Amphibious Habits Research Articles

A Late Cretaceous nodosaurid ankylosaur (Dinosauria: Ornithischia) from marine sediments of coastal California

A partial nodosaurid ankylosaur skeleton, consisting primarily of the ilia, hindlimbs, posterior dorsal armor, plus partial forelimb elements and additional armor, was recovered from the marine Point Loma Formation, late Campanian age, north of San Diego, California. The specimen is similar to contemporaneous species ofPanoplosaurusandEdmontoniafrom terrestrial sediments of the western interior, but there are also similarities to the armor ofStegopelta landerensisfrom marine sediments of earliest Cenomanian age from Wyoming. Skeletal elements critical for generic determination are not preserved, and the specimen is identified as Nodosauridae, incertae sedis. An associated marine invertebrate fauna and nannoplankton flora have revealed some discrepencies in the correlation systems used for Upper Cretaceous marine rocks of coastal California. Hollow limb bones of the specimen are interpreted as a preservational artifact. Nodosaurids had broad ecological tolerances, and visited riparian and coastal environments more frequently than other dinosaurs. However, a review of morphologic and distributional evidence fails to support a theory of amphibious or aquatic habits for nodosaurids.

Phylogenetic Studies of North American Callitriche (Callitrichaceae) Using Chloroplast DNA Restriction Fragment Analysis

Phylogenetic study in the Callitrichaceae is hampered by reduced floral structure and environmentally mediated phenotypic variation of both vegetative and reproductive (fruit) char- acters. Yet a phylogenetic perspective is requisite to an understanding of ecological, morphological, and reproductive system evolution in the family. Cladistic analysis of chloroplast DNA (cpDNA) restriction fragment variation, combined with several morphological characters, was conducted on 11 taxa of Callitriche (nine indigenous to North America and two European). These studies provide the first explicit phylogenetic hypotheses for the Callitrichaceae and support the monophyly of several groups. Callitriche hermaphroditica, the single obligately submerged species examined, aligned basal to all other North American taxa. The remaining indigenous North American taxa formed two opposing clades: 1) the terrestrial C. nuttallii, C. peploides, C. terrestris grouped with the am- phibious C. marginata, and 2) the amphibious C. heterophylla var. heterophylla and var. bolanderi, C. trochlearis, and C. verna. Relationships among the taxa within these clades are unresolved. These analyses indicate that the internal geitonogamous breeding system is synapomorphic for the latter clade, and suggest that the terrestrial growth habit may be derived from the amphibious growth habit in the family. This study demonstrates the utility of using cpDNA restriction fragment variation to gain phylogenetic perspectives in aquatic angiosperms.

Growth and reproduction in the freshwater crab, Potamon fluviatile (Decapoda, Brachyura)

SUMMARY. 1. The patterns of relative and absolute growth and the reproductive biology of the freshwater crab Potamon fluviatile were studied in a natural population inhabiting a hill stream close to Florence, Italy, over an annual cycle. Periodical inspections of a stretch of the stream were made and morphological and anatomical analysis carried out.2. As in other decapods, the females are smaller than the males (they can however occasionally reach larger dimensions). This may be determined by a lengthening of the moulting interval in the females, by their higher energetic cost of reproduction (since reproduction occurs simultaneously with moulting, at least in this habitat) and/or by a higher mortality rate resulting from the risks associated with carrying eggs and vagility.3. The analysis of relative growth in secondary sexual characters (abdomen width and major chela length) with respect to carapace length, shows that the pre‐puberty and puberty ecdysis occur at 15 and 35 mm carapace length respectively, which was also confirmed by the gonad weight, vas deferens in males, and the onset of vitellogencsis in females.4. A delay between anatomical and functional (i.e. the ability to copulate successfully) maturity was observed in the males. Being larger may be an advantage in intra‐sexual competition for mating, but larger males, being more vagile, are also more likely to meet receptive females. The females may mate before their puberty moult and store sperms in their seminal receptacles for when they attain full maturity; this could be adaptive since opportunities of encountering males are few and far between in their adult phase, characterized by their vagile and amphibious habits.

Cardiac responses of the anurans, Bufo bufo and Rana pipiens, during behavioural arousal and fright

1. 1. Electrocardiograms (ECGs) were recorded from B. bufo and R. pipiens whilst behaviourally aroused and frightened. 2. 2. A tachycardia was exhibited in both states, though in fright it was preceded by a “missed” beat. 3. 3. The difference between these responses and those of other vertebrates was discussed in relation to the amphibious habit. 4. 4. It is suggested that the cardiac responses of diving, fright and arousal may have a common evolutionary origin.

Occurrence of carotid labyrinth in the catfish group of teleost fishes

A structure similar in topography and morphology to the carotid labyrinth of amphibians has been found in 4 catfishes, namely,Clarias batrachus, Heteropneustes fossilis, Rita rita andMystus seenghala. The present finding of the presence of the carotid labyrinth in fishes is the first report, and the results are discussed in the light of the amphibious habit of these catfishes.

Sauropod habits and habitats

Sauropod natural history has been widely a discussed and sometimes controversial topic. All amphibious theories of sauropod behavior from Cope and Marsh onward may have been inspired by Owen. Sauropod narial morphology might indicate either aquatic or terrestrial habits, and some sauropods may have had a complex narial structure, possibly a proboscis. Sauropods were vegetarians, but the specific diet of Diplodocus is unclear. Long necks could have been used for browsing in trees, or long streambanks, or under water. Sauropod axial appendicular modifications point to primarily terrestrial behavior. Sauropods may have had bird-like lung system. Sauropods sometimes dragged their tails on the ground and may have used for defense. The deep thorax of sauropods is an adaptation to problems of terrestrial weight-bearing. Sauropod foot and limb structure is generally compartable to elephants, except in lack of joint ossification and development of large claws. Sauropods sometimes reared up on their hind limbs, and they definitely entered streams at least sometimes, but sedimentologic evidence does not support immersion in deep lakes as sauropods are frequently pictured. On the problem of terrestrial versus amphibious habits, most sauropod anatomy is equivocal, but where firm morphologic interpretations are possible, they usually point to terrestrial behavior.

A comparative study of the structure of the skin of certain air‐breathing fresh‐water teleosts

A comparative study of the skin, based on the micro‐anatomical investigation of skin fragments taken from a specific region of the body, has been made of three air‐breathing fishes, namely,Heteropneustes fossilis, Amphipnous cuchiaandMastacembelus pancalus.On the basis of their structure and histochemical nature, five types of skin glands have been distinguished in the epidermis of these fishes.The relative thickness of the epidermis (A. cuchia–119 μm (average value),H. fossilis– 98 μm (average value),M. pancalus–34 μm (average value)) and its vascularization has been considered and compared with other fishes and amphibians. The possibilities of cutaneous respiration in these air‐breathing fishes has been discussed.The presence of a well‐defined lymphatic system, comprising a series of lymph spaces containing small lymphocytes, in the stratum germinativum layer of the epidermis of these fishes has been established.The stratum laxum layer of the dermis inAmphipnousis characterized by the presence of definite areas containing “Substantia amorpha” having acidic mucopolysaccharides which may be related with the amphibious habit of the fishes. This is an adaptation against desiccation similar to that found in the Anura. InMastacembeluselliptical areas of the stratum laxum penetrate into the epidermis thus making these areas of the epidermis considerably thin (about 7 μm) for cutaneous respiration.There is an inverse relationship between the thickness of the stratum compactum and squamation.

SEASONAL VARIATION IN THE TEMPERATURE-EXTRUDING RESPONSE RELATION OF ONCOMELANIA NOSOPHORA, THE VECTOR SNAIL OF SCHISTOSOMA JAPONICUM IN JAPAN

Oncomelania nosophora, the vector snail of Schistosoma japonicum in Japan, has an amphibious habit. These snails are usually found on the moist soil just above the water edge of the brook or on moist vegetable matter above the level of water. If the habitat is changed into unfavorable condition such as the dryness, the cold or the heat, they shut themselves up into the shells. When the snails were submerged in water at room temperature, they open their opercula and extrude out the feet and the heads, from the shell. There are several factors which influence the mode of the response. Among them, temperature appears to be the most important one. As has already been pointed out by McMullen (1952), apparent limitations of molluscicides against Oncomelania snails, imposed by environmental conditions, have prompted increased emphasis on fundamental studies of snail biology. Although it has been found that temperature affects the biological process of the snails and molluscicidal activity against the snails, very little is known concerning the seasonal variation in the response of snails to temperature. Therefore, the study herein reported was conducted to know the seasonal variation and experimental acclimatization in the temperature-extruding response of O. nosophora.