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Further description of the Kerguelen sandpaper skate Bathyraja irrasa (Rajiformes: Arhynchobatidae) based on additional specimens, including egg cases and embryos

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Journal of Fish Biology
Authors:
William Toby White at CSIRO Oceans & Atmosphere Flagship
William Toby White
  • CSIRO Oceans & Atmosphere Flagship
Helen L. O'Neill at The Commonwealth Scientific and Industrial Research Organisation
Helen L. O'Neill
Jaimie Cleeland at University of Tasmania
Jaimie Cleeland
Tim D. Lamb
Tim D. Lamb
Tim D. Lamb
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Abstract and Figures

Adult specimens, additional juvenile specimens, egg cases and embryos were used to provide a more detailed anatomical description of the Kerguelen sandpaper skate Bathyraja irrasa, a species of skate endemic to the Kerguelen Plateau and listed as Vulnerable by the IUCN Red List of Threatened Species. The morphological and meristic data reveal a relatively high level of intraspecific variation, mostly related to size. Egg cases are described for the first time and were shown to vary in colour and fouling depending on the length of time spent in the marine environment. Embryos removed from egg cases represent all stages of embryonic development in this species and include the largest embryo recorded for this species, i.e., 230 mm total length (LT), which increases the range of size at hatching of B. irrasa to 178–230 mm LT. A number of morphometric and meristic characters varied ontogenetically in B. irrasa, in particular relative tail length, number of tail thorns in the median row and the size of orbits. This study highlights the importance of describing intraspecific variation in species and the importance of egg cases to taxonomic and biological research on oviparous species.
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REGULAR PAPER
Further description of the Kerguelen sandpaper skate
Bathyraja irrasa (Rajiformes: Arhynchobatidae) based
on additional specimens, including egg cases and embryos
William T. White
1
| Helen L. O'Neill
1
| Jaimie Cleeland
2
| Tim D. Lamb
2
1
CSIRO National Research Collections
Australia –Australian National Fish Collection,
Hobart, Tasmania, Australia
2
Australian Antarctic Division, Kingston,
Tasmania, Australia
Correspondence
William T. White, CSIRO National Research
Collections Australia –Australian National Fish
Collection, GPO Box 1538, Hobart, TAS, 7001,
Australia.
Email: william.white@csiro.au
Funding information
Australian Antarctic Division; Commonwealth
Scientific and Industrial Research Organisation
Abstract
Adult specimens, additional juvenile specimens, egg cases and embryos were used to
provide a more detailed anatomical description of the Kerguelen sandpaper skate
Bathyraja irrasa, a species of skate endemic to the Kerguelen Plateau and listed as
Vulnerable by the IUCN Red List of Threatened Species. The morphological and
meristic data reveal a relatively high level of intraspecific variation, mostly related to
size. Egg cases are described for the first time and were shown to vary in colour and
fouling depending on the length of time spent in the marine environment. Embryos
removed from egg cases represent all stages of embryonic development in this spe-
cies and include the largest embryo recorded for this species, i.e., 230 mm total
length (L
T
), which increases the range of size at hatching of B. irrasa to 178–230 mm
L
T
. A number of morphometric and meristic characters varied ontogenetically in B.
irrasa, in particular relative tail length, number of tail thorns in the median row and
the size of orbits. This study highlights the importance of describing intraspecific vari-
ation in species and the importance of egg cases to taxonomic and biological research
on oviparous species.
KEYWORDS
Bathyraja, endemic, Heard and MacDonald Islands, Kerguelen plateau, oviparous, subantarctic
1|INTRODUCTION
Skates are the most speciose elasmobranch group globally, with
301 species known, belonging to one of four families, ranging from
the tropics to the polar regions (Last et al., 2016b; Séret et al., 2016;
Weigmann et al., 2016,2021).ThesoftnoseskategenusBathyraja
(family Arhynchobatidae) is the most speciose chondrichthyan genus
with 52 currently recognized species in the world's oceans
(Stehmann et al., 2021). Only six Bathyraja species are known from
the Antarctic and Subantarctic regions (Stehmann et al., 2021):
Antarctic dark-mouth skate B. arctowskii (Dollo, 1904), Eaton's
skate B. eatonii (Günther, 1876), Kerguelen sandpaper skate B. irrasa
Hureau & Ozouf-Costaz, 1980,McCain'sskateB. maccaini
Springer, 1971, darkbelly skate B. meridionalis Stehmann, 1987 and
Murray's skate B. murrayi (Günther 1880). Four of these species,
B. eatonii,B. irrasa,B. maccaini and B. murrayi,areknownfromthe
Kerguelen Plateau with B. irrasa and B. murrayi endemic to this
region (Last, Stehmann, et al., 2016). A recent redescription of Bath-
yraja arctowskii found that B. eatonii from the Kerguelen Plateau is
genetically distinct from specimens from the South Shetland Islands,
off Mawson Station and the Ross Sea (Stehmann et al., 2021). This
suggests that B. eatonii is likely also endemic to the Kerguelen Pla-
teau as it was first described from Royal Sound, Kerguelen Island.
The Kerguelen sandpaper skate B. irrasa was described based on
four specimens collected off the Kerguelen Islands (46 47.70to
50 37.90S) at depths of 565–1218 m (Hureau & Ozouf-Costaz, 1980;
Figure 1).Thetypespecimensrangedfrom356to678mmtotal
length (L
T
).
Received: 21 April 2022 Accepted: 10 June 2022
DOI: 10.1111/jfb.15136
FISH
© 2022 Commonwealth of Australia. Journal of Fish Biology © 2022 Fisheries Society of the British Isles.
J Fish Biol. 2022;101:659–675. wileyonlinelibrary.com/journal/jfb 659
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