Typical Morphs Research Articles

Skin structure, coloration, and habitat utilization in typical and melanistic morphs of the grass snake (Natrix natrix).

Melanism is a polymorphic phenotype caused by the number and density of melanocyte cells producing melanin pigment in the skin and widely observed in snakes. The frequency of this coloration in populations is associated with its opposing fitness consequences and can be closely related to species-specific characteristics such as sex, reproduction, and nutrition, as well as environmental factors such as climate and geography. Although melanism is frequently seen in snakes, the skin structure of melanistic individuals has not been studied in detail. Also, the impact of the black phenotype on habitat use has not yet been clarified in this species. Here, we show a comparison of typical and melanistic morphs of the grass snake Natrix natrix population of Anatolia for the first time in terms of skin structure, habitat, and sex. We found that melanistic individuals, in which partial melanism is more abundant than total melanism, comprise 13% of the population. Melanocyte area of the skin is 1.4 times greater in melanistic compared to the typical individuals. The epidermis is thicker in typical morphs by 7.7%. Hinge regions between adjacent scales do not bare melanocytes in both morphs. As for habitat utilization, we revealed that melanistic individuals of the Işıklı population tend to occur closer to water bodies than typical ones. Our data provide a new perspective on poorly known aspects of color polymorphism and habitat use of widely distributed, semi-aquatic Natrix natrix.

Limited occurrence of the profunda morph of the quagga mussels (Dreissena rostriformis bugensis) in the Volga River reservoirs of Russia and limited genetic differences between morphs in Russia and North America

ABSTRACT The quagga mussel Dreissena rostriformis bugensis is a highly invasive species. It plays an important role in benthic communities, influencing their structure and functioning. Two morphs of this mussel have been described: a shallow-water (i.e. the typical) morph and a deep-water morph, profunda. Currently, profunda has been found in several water bodies only within the nonnative range of D. r. bugensis. In North America, the profunda morph is widespread and abundant in the Laurentian Great Lakes. In Europe, profunda was found for the first time in 2009 in the Cheboksary Reservoir, which is located on the central part of the Volga River. A 2016 search for profunda in the four deepest Volga reservoirs (Cheboksary, Kuybyshev, Saratov and Volgograd) failed to find this morph even at the site where it was found in 2009. Traditional and outline-based morphometric analyses showed that only the shallow-water morph individuals inhabited studied sites at depths of 25–33 m. The present study revealed that morphological differences between the typical and profunda morphs from both the European and North American ranges were accompanied by limited genetic differences. Microsatellite analysis showed only minor differences in allele frequencies between morphs sampled in 2019 from the Cheboksary Reservoir; these differences were not significant after correction for null alleles. High phenotypic and ecological plasticity of D. r. bugensis may facilitate its invasion success.

Relaxed predation selection on rare morphs ofEnsatinasalamanders (Caudata: Plethodontidae) promotes a polymorphic population in a novel dune sand habitat

AbstractThe ring species Ensatina represents a classic example of locally adapted lineages. The Monterey ensatina (Ensatina eschscholtzii eschscholtzii) is a cryptic subspecies with brown coloration, although a recently discovered polymorphic population within a wind-blown sand region also contains leucistic (pink) and xanthistic (orange) morphs. In the present study, the frequency of leucism/xanthism was mapped across the subspecies’ range, revealing that these morphs are generally rare or absent except within regions containing light-coloured substrate. Attack rates were estimated using clay models of the three morphs, deployed only at the crepuscular period and during the night, on both light and dark substrates at a site within the dune sand region. Model selection found that the interaction between morph and substrate colour best predicted attack rates. Typical morphs had equal attack rates on both substrates while xanthistic and leucistic morphs incurred significantly fewer attacks on light vs. dark substrate, and there was no significant difference in attack rates among morphs on light substrates. These results support the idea that xanthistic and leucistic morphs are poorly adapted for dark substrates compared to typical morphs, but they are more or less equally adapted for light substrates. We suggest that this microgeographic island of relaxed selection on light-coloured morphs helps to explain the existence of this polymorphic population.

First record of a highly melanic morph of Cyphostethus tristriatus (Fabricius, 1787) (Hemiptera: Heteroptera: Acanthosomatidae).

The term 'melanism' means the occurrence of variant(s) that is/are mostly or completely dark in pigmentation either as intraspecific polymorphisms or as fixed differences between closely related species. Melanism can refer to variation involving discrete melanic and non-melanic phenotypes (melanic and typical morphs) or to cases of continuously varying pigmentation (True 2003). Melanism of moths inhabiting areas with industrial pollution is a very well-known example involving melanic polymorphisms in insects. However, melanism is also known in other insect orders, e.g. Coleoptera and Diptera (Majerus 1998, True 2003).

Avian Prey Remains at Eyries of the Austral Peregrine Falcon (Falco peregrinus cassini) in Southern Atlantic Argentine Patagonia during the Breeding Season

The Austral Peregrine Falcon (Falco peregrinus cassini) is widely distributed in Argentina, although studies on its diet are limited. Here we report information on the diet of this falcon in southern Atlantic Patagonia, Argentina. During November and December in 2009 and 2010, we visited nest sites of Austral Peregrine Falcons to collect prey remains to investigate their diet during the breeding season. We identified 72 avian prey remains from seven eyries in 2009 and three eyries in 2010. We documented seven orders of nonpasserines (11 families representing at least 58 individuals [81% of total prey items]). For the order Passeriformes, seven families were represented by 14 individual birds (19% of total prey items). In all, we identified 52 prey remains (72% of total prey items) to the species level. Another 12 birds were identified only to genus and three only to family or subfamily. Body mass for avian prey identified to species (n = 51) ranged from 10.4 g (Troglodytes aedon) to 842 g (Mareca sibilatrix). Nonpasserines provided 96.2% of the estimated biomass of the prey. Although our sample size is limited, compared with previous reports conducted more than 30 yr ago or in recent years but limited to one pair, our observations for ten nests in 2 yr provide novel and current information on avian prey species of Austral Peregrine Falcons. Our study increased the number of prey species documented for these birds for a geographical region where diet information was almost nonexistent, and provided diet data for both the typical and pallid color morphs of this subspecies.

Ediacaran discs from South America: probable soft-bodied macrofossils unlock the paleogeography of the Clymene Ocean

The origin, affinity and paleoecology of macrofossils of soft-bodied organisms of the terminal Ediacaran Period have been highly debated. Previous discoveries in South America are restricted to small shelly metazoans of the Nama Assemblage. Here we report for the first time the occurrence of discoidal structures from the Upper Ediacaran Cerro Negro Formation, La Providencia Group, Argentina. Specimens are preserved in tabular sandstones with microbially-induced sedimentary structures. Flute marks and linear scours at the base of the sandstone layers indicate deposition under high energy, episodic flows. Stratigraphic, sedimentologic, petrographic and taphonomic analyses indicate that the origin of these structures is not related to abiotic process. Preservational and morphological features, as invagination and the presence of radial grooves, indicate that they resemble typical morphs of the Aspidella plexus. The large number of small-sized individuals and the wide range of size classes with skewed distribution suggest that they lived in high-density communities. The presence of Aspidella in the Cerro Negro Formation would represent the first reliable record of Ediacaran soft-bodied organisms in South America. It also supports the paleogeographic scenario of the Clymene Ocean, in which a shallow sea covered part of the southwest Gondwana at the end of the Ediacaran.

Cannibalistic-morph Tiger Salamanders in Unexpected Ecological Contexts

Abstract Barred tiger salamanders [Ambystoma mavortium (Baird, 1850)] exhibit two trophic morphologies; a typical and a cannibalistic morph. Cannibalistic morphs, distinguished by enlarged vomerine teeth, wide heads, slender bodies, and cannibalistic tendencies, are often found where conspecifics occur at high density. During 2012 and 2013, 162 North Dakota wetlands and lakes were sampled for salamanders. Fifty-one contained A. mavortium populations; four of these contained cannibalistic morph individuals. Two populations with cannibalistic morphs occurred at sites with high abundances of conspecifics. However, the other two populations occurred at sites with unexpectedly low conspecific but high fathead minnow [Pimephales promelas (Rafinesque, 1820)] abundances. Further, no typical morphs were observed in either of these later two populations, contrasting with earlier research suggesting cannibalistic morphs only occur at low frequencies in salamander populations. Another anomaly of all four populations ...

Phenotype-dependent mate choice in Propylea dissecta and its fitness consequences

Sexual selection in relation to male or female polymorphism has been investigated across the taxa. However, how polymorphism influences sexual selection has been investigated less in most organisms including ladybirds, with most studies in the latter on mating incidences in the field. Laboratory studies on morph-dependent sexual selection in ladybirds have assessed resultant reproductive performance but not consequences on offspring attributes, as well as maintenance of polymorphism. In the current study, we assessed mate choice in a dimorphic ladybird, Propylea dissecta, and its effects on fitness in terms of reproductive performance and offspring development. Females mate significantly more readily with typical darker morphs than with pale ones. Whether this is female choice or male–male competition requires more investigation. Better reproductive performance and increased offspring development and survival in monomorphic typical pairs indicated fitness benefits for individuals obtaining typical mates. Typical females had higher fecundity and their offspring developed faster and survived better than those of pale females. Females paired with typical males had higher egg hatchability than those paired with pale ones. Significantly more offspring of dimorphic pairs were of typical phenotypes whereas offspring of monomorphic pairs expressed the same phenotype as their parents. Female preference for typical males and the dominance of the typical trait likely explain the preponderance of typical morphs in the field.

Report on Some Remarkable Specimens with Unusual Color Morph Recorded from Two Species of Snakes (Reptilia: Serpentes) from Gujarat, India

The report is about abnormal individuals of Lycodon aulicus and Bungarus caeruleus exhibiting variation from the «typical morphs» of their respective species. First report about partial albinism observed in Bungarus caeruleus , which is a rare phenomenon in the species. All the specimens were found from the urban centers of Gujarat State, western India.

Report of certain noteworthy specimens and species of herpetofauna from South-east India

We report abnormal individuals of Ramanella variegata , Lycodon aulicus (sensu lato), Bungarus caeruleus which exhibited variation from the 'typical morphs' of their respective species. Also we report a rarely recorded species Polypedates cf . leucomystax (from south India), from the Mannampandal area of Tamil Nadu. These observations based on voucher photographs are presented for the first time. Keywords: Morph; aberration; variation; phenotypic plasticity; polymorphism DOI: http://dx.doi.org/10.4038/tapro.v3i1.3227 TAPROBANICA , April, 2011. Vol. 03, No. 01: pp. 5-10

Buoyancy studies of three morphs of the Antarctic fish Trematomus newnesi (Nototheniidae) from the South Shetland Islands

Phenotypic plasticity, a widespread phenomenon in boreal freshwater fishes, is less apparent in the marine realm and the organism–environment interactions producing this variation are undetermined. A sample of 40 specimens of Trematomus newnesi, an inshore Antarctic fish from King George/25 de Mayo Island in the South Shetlands, was composed of 52.5% typical morphs, 27.5% large-mouth morphs and 20% intermediate morphs. Measurements of percentage buoyancy on the morphs of this sample were 3.73, 3.84 and 3.83%, respectively with no significant differences among means. Both mean dry skeletal weight as a percentage of body weight and mean oral jaw weight as a percentage of dry skeletal weight were significantly greater in large-mouth morphs compared to typical morphs. Diversification in head and jaw morphology is not accompanied by diversification in ecology as represented by buoyancy and, in spite of external appearances, measurements of buoyancy offer no support for the hypothesis that the large-mouth morph is more benthic than the typical semipelagic morph. Although a trophic basis for this polymorphism is possible, it has not yet been documented. Our discussion centers on the status of key open questions regarding morphism and highlights areas requiring more research.

Detection of a colonizing, aquatic, non‐indigenous species

ABSTRACTDetecting the presence of rare species has interested ecologists and conservation biologists for many years. A particularly daunting application of this problem pertains to the detection of non‐indigenous species (NIS) as they colonize new ecosystems. Ethical issues prevent experimental additions of NIS to most natural systems to explore the relationship between sampling intensity and the detection probability of a colonizing NIS. Here we examine this question using a recently introduced water flea, Cercopagis pengoi, in Lake Ontario. The species has biphasic population development, with sexually‐produced ‘spring morphs’ developing prior to parthenogenetically‐produced ‘typical’ morphs. Thus, this biphasic morphology allows distinction between new colonists (spring morphs) from subsequent generations. We repeatedly sampled Hamilton Harbour, Lake Ontario for the presence of both spring and typical morphs. Probability of detection was positively related to both the number of samples taken and animal density in the lake; however, even highly intensive sampling (100 samples) failed to detect the species in early spring when densities were very low. Spatial variation was greatest when densities of Cercopagis were intermediate to low. Sub‐sampling, which increased space between adjacent samples, significantly decreased the number of samples required to reach greater, calculated detection probabilities on these dates. Typical sampling protocols for zooplankton have a low probability (< 0.2) of detecting the species unless population density is high. Results of this study suggest that early detection of colonizing, aquatic NIS may be optimized through use of a risk‐based sampling design, combined with high sampling intensity in areas deemed most vulnerable to invasion, rather than less intensive sampling at a wider array of sites.

Population Structure of Ambystoma tigrinum mavortium in Playa Wetlands: Landuse Influence and Variations in Polymorphism

Playa wetlands are the major habitat for amphibians in the Southern Great Plains, USA. Agricultural cultivation causes playa sedimentation and related hydroperiod reduction in this intensively-farmed region, which in turn affects amphibian community structure. The goals of our study were (1) to investigate the influence of landuse on larval salamander (Ambystoma tigrinum mavortium) occurrence and densities in playas and whether hydroperiod length is an environmental influence on that occurrence, (2) to examine the polymorphic structure (cannibal, intermediate, and typical morphotypes) of larval salamanders and whether the frequency of occurrence of intermediate and typical morphs is associated with the presence of cannibal morphs and variations in hydroperiod length and conspecific density, and (3) to investigate morphological and life history trait differences among morphotypes (i.e., larval periods, growth rates, and body sizes). Cultivation of watersheds negatively affected presence and density of larval salamanders in playas, and this effect was associated with reduced hydroperiods. Although cannibal morphs were rare in playas, their presence negatively influenced presence of intermediate morphs and, thus, in this situation the majority of larvae were typical morphs. When cannibal morphs were absent, intermediate and typical morphs developed in similar proportions among playas with a tendency for intermediate morphs to predominate. Larval density and hydroperiod length were positively associated with the presence of cannibal morphs. Intermediate morphs had distinct growth patterns compared to cannibal and typical morphs and had body size measures (snout-to-vent length and stomach size) in between the two extreme morphs. Cannibal morphs grew faster and reached larger body size at metamorphosis than non-cannibal morphs. When cannibal morphs were absent, intermediate and typical larvae reached larger sizes than when cannibal morphs were present. We conclude that cultivation surrounding playas can negatively influence Ambystoma occurrence in general and especially the cannibal morphotype by reducing wetland hydroperiod. Moreover, a polymorphic community structure in larval amphibians may be important to a properly functioning playa food web.

Feeding ecology of polymorphic larval barred tiger salamanders in playas of the Southern Great Plains

In playas of the Southern Great Plains, larval barred tiger salamanders ( Ambystoma tigrinum mavortium Baird, 1850) (= Ambystoma mavortium mavortium ) are present as polymorphic populations. Typical and cannibal morphs have been previously investigated but intermediate forms have received little attention and their role in playa food web structure is unknown. We investigated the diet composition of these three morphotypes and compared diet preferences of typical versus nontypical morphs. Typical and intermediate morphs had similar body morphology (snout to vent length and stomach content mass), but cannibal morphs had larger stomach content mass than the other morphotypes. However, the intermediate morph had a distinctive diet composition from cannibal and typical individuals as determined by diet composition rankings, diet overlap and similarity indices, and diet diversity. By comparing prey availability versus consumption, we determined that nontypical morphs preferred larger invertebrates such as tadpole shrimps (Triopsidae) and fairy shrimps (Streptocephalidae), whereas typical morphs preferred smaller prey taxa like ostracods (Cyprididae) and water boatmen (Corixidae). Several prey taxa were avoided by all larvae suggesting that feeding in A. t. mavortium in playas is not opportunistic. Our study demonstrates that larval A. t. mavortium are present not only as dimorphic but also as polymorphic populations in playas and indicates that identifying these morphs is essential for the proper understanding of aquatic food webs.

Typicality effects in face and object perception: Further evidence for the attractor field model

In a previous study, it was shown that a 50/50 morph of a typical and an atypical parent face was perceived to be more similar to the atypical parent face than to the typical parent face (Tanaka, Giles, Kremen, & Simon, 1998). Experiments 1 and 2 examine face typicality effects in a same/different discrimination task in which typical or atypical faces and their 80%, 70%, 60%, and 50% morphs were presented sequentially (Experiment 1) or simultaneously (Experiment 2). The main finding was that in both modes of presentation, atypical morphs were more poorly discriminated than their corresponding typical morphs. In Experiment 3, typicality effects were extended to the perception of nonface objects; in this instance, it was found that 50/50 morphs of birds and cars were judged to be more similar to their atypical parents than to their typical parents. These results are consistent with an attractor field model, in which it is proposed that the perception of a face or object stimulus depends not only on its fit to an underlying representation, but also on the representation's location in the similarity space.

Drastic growth effect may explain sympatric cannibalistic polymorphism

Cannibalistic polyphenism is observed in many fishes and amphibians. In the case of amphibian larvae, cannibal morph and typical morph coexist. Benefits and costs of the cannibal morph have been studied empirically but the mechanism of the maintenance of polymorphism is not well known. Here, we construct a game model of typical and cannibal morph strategies to obtain the condition of stable coexistence. Generally, once an individual succeeds in cannibalism, it grows very quickly, which facilitates the next cannibalism. In a model without this ‘drastic growth effect’, stable coexistence cannot occur. To represent drastic growth effect, it is assumed that cannibal/typical morph stage is followed by giant/normal stage. A cannibal morph that performs cannibalism in the first stage can become a ‘giant’ in the next stage. This model allows stable coexistence of cannibal and typical morphs. The condition for coexistence is that payoff of a giant is two times larger than normal individuals. As long as direct consumption of victim's body is considered as reward for successful cannibalism, coexistence cannot be explained. When the reward is considered as social standing of being outstanding size in a population, sympatric cannibalistic polymorphism is possible, without regard to the initial size variation or resource shortage.

Heterospecific Prey and Trophic Polyphenism in Larval Tiger Salamanders

Polyphenisms (environmentally cued polymorphisms) are ubiquitous, yet the specific proximate mechanisms producing alternative morphs are generally not well known. We tested hypotheses for the role of large heterospecific prey in the cannibalistic polyphenism within larval tiger salamanders, Ambystoma tigrinum nebulosum, to determine whether heterospecific prey directly or indirectly influence the production of cannibal morphs. Field surveys suggested, and laboratory experiments confirmed, that macroinvertebrate prey induce cannibals via an increase in body size variation within larval salamander populations. Dietary data and laboratory foraging experiments revealed that cannibals preferred conspecifics even when their capture success was greater on macroinvertebrates. Typical morphs, in contrast, consumed only macroinvertebrate and other prey and never successfully cannibalized conspecifics. Our results support the indirect hypothesis that cannibals are induced via increased body size variation within a population of larvae, as a result of differential consumption of large heterospecific prey, and do not rely on consumption of heterospecific prey once they are cannibals. The cannibalistic polyphenism is one example of phenotypic plasticity in which the functional significance and the proximate mechanisms producing the two morphs are becoming clearer, allowing further study of the molecular and physiological basis of the alternative phenotypes.

Shifts in Life-History Traits as a Response to Cannibalism in Larval Long-Toed Salamanders ( Ambystoma macrodactylum )

We examined the potential influence of cannibalism on life-history characteristics of larval long-toed salamanders (Ambystoma macrodactylum). Using a 2 × 2 factorial design, crossing morphology with diet, we exposed typical morph larvae to one of four types of stimulus animals: cannibal morphs fed a conspecific diet, cannibal morphs fed a heterospecific diet (i.e., Tubifex), typical morphs fed a conspecific diet, and typical morphs fed a heterospecific diet. Test larvae exposed to stimulus animals fed a conspecific diet exhibited a slower growth rate and an increase in the time taken to reach metamorphosis. These changes in life history likely represent a cost of antipredator behavior.

Head and Body Size Relationships in Polymorphic Tiger Salamander Larvae from Colorado

Trophic polyphenism in certain species of salamanders seems to have developed specifically for cannibalism (Powers, 1907; Collins and Holomuzki, 1984; Crump, 1992). The morph of Ambystoma tigrinum larvae is characterized by its larger body size, broader head, and enlarged vomerine tooth patch in comparison with the larval morph (Powers, 1907; Rose and Armentrout, 1976). These traits provide cannibals with the ability to consume conspecifics as well as large heterospecific prey (Loeb et al., 1994; Maret and Collins, 1996). The range of A. tigrinum extends from coast to coast in North America (Rose and Armentrout, 1976; Stebbins, 1985); however, the cannibal morph of this species has been documented only in midwestern and western populations: Nebraska (Powers, 1907), Oklahoma (Glass, 1951), Arizona (Gehlbach, 1967), Colorado (Reese, 1969), Texas (Rose and Armentrout, 1976), Iowa (Lannoo and Bachmann, 1984), and Indiana (D. Pfennig and H. Whiteman, unpubl. data). The nonuniform distribution of this trophic polymorphism suggests the potential for behavioral and morphological variation among populations of the A. tigrinum complex in North America, as well as variation in the selection pressures influencing cannibalism (Rose and Armentrout, 1976; Collins et al., 1980; Collins et al., 1993). There also appears to be variation across cannibalistic populations with respect to morphological characters, particularly those involved in the relationship between head shape and body size [e.g., populations from Texas (Pierce et al., 1983), Iowa (Lannoo and Bachmann, 1984), Arizona (Collins et al., 1993), and Colorado (this study)]. Pierce et al. (1983) envisioned three processes that may contribute to the development of the large head characteristic of the cannibal morphology (Fig. 1). Each hypothesis depends on the relationship between head size and body size, estimated using regression analysis. In the first hypothesized process, positive allometry results in a proportionately larger head in the largest individuals, which are cannibalistic; thus, the regression lines of both morphs should have similar slopes that are greater than one (Fig. 1A). The difference observed in the head size of the two morphs would simply be a result of the cannibal morph's larger body size. A second possibility is that cannibals exhibit a faster rate of head growth than that experienced by typicals, and thus the slope of the cannibal regression line should be greater than that of the typical morphs (Fig. 1B). In the third scenario, cannibals experience a rate of head growth that is high early in ontogeny but then reduced during later stages of development to a level similar to or less than that of typicals. This process would result in a greater y-intercept for the cannibal morph regression (Fig. 1C). Pierce et al. (1983) also suggested that some combination of these hypotheses might operate under some conditions (i.e., the processes are not mutually exclusive). In this study, we quantify the relationship between head size and body size in cannibal and typical A. tigrinum larvae from south-central Colorado. Although the relationship between head and body size can be explored using measurements of various head dimensions, gape width (width of head atjawjoint) holds particular relevance. Gape width is an important determinant of foraging success in A. tigrinum because it directly influences the type and sizes of prey that can be ingested (Loeb et al., 1994; Maret and Collins, 1996). We compare the head/body size relationship of our Colorado population to data published for other populations of this species [i.e., Texas (Pierce et al., 1983), Iowa (Lannoo and Bachmann, 1984), and Arizona (Collins et al., 1993)] with respect to the hypotheses outlined above. We also suggest possible explanations for apparent geographic differences in this relationship across populations.

Eastern Long‐toed Salamander (Ambystoma macrodactylum columbianum) Larvae Recognize Cannibalistic Conspecifics

AbstractLarval eastern long‐toed salamanders, Ambystoma macrodactylum columbianum, exhibit trophic polymorphism whereby some individuals (referred to as cannibal morphs) possess a cannibalistic morphology and others (referred to as typical morphs) do not. In a series of laboratory experiments, we documented that typical morphs show an antipredator response when exposed to cannibal morphs but not when exposed to other typical morphs. The antipredator response of the typicals was not dependent on the cannibals being fed conspecifics, as has been shown in other predator‐prey systems. In our experiments, the typicals responded regardless of whether the cannibals had been fed a diet of conspecifics or live Tubifex. Further experiments also showed that in the absence of visual cues, typicals still responded with an antipredator response. However, when only visual cues were available, typicals failed to exhibit a response. This suggests that chemical and/or mechanical cues are of prime importance in cannibal recognition by long‐toed salamander larvae.