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Home , Naticidae, Neverita duplicata

DePaul Discoveries

Volume 4 Issue 1 Article 16

2015

Predation in a Natural Community of Marine Mollusks: Using Morphology to Determine Predator-Prey Ecology

Danielle N. Araiza DePaul University, [email protected]

Erica Valdez DePaul University, [email protected]

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Recommended Citation Araiza, Danielle N. and Valdez, Erica (2015) " in a Natural Community of Marine Mollusks: Using Morphology to Determine Predator-Prey Ecology," DePaul Discoveries: Vol. 4 : Iss. 1 , Article 16. Available at: https://via.library.depaul.edu/depaul-disc/vol4/iss1/16

This Article is brought to you for free and open access by the College of Science and Health at Via Sapientiae. It has been accepted for inclusion in DePaul Discoveries by an authorized editor of Via Sapientiae. For more information, please contact [email protected]. Araiza and Valdez: Using Morphology to Determine Predator-Prey Ecology

Predation in a Natural Community of Marine Mollusks: Using Morphology to Determine Predator-Prey Ecology

Danielle N. Araiza*, Erica Valdez* Department of Biological Sciences

ABSTRACT Predatory gastropod mollusks in the family feed on bivalve mollusks and leave distinctive markings in the form of countersunk circular boreholes on the shells. These boreholes possess both an inner borehole diameter (IBD) and an outer borehole diameter (OBD) which are proportional to the size of the predator. It has been proposed that the ratio of IBD to OBD can be used to identify predator . Variation in the ratio of the IBD to OBD was examined in two prey species (dwarf surf clam, incongruous ark clam) collected from Otter Island beach in South Carolina to determine if clams were eaten by a single species or multiple species of predator. Measurements of borehole diameter (inner and outer) were recorded in random samples of Anadara brasiliana (incongruous ark, n = 100) and Mulinia lateralis (dwarf surf clam, n = 100) shells. Comparison of the frequency distributions of the ratios revealed a unimodal, normal distribution in the combined sample indicating the potential for a single species effect. A similar pattern was revealed in the M. lateralis sample. In contrast, a unimodal skewed distribution was identified in the A. brasiliana sample indicating the potential for a multi-species effect.

INTRODUCTION Naticidae gastropods are infaunal drilling marine used in paleontological research of predator-prey predators that leave traces of predation in the dynamics (Kowalewski, 2002). form of countersunk boreholes on the shells of Previous studies of naticid predation have bivalves and, in some cases, other gastropods examined site- and size-selectivity (Kitchell et al. (Kelley, P.H, 1991; Kowalewski, M. 2002; Grey, 1981; Dietl & Alexander, 1995; Chiba, T. & Sato, M., Boulding, E., & Brookfield, M., 2005; Dietl, S., 2011), valve-selectivity (Hasegawa, H. & G.P. & Kelley, P.H., 2006). Boreholes offer Sato, 2009), naticid cannibalism (Kelley, 1991), direct proof of biotic interactions between borehole morphology (Kitchell et al. 1981; predators and prey and have been extensively Kowalewski, 2002; Grey et al. 2005) and co- ______evolution (Kelley, 1992). Thus, research on * Faculty Advisor: Dr. Timothy C. Sparkes naticid boreholes has provided valuable insights Department of Biological Sciences into the evolutionary patterns of prey selection Research Completed in Winter 2014 and the adaptive evolutionary responses among Author Contact: [email protected] both predator and prey (Kitchell et al. 1981).

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Several studies of naticid predation have relied on image processing program, ImageJ, where two beach collections of predated and non-predated measurements of outer borehole diameter (OBD) shells to determine the evolutionary and and inner borehole diameter (IBD) were recorded ecological patterns. One concern with this (Figure 1). approach is that the identity of the predator is not

known. However, previous research has shown that naticid predators can be identified by their borehole characteristics (Kitchell et al. 1981; Grey et al. 2005; Dietl & Kelley, 2006). Grey et al. (2005) used a combination of live feeding trials and beach collections to examine the geometric differences in naticid boreholes and identified a species-specific component to borehole geometry. In this study, the boreholes Figure 1. Measurements of inner borehole diameter belonged to the only known predator in the area (left) and outer borehole diameter (right) taken in (Atlantic moon snail, duplicata). Thus, ImageJ. predator-prey dynamics in this system were regulated by a single predator species. Mulinia lateralis sample collection In the current study, we used this type of During December 2013, 542 shells of the morphological approach to attempt to identify the Mactridae family were collected from Otter predator-prey dynamics occurring in a natural Island, SC. After categorizing the sample by community of marine mollusks. In this genera and species, the most abundant species community, multiple species of bivalve mollusks was identified as M. lateralis (n = 469). Each exist and are preyed upon by unidentified naticid specimen was coded and placed into equally predators. We used beach collections of naturally sized vials. The vials were then mixed and placed predated bivalves (incongruous ark, Anadara into a large container, from which a blindfolded brasiliana; dwarf surf clam, Mulinia lateralis) anonymous subject was utilized to randomly from Otter Island, South Carolina to determine if select a set of ten vials. This sampling method predation was due to a single species or multiple was conducted ten times, mixing the vials in the species of naticid predator. container in between sets, until a final sample size of 100 shells was obtained. Due to the relatively METHODS small size of M. lateralis, cross-sectional Anadara brasiliana sample collection measurements of IBD and OBD were obtained using a dissecting microscope. Anadara brasiliana (n = 134) samples were collected at two different times. First, in IBD:OBD ratio December 2013 a random sample of 78 shells was The individual measurements (one horizontal, collected from three sites (distanced 30.5 m apart) one vertical) of IBD and OBD for each shell were on Otter Island, South Carolina using a shovel to averaged, and the subsequent values were used to scrape the surface of the sand. An additional 56 calculate an IBD:OBD ratio. A Pearson shells were randomly collected in December correlation analysis was used to determine the 2014 from the same location using the same relationship between IBD and OBD for each prey sampling method. After sorting and individually species. To determine whether A.brasiliana coding each shell, a random number generator samples differed in this relationship, we first was used to obtain a sub-sample of 100 shells obtained separate values for each sample (2013, from the original sample (Urbiniak and Plous, n = 77; 2014, n = 23) Frequency distributions of 2008). Once the sample size was complete (n = the IBD:OBD ratios were plotted and examined 100) each specimen was placed on a platform to determine the modality and normality of the affixed with a metric ruler, and digital images distributions of both M. lateralis and A. were captured using a VT300 portable brasiliana samples. microscope. The images were then uploaded to an

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RESULTS The frequency distributions of the IBD:OBD ratios for each species and the combined sample The relationship between IBD and OBD for each are shown in Figure 3. Analysis of normality species is shown in Figure 2. Pearson correlation using a Shapiro-Wilk test revealed that the analyses for M. lateralis and A. brasiliana distribution of ratios in the combined sample was revealed strong positive correlations between normal (p = 0.1). For the individual species, the IBD and OBD for each species. The IBD/OBD distribution of ratios for M. lateralis was normal relationship did not differ between the two (p = 0.8). In contrast, the distribution for A. samples collected for A. brasiliana (2013, r = p brasiliana was non-normal (p = 0.001) and 0.93; 2014, r = 0.93). p skewed. Graphical analysis of modality (unimodal vs. bimodal) revealed that all three of the distributions were unimodal. 4 rp = 0.93 30 3 All 25

2 20 15 IBD (mm)IBD 1 10

5 0 30 0 2 4 6 M. lateralis 25 OBD (mm) 20

5 15 rp = 0.93 10 4 5

3 35 30 A. brasiliana 2 25 IBD (mm)IBD 20 1 15 10 0 5 0 2 4 6 8 0 OBD (mm) 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85

IBD:OBD ratio

Figure 2. Relationship between inner borehole Figure 3. Frequency distribution of IBD:OBD ratio in diameter (IBD) and outer borehole diameter (OBD) in combined sample (top), Mulinia. lateralis (middle) Mulinia lateralis (top) and Anadara brasiliana and Anadara brasiliana (bottom). (bottom).

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DISCUSSION To determine whether multiple predators do exist in the community, an examination of borehole Results of the correlation analyses indicate strong geometry could be used. Kitchell et al. (1981) positive relationships between IBD and OBD for established methods for measuring borehole each species. Analyses of the frequency angles of numerous naticid species. Applying this distribution of the IBD:OBD ratios for the methodology to measure the angles of the combined sample, which included both prey boreholes within the A. brasiliana sample and species, identified a unimodal, normal referencing the angles of known naticid species distribution. This pattern most likely indicates a (Kitchell et al. 1981) would assist in identifying single predator species feeding in the bivalve the type of predators present. community. Consistent with this overall pattern, the IBD:OBD ratios obtained for M. lateralis Overall, the results obtained are consistent with were also unimodal and normal. Contrary to this the interpretation that predator-prey dynamics are pattern, the distribution of IBD:OBD ratios for A. regulated by a single naticid species. This type of brasiliana was unimodal but skewed. A similar pattern is consistent with the results obtained in pattern was seen in a previous study which another single-species dominated system from attempted to differentiate naticid species based on North Carolina (Grey et al. 2005). The dominant variability in IBD:OBD ratios (Dietl & Kelley, species in the North Carolina system was 2006). A frequency distribution of IBD:OBD identified as N. duplicata (Atlanic moon snail). ratios of two naticid gastropods ( Consistent with this finding, live N. duplicata fortunei, ) revealed similar have been observed in the area of Otter Island, ranges. However, a skewed distribution of N. SC, and N. duplicata shells have regularly been duplicata was observed which mirrors that of the found on the local beaches. Collectively, these distribution in the A. brasiliana sample. This findings suggest that N. duplicata may potentially pattern, although skewed, may indicate N. be the species dominating in the community duplicata as the dominant naticid predator studied on Otter Island. species in the community. Alternatively, the

skewed distribution identified in A. brasiliana could be due to a second predator present in the community.

ACKNOWLEDGEMENTS A special thank you to Sara Teemer and Mallory Davis for helping with data collection, Dr. Al Segars & Nick Wallover from the South Carolina Department of Natural Resources for their guidance and logistical support. Funding and support was provided by the Department of Biological Sciences at DePaul University and a donation honoring Dr. Mary Alice McWhinnie. For support and professional development: National Science Foundation, HRD 1411219, Illinois Louis Stokes Alliance for Minority Participation (IL-LSAMP); Dr. Jesus Pando, Department of Physics at DePaul University.

REFERENCES Dietl, G.P., Alexander, R.R. (1995). Borehole site Chiba, T., Sato, S. (2011). Size selective predation and prey size stereotypy in naticid and drillhole-site selectivity in Euspira predation on Euspira () heros Say fortunei (: Naticidae): and Neverita (Polinces) duplicata Say implications for ecological and from the southern New Jersey coast. palaeoecological studies. Journal of Journal of Shellfish Research 4: 307-314. Molluscan Studies 78: 205-212.

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Dietl, G.P., Kelley, P.H. (2006). Can naticid gastropod predators be identified by the holes they drill? Ichnos 13: 103-108.

Grey, M., Brookfield, M.E., Boulding, E.G. (2005). Shape differences among boreholes drilled by three species of naticid gastropods. Journal of Molluscan Studies, 71: 253-256.

Grey, M., Boulding, E.G., Brookfield, M.E. (2006). Estimating multivariate selection gradients in the fossil record: a naticid gastropod case study. Paleobiology 32: 100-108.

Hasegawa, H., Sato, S. (2009). Predatory behavior of the naticid Euspira fortunei: why does it drill the left shell valve of Ruditapes philippinarum? Journal of Molluscan Studies, 75: 147-151.

Kelley, P.H. (1991). Apparent cannibalism by Chesapeake group naticid gastropods: a predictable result of selective predation. Journal of Paleontology, 65: 75-79.

Kelley, P.H. (1992). Evolutionary patterns of naticid gastropods of the Chesapeake group: an example of coevolution? Journal of Paleontology, 66: 791-800.

Kitchell, J. A., Boggs, C.H., Kitchell, J.F., Rice, J.A. (1981). Prey selection by naticid gastropods: experimental tests and application to the fossil record. Paleobiology, 7: 533-552.

Kowaleski, M. (2002). The fossil record of predation: an overview of analytical methods. Paleontological Society Press, 8: 3-42.

Urbiniak, G.C., Plous, S. (2008). Reseaerch randomizer. http://www.randomizer.org/form.htm

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