Giant embryos and hatchlings of Antarctic nudibranchs (Mollusca: Gastropoda: Heterobranchia)
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Bathydoris hodgsoni and Doris kerguelenensis are two of the largest Antarctic nudibranchs. They are both common circumpolar species with broad bathymetric distributions, although B. hodgsoni is restricted to deep waters in the Antarctic high latitude. Egg masses and juveniles of these species were collected over multiple years (1998–2012) in the eastern Weddell Sea and the South Shetland Islands, and here new data are provided about egg mass characteristics and ontogeny using histological techniques. The egg mass of B. hodgsoni has a maximum length of 12.4 cm with one or two egg capsules with a mean diameter of 4.9 cm. The capsules either contained non-developing eggs or ready-to-hatch juveniles up to 2.9 cm long. The egg mass of D. kerguelenensis is a semicircular ribbon-like structure including 1,500–2,400 oval capsules (~1.7 × 1.2 mm) containing various stages of development up to ready-to-hatch juveniles 2.5 mm in length. Based on their morphology and development in egg masses maintained in the laboratory, the embryonic period for B. hodgsoni is estimated to be up to 10 years, and for D. kerguelenensis 13 months. Thus, B. hodgsoni has the largest egg capsules and probably the largest hatchlings of any mollusc. Chemical analyses of D. kerguelenensis egg masses showed no trace of terpenoid acylglycerols, although these compounds were present in field-collected juveniles and adults. None of four sponges that likely serve as food for D. kerguelenensis had the glycerides, or their precursors, found in the nudibranch.
KeywordsSponge Digestive Gland Embryonic Period Capsule Element Early Juvenile
We thank Y. Grzymbowski, L. Núñez-Pons, C. Debenham, M. Lavaleye, M. Rauschert, U. Jacobs, K. Beyer, T. Brey, W. Arntz, and the crew of the RV Polarstern for their help during sampling and rearing of the nudibranchs. Thanks are due to J. Cristobo, J. Vázquez, and the crew of BIO Las Palmas for their support while diving at Livingston Is. Funding was provided by the Spanish Government through the ECOQUIM (REN2003-00545, REN2002-12006E ANT, CGL2004-03356/ANT), ACTIQUIM (CGL2007-65453, CTM2010-17415/ANT), and DISTANTCOM (CTM2013-42667/ANT) projects. J. Moles was supported by a PhD grant from the Spanish Government (MEC; BES-2011-045325). This work is part of the AntEco (State of the Antarctic Ecosystem) Scientific Research Programme.
Compliance with ethical standards
This study was funded by the Spanish Government through the ECOQUIM (REN2003-00545, REN2002-12006E ANT, CGL2004-03356/ANT), ACTIQUIM (CGL2007-65453, CTM2010-17415/ANT), and DISTANTCOM (CTM2013-42667/ANT) Projects. J. Moles was supported by a PhD Grant of the Spanish Government (MEC; BES-2011-045325).
Conflict of interest
The authors declare that they have no conflict of interest.
All applicable international, national, and/or institutional guidelines for the care and use of animals were followed.
“Informed consent was obtained from all individual participants included in the study.”
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