | 13.0 ± 0.35 |
Internasal width | 46.6 | 126.0 | 84.1 | 11.8 | 13.0 | 12.4 ± 0.22 | 28.5 | 133.0 | 76.5 | 11.1 | 13.7 | 12.3 ± 0.36 |
Nasal curtain, length | 20.5 | 56.4 | 34.6 | 3.7 | 5.6 | 5.1 ± 0.35 | 18.0 | 65.3 | 36.3 | 3.4 | 6.7 | 5.4 ± 0.56 |
width each lobe | 10.0 | 23.6 | 13.8 | 1.5 | 2.8 | 2.1 ± 0.24 | 6.8 | 29.0 | 18.5 | 1.9 | 4.2 | 2.6 ± 0.41 |
space between lobes | 30.4 | 107.0 | 65.7 | 8.2 | 10.1 | 9.4 ± 0.34 | 21.8 | 115.0 | 70.5 | 7.8 | 12.1 | 9.7 ± 0.85 |
Gill slit length, first | 5.2 | 14.2 | 8.7 | 1.3 | 1.4 | 1.3 ± 0.02 | 2.9 | 18.5 | 9.6 | 1.3 | 1.7 | 1.4 ± 0.09 |
third | ||||||||||||
fifth | 4.4 | 14.9 | 7.3 | 0.9 | 1.4 | 1.1 ± 0.08 | 2.2 | 16.9 | 8.2 | 0.9 | 1.5 | 1.2 ± 0.12 |
Space btwn first gill slits | 68.7 | 186.0 | 137.5 | 17.5 | 22.1 | 20.2 ± 0.62 | 42.1 | 225.0 | 135.1 | 16.3 | 24.8 | 20.4 ± 1.43 |
fifth gill slits | ||||||||||||
V-length, anterior lobe | 55.7 | 123.0 | 81.0 | 11.5 | 15.1 | 12.5 ± 0.54 | 23.9 | 143.0 | 78.2 | 10.7 | 15.2 | 12.4 ± 0.63 |
posterior lobe | 74.6 | 206.0 | 131.5 | 18.1 | 20.2 | 19.3 ± 0.36 | 54.0 | 229.0 | 138.3 | 16.7 | 20.6 | 19.0 ± 0.81 |
Clasper, postanus length | na | na | na | na | na | na | 20.5 | 240.0 | 116.9 | 7.6 | 23.2 | 13.5 ± 3.51 |
Snout tip to center of anus | 196.0 | 625.0 | 367.8 | 52.8 | 58.7 | 55.2 ± 1.02 | 114.8 | 678.0 | 359.1 | 51.1 | 60.9 | 54.8 ± 1.65 |
to max. disc width | 142.0 | 358.0 | 259.2 | 33.6 | 42.6 | 38.6 ± 1.44 | 105.0 | 400.0 | 255.8 | 31.4 | 39.7 | 36.5 ± 1.63 |
Center of anus to D1 | ||||||||||||
to D2 | ||||||||||||
to tail tip | 175.0 | 470.0 | 306.7 | 42.7 | 47.4 | 45.0 ± 0.81 | 108.2 | 475.0 | 270.5 | 38.1 | 48.5 | 43.7 ± 1.47 |
Snout angle | 85 | 91 | 88.0 ± 3.00 | 89 | 103 | 94.0 ± 4.51 | ||||||
No. preorbital thorns | 1 | 2 | 1.6 ± 0.24 | 1 | 3 | 2.0 ± 0.32 | ||||||
No. postorbital thorns | 1 | 2 | 1.8 ± 0.20 | 1 | 2 | 1.8 ± 0.20 | ||||||
No. interspiracular thorns | 1 | 2 | 1.6 ± 0.24 | 1 | 2 | 1.4 ± 0.24 | ||||||
No. scapular thorns | 3 | 5 | 4.0 ± 0.45 | 3 | 6 | 4.0 ± 0.63 | ||||||
No. nuchal thorns | 1 | 2 | 1.6 ± 0.24 | 0 | 2 | 1.6 ± 0.40 | ||||||
No. interscapular thorns | 1 | 1 | 1.0 ± 0.00 | 1 | 3 | 1.4 ± 0.40 | ||||||
No. median thorns | 23 | 28 | 25.0 ± 0.95 | 20 | 31 | 24.4 ± 1.91 | ||||||
No. middorsal thorns | 0 | 1 | 0.2 ± 0.20 | 0 | 1 | 0.2 ± 0.20 | ||||||
Tooth rows upper jaw | 52 | 63 | 58.5 ± 2.53 | 59 | 64 | 61.3 ± 1.11 | ||||||
lower jaw | 54 | 61 | 57.3 ± 1.89 | 52 | 64 | 57.8 ± 2.53 |
Maximum differences between male and female
Morphometrics and meristics of male and female pale ray Bathyraja pallida from different areas of the North Atlantic (significant differences are given in bold, number of specimens examined are shown in parentheses, m = standard error, na = not available).
Females (3) | Males (7) | |||||||||||
Character | Absolute | % TL | Absolute | % TL | ||||||||
Min | Max | Mean | Min | Max | Mean | Min | Max | Mean | Min | Max | Mean ± | |
TL, mm | 1285.0 | 1565.0 | 1437.0 | 311.0 | 1490.0 | 948.3 | ||||||
Disc, width | 845.0 | 1015.7 | 932.2 | 64.0 | 65.8 | 64.9 ± 0.50 | 197.0 | 1050.0 | 623.0 | 60.5 | 70.5 | 65.5 ± 1.19 |
length | 672.0 | 859.0 | 791.0 | 52.3 | 58.8 | 55.0 ± 1.95 | 174.0 | 851.0 | 531.7 | 54.2 | 57.1 | 56.1 ± 0.48 |
Snout length, preorbital | 246.0 | 261.4 | 253.7 | 16.7 | 16.8 | 16.8 ± 0.06 | 55.4 | 215.0 | 132.8 | 14.0 | 19.2 | 16.1 ± 0.89 |
preoral | 228.5 | 228.5 | 228.5 | 14.6 | 14.6 | 14.6 ± na | 54.3 | 285.0 | 143.1 | 13.2 | 19.2 | 16.8 ± 1.13 |
prenasal | na | na | na | na | na | na | 45.8 | 184.0 | 111.8 | 12.1 | 15.7 | 13.5 |
Orbit, horizontal diameter | 36.0 | 68.4 | 56.4 | 2.3 | 5.1 | 4.0 ± 0.86 | 13.5 | 63.9 | 34.3 | 1.8 | 4.7 | 3.9 ± 0.49 |
Interorbital width | ||||||||||||
Spiracle length | 38.5 | 39.9 | 39.2 | 2.7 | 3.0 | 2.9 ± 0.13 | 8.3 | 50.5 | 26.6 | 2.4 | 3.4 | 2.8 ± 0.13 |
Interspiracular width | ||||||||||||
Orbit + spiracle length | 83.6 | 91.5 | 87.6 | 5.7 | 7.1 | 6.4 ± 0.70 | 17.1 | 85.7 | 49.9 | 4.3 | 6.1 | 5.5 ± 0.29 |
D1, height | ||||||||||||
base length | ||||||||||||
D2, height | 25.7 | 32.9 | 29.3 | 1.8 | 2.1 | 1.9 ± 0.17 | 6.7 | 32.4 | 19.3 | 1.8 | 2.4 | 2.0 ± 0.07 |
base length | ||||||||||||
Interdorsal space | 9.9 | 23.5 | 16.7 | 0.7 | 1.5 | 1.1 ± 0.41 | 6.4 | 27.8 | 14.2 | 0.9 | 2.4 | 1.7 ± 0.27 |
C, base length | 21.9 | na | na | 1.5 | na | 1.5 ± na | 12.2 | 34.5 | 18.8 | 1.0 | 3.9 | 2.2 |
Tail, postdorsal length | 34.4 | na | na | 2.2 | na | 2.2 ± na | 17.0 | 32.1 | 24.6 | 2.2 | 2.7 | 2.4 ± 0.26 |
height at V-tips | ||||||||||||
width at V-tips | 38.2 | 43.9 | 41.1 | 2.6 | 3.4 | 3.0 ± 0.40 | 8.5 | 52.0 | 28.7 | 1.6 | 3.6 | 2.9 ± 0.15 |
height at D1 origin | 16.1 | na | na | 1.1 | na | 1.1 ± na | 3.4 | 17.1 | 10.3 | 0.9 | 1.2 | 1.1 ± 0.04 |
width at D1 origin | 22.4 | na | na | 1.5 | na | 1.5 ± na | 3.2 | 25.3 | 13.0 | 0.9 | 1.7 | 1.2 ± 0.13 |
lateral fold length | 455.0 | na | na | 31.1 | na | 31.1 ± na | 129.0 | 544.0 | 360.0 | 25.2 | 41.5 | 35.1 ± 3.15 |
Head length, ventrally | 351.0 | 455.0 | 403.0 | 27.3 | 31.1 | 29.2 ± 1.90 | 92.5 | 429.0 | 276.7 | 28.2 | 30.7 | 29.5 ± 0.34 |
Mouth width | ||||||||||||
Internasal width | 134.6 | 147.0 | 140.0 | 8.6 | 10.8 | 9.8 ± 0.64 | 26.6 | 157.0 | 86.6 | 8.2 | 10.5 | 9.0 ± 0.37 |
Nasal curtain, length | ||||||||||||
width | ||||||||||||
width each lobe | ||||||||||||
space between lobes | na | na | na | na | na | na | 10.0 | 86.3 | 48.2 | 1.6 | 5.8 | 3.7 ± 0.26 |
Gill slit length, first | ||||||||||||
third | 23.7 | 30.4 | 27.4 | 1.8 | 2.1 | 1.9 ± 0.09 | 5.0 | 37.2 | 18.1 | 1.4 | 2.5 | 1.8 ± 0.16 |
fifth | 17.1 | 23.5 | 20.3 | 1.3 | 1.6 | 1.4 ± 0.10 | 3.6 | 23.9 | 12.8 | 0.9 | 1.6 | 1.3 ± 0.07 |
Space between first gill slits | ||||||||||||
fifth gill slits | ||||||||||||
V-length, anterior lobe | 87.0 | 167.0 | 127.0 | 6.8 | 11.4 | 9.1 ± 2.33 | 43.9 | 177.0 | 106.8 | 9.9 | 15.4 | 12.2 ± 0.98 |
posterior lobe | 174.0 | 255.0 | 214.5 | 13.5 | 17.4 | 15.5 ± 1.95 | 46.3 | 269.0 | 156.6 | 14.5 | 18.1 | 16.1 ± 0.51 |
Clasper, postanus length | na | na | na | na | na | na | 24.5 | 402.0 | 212.3 | 7.9 | 27.6 | 17.3 ± 4.20 |
Snout tip to center of anus | ||||||||||||
to max. disc width | 435.0 | 539.0 | 487.0 | 33.9 | 36.9 | 35.4 ± 1.51 | 110.3 | 545.0 | 331.8 | 31.8 | 37.5 | 35.4 ± 0.88 |
Center of anus to D1 | 505.0 | 519.6 | 512.3 | 33.2 | 34.5 | 33.9 ± 0.67 | 109.0 | 529.0 | 332.5 | 32.6 | 36.9 | 35.2 ± 0.69 |
to D2 | 599.0 | na | na | 41.0 | na | 41.0 ± na | 129.0 | 602.0 | 378.0 | 36.9 | 42.7 | 40.4 ± 0.90 |
to tail tip | ||||||||||||
No median thorns | 16 | na | 16.0 ± na | 16 | 19 | 17.6 ± 0.60 | ||||||
No middorsal thorns | 1 | na | 1.0 ± na | 0 | 2 | 0.8 ± 0.31 | ||||||
Tooth rows upper jaw | 25 | 31 | 28.0 ± 3.00 | 24 | 30 | 26.2 ± 0.95 | ||||||
lower jaw | 22 |
The morphological and meristic characters of
Our results show
Morphometrics and meristics of male and female Richardson’s ray Bathyraja richardsoni from different areas of the North Atlantic (significant differences are given in bold, number of specimens examined are shown in parentheses, m = standard error).
Females (14) | Males (13) | |||||||||||
Character | Absolute | % TL | Absolute | % TL | ||||||||
Min | Max | Mean | Min | Max | Mean ± | Min | Max | Mean | Min | Max | Mean ± m | |
TL, mm | 240.0 | 1530.0 | 924.0 | 182.0 | 1133.0 | 570.2 | ||||||
Disc, width | ||||||||||||
length | ||||||||||||
Snout length, preorbital | 21.6 | 211.0 | 118.3 | 9.0 | 15.4 | 12.9 ± 0.53 | 14.6 | 145.0 | 74.5 | 7.5 | 15.3 | 12.2 ± 0.78 |
preoral | 24.5 | 206.6 | 120.5 | 10.2 | 14.5 | 13.2 ± 0.38 | 14.9 | 147.3 | 76.1 | 8.2 | 16.3 | 12.7 ± 0.72 |
prenasal | 15.4 | 139.0 | 76.3 | 6.4 | 11.5 | 9.4 ± 0.56 | 12.0 | 102.0 | 52.0 | 5.9 | 11.9 | 9.2 ± 0.62 |
Orbit, horizontal diameter | ||||||||||||
Interorbital width | 16.8 | 161.5 | 70.5 | 5.2 | 11.1 | 7.5 ± 0.45 | 9.6 | 117.8 | 41.7 | 5.3 | 10.4 | 6.9 ± 0.34 |
Spiracle length | 5.3 | 53.3 | 23.2 | 2.0 | 3.5 | 2.6 ± 0.15 | 4.0 | 20.0 | 11.9 | 1.8 | 3.4 | 2.4 ± 0.15 |
Interspiracular width | 28.8 | 180.4 | 104.7 | 9.0 | 12.8 | 11.3 ± 0.25 | 23.5 | 122.4 | 63.9 | 10.2 | 14.1 | 11.3 ± 0.27 |
Orbit + spiracle length | ||||||||||||
D1, height | 5.8 | 20.5 | 13.8 | 1.1 | 2.4 | 1.6 ± 0.10 | 4.2 | 16.6 | 9.1 | 1.3 | 2.8 | 1.8 ± 0.13 |
base length | 10.1 | 50.9 | 30.8 | 2.8 | 4.6 | 3.4 ± 0.12 | 9.5 | 38.3 | 19.8 | 2.8 | 5.4 | 3.7 ± 0.21 |
D2, height | 5.0 | 20.4 | 12.7 | 1.0 | 2.1 | 1.6 ± 0.10 | 4.4 | 20.4 | 9.8 | 1.4 | 2.5 | 1.8 ± 0.11 |
base length | 10.3 | 45.0 | 28.4 | 2.9 | 4.3 | 3.5 ± 0.12 | 9.1 | 36.0 | 19.6 | 2.8 | 5.0 | 3.8 ± 0.23 |
Interdorsal space | 0.0 | 14.5 | 5.2 | 0.0 | 1.0 | 0.6 ± 0.08 | 0.0 | 7.9 | 3.6 | 0.0 | 1.0 | 0.6 ± 0.08 |
C, base length | 11.4 | 44.2 | 27.1 | 2.8 | 5.5 | 3.8 ± 0.27 | 11.8 | 32.8 | 19.7 | 2.9 | 7.0 | 4.4 ± 0.43 |
Tail, postdorsal length | 0.0 | 52.4 | 29.1 | 0.0 | 7.9 | 4.0 ± 0.65 | 0.0 | 44.2 | 21.9 | 0.0 | 8.1 | 4.4 ± 0.68 |
height at V-tips | 8.6 | 47.7 | 25.1 | 2.5 | 3.6 | 2.9 ± 0.10 | 7.8 | 38.8 | 15.7 | 2.4 | 4.3 | 3.1 ± 0.16 |
width at V-tips | ||||||||||||
height at D1 origin | 3.8 | 18.8 | 10.0 | 1.0 | 1.7 | 1.2 ± 0.06 | 3.3 | 13.4 | 6.3 | 0.9 | 2.0 | 1.3 ± 0.08 |
width at D1 origin | 3.3 | 20.3 | 11.1 | 1.1 | 2.3 | 1.3 ± 0.10 | 4.0 | 15.1 | 7.1 | 1.0 | 2.7 | 1.5 ± 0.16 |
lateral fold length | ||||||||||||
Head length, ventrally | 53.3 | 413.0 | 221.3 | 22.2 | 28.3 | 26.0 ± 0.53 | 44.4 | 264.0 | 133.6 | 20.0 | 28.7 | 25.1 ± 0.78 |
Mouth width | ||||||||||||
Internasal width | 26.4 | 174.6 | 99.6 | 8.0 | 12.8 | 11.0 ± 0.31 | 16.0 | 124.6 | 62.6 | 8.8 | 14.2 | 10.9 ± 0.37 |
Nasal curtain, length | 11.8 | 70.6 | 37.3 | 3.0 | 5.5 | 4.6 ± 0.17 | 6.6 | 37.6 | 24.6 | 3.4 | 12.0 | 5.0 ± 0.65 |
width each lobe | 5.0 | 77.7 | 22.0 | 1.6 | 12.4 | 2.9 ± 0.87 | 2.2 | 20.7 | 10.3 | 1.2 | 2.4 | 2.0 ± 0.1 |
space between lobes | 13.8 | 117.7 | 61.0 | 2.2 | 8.5 | 7.0 ± 0.48 | 12.7 | 84.4 | 42.2 | 5.8 | 8.3 | 7.2 ± 0.28 |
Gill slit length, first | 2.6 | 26.2 | 14.9 | 1.1 | 1.9 | 1.5 ± 0.06 | 2.0 | 20.4 | 8.7 | 0.9 | 1.8 | 1.4 ± 0.08 |
third | ||||||||||||
fifth | ||||||||||||
Space between first gill slits | 46.6 | 308.5 | 171.7 | 13.6 | 21.4 | 18.5 ± 0.59 | 27.5 | 235.7 | 102.8 | 14.8 | 20.8 | 17.9 ± 0.56 |
fifth gill slits | 36.5 | 227.2 | 129.9 | 10.3 | 16.6 | 14.2 ± 0.51 | 20.9 | 174.5 | 80.2 | 11.1 | 15.9 | 13.9 ± 0.40 |
V-length, anterior lobe | 19.2 | 149.0 | 77.9 | 6.2 | 10.1 | 8.7 ± 0.38 | 11.5 | 118.3 | 55.2 | 6.1 | 11.7 | 9.2 ± 0.59 |
posterior lobe | 33.4 | 238.0 | 132.5 | 12.9 | 18.7 | 15.6 ± 0.56 | 20.7 | 147.0 | 79.5 | 11.0 | 18.6 | 14.4 ± 0.77 |
Clasper, postanus length | na | na | na | na | na | na | 12.2 | 127.7 | 48.6 | 6.4 | 12.0 | 8.6 ± 0.47 |
Snout tip to center of anus | ||||||||||||
to max. disc width | ||||||||||||
Center of anus to D1 | 90.5 | 566.0 | 298.1 | 25.1 | 37.7 | 31.5 ± 0.96 | 68.4 | 362.6 | 171.9 | 25.7 | 38.2 | 31.5 ± 1.22 |
to D2 | 103.0 | 471.0 | 276.4 | 29.3 | 42.9 | 35.3 ± 1.22 | 80.4 | 358.0 | 176.3 | 29.1 | 44.2 | 35.6 ± 1.54 |
to tail tip | 129.1 | 601.0 | 358.4 | 37.4 | 53.8 | 43.1 ± 1.42 | 109.6 | 471.3 | 236.7 | 36.2 | 60.2 | 44.3 ± 2.15 |
Number of median thorns | ||||||||||||
Snout angle | 70 | 120 | 90.8 ± 3.69 | 70 | 133 | 96.4 ± 5.41 |
The morphology of
Morphometrics and meristics of male and female Bigelow’s ray Rajella bigelowi from different areas of the North Atlantic (significant differences are given in bold, number of specimens examined are shown in parentheses, m = standard error, na = not available).
Females (4) | Males (8) | |||||||||||
Character | Absolute | % TL | Absolute | % TL | ||||||||
Min | Max | Mean | Min | Max | Mean ± | Min | Max | Mean | Min | Max | Mean ± | |
TL, mm | 102.0 | 453.0 | 283.8 | 101.0 | 436.0 | 231.0 | ||||||
Disc width | 57.0 | 234.0 | 144.3 | 47.9 | 55.9 | 51.3 ± 0.87 | 54.0 | 215.0 | 116.1 | 47.8 | 54.3 | 50.6 ± 0.70 |
length | 43.0 | 209.0 | 128.9 | 40.6 | 47.1 | 44.8 ± 0.82 | 46.0 | 196.0 | 102.8 | 41.3 | 49.0 | 44.5 ± 0.72 |
Snout length, preorbital | 10.5 | 55.3 | 31.5 | 9.4 | 13.4 | 11.0 ± 0.44 | 8.0 | 41.0 | 23.1 | 7.9 | 12.7 | 10.2 ± 0.45 |
preoral | 10.5 | 56.4 | 33.5 | 10.3 | 14.4 | 11.7 ± 0.48 | 11.0 | 44.5 | 26.6 | 10.2 | 14.8 | 11.8 ± 0.44 |
prenasal | 8.5 | 46.0 | 28.5 | 8.3 | 12.7 | 10.0 ± 0.46 | 8.0 | 37.0 | 21.8 | 7.9 | 11.8 | 9.5 ± 0.35 |
Orbit, horizontal diameter | 4.2 | 19.0 | 11.8 | 3.8 | 4.7 | 4.2 ± 0.12 | 4.0 | 17.0 | 9.4 | 3.1 | 5.3 | 4.1 ± 0.19 |
Interorbital width | ||||||||||||
Spiracle length | 2.2 | 12.6 | 6.7 | 2.0 | 2.8 | 2.3 ± 0.10 | 2.0 | 11.5 | 5.7 | 2.0 | 3.0 | 2.4 ± 0.10 |
Interspiracular width | 7.2 | 29.9 | 19.5 | 6.6 | 7.1 | 6.9 ± 0.06 | 8.0 | 30.0 | 14.9 | 6.4 | 8.0 | 7.1 ± 0.19 |
Orbit + spiracle length | ||||||||||||
D1, height | 1.4 | 12.0 | 6.5 | 1.4 | 2.6 | 2.1 ± 0.18 | 2.0 | 12.0 | 5.4 | 1.7 | 3.2 | 2.2 ± 0.15 |
base length | 7.7 | 23.8 | 15.3 | 4.1 | 7.5 | 5.5 ± 0.36 | 5.0 | 24.0 | 12.4 | 4.1 | 6.1 | 5.1 ± 0.19 |
D2, height | 1.6 | 12.1 | 6.3 | 1.4 | 2.7 | 2.1 ± 0.19 | 2.0 | 13.0 | 5.4 | 1.7 | 3.0 | 2.2 ± 0.15 |
base length | 6.2 | 21.0 | 13.9 | 3.5 | 6.2 | 5.0 ± 0.34 | 5.5 | 22.0 | 12.4 | 4.7 | 5.9 | 5.4 ± 0.15 |
Interdorsal space | 0.0 | 5.0 | 1.1 | 0.0 | 2.8 | 0.6 ± 0.37 | 0.0 | 3.0 | 0.7 | 0.0 | 1.9 | 0.5 |
C, base length | 3.9 | 12.0 | 8.9 | 1.9 | 5.9 | 3.4 ± 0.57 | 3.0 | 14.0 | 6.7 | 1.6 | 3.6 | 2.9 ± 0.21 |
Tail, postdorsal length | 4.0 | 12.0 | 8.6 | 1.9 | 5.9 | 3.4 ± 0.50 | 3.0 | 14.0 | 7.0 | 2.1 | 3.9 | 3.1 ± 0.18 |
height at V-tips | 3.2 | 12.5 | 8.2 | 2.6 | 3.1 | 2.9 ± 0.07 | 3.5 | 11.5 | 6.4 | 2.3 | 3.5 | 2.8 ± 0.10 |
width at V-tips | 4.5 | 18.7 | 11.4 | 3.2 | 4.6 | 4.0 ± 0.15 | 4.0 | 19.5 | 9.3 | 3.1 | 4.5 | 4.0 ± 0.14 |
height at D1 origin | 1.4 | 4.8 | 3.0 | 1.0 | 1.4 | 1.1 ± 0.04 | 1.5 | 5.0 | 2.7 | 1.0 | 1.8 | 1.2 ± 0.09 |
width at D1 origin | 1.8 | 8.0 | 4.4 | 1.1 | 1.8 | 1.5 ± 0.12 | 1.8 | 8.3 | 3.6 | 1.1 | 2.0 | 1.6 ± 0.09 |
lateral fold length | 21.3 | 122.0 | 66.1 | 12.1 | 29.0 | 20.5 ± 2.59 | 17.0 | 106.0 | 55.7 | 14.0 | 27.0 | 20.6 ± 1.72 |
Head length, ventrally | ||||||||||||
Mouth width | 8.3 | 28.3 | 17.0 | 4.9 | 8.1 | 6.3 ± 0.32 | 7.0 | 35.0 | 15.4 | 5.9 | 8.0 | 6.7 ± 0.22 |
Internasal width | 7.2 | 33.2 | 19.0 | 5.8 | 7.3 | 6.7 ± 0.17 | 8.0 | 29.0 | 14.5 | 5.5 | 7.9 | 6.9 ± 0.23 |
Nasal curtain, length | ||||||||||||
width each lobe | ||||||||||||
space between lobes | 5.2 | 13.0 | 9.8 | 2.9 | 5.7 | 4.1 ± 0.49 | 4.8 | 16.0 | 9.6 | 3.0 | 5.9 | 4.6 ± 0.44 |
Gill slit length, first | ||||||||||||
third | ||||||||||||
fifth | 1.0 | 7.1 | 3.3 | 1.0 | 1.6 | 1.1 ± 0.07 | 1.0 | 4.8 | 2.3 | 0.7 | 1.6 | 0.9 ± 0.09 |
Space between first gill slits | 13.8 | 62.9 | 37.6 | 12.4 | 14.0 | 13.2 ± 0.21 | 14.0 | 58.0 | 30.5 | 12.3 | 14.2 | 13.3 |
fifth gill slits | 9.7 | 38.6 | 24.3 | 7.7 | 9.5 | 8.6 ± 0.21 | 9.0 | 35.0 | 18.4 | 6.8 | 9.1 | 8.2 ± 0.23 |
V-length, anterior lobe | 11.0 | 62.3 | 36.2 | 10.7 | 13.8 | 12.5 ± 0.42 | 13.0 | 56.0 | 29.7 | 11.5 | 13.8 | 12.8 ± 0.25 |
posterior lobe | 14.5 | 81.2 | 43.0 | 12.8 | 17.9 | 14.7 ± 0.55 | 13.0 | 61.0 | 32.6 | 11.9 | 16.0 | 13.8 ± 0.42 |
Clasper, postanus length | na | na | na | na | na | na | 7.0 | 45.0 | 17.7 | 5.4 | 10.3 | 7.2 ± 0.43 |
Snout tip to center of anus | 38.0 | 195.0 | 116.1 | 37.3 | 43.4 | 40.3 ± 0.85 | 39.0 | 180.0 | 91.3 | 36.0 | 41.3 | 39.4 ± 0.49 |
to max. disc width | 31.5 | 125.0 | 73.1 | 12.5 | 32.8 | 27.2 ± 2.23 | 23.3 | 130.0 | 56.5 | 10.2 | 30.1 | 24.5 ± 2.30 |
Center of anus to D1 | 40.0 | 199.0 | 128.9 | 39.2 | 48.5 | 45.2 ± 0.99 | 47.0 | 190.0 | 106.5 | 43.0 | 48.9 | 46.1 ± 0.61 |
to D2 | 46.0 | 222.0 | 144.5 | 45.1 | 53.6 | 50.9 ± 1.00 | 53.0 | 215.0 | 119.5 | 49.3 | 54.5 | 51.9 ± 0.43 |
to tail tip | 62.0 | 254.0 | 166.2 | 56.1 | 63.2 | 59.2 ± 0.82 | 59.0 | 249.0 | 137.4 | 57.1 | 61.7 | 59.5 ± 0.50 |
Snout angle | 106.0 | 111.0 | 108.5 ± 2.50 | 107.0 | 110.0 | 108.3 ± 0.88 | ||||||
No. preorbital thorns | ||||||||||||
No. postorbital thorns | 2 | 4 | 2.4 ± 0.26 | 1 | 4 | 2.1 ± 0.26 | ||||||
No. interspiracular thorns | 0 | 4 | 1.3 ± 0.53 | 0 | 3 | 0.8 ± 0.42 | ||||||
No. scapular thorns | 2 | 8 | 4.6 ± 0.75 | 2 | 10 | 3.6 ± 0.79 | ||||||
No. nuchal thorns | 2 | 4 | 2.6 ± 0.32 | 2 | 4 | 2.4 ± 0.22 | ||||||
No. interscapular thorns | 1 | 1 | 1.0 ± na | 1 | 1 | 1.0 ± na | ||||||
No. median thorns | 25 | 33 | 29.4 ± 0.96 | 26 | 33 | 28.6 ± 0.69 | ||||||
No. middorsal thorns | 0 | 1 | 0.1 ± 0.13 | 0 | 1 | 0.1 ± 0.10 | ||||||
Tooth rows upper jaw | 22 | 38 | 30.7 ± 2.35 | 22 | 40 | 32.3 ± 2.63 | ||||||
lower jaw | 24 | 36 | 29.2 ± 2.15 | 22 | 38 | 30.3 ± 2.60 |
Morphometric and meristic data from
The males and females we examined differ in the following characters (Table
Morphometrics and meristics of male and female Mid-Atlantic skate Rajella kukujevi from different areas of the North Atlantic (significant differences are given in bold, number of specimens examined are shown in parentheses, m = standard error, na = not available).
Females (2) | Males (6) | |||||||||||
Character | Absolute | % TL | Absolute | % TL | ||||||||
Min | Max | Mean | Min | Max | Mean ± m | Min | Max | Mean | Min | Max | Mean ± m | |
TL, mm | 602.0 | 604.0 | 603.0 | 597.0 | 757.0 | 716.2 | ||||||
Disc, width | ||||||||||||
length | 301.0 | 308.0 | 304.5 | 50.0 | 51.0 | 50.5 ± 0.50 | 299.0 | 394.0 | 366.5 | 50.1 | 52.3 | 51.1 ± 0.35 |
Snout length, preorbital | 83.3 | 86.6 | 85.0 | 13.8 | 14.3 | 14.1 ± 0.25 | 83.8 | 111.0 | 99.4 | 13.2 | 15.0 | 13.9 ± 0.26 |
preoral | 85.7 | 90.7 | 88.2 | 14.2 | 15.0 | 14.6 ± 0.39 | 94.2 | 111.5 | 103.9 | 13.2 | 16.0 | 14.6 ± 0.48 |
prenasal | 74.5 | 81.2 | 77.9 | 12.4 | 13.4 | 12.9 ± 0.53 | 80.1 | 96.9 | 89.1 | 11.8 | 13.4 | 12.5 ± 0.27 |
Orbit, horizontal diameter | 21.8 | 27.5 | 24.7 | 3.6 | 4.6 | 4.1 ± 0.47 | 24.0 | 37.2 | 29.0 | 3.2 | 4.9 | 4.1 ± 0.26 |
Interorbital width | ||||||||||||
Spiracle length | 15.7 | 17.8 | 16.8 | 2.6 | 2.9 | 2.8 ± 0.17 | 14.0 | 21.7 | 19.1 | 1.8 | 3.1 | 2.7 ± 0.19 |
Interspiracular width | 40.8 | 42.5 | 41.7 | 6.8 | 7.0 | 6.9 ± 0.13 | 42.4 | 56.8 | 51.0 | 6.7 | 7.5 | 7.1 ± 0.14 |
Orbit + spiracle length | 28.6 | 30.9 | 29.8 | 4.8 | 5.1 | 4.9 ± 0.18 | 33.3 | 42.9 | 36.3 | 4.5 | 5.7 | 5.1 ± 0.19 |
D1, height | 14.7 | 18.3 | 16.5 | 2.4 | 3.0 | 2.7 ± 0.30 | 14.0 | 27.6 | 22.2 | 2.3 | 3.7 | 3.1 ± 0.19 |
base length | 29.0 | 31.6 | 30.3 | 4.8 | 5.2 | 5.0 ± 0.22 | 31.0 | 38.0 | 34.6 | 4.1 | 5.9 | 4.9 ± 0.24 |
D2, height | 17.1 | 18.2 | 17.7 | 2.8 | 3.0 | 2.9 ± 0.10 | 17.9 | 28.6 | 22.0 | 2.7 | 3.8 | 3.1 ± 0.16 |
base length | ||||||||||||
Interdorsal space | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
C, base length | 8.9 | 10.8 | 9.9 | 1.5 | 1.8 | 1.6 ± 0.16 | 8.2 | 12.0 | 10.2 | 1.2 | 1.6 | 1.4 ± 0.06 |
Tail, postdorsal length | 8.9 | 10.8 | 9.9 | 1.5 | 1.8 | 1.6 ± 0.16 | 8.2 | 12.0 | 10.2 | 1.2 | 1.6 | 1.4 ± 0.06 |
height at V-tips | 17.2 | 17.4 | 17.3 | 2.8 | 2.9 | 2.9 ± 0.02 | 15.9 | 23.0 | 20.2 | 2.4 | 3.0 | 2.8 ± 0.10 |
width at V-tips | 25.2 | 26.0 | 25.6 | 4.2 | 4.3 | 4.2 ± 0.06 | 20.7 | 38.9 | 29.1 | 3.0 | 5.1 | 4.0 ± 0.34 |
height at D1 origin | 6.7 | 7.2 | 7.0 | 1.1 | 1.2 | 1.2 ± 0.04 | 6.2 | 11.0 | 8.0 | 1.0 | 1.5 | 1.1 ± 0.07 |
width at D1 origin | 11.3 | 11.4 | 11.4 | 1.9 | 1.9 | 1.9 ± 0.01 | 9.2 | 16.4 | 13.3 | 1.5 | 2.2 | 1.8 ± 0.12 |
lateral fold length | ||||||||||||
Head length, ventrally | 151.4 | 162.0 | 156.7 | 25.1 | 26.8 | 26.0 ± 0.84 | 156.6 | 203.5 | 182.9 | 22.8 | 26.9 | 25.6 ± 0.63 |
Mouth width | 45.0 | 45.8 | 45.4 | 7.5 | 7.6 | 7.5 ± 0.05 | 45.5 | 57.8 | 54.4 | 7.3 | 7.8 | 7.6 ± 0.06 |
Internasal width | 58.0 | 64.2 | 61.1 | 9.6 | 10.6 | 10.1 ± 0.50 | 58.0 | 79.0 | 67.6 | 7.7 | 10.5 | 9.5 ± 0.44 |
Nasal curtain, length | 25.6 | 26.9 | 26.3 | 4.2 | 4.5 | 4.4 ± 0.12 | 22.9 | 35.9 | 31.1 | 3.8 | 4.8 | 4.3 ± 0.13 |
width | 48.4 | 50.6 | 49.5 | 8.0 | 8.4 | 8.2 ± 0.17 | 42.5 | 67.5 | 57.4 | 7.1 | 9.0 | 8.2 ± 0.40 |
width each lobe | 11.2 | 12.9 | 12.1 | 1.9 | 2.1 | 2.0 ± 0.14 | 8.6 | 16.0 | 13.9 | 1.4 | 2.1 | 1.9 ± 0.11 |
space between lobes | na | na | na | na | na | na | 33.0 | 33.7 | 33.4 | 4.4 | 4.5 | 4.5 ± 0.09 |
Gill slit length, first | 8.5 | 9.8 | 9.2 | 1.4 | 1.6 | 1.5 ± 0.11 | 8.9 | 12.8 | 10.8 | 1.3 | 1.7 | 1.5 ± 0.06 |
third | 8.8 | 12.2 | 10.5 | 1.5 | 2.0 | 1.7 ± 0.28 | 9.0 | 13.1 | 11.7 | 1.2 | 1.8 | 1.6 ± 0.10 |
fifth | 7.0 | 9.6 | 8.3 | 1.2 | 1.6 | 1.4 ± 0.21 | 7.0 | 10.5 | 8.5 | 1.0 | 1.4 | 1.2 ± 0.06 |
Space between first gill slits | ||||||||||||
fifth gill slits | 51.4 | 53.8 | 52.6 | 8.5 | 8.9 | 8.7 ± 0.18 | 62.9 | 68.7 | 64.9 | 8.3 | 10.6 | 9.1 ± 0.33 |
V-length, anterior lobe | 79.4 | 83.2 | 81.3 | 13.1 | 13.8 | 13.5 ± 0.34 | 85.0 | 109.1 | 98.4 | 11.2 | 14.9 | 13.8 ± 0.56 |
posterior lobe | 103.0 | 105.2 | 104.1 | 17.1 | 17.5 | 17.3 ± 0.21 | 101.2 | 149.0 | 129.6 | 15.2 | 19.8 | 18.1 |
Clasper, postanus length | na | na | na | na | na | na | 49.9 | 168.0 | 118.4 | 8.4 | 22.2 | 16.2 ± 2.43 |
Snout tip to center of anus | 275.0 | 283.0 | 279.0 | 45.7 | 46.9 | 46.3 ± 0.59 | 276.0 | 367.0 | 335.7 | 44.9 | 48.7 | 46.9 ± 0.53 |
to max. disc width | ||||||||||||
Center of anus to D1 | 237.0 | 248.0 | 242.5 | 39.2 | 41.2 | 40.2 ± 0.98 | 243.0 | 317.0 | 289.5 | 39.0 | 41.9 | 40.4 |
to D2 | 269.0 | 279.0 | 274.0 | 44.5 | 46.3 | 45.4 ± 0.90 | 273.0 | 351.0 | 322.5 | 43.4 | 46.4 | 45.0 ± 0.43 |
to tail tip | 311.0 | 321.0 | 316.0 | 51.5 | 53.3 | 52.4 ± 0.92 | 315.0 | 403.0 | 364.5 | 47.2 | 53.2 | 51.0 |
Snout angle | 87.0 | 91.0 | 89.0 ± 2.00 | 79.0 | 96.0 | 87.0 ± 2.44 | ||||||
No. of preorbital thorns | 2 | 6 | 3.5 ± 1.00 | 3 | 6 | 4.1 ± 0.54 | ||||||
No. of postorbital thorns | 2 | 4 | 2.8 ± 0.75 | 0 | 5 | 3.0 ± 0.79 | ||||||
No. of orbital thorns | 5 | 8 | 6.3 ± 0.25 | 2 | 10 | 6.6 ± 1.21 | ||||||
No. of interspiracular thorns | ||||||||||||
No. of nuchal thorns | 4 | 8 | 6.0 ± 2.00 | 2 | 5 | 3.8 ± 0.54 | ||||||
No. of scapular thorns | 2 | 4 | 3.0 ± 1.00 | 0 | 5 | 2.4 ± 0.62 | ||||||
No. of interscapular thorns | 0 | 2 | 1.0 ± 1.00 | 0 | 4 | 2.0 ± 0.63 | ||||||
Total no. of median thorns | ||||||||||||
Lateral spines right | ||||||||||||
Lateral spines left | ||||||||||||
No. trunk vertebrae | ||||||||||||
No. caudal vertebrae | 105 | 113 | 109.0 ± 4.00 | 99 | 118 | 106.4 ± 3.44 | ||||||
Tooth rows upper jaw | 40 | na | 40.0 ± na | 35 | 43 | 38.7 ± 1.17 | ||||||
Tooth rows lower jaw | 38 | 40 | 39.0 ± 1.00 | 31 | 44 | 39.7 ± 1.91 |
Studies of sexual dimorphism in batoids are limited. However, these previous studies found sexual dimorphism in various morphological characters. For example, males and females of the South American apron ray,
Our study shows that North Atlantic deepwater skates from the genera
Sexual dimorphism in disc length and the distance from the snout tip to the anus has been noted for other skate species [
Our study shows that females of some species have a relatively wider disc compared to males and this is likely responsible for the observed differences in interorbital width, length of gill slits, length of the orbit + spiracle (measured together), and the space between the gill slits. Differences in mouth width in some species may be caused by sexual dimorphism of the shape and number of teeth in adult skates, as well as differences in diet [
We also observed differences between males and females in the tail height at the tips of pelvic fins. Since the tail is used in courtship and copulation, it is reasonable to assume that these differences can be attributed to reproductive behaviour.
Forster [
This paper would not have been possible without the input of our many colleagues. Matthias Stehmann (ICHTHYS, Hamburg, Germany) helped with the ID of skates. James Orr (Alaska Fisheries Science Center, Seattle, USA) and Hajime Ishihara, (W & I Associates Corporation, Fujisawa, Japan) explained some specific measurements. Romain Causse (Museum National d’Histoire Naturelle, Paris, France) made X-ray images of