2008 SOUTHEASTERN NATURALIST 7(1):173–179 A Complex Mimetic Relationship Between the Central Newt and Ozark Highlands Leech Malcolm L. McCallum1,*, Stacy Beharry2, and Stanley E. Trauth3 Abstract - In response to their strikingly similar coloration, we tested for a mimetic relationship between Notophthalmus viridescens louisianensis (Central Newt) and Macrobdella diplotertia (Ozark Highlands leech). Early observations took place in a south-central Missouri woodland pond. Later, feeding experiments involving ducks, geese, and native fishes were conducted. Our results support a mimetic relationship between these 2 species that is not a simple classification. More in-depth study may be needed to elucidate the true nature of this relationship. Introduction Three forms of mimicry have been defined. They are aggressive, Mullerian, and Batesian mimicry. In aggressive (Peckhamian) mimicry, the mimic uses its conformation to intimidate or attack the model or the model’s predator (Lloyd 1965). In Batesian mimicry, a palatable prey mimics a distasteful animal for protection (Bates 1862). The usual example of this is the viceroy/monarch butterfly mimicry system (Brower 1958), although we now know this is a false example (Ritland and Brower 1991). Müllerian mimicry involves a system of species that may or may not be taxonomically related but share similar warning colors or behaviors (Muller 1878). The striped pattern of many bees is a classic example of such a system. We investigated a potential mimetic relationship between Macrobdella diplotertia Meyer (Ozark Highlands Leech) and Notophthalmus viridescens louisianensis (Wolterstorff) (Central Newt). Despite the importance of gathering natural history information on all species (Bury 2006, Fitch 2006, McCallum and McCallum 2006, Trauth 2006), we know little about the life history of the Ozark Highlands Leech. Its documented range includes several counties in Arkansas, two counties in Missouri (Trauth and Neal 2004), and 3 counties in Kansas (Tuberville and Briggler 2003). Studies conducted on the foraging habits of the Ozark Highlands Leech suggest that this species is an amphibian-egg predator (Trauth and Neal 2004) and a predacious sanguivore (Tuberville and Briggler 2003). There is, however, little known about the palatability of Ozark Highlands Leech to potential predators. 1Biological Sciences Program, Texas A&M University-Texarkana, 2600 Robison Road, Texarkana, TX 75501. 2Department of Biology, Morgan State University, 1700 East Coldspring Lane, Baltimore, MD 21251. 3Department of Biological Sciences, Arkansas State University, PO Box 599, State University, AR 72467. *Corresponding author - Malcolm.mccallum@tamut.edu. 174 Southeastern Naturalist Vol.7, No. 1 The Central Newt is a small salamander occurring in the eastern half of North America. This animal has a unique life cycle in that eggs hatch into larvae that grow to about 3 cm, then emerge from the water as aposematically colored efts. They live a terrestrial existence for 6 months to 5 years, then return to the water as aquatic adults (Trauth et al. 2004). All life stages produce tetrodotoxin, a potent poison (Formanowicz and Brodie 1982), and are avoided by many predators (Brandon et al. 1979, Brodie 1968, Brodie and Howard 1972). Despite this general aversion by predators, Central Newts can be taken as food by various species of reptiles and other organisms (McCallum 2001). This study follows on observations of Ozark Highlands Leech and Central Newts in a fishless pond located in the Owls Bend area in the Ozark National Scenic Riverways of the Ozark Plateau (Shannon County, MO). We observed similarities in the coloration (Fig. 1) and swimming behavior of these two species. Both species share speckled patterns of black spots on their ventrum and dorso-laterally positioned rows of red spots. The dorsal background coloration in both species is olive-green. The ventrum of both species is yellow to cream colored. Ozark Highlands Leeches and Central Newts also swim in a similar undulating fashion. The similarities between the Central Newt and Ozark Highlands Leech suggested a mimetic complex. Herein, we test for the presence of mimicry between these two species, and identify what kind of mimicry is exhibited. If potential predators find 1 of these 2 species palatable, but not the other, this Figure 1. Comparison of lateral (top two photos) and ventral (lower two photos) spotting pattern between Notophthalmus viridescens louisianensis (Central Newt) and Macrodbella diplotertia (Ozark Highlands Leech). 2008 M.L. McCallum, S. Beharry, And S.E. Trauth 175 would suggest Batesian mimicry. If neither species is found to be palatable, the results would suggest Müllerian mimicry. Finally, if one species mimics the other to obtain food or partake in other kinds of aggression, the results would favor aggressive mimicry. Materials and Methods Avian predation Palatability of Ozark Highlands Leech and Central Newt were examined by offering them to free-ranging resident Anas platyrhynchos L. (Peking and Mallard Ducks), Anser cygnoides (Swan Goose), and Branta canadensis L. (Canada Geese) housed at Craighead Forest Park (Craighead County), Jonesboro, AR. These species were chosen based on the observation that Peking Ducks and Chinese Geese will eat other leeches (species unknown) and earthworms (M.L. McCallum, pers. observ.). We conducted 3 feeding trials, each time using a randomly selected member of the fl ock (n = 8). All waterfowl were believed to be naïve to Central Newts and Ozark Highland Leeches because neither species has been observed at Craighead Forest Park since at least 1983. Each bird was presented an Ozark Highlands Leech, Central Newt, or Lumbricus terrestris (nightcrawler) on the initial offering, and the feeding response was recorded. Thereafter, individual birds were offered a modified randomized selection of either Ozark Highlands Leech or Central Newt so that no prey species was offered 3 times in succession (Fig. 2). The acceptability of each prey type was also tested using a captive fl ock of Anas platyrhynchos ducklings. Five trials were conducted with each of 2 male and 3 female ducks. These ducks were naïve to both potential prey species, and were not fed for 24 hr prior to the experiment. In each trial, three of each prey type were placed in a 1.2 x 1.2 m plastic wading pool filled with water. Each duckling was chosen at random and allowed to forage in the pool for 30 min. The survivorship of prey was observed and scored as follows: 1) eaten, 2) pecked only, or 3) killed but not eaten. The data were analyzed via decision theory using chi-square (α = 0.05). Figure 2. Experimental design for presentation of prey to avian predators. 176 Southeastern Naturalist Vol.7, No. 1 Fish predation In our third experiment, we tested the acceptability of these prey to 3 Lepomis cyanellus Rafinesque (Green Sunfish; mean mass = 104 g, mean body length = 175 mm) and 3 Micropterus salmoides Lacépede (Largemouth Bass; mean =156 g, mean body length = 180 mm). Fish were collected from a private pond in Jonesboro, AR, where neither of our proposed mimics occurred. Green Sunfish and Largemouth Bass were communally housed in a 120-L aquarium prior to experimentation. They were transferred separately to a 200-L aquarium where fish were individually tested. In each trial, a single fish was placed in the test aquarium along with three specimens of each prey type. Observations were made every three hours during the first 12 hr of the study, and then again at the end of the 24 hr period. Results were tabulated (as eaten or killed but not eaten) and analyzed via decision theory with chi-square (α = 0.05). Results Avian predation Feral ducks and geese found both Ozark Highlands Leeches and Central Newts unpalatable. These waterfowl refused to eat Ozark Highlands Leech (0/8, 0% eaten). Similarly, no newts were consumed. Nightcrawlers were largely palatable. Seven of the 8 nightcrawlers offered were consumed. Ducklings found both Ozark Highlands Leeches and Central Newts unpalatable. Of the 15 Ozark Highlands Leeches presented, none was consumed, whereas 1 of the 15 Central Newt was eaten. Conversely, 12 of 15 nightcrawlers were eaten. A single duckling refused all prey items offered. Results of these trials are provided in Table 1. Ducks would peck at a leech when it swam by, but would quickly release it. After a short period, some ducks would attack again. Ducks tried to eat newts on their first introduction. There were no statistical differences between individual birds in response to Central Newt (χ2 = 4.0, df = 4, P > 0.25), Ozark Highlands Leech (χ2 = 4.0, df = 4, P = 1), or nightcrawler (χ2 = 4.0, df = 4, P = 1). Fish predation Sunfish refused to eat Ozark Highlands Leeches and Central Newts. Of the 9 nightcrawlers presented, only 1 was consumed (Table 2). During each trial, Ozark Highlands Leeches constantly attached themselves to the fish. They then remained attached until the fish were able to remove it by hitting Table 1. Responses of the five ducks to each prey type (n = 15). E = number eaten; K = killed, but not eaten; P = pecked only (attacked); and % S = percent survivorship. Prey Item P-value E K P % S Lumbricus terrestris (nightcrawler) 0.97 12 0 0 20.0 Notophthalmus viridescens louisianensis (Central Newt) 0.03 1 3 13 73.3 Macrobdella diplotertia (Ozark Highlands Leech) 0.00 0 0 36 100.0 2008 M.L. McCallum, S. Beharry, And S.E. Trauth 177 on the side of the container. Each fish was attacked several times over the 24 hr period. However, there were no visible wounds on the fish and they appeared to be uninjured. Largemouth Bass refused to eat all Central Newts or Ozark Highlands Leeches, whereas 6 of 9 nightcrawlers were consumed. Ozark Highlands Leeches attacked Largemouth Bass as described earlier with Sunfish. During the second trial, 2 bass died, presumably from attacks by leeches. These fish were found with Ozark Highlands Leeches attached to and feeding on the gills. Ozark Highlands Leeches migrated from the opercular region into the mouth and appeared to be feeding on the fish from within the pharyngeal region. These fish were examined and found to have wounds in the pharynx and opercular sinuses. Discussion Avian predation: evidence for Müllerian mimicry? Both Central Newts and Ozark Highlands Leeches were rejected as food by all species. Of the 8 Ozark Highlands Leeches offered, none was accepted as food by feral ducks or geese. At present, it is unknown if secretions of Ozark Highlands Leech are noxious or toxic; however, the leeches were rejected at nearly equal rates as were the Central Newts, suggesting neither was palatable and providing limited evidence that a Müllerian complex might exist. There were higher acceptance rates and lower survivorship for Central Newts with juvenile ducks than with adult feral ducks. Of the newts offered to the juvenile ducks, 73.3% were rejected, whereas there was a 100% rejection rate by adult ducks. This may reflect the naïveté of the juveniles. Juveniles were less than 3 months old and were conditioned to captivity. Whenever they were previously fed by humans, they received palatable items. This preconditioning might have confounded the results because these ducks could have learned that food offered by humans is always palatable. The feral ducks undoubtedly encountered many noxious items in their lives and learned to test unfamiliar foods before eating them. This comparison of two extremes in avian experience regarding human food offerings strengthens the rejection results, reinforcing that both of these species are quite unacceptable to waterfowl. Table 2. Response of each fish predator to each prey type. E = eaten, and % S = percent survivorship. Largemouth Bass Sunfish Prey Item % S E % S E Macrobdella diplotertia (Ozark Highlands Leech) 100.0 0 100.0 0 Notophthalmus viridescens louisianensis (Central Newt) 100.0 0 100.0 0 Lumbricus terrestris (nightcrawler) 33.3 6 88.9 1 178 Southeastern Naturalist Vol.7, No. 1 Fish predation Except with Green Sunfish, Nightcrawlers were acceptable food types, but both Central Newts and Ozark Highlands Leeches were rejected by fish. The fish however, were found quite palatable by Ozark Highlands Leeches. This result suggests aggressive mimicry might occur with fish. Studies conducted by Tuberville and Briggler (2003) indicate that these leeches are sanguivorous, yet no information on host preference has been given. In their native habitat, Central Newts can be found swimming about among sunfish unharmed (M.L. McCallum, pers. observ.; R. Brandon, Southern Illinois University, Carbondale, IL, pers. comm.). If fish learned that Central Newts were noxious, they might also have learned that this species doesn’t present a threat. In this case, fish might ignore the leeches due to the swimming behavior and color pattern they share in common with Central Newt. This behavior would allow Ozark Highlands Leeches to approach closer to fish than normally possible, providing a better opportunity to prey upon the fish in this study. Additionally, both species were from the same pond. Further investigations are needed to elucidate community effects on Central Newt’s role as a Batesian mimic of this leech. The function of these schemes requires that predators can and do interpret signals from both organisms in the same way. These 2 unrelated species demonstrate similar swimming behavior, coloration, and patterning. These results demonstrate the confusing behavioral patterns, suggesting a highly complex relationship. 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