Maternal provisioning gives young-of-the-year Hammerheads a head start in early life
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ORIGINAL PAPER
Maternal provisioning gives young‑of‑the‑year Hammerheads a head start in early life Kady Lyons1,6 · Ashley S. Galloway2 · Douglas H. Adams3 · Eric A. Reyier4 · Amanda M. Barker5 · David S. Portnoy5 · Bryan S. Frazier2 Received: 3 July 2020 / Accepted: 9 September 2020 © The Author(s) 2020
Abstract For species that do not provide parental care after birth, excess maternal provisioning during development, beyond what is required for embryogenesis, provides offspring with resources to increase their chances of survival. Maternally derived resources are expected to be important for buffering offspring against limited food resources at birth or time needed to learn how to properly feed. Young-of-the-year (YOY) cryptic Scalloped Hammerheads (Sphyrna lewini) and Carolina Hammerheads (Sphyrna gilberti) were sampled from nurseries along the US Atlantic Coast and compared for a number of biological condition metrics across three developmental stages. Large declines in liver lipid content and hepatosomatic indices were found in neonatal sharks, using umbilical scar healing as a proxy for time since birth. Feeding commenced quickly as 96% of sharks had prey remnants in their stomachs. The combination of rapid exhaustion of maternally provided resources and high occurrence of stomachs with prey contents indicate that nursery quality, with respect to prey availability, may be important for YOY hammerhead survivorship. While externally the two species are morphologically similar, longer length-at-birth in S. lewini and higher hepatic condition in neonatal S. gilberti suggest that aspects of reproductive biology, including physiology, may differ between species. While more information is needed to distinguish life history differences between these two species, data collected from YOY may serve as a useful proxy to inform management when adult samples of cryptic species are difficult to collect.
Introduction Responsible Editor: J. Carlson. Reviewed by undisclosed experts. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00227-020-03766-y) contains supplementary material, which is available to authorized users. * Kady Lyons [email protected] 1
Department of Biological Sciences, California State University Long Beach, Long Beach, CA, USA
2
South Carolina Department of Natural Resources, Charleston, SC, USA
3
Florida Fish and Wildlife Conservation Commission, Fish and Wildlife Research Institute, Melbourne, FL, USA
4
Kennedy Space Center Ecological Program and Integrated Mission Support Services, Kennedy Space Center, FL, USA
5
Department of Life Sciences, Texas A&M University-Corpus Christi, Corpus Christi, TX, USA
6
Georgia Aquarium, Atlanta, GA, USA
Female elasmobranchs (sharks, skates, and rays) invest heavily in reproduction, employing a gamut of energetic investment strategies to provision their young during development (e.g., egg laying to pseudoplacental; Cotton et al. 2015; Musick and Ellis 2005). Approximately 30% of elasmobr
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