Siren Lacertina Research Articles

Influence of Hydroperiod, Isolation, and Heterospecifics on the Distribution of Aquatic Salamanders (Siren and Amphiuma) among Depression Wetlands

We used occurrence data gathered over a four-year period to assess relationships among hydroperiod length (amount of time a wetland holds water during a year), wetland isolation from other aquatic habitats, and the occurrence of sirens (Siren intermedia and S. lacertina) and amphiumas (Amphiuma means) among depression wetlands of the upper Atlantic Coastal Plain. The combined occurrence of sirens and amphiumas was positively correlated with hydroperiod length and negatively correlated with distance to the nearest intermittent aquatic habitat. Occurrences of individual species were negatively correlated with either distance to the nearest intermittent aquatic habitat or elevation difference between wetlands and the nearest permanent aquatic habitat. Siren lacertina showed higher than expected allopatric distribution in relation to other species, suggesting biological interactions may further limit the distribution of sirens and amphiumas among depression wetlands.

Mechanics of lung ventilation in a large aquatic salamander, siren lacertina

Lung ventilation in Siren lacertina was studied using X-ray video, measurements of body cavity pressure and electromyography of hypaxial muscles. S. lacertina utilizes a two-stroke buccal pump in which mixing of expired and inspired gas is minimized by partial expansion of the buccal cavity during exhalation and then full expansion after exhalation is complete. Mixing is further reduced by the use of one or two accessory inspirations after the first, mixed-gas cycle. Exhalation occurs in two phases: a passive phase in which hydrostatic pressure and possibly lung elasticity force air out of the lungs, and an active phase in which contraction of the transverse abdominis (TA) muscle increases body cavity pressure and forces most of the remaining air out. In electromyograms of the lateral hypaxial musculature, the TA became active 200-400 ms before the rise in body cavity pressure, and activity ceased at peak pressure. The TA was not active during inspiration, and no consistent activity during breathing was noted in the external oblique, internal oblique and rectus abdominis muscles. The finding that the TA is the primary expiratory muscle in S. lacertina agrees with findings in a previous study of another salamander, Necturus maculosus. Together, these results indicate that the use of the TA for exhalation is a primitive character for salamanders and support the hypothesis that the breathing mechanism of salamanders represents an intermediate step in evolution between a buccal pump, in which only head muscles are used for ventilation, and an aspiration pump, in which axial muscles are used for both exhalation and inhalation. <P>

Siren lacertina (Amphibia: Caudata) in northeastern Mexico and southern Texas

Siren lacertina (Amphibia: Caudata) in northeastern Mexico and southern Texas

Acid-base regulation in response to environmental hypercapnia in two aquatic salamanders, Siren lacertina and Amphiuma means

The partial pressure of CO 2 (P CO 2 ) in certain areas of the aquatic habitat of the salamanders Siren lacertina and Amphiuma means frequently rises to values of up to 60 mm Hg. This ambient hypercapnia occurs due to hindrance of gas exchange between water and air caused by dense water-surface vegetation. In order to investigate the acid-base regulation in response to the respiratory acidosis, which would be expected to result from the high CO 2 conductance of the amphibian skin, specimens of both species were subjected to water P CO 2 of 47 mm Hg while having free access to normocapnic air in a closed water recirculation system. Arterial P CO 2 rose considerably from 12 to 35 mm Hg in Siren and from 17 tp 36 mm Hg in Amphiuma. The resultant fall in plasma pH remained uncompensated, whereas intracellular pH of white muscle and heart muscle of Siren were little affected owing to elevated intracellular bicarbonate concentrations. The bicarbonate accumulated in the intracellular compartments was in part produced by intracellular and extracellular nonbicarbonate buffering, and in part gained from the environment in exchange for Cl − ions. Elevated water bicarbonate concentration or bicarbonate infusion into Siren had no effect on effect on the acid-base regulation. These data suggest that the availability of bicarbonate is not a limiting factor for extracellular compensation of increased P CO 2 , but that the threshold of the bicarbonate-regulating structures is simply not readjusted in hypercapnia. This type of regulation may have evolved as a result of the specific environmental conditions of these animals and may be considered as an energetically efficient way of maintaining a constant milieu for the pH-sensitive intracellular structures.

Occurrence and binding affinity of prolactin receptors in amphibian tissues

The binding of [ 125I]oPRL to particulate fractions of kidney, bladder, gut, and liver homogenates from representatives of 12 amphibian species was examined. The general pattern of the degree of binding (from highest to lowest) was kidney (range 0–20.5%), bladder (2–15%), gut (0–3.7%), and liver (0–4.8%). Prolactin binding to kidney fractions was generally high except for the more aquatic and larval-like species, Siren lacertina, Cryptobranchus alleganiensis, Necturus maculosus, and Xenopus laevis. Renal receptors from 6 species showed high affinity ( K d = 2–6 × 10 −10 M) and low capacity (less than 300 fmol/mg protein) for the ovine ligand. Prolactin binding to bladder was readily detectable in all of the 6 species examined. Prolactin binding to gut and liver fractions was generally low or nondetectable (less than 0.5%). The physiological implications of these binding data are discussed, particularly in the context of a role for prolactin in osmoregulation in amphibians.

Ventilatory Activity in Amphiuma tridactylum and Siren lacertina (Amphibia, Caudata)

Siren lacertina obtains 75% of its oxygen and eliminates 60% of its carbon dioxide via the lungs (Guimond and Hutchison, 1973a), and Amphiuma tridactylum obtains 56% of its oxygen and releases 23% of its carbon dioxide aerially (Guimond and Hutchison, 1974). Siren can utilize up to 26%, and Amphiuma up to 50%, of the inspired oxygen (Guimond and Hutchison, 1973a; Toews, 1973), the most efficient oxygen utilization in amphibian lungs studied. (Guimond and Hutchison, 1974). These two aquatic genera have the smallest total surface area of respiratory capillaries per g found in amphibians (Czopek, 1962b), and lowest metabolic rate at comparable temperatures of all amphibians studies (Whitford, 1973; Guimond and Hutchison, 1976). These respiratory adaptations enable Siren and Amphiuma to survive in hypoxic, hypercarbic shallow and warm water which would be inhospitable to other amphibians

Food Habits of the Greater Siren, Siren lacertina, in an Alabama Coastal Plain Pond

Food Habits of the Greater Siren, Siren lacertina, in an Alabama Coastal Plain Pond

Anatomy of the Heart of the Amphibia. I. Siren lacertina

Gross morphology and histology of the heart in Siren lacertina are examined. This work is the first histological study of the heart in this species and for that matter in the Sirenoidea. The gross study is the only complete, modern work on the heart. The heart of Siren is composed of the partially septate sinus venosus, two atria, partially septate ventricle and conus arteriosus. The truncus arteriosus is transitional between cardiac and vascular systems. Many characteristics in the heart are studied, including the relation of chambers one to the other, connective tissue ligaments stabilizing the heart within the pericardial cavity and organization of cardiac muscular trabeculae and connective tissue bands. Additional structures examined

Some Platyhelminth Parasites of Sirens (Amphibia: Sirenidae) from North America

A new genus and species of digenean and a new species of cestode are described and a previously described species of digenean reported for the first time from Siren intermedia from Illinois. A new genus is proposed for a previously described digenean, and another known species of digenean reported from Siren lacertina in Florida. Progorgodera foliata from S. intermedia has a foliate hindbody characteristic of members of Phyllodistomum and multiple testes arranged in 2 longitudinal rows characteristic of members of Gorgodera. Ophiotaenia sireni from the same host resembles 0. filaroides in number of testes, 0. amphiumae and 0. alternans in number of uterine branches, and 0. grandis and 0. marenzelleri in scolex size. Allassostomoides louisianaensis is reported for the first time from Siren intermedia. The new genus Cephalogonimoides is proposed for Cephalogonimus sireni from Siren lacertina, which differs from members of Cephalogonimus by having symmetrical testes, ceca extending to the posterior end of the body, an acetabulum twice as large as the oral sucker, and a muscular prepharynx; and by lacking a seminal receptacle. Telorchis stunkardi is reported from S. lacertina for the first time. The amphibian genus Siren L. is represented in North America by two species, Siren lacertina L. and S. intermedia LeConte. Five species of adult platyhelminths have been reported from S. lacertina: Cercorchis (= Telorchis) sireni Zeliff 1937, Stomatrema guberleti Byrd 1937, Gorgodera minima Cort 1911, Cephalogonimus sireni Premvati 1969, and Ophiotaenia sp. (Zeliff, 1937; Walton, 1958; Premvati, 1969; Loftin, 1960). Manter (1938) reported Cephalogonimus amphiumae Chandler 1923 from Siren sp. To date, no adult platyhelminths have been reported from Siren intermedia. From 1970 to 1975 adult platyhelminths were collected from Siren intermedia captured in southern Illinois. All specimens were fixed with AFA. Cestodes were first relaxed in cold tap water; digeneans were flattened with slight coverslip pressure. Worms were stained with Mayer's hematoxylin and mounted in Canada balsam. Measurements are in micrometers unless otherwise stated; figures were drawn with the aid of a drawing tube.

Respiratory surface area as a factor controlling the standard rate of O 2 consumption of aquatic salamanders

The standard rate of O 2 consumption of various aquatic lunged salamanders is compared for animals breathing water only and for animals breathing both air and water. When submerged and prevented from surfacing in air-equilibrated water, most species studied were capable of survival for periods of at least two weeks. The animals that were allowed to respire bimodally exhibited an increased rate of O 2 consumption relative to their submerged counterparts who were denied the use of pulmonary respiration. The standard rate of oxygen consumption in submerged and air-and-water-breathing Siren lacertina was determined over a large range of body size. The rate of the bimodally breathing animals was higher than that of the submerged animals, and the difference increased with increasing body size. These data suggest that it is the oxygen transport capacity of these animals that at least partially regulates the standard rate of O 2 consumption rather than all such control being exerted at the cellular level.

The electrical P.D. across the integument of some neotenous urodele amphibians

1. 1. An electrical P.D. (inside positive) was recorded in vivo across the integument of the neotenous urodeles Amphiuma means, Siren lacertina and Necturus maculosus and this was related to the sodium concentration in the external bathing media. 2. 2. Like in the frog, Rana pipiens, this P.D. in vivo was inhibited when amiloride was placed in the external solutions bathing Amphiuma and Siren but not Necturus. 3. 3. A P.D. and short-circuit current (SCC) was also observed across the skin of Amphiuma and Siren (but not Necturus) in vitro and this was also inhibited by amiloride. In contrast to the responses of the skin of fully metamorphosed amphibians vasotocin did not stimulate the SCC in these neotenous species. 4. 4. Substitution of sulfate for chloride in the external solution in vitro markedly increased the P.D. of frog skin but had no effect on that of Amphiuma or Siren. 5. 5. The results suggest that the exchanges of ions across frog skin are much greater than in the skin of Amphiuma or Siren. A mechanism for active transmural transport of sodium would appear to exist in the skin of these urodeles but the evidence for this in Necturus was equivocal.

Cutaneous respiration in the Congo eel Amphiuma means (Amphibia: Urodela)

Abstract o 1. At 20°C the Congo eel, Amphiuma means , can survive for at least 24 hr when submerged in aerated tap water. Oxygen is readily taken up, from the bathing water, across the skin of these amphibians. 2. The rate of oxygen uptake declines linearly as the oxygen tension in this solution decreases. 3. In air, A. means breathes sporadically; the rate of oxygen consumption was similar to that when they were submerged in water nearly saturated with air. 4. When pulmonary ventilation was pharmacologically blocked (with gallamine triethiodide) the rate of metabolism was maintained by O 2 uptake across the integument. 5. The ability of A. means to utilize its skin for respiration in air and water is compared to that in two other urodeles Siren lacertina and Necturus maculosus .

Aerial and aquatic respiration in the congo eel Amphiuma means means (GARDEN)

Direct separate and simultaneous determinations of pulmonary and cutaneous V̇ O 2 and V̇ CO 2 were made on the large aquatic salamander Amphiuma means means acclimated to 5, 15 and 25 °C. Differences in temperature significantly affected metabolic rate- and the relative partitioning of gas exchange. The animals were predominantly water breathers at 5 °C (92% of total V̇ O 2 and 100% of total V̇ CO 2 At 25 °C, the lungs assumed a greater role and accounted for 56% of the total V̇ O 2 and 23% of the total V̇ CO 2 Eleven Amphiuma submerged at 25 °C in air saturated water perished within 2 days; this aquatic animal, therefore, is an obligate air breather at higher metabolic rates. The lungs of Amphiuma are long, profusely vascularized and highly septated. Cineradiographic studies show that the lungs are efficiently ventilated when the animal surfaces for air. The pulmonary capacity of Amphiuma is similar to that of Siren lacertina and is of substantial adaptive value to both species which frequently find themselves in adverse aquatic environments ( e.g. warm, shallow and stagnant bodies of water which are often both hypoxic and hypercarbic).

Gas exchange and metabolism in the sirenidae (Amphibia: Caudata)—I. Oxygen consumption of submerged sirenids as a function of body size and respiratory surface area

1. 1. Cutaneous oxygen consumption for three species of sirenid salamanders submerged at 25°C was determined. 2. 2. The relationship between metabolic rate (submerged) and body weight was approximately the same for each of the three species. This relationship for the Sirenidae is given by the equation; MR (submerged) = 72 W 0.66. 3. 3. The surface area of the skin was found to have a similar relationship to body weight: SA = 10.5W 0.65. 4. 4. Critical oxygen tension ( P c ) increases with increasing body size in the Sirenidae. 5. 5. Preliminary experiments indicate that Siren lacertina elevates its standard metabolic rate when allowed to breath both air and water, compared to the rate when breathing water alone. 6. 6. A discussion of the possibility that standard metabolic rate in poikilotherms may be determined by the availability of oxygen is presented.

Trimodal gas exchange in the large aquatic salamander, Siren lacertina (Linnaeus)

1. 1. Pulmonary, cutaneous and branchial gas exchange ( V ́ O2 and V ́ CO2 ) was determined on the large aquatic salamander Siren lacertina acclimated to 5, 15 and 25°C. 2. 2. Gas exchange was predominantly aquatic at 5°C (86 per cent of the total V ́ O2 and 98 per cent of the total V ́ CO2 ). At 25°C the lungs assumed a greater role in gas exchange and accounted for 50–75 per cent of the total V ́ O2 and up to 60 per cent of the total V ́ CO2 ; the latter value shows that Siren lungs are the most efficient of any amphibian thus far investigated. 3. 3. The gills of Siren did not contribute materially to the total V ́ O2 . The gills showed a greater participation in V ́ CO2 (18 and 12 per cent of the total V ́ CO2 at 15 and 25°C, respectively). Most of the aquatic gas exchange in Siren occurs via the integumentary surfaces. 4. 4. The air-dried lungs of Siren are extremely long, about two-thirds of the body length, and show a considerable degree of septation. The increased infolding of the lung tissues increases the respiratory surface area some fourfold. 5. 5. The efficient pulmonary respiration in Siren is an adaptation for survival in shallow, weed-choked, and often hypoxic and hypercarbic waters.

Respiration of some urodele and anuran amphibia—II. In air, role of the skin and lungs

1. 1. In air the “resting” rate of O 2 consumption of Siren lacertina, Bufo marinus, Rana pipiens and Xenopus laevis were similar, 27 μl cm −2 hr −1 (at 22°C). 2. 2. In Necturus (which apparently does not utilize its lungs in air) it was 14 μl cm −2 hr −1 but when in water the O 2 uptake of this species was similar to the others (in air). 3. 3. Pulmonary respiration was abolished in all these species by injecting gallamine and respiration was maintained through the skin. This approached normal “resting” levels in all species except for Siren. 4. 4. The rate of cutaneous O 2 accumulation was 10–16 μl cm −2 hr −1 in Siren, Necturus and Xenopus (all aquatic species) and 25 μl cm −2 hr −1 in Bufo and Rana (terrestrial). 5. 5. While cutaneous 0 2 uptake may support a “resting level” of metabolism it is inadequate for the large increases in respiration which occur during activity. 6. 6. The physiological importance and limitations of cutaneous O 2 accumulation are discussed in relation to an amphibious life and the evolutionary transition from an aquatic to terrestrial environment.

A theoretical and experimental investigation of the relationships between metabolic rate, body size, and oxygen exchange capacity

The influence of body size upon the decrease in weight-specific metabolic rate of organisms with increasing size is discussed. It is suggested that metabolic rate is closely correlated with, and perhaps dependent upon, the ability of an organism to obtain oxygen from the external environment. A model is presented that illustrates the advantage of having a decreasing weight-specific metabolic rate with increasing body size, rather than a linear relationship between the two. Support for the model is presented in the form of a literature review and with experimentation conducted with the aquatic salamander Siren lacertina.

Osmoregulation in the aquatic urodeles Amphiuma means (the Congo eel) and Siren lacertina (the myd eel). Effects of vasotocin

Vasotocin injected into the aquatic urodeles Siren lacertina and Amphiuma means results in water retention (about 4% body weight). Bullfrogs Rana catesbeiana respond much more strongly (13% body weight for 10 times less vasotocin). In the urodeles this response is the result of an antidiuresis, water transfer across the skin and urinary bladder being unchanged. The urodeles take up water, principally across the skin (there is little drinking), and this is excreted as a dilute (<50 Osmoles/kg H 2O) urine containing little sodium. Sodium reabsorption from the urine is aided by active transport from the urinary bladder (inhibited by ouabain and amiloride), but neither vasotocin nor aldosterone altered this.

Body Size and Metabolic Rate in Salamanders

Body Size and Metabolic Rate in Salamanders

Action of ouabain on sodium transport in the toad urinary bladder.

Action of ouabain on sodium transport in the toad urinary bladder.