Showing papers in "Copeia in 1988"
983 citations
TL;DR: This volume constitutes a series of invited chapters based on presentations given at an International Conference on the Sensory Biology of Aquatic Animals held June 24-28, 1985 at the Mote Marine Laboratory in Sarasota, Florida.
Abstract: This volume constitutes a series of invited chapters based on presentations given at an International Conference on the Sensory Biology of Aquatic Animals held June 24-28, 1985 at the Mote Marine Laboratory in Sarasota, Florida. The immediate purpose of the conference was to spark an exchange of ideas, concepts, and techniques among investigators concerned with the different sensory modalities employed by a wide variety of animal species in extracting information from the aquatic environment. By necessity, most investigators of sensory biology are specialists in one sensory system: different stimulus modalities require different methods of stimulus control and, generally, different animal models. Yet, it is clear that all sensory systems have principles in common, such as stimulus filtering by peripheral structures, tuning of receptor cells, signal-to-noise ratios, adaption and disadaptation, and effective dynamic range. Other features, such as hormonal and efferent neural control, circadian reorganization, and receptor recycling are known in some and not in other senses. The conference afforded an increased awareness of new discoveries in other sensory systems that has effectively inspired a fresh look by the various participants at their own area of specialization to see whether or not similar principles apply. This inspiration was found not only in theoretical issues, but equally in techniques and methods of approach. The myopy of sensory specialization was broken in one unexpected way by showing limitations of individual sense organs and their integration within each organism. For instance, studying vision, one generally chooses a visual animal as a model.
664 citations
TL;DR: Age and growth of fish, Age and growing of fish , مرکز فناوری اطلاعات و اشاوρزی رسانی, ک اوشا�رزات, £1,000, £2,500, and £3,000 are suggested to be reasonable guesses for the ages of these fish.
Abstract: Age and growth of fish , Age and growth of fish , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
252 citations
251 citations
TL;DR: Analysis of gut contents of museum specimens showed that lizards constitute a major fraction of prey taken by juvenile rattlesnakes, aiding in the digestion of prey in a thermally variable environment, which facilitates efficient handling of lizards and young rodents.
Abstract: Ontogenetic variation in venom composition was examined in the Pacific rattlesnakes Crotalus viridis helleri and C. v. oreganus. Venoms were analyzed for protease, phospholipase A2, L-amino acid oxidase, exonuclease and elastinolytic activities, and toxicity toward a native prey (Sceloporus graciosus). Protease activity increased significantly with size; L-amino acid oxidase and exonuclease activities also tended to increase. Phospholipase A2 activity decreased significantly with size, as did venom toxicity. These factors produce a highly toxic venom with low protease activity in juvenile snakes, which facilitates efficient handling of lizards and young rodents. Analysis of gut contents of museum specimens showed that lizards constitute a major fraction of prey taken by juvenile rattlesnakes. Lizards continue to be taken with high frequency until snakes reach approx. 500 mm in total length; above this size, mammals are taken exclusively. As snakes increase in size, they feed on larger mammalian prey, and a functionally different venom is produced. Venom from adult Pacific rattlesnakes is less toxic but has high protease activity, aiding in the digestion of prey in a thermally variable environment.
220 citations
TL;DR: The geographic and depth frequency distribution of 124 common demersal fish species in the northeastern Pacific were plotted from data on me at the Northwest and Alaska Fisheries Center (NWAFC), National Marine Fisheries Service.
Abstract: The geographic and depth frequency distribution of 124 common demersal fish species in the northeastern Pacific were plotted from data on me at the Northwest and Alaska Fisheries Center (NWAFC), National Marine Fisheries Service. The data included catch records of fishes and invertebrates from 24,881 samples taken from the Chukchi Sea, throughout the Bering Sea, Aleutian Basin, Aleutian
Archipelago, and the Gulf of Alaska, and from southeastern Alaska south to southern California. Samples were collected by a number of agencies and institutions over a 30-year period (1953-83), but were primarily from NWAFC demersal
trawls. The distributions of all species with 100 or more occurrences in the data set were plotted by computer.
Distributions plotted from these data were then compared with geographic and depth-range limits given in the literature. These data provide new range extensions
(geographic, depth, or both) for 114 species. Questionable extensions are noted, the depth ranges determined for 95% of occurrences, and depths of most frequent occurrence are recorded.
Ranges of the species were classified zoogeographically, according to life zone, and with regard to the depth zone of greatest occurrence. Because most species examined have broad geographic ranges, they do not provide the best information for testing the validity of proposed zoogeographic province boundaries. Because of the location of greatest sampling effort and methods used in sampling,
most fIShes examined were eastern boreal Pacific, sublittoral-bathyal (outer shelf) species. (PDF file contains 158 pages.)
204 citations
TL;DR: The phylogeny of hominoid phylogeny revealed by coevolution of molecules and morphologies in vertebrate phylogeny is reconstructed from comparisons of the genetic material, DNA and morphological data.
Abstract: Preface 1. Introduction Colin Patterson 2. Aspects of hominoid phylogeny Peter Andrews 3. Molecular and morphological analysis of high-level mammalian interrelationships Malcolm C. McKenna 4. Avian phylogeny reconstructed from comparisons of the genetic material, DNA Charles G. Sibley and Jon E. Ahlquist 5. Tetrapod relationships: the molecular evidence M. J. Bishop and A. E. Friday 6. Pattern and process in vertebrate phylogeny revealed by coevolution of molecules and morphologies Morris Goodman, Michael M. Miyamoto and John Czelusniak 7. Macroevolution in the microscopic world C. R. Woese 8. Divergence in inbred strains of mice: a comparison of three different types of data Walter M. Fitch and William R. Atchley Index.
180 citations
154 citations
TL;DR: In this article, the authors examined the long term stability of summer fish assemblages in three distinct systems: Piney Creek, a medium-sized Ozark upland tributary of the White River, Arkansas; Brier Creek and the Kiamichi River, a small prairie-margin stream draining into the Red River, Oklahoma, and concluded that at the level of whole-stream faunas, all three of these midwestern streams were stable across the survey years.
Abstract: Long term stability of summer fish assemblages was examined in three distinct systems: Piney Creek, a medium-sized Ozark upland tributary of the White River, Arkansas; Brier Creek, a small prairie-margin stream, tributary to the Red River, Oklahoma; and the Kiamichi River, a medium-sized river in the Ouachita Uplands draining into the Red River, Oklahoma. Sampling periods and numbers of surveys of the three stream systems were 14 yr and six collections for Piney Creek, 17 yr and five surveys for Brier Creek, and 5 yr and three surveys for the Kiamichi River. The fish faunas of all three streams were persistent (regarding presence-absence of species). In all three streams overall faunal structure was stable, as indicated by similarity indices and by concordance of rank abundance of the common species in each stream across all collection years. The results corroborated a conclusion from earlier work that the total fish fauna is more stable in a more environmentally benign stream (Piney Creek) than in a stream subject to greater environmental extremes (Brier Creek). The fish fauna of the Kiamichi River was also stable across three survey periods with respect to rank order of species abundance. Stability of the fish assemblages at individual locations on all three streams was variable, but four of five locations on Brier Creek, and all five locations on Piney Creek exhibited significant concordance overall in ranks of species abundance. Of 59 possible cases, assemblages at 27 individual locations (=46%) on the three streams showed assemblage stability >0.60 between survey periods. We conclude that at the level of whole-stream faunas, all three of these midwestern streams were stable across the survey years, and that many, but not all, individual locations had relatively stable fish assemblages.
140 citations
TL;DR: In the study area, green turtles grow more slowly than hawksbills, Eretmochelys imbricata, or loggerheads, Caretta caretta, of similar size, so equations were developed to convert carapace length or plastron length to mass so that growth in mass could be modeled from data for either linear parameter.
Abstract: Growth in carapace length, carapace width, plastron length and body mass was measured in 149 growth increments for 122 green turtles, Chelonia mydas, at Great Inagua, Rahamas. Initial carapace length of the 149 growth increments ranged from 28.3-75.5 cm. Absolute growth rates for all linear parameters decreased with increasing size, but no significant difference in absolute growth rates for body mass was noted over the size range measured. Equations were developed to convert carapace length or plastron length to mass so that growth in mass could be modeled from data for either linear parameter. Three sizespecific growth models-Von Bertalanffy, Gompertz and logistic-were tested for goodness of fit. The Von Bertalanffy model had the best fit for seven body size parameters. With increasing size, there was a significant negative allometric relationship between carapace width and carapace length, but the relationship between plastron length and carapace length was isometric. Growth rates were compared with those of other green turtle populations. In our study area, green turtles grow more slowly than hawksbills, Eretmochelys imbricata, or loggerheads, Caretta caretta, of similar size.
TL;DR: Age estimates were obtained using circulus counts for a total of 110 sharks, with a plot of precaudal length against estimated age for both sexes fitting a von Bertalanffy growth curve and showing that this species is slow growing and long-lived.
Abstract: Vertebral centra were removed from 55 tag-recaptured lemon sharks, Negaprion brevirostris, that had been injected intramuscularly with tetracycline hydrochloride at a dosage level of 12.5 mg/kg at the time of release. Tetracycline deposited at sites of active calcification on the vertebral centra served as a fluorescent marker along the periphery of each centrum at the time of injection. Thin growth zones, or circuli, were observed in ground and stained sections. A lunar periodicity of approx. 29 d was validated for circulus deposition. Precision of circulus counts was evaluated, with an index of average percent error of 3.4% for a single reader. Age estimates were then obtained using circulus counts for a total of 110 sharks, with a plot of precaudal length against estimated age for both sexes fitting a von Bertalanffy growth curve with the parameters Loo = 317.65, k = 0.057, and to = -2.302. The predicted age at maturity for males is 11.6 yr and for females is 12.7 yr. These results show that this species is slow growing and long-lived.
TL;DR: A seasonal cycle of the testis of the spurdog, Squalus acanthias, and the sites of 3B-hydroxysteroid dehydrogenase activity is described and a study of Urogenital morphology in the chimaeroid fish Hydrolagusiei is presented.
Abstract: ROMER, A. S. 1962. The vertebrate body. 3rd ed. W. B. Saunders Co., Philadelphia, Pennsylvania. SIMPSON, T. H., AND C. S. WARDLE. 1967. A seasonal cycle of the testis of the spurdog, Squalus acanthias, and the sites of 3B-hydroxysteroid dehydrogenase activity. J. Mar. Biol. Assoc. U.K. 47:699-708. STANLEY, H. P. 1963. Urogenital morphology in the chimaeroid fish Hydrolagus colliei (Lay and Bennett). J. Morph. 112:99-127. hark, Cetorhinus maximus (Gunner). Philos. Trans. . Soc. Lond., Ser. B. Biol. Sci. 234:247-316. EL INGER, J. 1965. Studes de la spermatogen se hez Scyliorhinus caniculus (L.). Description, donees histochimiques, variations normales et experi entals. Z Zellforsch. Mikroskop. Anat. 67:65373.
TL;DR: Effets de la duree d'assechement de la mare (manipulee experimentalement) sur la taille corporelle au moment de the metamorphose, le timing de la metamorphOSE, la survie apres metamorphoses chez A.t..
Abstract: Effets de la duree d'assechement de la mare (manipulee experimentalement) sur la taille corporelle au moment de la metamorphose, le timing de la metamorphose, la survie apres metamorphose chez A.t..
TL;DR: Time series analyses indicated that movement patterns of males and non-gravid females consisted of constantly shifting, non-overlapping activity areas, and in most cases these snakes moved in a looping pattern during the active season that returned them to the same hibernation site from which they departed.
Abstract: Radiotelemetry was used to monitor the movements and habitat use of timber rattlesnakes (Crotalus horridus) in the Pine Barrens of southern New Jersey. Reproductive condition strongly influenced both aspects of behavior. Males generally exhibited the largest activity ranges, and the sizes of their ranges were positively correlated with the number of days the snakes were monitored. This was not true for gravid or non-gravid females. Time series analyses indicated that movement patterns of males and non-gravid females consisted of constantly shifting, non-overlapping activity areas. In most cases these snakes moved in a looping pattern during the active season that returned them to the same hibernation site from which they departed. Gravid females exhibited more static, overlapping activity areas and shorter dispersal distances from hibernacula. Males and non-gravid females utilized forested habitat with greater than 50% canopy closure, thick surface vegetation (approx. 75%), and few fallen logs. This habitat occurred with high frequency throughout the study area. Gravid snakes utilized less densely forested sites with approx. 25% canopy closure, an equal mixture of vegetation and leaf litter covering the surface, frequent fallen logs, and warmer climatic conditions. This habitat occurred in low frequency on the study area and was largely restricted to the edge of sand roads.
TL;DR: Alteration of temperature in the larval environment may explain some of the temporal and spatial variation in: 1) time to metamorphosis; 2) size at metamorphotic; and 3) relative frequency of color morphs in natural populations of P. ornata and amphibians, in general.
Abstract: We studied the effects of five temperature treatments (10 C, 15 C, 20 C, 25 C, 30 C) on larval development, growth, and color polymorphism of Pseudacris ornata in the laboratory. Body mass and developmental stage on day 32 increased with increasing temperature to 25 C, then decreased at 30 C. Mass at metamorphosis and time to metamorphosis decreased with increasing temperature treatments. Fewer deformities and greater average survival were found at intermediate temperature treatments of 20 C and 25 C than at the two extremes of 10 C and 30 C. No larvae metamorphosed from the 10 C treatment after 111 d and individuals only reached Gosner stage 30. Copper, brown, and gray metamorphs were produced from brown and gray parents; green morphs were not present. The proportion of brown metamorphs increased with increasing temperatures, but there was no change in gray metamorphs with temperature. The copper color morph was not observed at metamorphosis, but was distinguishable several weeks after metamorphosis. Alteration of temperature in the larval environment may explain some of the temporal and spatial variation in: 1) time to metamorphosis; 2) size at metamorphosis; and 3) relative frequency of color morphs in natural populations of P. ornata and amphibians, in general.
TL;DR: This paper demonstrates the existence of significant individual variation in reproductive traits within a single population in Maryland as well as the ecological and evolutionary implications of such variation relative to the potential effects of egg size on fitness.
Abstract: Previous studies have demonstrated a great deal of geographic variation in reproductive traits of the wood frog Rana sylvatica. This paper demonstrates the existence of significant individual variation in reproductive traits within a single population in Maryland. Egg size, clutch size and total-egg-volume all varied positively with body size for each female age class. When adjusted for body size differences, clutch size and egg size had an inverse relationship to each other across age classes of females. One-year-old females had the largest clutches with the smallest eggs whereas 3 yr old females had the smallest clutches but the largest eggs. Two-year-olds were intermediate in both egg size and clutch size. Reproductive traits also showed year to year variation that was independent of body size and initial size at metamorphosis. The ecological and evolutionary implications of such variation are discussed relative to the potential effects of egg size on fitness.
TL;DR: The opportunity to publish the six collected papers as a block within COPEIA is gratefully acknowledged as are the efforts of those involved in the planning and the execution of the meeting.
Abstract: THE second annual meeting of the American Elasmobranch Society (AES) was held in June 1986 in conjunction with the 66th annual meeting of the American Society of Ichthyologists and Herpetologists (ASIH) at the University of Victoria, Victoria, British Columbia, Canada. Thirty-two papers were presented on aspects of the natural history, biology, physiology and behavior of sharks, skates and rays including a one-half day symposium entitled "Shark-Human Interaction." Six of those papers are included here as the first AES symposium. The success of the second AES meeting was mostly due to the help of a number of people, some of whom are also ASIH members. The opportunity to publish the six collected papers as a block within COPEIA is gratefully acknowledged as are the efforts of those involved in the planning and the execution of the meeting. The AES was spawned, in part, as an outgrowth of ASIH to encompass those researchers with an interest in elasmobranch biology. It wa nurtured by Sonny Gruber whose determination, hard work and commitment to the Society has resulted in this first published compil tion of AES papers.
TL;DR: Based on geographic patterns of allele frequencies, abrupt differentiation in local genetic constituency, and previously reported data on the existence of a reproductive barrier between the forms, the original taxonomic designations recognizing G. holbrooki and G. affinis as separate species are preferred.
Abstract: Mosquitofish were sampled from 76 locations in 19 drainages in the southeastern United States. Thirteen polymorphic loci were resolved for fish from each location. Populations from eastern drainages had significantly higher levels of heterozygosity (H = 0.113) than those in western drainages (H = 0.055). Abrupt changes in allele frequencies for several loci occurred in the area of Mobile Bay, which corresponds with discontinuities previously reported for chromosomal and morphological data. Based on geographic patterns of allele frequencies, abrupt differentiation in local genetic constituency (DR = 0.443 between eastern Gambusia affinis holbrooki and G. a. afinis) and previously reported data on the existence of a reproductive barrier between the forms, the original taxonomic designations recognizing G. holbrooki and G. affinis as separate species are preferred. Populations in drainages west of Mobile Bay should be considered G. affinis, with those east of this divide being G. holbrooki.
TL;DR: D dissimilarity in the developmental sequence and position of pterygiophores and supraneurals (=predorsals) of centrarchid fishes, in conjunction with a reinterpretation of phylogenetic correlations, indicates that supranural, the more widely-used, senior synonym, be used to refer to these elements in teleosts.
Abstract: Homologies among supraneurals, predorsals, median neural spines, and pterygiophores in fishes are reassessed in a phylogenetic context with new comparative developmental information. Phylogenetic and developmental evidence fails to suggest a relationship of serial homology among supraneurals and median neural spines. Median neural spines in fishes do not form through the fusion of the neural arch anlagen to a separate median element. Dissimilarity in the developmental sequence and position of pterygiophores and supraneurals (=predorsals) of centrarchid fishes, in conjunction with a reinterpretation of phylogenetic correlations, indicates that supraneurals and pterygiophores are not serial homologues. Because supraneurals are found in all teleostean sister taxa, teleost "predorsals" are most parsimoniously interpreted as the phylogenetic homologues of supraneurals. Accordingly, it is recommended that supraneural, the more widely-used, senior synonym, be used to refer to these elements in teleosts.
TL;DR: Reproduction, embryonic development, and general biology are described from more than 100 chain dogfish, Scyliorhinus retifer, a common catshark found on the continental slopes of the western North Atlantic.
Abstract: Reproduction, embryonic development, and general biology are described from more than 100 chain dogfish, Scyliorhinus retifer, a common catshark found on the continental slopes of the western North Atlantic. Females and males reached sexual maturity at about 520 mm TL and 500 mm TL, respectively. Follicles are ovulated in pairs when they reach 18 mm diameter. In the laboratory, females lay one egg pair at approx. 15.3 d intervals, attaching the eggs to bottom structures. Development at 11.7-12.8 C in artificial seawater averaged 256 d (?SD 8 d, n = 62) to hatching. Embryos averaged 106 mm (?SD 5 mm, n = 63) at hatching. In the wild, juveniles are often found in large numbers over smooth bottoms. Adults congregate in areas with upright structures which females use for egg attachment. Chain dogfish feed on squid, small bony fishes, polychaete worms, and crustaceans.
TL;DR: The larval morphology and captive breeding of Lepidobatrachus laevis (Leptodactylidae, Ceratophryinae) from the Paraguayan Chaco is described, which is an obligate carnivores that swallow large, living prey whole.
Abstract: The larval morphology and captive breeding of Lepidobatrachus laevis (Leptodactylidae, Ceratophryinae) from the Paraguayan Chaco is described. The larvae are obligate carnivores that swallow large, living prey whole. The larva has a large dorsoventrally flattened head with a beakless wide mouth. By means of buccal suction they can ingest tadpoles that are nearly equal to themselves in size. The chondrocranial cartilages are simple in comparison to microphagous larvae, and the chondrocranium is wider than long. Larval development is rapid, and some tadpoles reach metamorphosis in 20 d. The brachial chambers are like those of Type IV (Orton, 1953) larvae, but the paired branchial openings are lateral and different from the spiracles of other anuran larvae. The branchial chambers show asymmetrical development with the opercular fold closing the right branchial opening prior to the formation of the left branchial opening. The right branchial chamber reopens and the fully developed larva has two large symmetrical branchial openings. The digestive tract is adult-like and the stomach has a large fundic portion that distends to accept the large prey, a typical muscular pyloric region and sphincter, and a short intestine less than 2 x the SVL of the larva. In many of its characteristics the larva of Lepidobatrachus resembles the adult.
TL;DR: Correlation and multiple regression analyses showed that fish distributions were significantly related to environmental variables, but comparison of upland fish faunas among major river drainages within the state showed that a strong component of historical zoogeography also influences patterns in fish distribution.
Abstract: other ichthyologists. These collections, in 101 defined drainage units covering the entire state, permit detailed assessment of extant fish distribution patterns. Principal components analysis showed presence within the state of four distinct (but not mutually exclusive) groups of fishes. A complementary detrended correspondence analysis permitted definition of fish faunal regions within the state, and allowed clarification of patterns in fish distribution with respect to natural northwest-to-southeast gradients in environmental conditions. Many of the environmental variables and associated distributions of fishes corresponded to patterns contrasting upland with lowland species, but even within the upland or the lowland regions there were distinct groupings of fishes. The White River drainage, in uplands of north Arkansas, emerges as a distinct fish faunal region. The southern Ozark Mountains (i.e., streams tributary to the Arkansas River) and most of the Ouachita Mountains comprise another faunal region for fishes. A third fish faunal region exists at the ecotone between uplands and lowlands, and two distinct lowland faunal regions exist (including one of big rivers). Correlation and multiple regression analyses showed that fish distributions were significantly related to environmental variables, but comparison of upland fish faunas among major river drainages within the state showed that a strong component of historical zoogeography also influences patterns in fish distribution.
TL;DR: Review of the literature on reptilian placental terminology reveals that confusion associated with the assignment of terms to different placental organs is unwarranted, and both chorioallantoic and choriovitelline placentation occur among reptiles, marsupials and eutherians, whereas omphaloplacentation and amphal allantoic placenta are unique to squlamates.
Abstract: Review of the literature on reptilian placental terminology reveals that confusion associated with the assignment of terms to different placental organs is unwarranted. Reptilian placentae can be assigned easily to one of four distinct structural types defined by the extraembryonic membranes that are involved in placental formation. The terms "allantoplacenta" and "chorioallantoic placenta" have consistently been applied to the organ formed by the chorioallantoic membrane and adjacent uterine epithelium. Some confusion, however, has been associated with the assignment of terms to regions of the yolk sac that participate in placentation. We recognize two distinct types of yolk sac placentation: 1) the "choriovitelline placenta," defined as the apposition of the vascularized trilaminar omphalopleure (ectoderm, mesoderm, endoderm) and the uterine epithelium; and 2) the "omphaloplacenta," which consists of the non-vascular omphalopleure (ectoderm, endoderm) of the isolated yolk mass and associated structures, in apposition to the uterine epithelium. The "omphalallantoic placenta," constituting the fourth structural category, forms as the outer allantoic membrane becomes apposed to the inner margin of the omphaloplacenta. Based upon these definitions, both chorioallantoic and choriovitelline placentation occur among reptiles, marsupials and eutherians, whereas omphaloplacentation and amphalallantoic placentation are unique to squlamates.
TL;DR: Soil pH in the eastern United States is within the range that can be lethal to some species and inhibits the growth of others and more information is needed to assess the long term consequences of soil acidification on amphibian populations.
Abstract: distributions of Bufo americanus, Plethodon cinereus, Eurycea bislineata, Desmognathus fuscus and Ambystoma maculatum were significantly influenced by soil pH. Soil moisture also influenced species distributions. Rana sylvatica, E. bislineata, D. fuscus, Notophthalmus viridescens and A. maculatum occurred on quadrats with a significantly higher average moisture content than quadrats without amphibians. Both soil moisture and soil pH should be determined when factors influencing amphibian distributions are being examined. Soil pH in the eastern United States is within the range that can be lethal to some species and inhibits the growth of others. More information is needed to assess the long term consequences of soil acidification on amphibian populations.
TL;DR: Of 35 species of reef fishes studied in the Gulf of California (Sea of Cortez), 17 spent some portion of their time following heterospecifics, which provides unique feeding opportunities for following individuals and is an important aspect of the foraging ecology of some reef species.
Abstract: Of 35 species of reef fishes studied in the Gulf of California (Sea of Cortez), 17 spent some portion of their time following heterospecifics. A total of 71 interspecific combinations were observed. These foraging associations provide unique feeding opportunities for following individuals and are an important aspect of the foraging ecology of some reef species. Several species spent significant amounts of time in these associations. Small Mycteroperca rosacea (Serranidae) spent 25% of their time, and female Bodianus diplotaenia (Labridae) spent 12.8% of their time following heterospecifics. Species followed were those whose behavior caused the uncovering or flushing of small invertebrates and fishes. Most species were only followed while foraging, and their foraging behavior apparently elicited following by heterospecifics. Followers were highly selective, spending more time with those individuals whose foraging activities created the greatest disturbance. Two species, the moray eel (Gymnothorax castaneus) and Octopus sp. were followed whenever they moved across the reef. Animals that were followed were often in different foraging guilds from the followers. In situations where both were in the same guild, interactions ranged from food pilfering and competition to opportunistic predation upon prey which had escaped the animal being followed.
TL;DR: A sexual dimorphism in tail width and in the peak-to-peak voltage of the EOD existed among reproductive animals in the wild, which was tested in the laboratory and showed an underestimation of population size by 18.3%.
Abstract: inherent in this assessment technique was tested in the laboratory and the results showed an underestimation of population size by 18.3%. In this stream, females remained relatively site retentive, 90% of the marked animals were recaptured at the same spot over a 3 mo period, whereas, males are less site retentive, only 50% of the marked animals were recaptured at the same spot over a 3 mo period. In addition, marked animals were observed moving as much as 130 m in 1 mo. Approximately 80% of the population became gravid at the transition of the wet-dry season (Nov.-Dec.) and bred throughout the dry season (Dec.-April). Fry had an initial growth rate of 1.3 cm/mo and the breeding period was followed by a reduction of the adult population at the end of the dry season. The courtship signals of a pulse-type gymnotiform were examined for the first time. Two distinct EOD patterns were used by Hypopomus during courtship: a Decrement-Burst and periods of silence punctuated by a burst of EOD producing an off-on-off pattern. In addition, a sexual dimorphism in tail width and in the peak-to-peak voltage of the EOD existed among reproductive animals in the wild.
TL;DR: Reproduction in bat rays collected from Elkhorn Slough in central California appears to follow a well-defined annual cycle in which mature individuals use theSlough in the spring and summer months to give birth and mate.
Abstract: Reproduction in bat rays collected from Elkhorn Slough in central California appears to follow a well-defined annual cycle in which mature individuals use the Slough in the spring and summer months to give birth and mate. The bat ray's gestation period is estimated to be between 9-12 mo. Embryo number in pregnant females ranged between 2-5. Disc width at birth ranged between 220305 mm. In male bat rays, three indicators of sexual maturity (presence of mature spermatozoa, clasper/disc-width relationship, and internal morphology) showed that at 2-3 yr of age sexual maturity occurs at a disc width of about 450-622 mm. In females, presence of mature ova, ranging from means of 25-279 per female, indicates that 50% maturity occurs at about 881 mm disc width and approx. 5 yr of age.