Molecular investigation of the invasive sponge Hymeniacidon sinapium (de Laubenfels, 1930) in Elkhorn Slough, California

Timothy Fuller,Jeffery Hughey

doi:10.3391/ai.2013.8.1.07

Timothy Fuller, Jeffery Hughey

Open Access

https://doi.org/10.3391/ai.2013.8.1.07

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Abstract

A large number of invasive marine invertebrates are recognized from Elkhorn Slough (ES), California. One of these species in the slough is treated as Hymeniacidon sinapium (Family Halichondriidae) but its species identity is in doubt pending molecular confirmation. The purpose of this investigation was to confirm the presence of H. sinapium in ES, determine its distribution in the slough, and compare its genetic diversity to others in California and worldwide. To address these goals, 23 specimens of Hymeniacidon were analyzed using DNA sequences of the nuclear rDNA internal transcribed spacers (ITS1 + ITS2) and the 5.8S exon. The sequences were compared against those of H. sinapium from: San Diego and Tomales Bay in California; Japan; and South Korea. All ES sequences were found to be nearly identical to the other H. sinapium sequences, differing by only 1-3 nucleotides. ES specimens displayed five unique genotypes: three showed intragenomic polymorphisms (IGPs) in the ITS1 region (positions 155, 181, and 195). These data conclusively document the presence of H. sinapium in ES as well as define the species to a relatively narrow portion of its eastern shores (~4 km long). Since the genetic diversity of H. sinapium in ES is higher than that reported worldwide, its presence in ES is likely the result of multiple introductions. One of the IGPs in ES was found to be the most abundant and was widely distributed in the slough: an indication that it may be spreading.

Highlights

Elkhorn Slough (ES) is an 8,000 year old, transform-margin estuary that feeds the Monterey Bay in central California (Schwartz et al 1986)
All sequences were matched greater than 98% to sequences of H. sinapium published in GenBank by Park et al (2007) and Hoshino et al (2008) with 22 of the sequences matching greater than 99%
The DNA sequences of H. sinapium from ES are consistent with sequences of H. sinapium reported by Park et al (2007) and Hoshino et al (2008)

Summary

Introduction

Elkhorn Slough (ES) is an 8,000 year old, transform-margin estuary that feeds the Monterey Bay in central California (Schwartz et al 1986). Due to early anthropogenic activities, a number of changes to the biodiversity in ES have occurred (Van Dyke and Wasson 2005) One of these activities is the brief mariculture of the Atlantic oyster (Crassostrea virginica Gmelin, 1791) during the 1920s and, during the 1930s, the more active cultivation of the Japanese oyster (C. gigas Thunberg, 1793) (Barrett 1963). The latter is implicated in the introduction of many invasive invertebrates to ES (Wasson et al 2001). Attempts to reclaim the marsh habitat by intentional levee breaches were somewhat successful; locations like Parsons Slough and South Marsh that together compose the Parsons Slough Complex (Figure 1A), had become mudflats and have yet to recover to fully restored marshland (Van Dyke and Wasson 2005)

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