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We describe for the first time reproductive behaviors in the Pirate Perch (Aphredoderus sayanus), a secretive nocturnal fish whose urogenital opening is positioned far anteriorally, under its throat. Some naturalists had speculated that this peculiar morphological condition might serve to promote egg transfer to the fish's branchial chamber for gill-brooding; others hypothesized that Pirate Perch spawn in the substrate of streams but offered no adaptive rationale for the odd placement of the fish's urogenital pore. Here we solve the conundrum through a combination of intensive field investigations, underwater filming, and molecular parentage analyses. We show that Pirate Perch spawn in underwater root masses, the first documentation of such nesting behavior in any species of North American fish. Female Pirate Perch thrust their heads and release their eggs into sheltered canals of these masses. Males congregate at these sites and likewise enter the narrow canals headfirst, to release sperm. Thus, the forward-shifted urogenital pore may facilitate spawning under this special nesting circumstance. We found no evidence of extended parental care. Fish formed their own canals or used burrows made by aquatic macro-invertebrates and salamanders. Genetic analyses based on three polymorphic microsatellite loci demonstrate that a total of at least five to 11 sires and dams were the parents of embryos within each of three assayed root-mass nests (of a total of 23 nests found). Males defended the oviposition sites by body-plugging canal entrances after spawning. This and more direct aggressive behaviors by males probably relate to selection pressures imposed by intense competition for fertilization success under these group-spawning conditions.
Introduced American Bullfrogs (Rana catesbeiana) have become widely established in the Pacific Northwest over the last century and are thought to be an important predator of native amphibians throughout the western United States. The Northern Red-Legged Frog (Rana aurora aurora) and Oregon Spotted Frog (Rana pretiosa) historically coexisted in portions of the Pacific Northwest now invaded by R. catesbeiana, but R. pretiosa has declined more severely than R. a. aurora. We investigated whether microhabitat and behavioral differences that facilitate sympatric coexistence of the natives predict which species is more susceptible to predation by introduced R. catesbeiana. Our laboratory experiments demonstrate that R. catesbeiana adults prefer aquatic microhabitats, that R. pretiosa juveniles are more aquatic than R. a. aurora, and that adult R. catesbeiana consume more R. pretiosa than R. a. aurora juveniles. Mean and maximum jump distances of R. pretiosa were shorter than equally sized R. a. aurora, and the difference between these two species increased with larger frog sizes. Our examination of field survey data indicates that R. pretiosa coexist with R. catesbeiana less frequently than R. a. aurora. We conclude that R. catesbeiana is a greater threat to survival of R. pretiosa than to R. a. aurora and suggest that microhabitat use and escape abilities of native ranid frogs may be linked to this asymmetrical effect. Analysis of behavioral and microhabitat differences among related native species may be a useful tool in predicting the effects of introduced predators on amphibians and can assist in developing conservation priorities for these species.
This study provides the first detailed description of the events at hatching for an anamniotic vertebrate egg. California Grunion are ideally suited for this study, because these fish eggs incubate fully terrestrially and delay hatching until presented with an environmental trigger. Grunion eggs can be induced to hatch on demand within a few minutes, by mechanical agitation in seawater. We suggest that the process of hatching in grunion involves an enzymatic weakening of the chorion followed by the embryo's active efforts to escape. Using a dissecting microscope, microscope camera, and digital video camera, we compared embryonic movements within the chorion prior to hatching. Then, we recorded the exact moment of hatching with digital video to identify events that occur consistently. Prior to exposure to the hatching trigger, Grunion embryos move minimally within the egg. After the hatching trigger, embryos significantly increase the amount and types of movements within the egg. The chorion distorts in a location superior to the caudal region, and fluid escapes from the egg. Embryonic activity usually culminates in a vigorous tail lash that splits the chorion open. Ultimately, usually within two minutes, the Grunion larva emerges from the chorion into its new aquatic environment.
We examined trade-offs between current reproduction and future reproductive potential in a terrestrial salamander (Plethodon cinereus) in outdoor enclosures. We raised females that differed in brooding status under manipulations of food level and tail condition in two years (1993 and 1994), and measured the effects of our treatments on current reproductive success (egg survival) and indicators of future reproductive potential (female growth and production of ova). Current reproductive success depended strongly on clutch size but not resource availability. Brood abandonment was higher among females with small clutches. Both brooding status and tail condition affected future reproductive potential. Brooding females gained less mass and produced fewer new ova than nonbrooders. Tail loss resulted in increased tail regeneration but decreased production of new ova. These strong main effects were consistent between years, despite differences in experimental protocol and limited sample sizes. Food levels affected female growth only in interaction with brooding status, and these effects differed between years. Gain in mass was affected by this interaction more strongly in 1993 than in 1994, and tail regeneration was only affected in 1994. Understanding costs of reproduction in natural populations will require understanding how the condition of both the organism and its environment influence energy allocation to current reproduction and different components of future reproductive potential.
In ectotherms, age, and length at maturity typically decrease with an increase in temperature; however, it is unclear whether this occurs in the absence of accelerated juvenile growth rates that are usually associated with warmer thermal regimes. We investigated whether (1) life-history traits are affected by temperature in the absence of a growth effect, and (2) faster growth rates cause a reduction in age and size at maturity. Japanese Medaka were exposed to temperatures of 24, 27, 30, and 33 C and fed either ad libitum rations (at all temperatures) or limiting rations (at higher temperatures) to equalize growth rates across thermal regimes. Both age and size at maturity decreased as rearing temperature increased from 24 to 30 C, even when somatic growth rates were equivalent. However, age and length at maturity actually increased with a further temperature increase from 30 to 33 C. Medaka given ad libitum rations grew faster and matured earlier and at a larger size than those given limiting rations and reared at the same temperature. We conclude that temperature can affect the life-history traits of fishes independently of any effect of temperature on somatic growth. However, the direction of the effect may be reversed when the temperature approaches the maximum tolerance of the species and when food availability is low enough to impose severe limits on the amount of surplus energy available to the fish. In this case, the unexpected reversal of life-history effects at the highest temperature may have been caused by the disturbance of normal gonadal development in Medaka.
A new species of colubrid snake, genus Drymoluber, is described from three localities (1920–3300 m elevation) in southeastern Peru (Departamento de Apurímac). The characteristics of the new species include dorsal scales smooth with two apical pits, in 13 rows throughout body; 14–16 maxillary teeth; one preocular; two postoculars; one anterior and two posterior temporals; anal plate entire; ventrals 158–182; subcaudals 82–92; and a dorsal pattern of transverse blackish blotches (1.0–1.5 scales wide) and narrower hazelnut brown interspaces (2.0–2.5 scales wide) in juveniles, whereas adults are dorsally uniform olive-grey and ventrally yellowish-grey. The new species differs from all species of the genus in number of dorsal scales, number of temporals, number of maxillary teeth, and in several aspects of coloration and pattern.
Phylogenetic relationships within the studfish clade, subgenus Xenisma, were elucidated using parsimony analysis of 21 morphological transformation series, primarily osteology and external morphology. The analysis supports monophyly of subgenus Xenisma and the studfishes sensu strictu (Fundulus bifax, Fundulus catenatus, and Fundulus stellifer). Fundulus julisia and Fundulus albolineatus are recognized as sister taxa and together are recognized as sister to the F. bifax, F. catenatus, and F. stellifer clade. Contrary to a previous allozyme study of the subgenus, Fundulus rathbuni is recognized as sister to a monophyletic group composed of all other Xenisma species. This relationship is biogeographically consistent with the vicariant pattern previously demonstrated within darters of the subgenus Percina and suckers of the genus Hypentelium. The biogeography of the rest of subgenus Xenisma is complex and the sister-group relationship between F. catenatus and F. bifax is recognized as anomalous when compared to other Mississippi-Mobile basin biogeographic relationships in North American fishes.
A specimen of Encheliophis was found in the coelomic cavity of a sea cucumber in Moorea (French Polynesia). The skeletal morphology (skull, girdles, vertebrae) reveal it to be a new species, described herein as Encheliophis chardewalli. It is separable from all described species of Encheliophis (except Encheliophisvermicularis) by the lack of pectoral fins and from E. vermicularis by the larger and fewer teeth on the lower jaw (14 vs more than 20 in E. vermicularis) and by seven branchiostegal rays (vs six in E. vermicularis).
Moenkhausia bonita, new species, is described from the Rio Baía Bonita, a tributary of the Rio Miranda, Rio Paraguay basin, Bonito, Mato Grosso do Sul, southwestern Brazil. The new species is distinguished from all congeners by the combination of the presence in alcohol-preserved specimens of a black midlateral stripe, a black posterior margin on each caudal fin lobe, the presence of a black lozenge-shaped blotch on the caudal peduncle that extends to the posterior limit of the median caudal fin rays, and the presence of seven gill rakers on the upper limb and 12 gill rakers on the lower limb of the first gill arch. Comments are included on the phylogenetic placement, ecology, and behavior of the species.
A new deep-sea ceratioid anglerfish of the genus Oneirodes Lütken is described on the basis of three specimens collected from off Hawaii, Japan, and the southwest coast of Taiwan. The new species, Oneirodes pietschi, should belong to the member of the Oneirodes schmidti-group, in having a relatively long illicium and subopercular bone. It differs from all known species of the O. schmidti-group, as well as from all previously described species of the genus, in details of its escal morphology.
Steatogenys ocellatus sp. nov. is described from the lowland Amazon basin at localities near Tefé (Brazil) and Iquitos (Peru). This species is described using features of external morphology, meristics, pigmentation, osteology, and the electric organ discharge. The new species is diagnosed by (1) a relatively large maximum body size (maximum length to end of anal fin 320 mm vs 172 mm in other species); (2) a distinctive round or oval spot on the pectoral-fin base; and (3) irregular dark blotches on the pectoral fin forming a mottled pattern. Several morphometric and meristic features also unambiguously distinguish S. ocellatus sp. nov. from the two known congeners, Steatogenys elegans and Steatogenys duidae. Steatogenys elegans is common in riverine and lacustrine habitats throughout the lowland Amazon and Orinoco basins and the Guyanas. Steatogenys duidae is found in terra firme forest creeks throughout the Amazon and Orinoco basins. Steatogenys ocellatus sp. nov. inhabits static or slow-flowing habitats such as seasonally flooded forests in low conductivity blackwater systems. In the Tefé region it is found in sympatry with S. elegans and S. duidae but in syntopy only with the former.
A new species of silurid catfish in the genus Wallago is described from the Mekong River drainage in Cambodia, Laos and Thailand, and the Chao Phraya River drainage in Thailand. Wallago micropogon can be distinguished from congeners in having a unique combination of the following characters: pelvic-fin length 8.9–10.6% SL, pectoral-spine length 14.3–16.7% SL, eye diameter 8.7–10.1% HL, maxillary barbels reaching to middle of pectoral-fin base, branchiostegal rays 14–16, gill rakers on first branchial arch 14–16, anal-fin rays 68–73, vertebrae 63–65, brown color with few pale patches on sides of body, gape extending to anterior margin of eye, and a broadly rounded pectoral fin with fourth branched ray longest.
The deep-sea ceratioid anglerfish genus Bufoceratias Whitley is revised on the basis of all known material. Three species are recognized: Bufoceratias wedli (Pietschmann), now represented by 69 specimens collected from both sides of the Atlantic Ocean; Bufoceratias thele (Uwate), 11 specimens from the western Pacific; and a new species, Bufoceratias shaoi, described on the basis of four specimens from the Western Indian and Western Pacific oceans. The new species differs from its congeners by having a short illicium and an unusually large and morphologically complex esca. Diagnoses and descriptions are given for all taxa and a revised key to the species of the genus is provided. Diceratiids are found in all three major oceans of the world, but they are conspicuously absent from the eastern Pacific. In contrast to the midwater life style generally assumed for most ceratioids, at least some diceratiids, especially larger individuals, are associated with the bottom.
As a part of the general revision of anguilliform clariid genera and species, the status of Dolichallabes microphthalmus Poll, 1942, is reviewed, based on morphology and osteology of all available museum specimens. Dolichallabes microphthalmus, the most elongate species within the Clariidae, has been redescribed. Compared to Channallabesapus and Gymnallabestypus, D. microphthalmus is characterized by, in addition to some meristic differences, an elongate body, reduced skull ossification, with (1) one elongate fontanel, (2) antorbital and infraorbital IV the only circumorbital bones present, (3) only one or two suprapreopercular bones on each side, and (4) a sphenotic bearing only one process. Osteological evidence suggests that D. microphthalmus could be considered a paedomorphic clariid.
A new species of the deep-sea dragonfish genus Eustomias is described from 14 specimens from the western North Atlantic. This species belongs to the subgenus Neostomias, which is defined principally by the presence of a single pectoral ray, plus one small rudimentary ray. It is unique among members of the subgenus in having a combination of characters that includes a short mental barbel, multiple proximal bulbs on the barbel main stem, and a unique terminal bulb morphology. Analysis of similar species warrants resurrection of Eustomias monodactylus, previously placed in synonymy with Eustomias filifer. A revised key to the species of the subgenus Neostomias is provided.
Pietschichthys horridusKharin, 1989, of the lophiiform suborder Ceratioidei, family Oneirodidae, is shown to be a junior synonym of Dermatiasplatynogaster Smith and Radcliffe, in Radcliffe, 1912, the latter now known only from the two holotypes, one collected from off the east coast of Luzon in the Philippines, the other from the Magellan Seamounts in the western North Pacific Ocean. The genus and only known species are diagnosed and redescribed, and a revised key to the genera of the Oneirodidae is provided.
Leptodactylus fallax is an endangered frog (Leptodactylidae) found only on Montserrat and Dominica in the eastern Caribbean. Here we report the first captive breeding of this species and document a unique reproductive strategy with an unprecedented level of maternal care. Male frogs fought and dominant animals occupied a nesting burrow. Males enticed females into the burrow with a trilling bark call (100–120 calls/min). A terrestrial foam nest was produced after 9–14 h. Female frogs remained close to their foam nests and defended them aggressively throughout larval development (42–57 days). Females fed larvae (26–43 per nest) trophic (unfertilized) eggs. Many provisioning events (10–13) were recorded, supplying a total of 10,000—25,000 eggs. Male frogs also remained close to the burrow and defended the site. Trophic eggs were the exclusive food source for the developing larvae, and L. fallax is therefore probably displaying a new form of amphibian endotrophy.
This study uses allele frequency and genotype array data from allozyme electrophoresis to investigate the phylogeographic and taxonomic affinities of groups within the salamander genus Pseudobranchus. Phylogenetic and population genetic analyses of the allozyme data confirm the validity of the two currently recognized species (Pseudobranchus axanthus from peninsular Florida and Pseudobranchus striatus from central and northern Florida, Georgia, and South Carolina). In concert with biogeographic data for other freshwater taxa, these analyses further support the recognition of western, southeastern, and northeastern phylogeographic groups within P. striatus. These species and phylogeographic groups offer new insights into the evolutionary history of this endemic genus in the southeastern United States and the taxonomic status of its nominal subspecies.
Determining the consequences of body size and body temperature (Tb) variation is critical to understanding many aspects of snake ecology, because size and temperature play such important roles in the biology of ectotherms. Here, we investigate the effects of body size and temperature variation on the energetics of the largest species of rattlesnake, the Eastern Diamondback Rattlesnake (Crotalus adamanteus). Specifically, we measured oxygen consumption to estimate the standard metabolic rate (SMR) of five C. adamanteus (mass range 800–4980 g) at 5-degree increments from 5–35 C. A multiple regression model indicated that SMR increased with body size and temperature. Q10s were generally high (range 1.82–4.20) compared to other squamates but were similar to the high values calculated for other large rattlesnakes. An energy balance model for C. adamanteus predicted that as Tb increases, so must prey consumption to meet annual SMR energy demands. Thus, Tb variation likely affects patterns of energy acquisition and use and, in turn, influences processes such as growth and reproduction.
The spotted salamander (Ambystoma maculatum) is a pool-breeding species thought to depend on small mammal burrows for survival in terrestrial habitats. We investigated burrow occupancy patterns using laboratory and field experiments where salamanders were housed alone or in pairs, in arenas with either one or two burrows. In the single-burrow field experiment, intruders were significantly less likely than residents to occupy burrows, and the probability of burrow occupancy declined following nighttime rain. However, spotted salamanders frequently co-occupied burrows (mean burrow co-occupancy rate, 59%). In the single-burrow laboratory experiment, mean burrow occupancy rate was 98%, both when salamanders were housed alone and in pairs. However, salamanders housed in pairs with two burrows co-occupied burrows less frequently than expected by chance, and greater size disparity was associated with lower burrow co-occupancy rates. Our results suggest that spotted salamanders may often fail to effectively defend burrows and exclude conspecifics, although avoidance of occupied burrows could, in some contexts, affect spacing in terrestrial habitats.
Many anurans are thought to be territorial only during breeding; thus these species should exhibit seasonal differences in social behavior. Aggressive behavior and site tenacity, two components of territoriality, were examined in male Rana clamitans (Green Frogs) to test for differences between breeding and nonbreeding seasons. I predicted that aggression and site tenacity should be increased during the breeding season and reduced during the nonbreeding season. Aggression (male wrestling) was observed only during the breeding season. Males moved at a constant rate regardless of size (snout–vent length) or season (breeding or nonbreeding); however, males moved greater total distances during the breeding season but restricted movements to small areas throughout the nonbreeding season.
In territorial salamanders and lizards, tail loss may immediately reduce the resource holding power (RHP) of residents, making defense of territories more difficult. Residents of the Red-Backed Salamander, Plethodon cinereus, defend territories using scent marks and agonistic displays. We examined (1) the marking behavior of tailed and tailless residents when establishing new territories, and (2) the behavioral responses of intruders to chemical cues produced by tailed and tailless residents. In the first experiment, we counted the number of postcloacal presses (PCP: a scent-marking behavior) by tailed and tailless salamanders (future residents) placed into unmarked test chambers. Tailless salamanders performed significantly more PCPs than tailed salamanders. Increased marking may have provided a benefit for tailless residents: tailed intruders, when placed in chambers marked by tailless residents, showed significantly less aggression when the residents performed more PCPs. In the second experiment, we observed the agonistic behavior of intruders placed into test chambers previously occupied by tailed or tailless residents. Tailed, but not tailless, intruders were significantly less aggressive in chambers marked by tailed residents than in chambers marked by tailless residents. Our results suggest that scent marks, in the absence of visual cues, provide intruders with information associated with tail condition (e.g., RHP) of residents.
We examined the role of habitat complexity in influencing predator–prey interactions between fish and tadpoles. Tadpoles of the Squirrel Treefrog (Hyla squirella) and the Eastern Narrow-Mouth Toad (Gastrophryne carolinensis) were exposed to Eastern Mosquitofish (Gambusia holbrooki) under different degrees of habitat complexity (no cover, low cover, and high cover) in a randomized block, replicated, controlled experiment using wading pools. This study indicates that Gambusia can quickly and dramatically impact tadpole populations even at low predator densities and can forage effectively in vegetated areas that might normally serve as prey refugia from larger predatory fish (e.g., Lepomis spp.). Moreover, the influence of habitat complexity on predator-prey interactions may be species-specific. The number of H. squirella tadpoles consumed was not affected significantly by the degree of habitat complexity; however, consumption of G. carolinensis by Gambusia decreased with increasing habitat complexity. We attribute this finding to the observation that G. carolinensis are less active than H. squirella and, therefore, more difficult for Gambusia to detect with increasing habitat complexity.
The reptile immune response is performed by a well-developed immune system whose leukocytes have been characterized as lymphocytes, monocytes and granulocytes. A main characteristic of the reptile immune system is the effect of the seasonal cycle on its histology and function, as has been reported in the turtle Mauremys caspica. In the present study, we have assessed the presence of lymphocytes in the main lymphoid tissues (blood, spleen, and thymus) searching for putative seasonal variations and sex-associated differences in lymphoid distribution. Our results show that lymphocytes are the most commonly observed leukocyte subpopulation in blood. The highest percentages of blood lymphocytes were obtained in spring. Lymphoid tissues showed higher proportions of lymphocytes in spring and summer. Finally, females showed higher lymphocyte proportions than males in the spleen during spring and in the thymus during summer. Summarizing, the lymphoid redistribution of M. caspica is affected by the seasonal cycle. The major proportion of lymphocytes was obtained in spring and summer; the seasonal periods when these turtles are more active, and the risk of infections is higher.