AB 26:15-26 (2017)  -  DOI: https://doi.org/10.3354/ab00670

ABSTRACT: Understanding which food sources are nutritionally important at nursery grounds is critical in the conservation of the dwindling populations of horseshoe crabs in Asia. We used δ¹³C and δ¹⁵N values to define life-stage changes in dietary carbon sources and trophic position of 2 co-occurring horseshoe crab species, Tachypleus tridentatus and Carcinoscorpius rotundicauda, in a mangrove- and seagrass-vegetated estuary, Pearl Bay, in Guangxi, China. δ¹³C signatures in tissues of T. tridentatus and C. rotundicauda varied between species and among life stages within species, with the greatest differences occurring among earlier life stages (instars 5-7; 20-30 mm prosomal width). Life-stage specific diets were consistent with known habitat use by the 2 horseshoe crab species, with T. tridentatus reflecting slightly enriched seagrass carbon sources and C. rotundicauda reflecting influences of lighter sediment particulate organic matter (POM; -15.1 vs. ~ -15.8‰). Overall, seagrass contributed most to dietary carbon of both species (~60%), followed by sediment POM (35%). δ¹⁵N signatures were similar between species (~11.6‰), with C. rotundicauda adults exhibiting a slightly more enriched signal than juveniles (12.7 vs. 11.6‰), and all horseshoe crabs occupied secondary consumer trophic levels. The δ¹⁵N signatures in horseshoe crabs at Pearl Bay were lighter than those from more urbanized waters, likely due to lower anthropogenic nitrogen loading. Our data and those of previous studies suggest that effective international and national strategies for conserving threatened Asian horseshoe crabs would benefit from incorporating efforts to protect seagrass and mangrove habitats.

KEY WORDS: Horseshoe crabs · Life stages · Seagrass · Mangrove · δ¹³C · δ¹⁵N

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Cite this article as: Fan LF, Chen CP, Yang MC, Qiu G, Liao YY, Hsieh HL (2017) Ontogenetic changes in dietary carbon sources and trophic position of two co-occurring horseshoe crab species in southwestern China. Aquat Biol 26:15-26. https://doi.org/10.3354/ab00670 Export citation Share:    Facebook - - linkedIn