The Common Sunstar Crossaster papposus-A Neurotoxic Starfish

Abstract

Saxitoxins (STXs) are a family of potent neurotoxins produced naturally by certain species of phytoplankton and cyanobacteria which are extremely toxic to mammalian nervous systems. The accumulation of STXs in bivalve molluscs can significantly impact animal and human health. Recent work conducted in the North Sea highlighted the widespread presence of various saxitoxins in a range of benthic organisms, with the common sunstar (Crossaster papposus) demonstrating high concentrations of saxitoxins. In this study, an extensive sampling program was undertaken across multiple seas surrounding the UK, with 146 starfish and 5 brittlestars of multiple species analysed for STXs. All the common sunstars analysed (n > 70) contained quantifiable levels of STXs, with the total concentrations ranging from 99 to 11,245 µg STX eq/kg. The common sunstars were statistically different in terms of toxin loading to all the other starfish species tested. Two distinct toxic profiles were observed in sunstars, a decarbomylsaxitoxin (dcSTX)-dominant profile which encompassed samples from most of the UK coast and an STX and gonyautoxin2 (GTX2) profile from the North Yorkshire coast of England. Compartmentalisation studies demonstrated that the female gonads exhibited the highest toxin concentrations of all the individual organs tested, with concentrations >40,000 µg STX eq/kg in one sample. All the sunstars, male or female, exhibited the presence of STXs in the skin, digestive glands and gonads. This study highlights that the common sunstar ubiquitously contains STXs, independent of the geographical location around the UK and often at concentrations many times higher than the current regulatory limits for STXs in molluscs; therefore, the common sunstar should be considered toxic hereafter.

Keywords: benthos; north east Atlantic; paralytic shellfish toxins; solasteridae; sunstars.

Figure A1

Comparison of LC–FLD and HILIC–MS/MS methods. Correlation coefficient (top right), scatter plot (bottom left) and distributions (HILIC–MS/MS (top left) and LC–FLD (bottom right)). The x axis is HILIC–MS/MS in µg STX eq/kg and y axis is LC–FLD in µg STX eq/kg.

Figure A2

LC–HRMS chromatogram showing accurate mass and fragmentation pattern of doSTX in a standard (not certified) and a sunstar sample.

Figure 1

Chemical structures and TEFs (toxin equivalence factors) of the common STXs. TEFs primarily based on EFSA recommendations.

Figure 2

Sampling locations of all starfishes collected, with mean toxic profiles of sunstars at each sampling region expressed as toxin load % in µg STX eq/kg.

Figure 3

Box-and-whisker plot highlighting species means (cross), 1st and 3rd quartiles, outliers (dots) and interquartile ranges for the starfish and brittlestar species analysed (sample numbers (n) can be found in Table A2).

Figure 4

Box-and-whisker plot highlighting sampling region means (cross), 1st and 3rd quartiles, outliers (dots) and interquartile ranges for all sunstars analysed.

Figure 5

Mean toxic profiles of all sunstars expressed as toxin load % in µg STX eq/kg (left) and µmol/kg (right).

Figure 6

Box-and-whisker plot highlighting individual sunstar organ means for each sex (cross), 1st and 3rd quartiles, outliers (dots) and interquartile ranges.

Figure 7

The relationship between the diameter of sunstars and toxicity.

Figure 8

Hypothetical production route for the dcSTX profile. Enzymatic transformations from [29].

Figure 9

Chromatogram of LC–FLD analysis for a sunstar (top) and for certified standards (bottom). A—dcSTX (quantitative peak), B—dcSTX (qualitative peak), C—GTX2&3, D—GTX5, E—STX, F—Matrix.

Figure 10

Chromatograms showing dMRMs and associated m/z transitions for (A) dcSTX, (B) GTX5 and (C) STX using the HILIC–MS/MS method. Grey peaks represent analytical standards and orange peaks represent sunstar sample SBS 50. X-axis = time in mins.

Figure 11

Histological examination of sunstar gonads and determination of male and female animals: (a) male gonads partially spawned, (b) higher magnification of area highlighted by box in (a), (c,d) female gonads spawned and spent. sg, spermatogenic layer; S, spermatozoa; RO residual oocytes.