Interdigitating cells in the thymus of the turtle Mauremys caspica

Summary Interdigitating cells are non-lymphoid elements in the thymus and peripheral, secondary lymphoid organs of higher vertebrates. Their origin and functional significance are a matter of controversy. In the present investigation we analyze, for the first time, the nature of presumptive interdigitating cells of the thymus of an ectothermic vertebrate, the turtle Mauremys caspica. This model is specially useful because of the seasonal variations that affect the reptilian lymphoid organs. Immature pro-interdigitating cells and phagocytosing mature interdigitating cells are described with special emphasis on their ultrastructural characteristics and possible relationships with monocytes and macrophages.     

AMONG-FAMILY VARIATION FOR ENVIRONMENTAL SEX DETERMINATION IN REPTILES

Unlike birds and mammals, in many reptiles the temperature experienced by a developing embryo determines its gonadal sex. To understand how temperature-dependent sex determination (TSD) evolves, we must first determine the nature of genetic variation for sex ratio. Here, we analyze among-family variation for sex ratio in three TSD species: the American alligator (Alligator mississipiensis), the common snapping turtle (Chelydra serpentina) and the painted turtle (Chrysemys picta). Significant family effects and significant temperature effects were detected in all three species. In addition, family-by-temperature interactions were evident in the alligator and the snapping turtle, but not in the painted turtle. Overall, the among-family variation detected in this study indicates potential for sex-ratio evolution in at least three reptiles with TSD. Consequently, climate change scenarios that are posited on the presumption that sex-ratio evolution in TSD reptiles is genetically constrained may require reevaluation.     

Naturally abundant basophils in the snapping turtle, Chelydra serpentina, possess cytophilic surface antibody with reaginic function

Basophils constitute 50 to 63% of the blood leukocytes in Chelydra serpentina, the snapping turtle. Immunoglobulin (Ig) on the surface of the turtle basophil was detected by indirect immunofluorescence by using an IgG fraction from rabbit anti-turtle Ig serum (RATIg) and a fluoresceinated goat anti-rabbit antibody incubated at 4 degrees C. However, when the cells were incubated with RATIg at 22 degrees C, the basophil number, as determined by Wright's stain and neutral red counts, decreased dramatically. This morphologic evidence of degranulation was directly proportional to the antiserum concentration. Degranulation also correlated with cell histamine release (r = 0.73). In other experiments, turtle basophils were found to express antigen-specific surface Ig after immunization with sheep red blood cells (SRBC). Washed basophils from immunized turtles formed basophil-SRBC rosettes in vitro. Basophils from control turtles did not. Basophil-SRBC rosettes could also be induced by in vitro passive sensitization by preincubation of normal turtle basophils in the SRBC immune turtle sera. This study shows clearly that the turtle basophil has an immune capacity analogous to the mammalian basophil/mast cell. This study also contains the first direct evidence for the existence of reaginic antibody (or antibodies) in an ectothermic vertebrate. Finally, C. serpentina is proposed as a unique animal model for the study of basophil function.     

The complete mitochondrial genome of the enigmatic bigheaded turtle (Platysternon): description of unusual genomic features and the reconciliation of phylogenetic hypotheses based on mitochondrial and nuclear DNA

Background  

The big-headed turtle (Platysternon megacephalum) from east Asia is the sole living representative of a poorly-studied turtle lineage (Platysternidae). It has no close living relatives, and its phylogenetic position within turtles is one of the outstanding controversies in turtle systematics. Platysternon was traditionally considered to be close to snapping turtles (Chelydridae) based on some studies of its morphology and mitochondrial (mt) DNA, however, other studies of morphology and nuclear (nu) DNA do not support that hypothesis.     

Phylogeny of Gut-Associated Lymphoid Tissue

Gastrointestinal (GI) tracts from four anuran and four urodelespecies were examined macroscopically and histologically fromthe esophagus to the cloaca. Anatomic observations were facilitatedby treating the GI tracts with acetic acid, a procedure whichremoves gut epithelium and exposes underlying structures. Histologicanalysis involved routine as well as specific histochemicaltechniques. Detailed observations reveal that anuran amphibianspossess nodular, well-organized gut-associated lymphoid tissue(GALT) throughout their GI tracts. In striking contrast, nosuch patterns of lymphoid tissue have been noted in the Urodela. Similar techniques have revealed the location of lymphoid tissuesin the urogenital system (e.g., cloaca and bladder) of advancedanurans. These nodules appear to be lacking in the primitiveanuran Xenopus and in all the urodele species we examined. Preliminary observations have confirmed GALT and urogenital-associatedlymphoid tissues in the snapping turtle.     

Cranial variation amongst independent lineages of the alligator snapping turtle (Macrochelys temminckii)

Recent interest in diagnoses and relationships between lineages of the alligator snapping turtle (Macrochelys temminckii) present conflicting patterns of molecular variation across the taxon's range. This study uses geometric morphometric techniques to test molecular hypotheses. We analyse alligator snapping turtle cranial variation amongst populations (i.e. drainages) with the hypothesis that populations of turtles recovered as monophyletic by previous molecular studies are more similar to each other in cranial shape. Dorsal, lateral and ventral cranial shape analyses corroborate the uniqueness of populations recovered by molecular genetic hypotheses. Additionally, analyses reveal near equal separation between drainages that were assigned to monophyletic clades by previous phylogenetic studies. These results reveal the potential for more independent lineages that have yet to be diagnosed, and unique cranial shapes are described for our three most heavily sampled drainages.     

A Test of Temporal Variation in Risk and Food Stimuli on Behavioral Tradeoffs in the Rusty Crayfish, Orconectes rusticus: Risk Allocation and Stimulus Degradation

The effects of temporal variation in exposure to predation risk on behavioral tradeoffs were tested in the rusty crayfish, Orconectes rusticus. Based on the risk allocation hypothesis, we predicted that increasing the frequency of encounter with predation risk would yield increasing responses to a food stimulus in the presence of both a risk stimulus and a food stimulus. Crayfish were exposed to risk every 12 h, every 6 h, or left undisturbed for 24 h prior to testing. The risk stimuli used were a plain water control, snapping turtle (Chelydra serpentina) cue, and conspecific alarm cue. After 24 h of conditioning, the crayfish were exposed to a combination of risk cue and food cue. The behavioral responses of the crayfish were recorded for 5 min immediately following the introduction of the cues and again for 5 min, 1 h after stimulus exposure. The crayfish were observed at the two times to determine how their responses to the combination of risk and food cues changed over time. The responses of the crayfish were significantly influenced by stimulus treatment, time, and the interaction of time and stimulus treatment. Further analysis indicated that responses to the stimulus treatments changed differently over time. Immediately after exposure, the crayfish were more active in the control and snapping turtle treatments than in the conspecific alarm treatment. The high levels of activity initially observed in the control and snapping turtle treatments waned over time, such that the behaviors recorded 1 h after exposure were not significantly affected by stimulus treatment. Neither frequency nor the interactions of frequency with stimulus and/or time significantly affected crayfish behavior. The results of this study did not support the risk allocation model and contrast with results from similar work on the virile crayfish, Orconectes virilis.     

Observations on Haemogregarina balli sp. n. from the Common Snapping Turtle,Chelydra serpentina*

SYNOPSIS. Haemogregarina balli sp. n. is described from the blood and organs of the common snapping turtle Chelydra serpentina serpentina and from the gastric and intestinal ceca of the presumed invertebrate hosts, the leeches Placobdella parasitica and Placobdella ornata. In the peripheral blood of the turtle, male and female gametocytes and immature erythrocytic schizonts are found within erythrocytes. The maturation of erythrocytic schizonts containing 6–8 merozoites is recorded from liver imprints. Schizonts with 13–25 merozoites are found in various cells of the liver, lung and spleen. In the gastric ceca of the leeches the host erythrocytes are digested, releasing the gametocytes and immature erythrocytic schizonts. Immature erythrocytic schizonts degenerate. Association of the gametocytes occurs in the intestinal ceca. The microgametocyte apparently gives rise to 4 nonmotile microgametes, one of which fertilizes the macrogamete while the other remain as condensed, residual nuclei on the periphery of the developing oocyst. The oocyst increases in size with maturity. A mature oocyst produces 8 sporozoites from a single germinal center. Sporozoites liberated from the oocyst are found in the tissues of the leech. Transovarial transmission of the parasite does not occur in the turtle. Attempts at experimental transmission failed. Previously unfed (control) leeches were negative for the parasite. Haemogregarina balli is compared with other haemogregarines described from C. serpentina. Features of species of Haemogregarina and Hepatozoon as well as the taxonomy of these genera are discussed.     

The fate of intraperitoneally injected carbon particles in cyprinid fish

Summary The lymphoid organs of rosy barb (Barbus conchonius) and carp (Cyprinus carpio) were investigated for their phagocytic uptake of carbon, after its intraperitoneal injection. Carbon handling was similar in both species. It was first detected in the lymphoid organs at 30 min after injection. During the first day, carbon was phagocytized by macrophages situated in the spleen within the ellipsoids and in the red pulp. In head and trunk kidney, carbon was found in macrophages scattered throughout the haemopoietic parenchyma, and in cells lining the blood sinuses. In the spleen, macrophages replete with carbon left the ellipsoidal structures and formed aggregates with pigment-containing macrophages from day 6 onwards. In all lymphoid organs, almost all carbon was ultimately concentrated in the melano-macrophage centres.     

Phylogeny of Regulatory Regions of Vertebrate Tyrosinase Genes

Highly homologous DNA elements were found to be shared by the upstream regions of the mouse tyrosinase and tyrosinase related protein (TRP-1) genes. Several nuclear proteins were shown to bind to both of these upstream regions. Shared homologous DNA elements were also found in the 5’ flanking sequences of Japanese quail and snapping turtle tyrosinase genes. Shared homologous nucleotide sequences were found to be scattered like an archipelago in the 5’ upstream regions of mouse and human tyrosinase genes. Comparisons between Japanese quail and snapping turtle tyrosinase genes gave similar results. On the contrary, mammalian (mouse and human) and nonmammalian (quail and snapping turtle) tyrosinase genes did not show significant homology in their 5’ upstream regions. In contrast, coding sequences in the first exons of vertebrate tyrosinase genes and their deduced amino acid sequences were found to be highly conserved except for their putative leader sequence-coding regions.     

A series of stages in the embryonic development of Chelydra serpentina

Eggs of the common snapping turtle, Chelydra serpentina serpentina were incubated at 30°C and at 20°C. The incubation period at the higher temperature was about 63 days. At the lower temperature, the period was estimated to be 140 days. Lengths of the embryos at various times of development were recorded. A series of 26 stages is described. The staging is based on timed intervals at a constant temperature, 20°C.     

Could the elongate yellow-orange nostrils of Anguilla bicolor McClelland, 1844 function as fishing lures?

The shortfin eel Anguilla bicolor has elongate, yellow nostrils tipped with orange that protrude forward above the mouth. They are a striking, highly visible feature and it is hypothesised that they function as lures to attract prey, analogous to the illicium and esca of anglerfishes and frogfishes and the lingual appendage of the alligator snapping turtle. Another possible function is as an intraspecific signalling device. The first hypothesis is favoured here.     

White pulp compartments in the spleen of the turtle Mauremys caspica

Summary The aim of the present study was to analyze the nature of lymphoid and non-lymphoid cellular components occurring in distinct histological compartments of the splenic white pulp of the turtle, Mauremys caspica, in order to define their possible correlations with those of the spleen of higher vertebrates, principally mammals. The white pulp of M.caspica consisted of 3 clearly distinguishable regions: (1) the periateriolar lymphoid sheath, and (2) the inner and (3) the outer zones of the periellipsoidal lymphoid sheath. Reticular cells intimately associated with reticular fibres constituted an extensive meshwork in the periarteriolar lymphoid sheath which housed principally Ig-negative lyphoid cells, mature and immature plasma cells, and interdigitating cells. A few Ig-positive cells were also present in the peripheral region of the periarteriolar lymphoid sheath. The inner and outer zones of the periellipsoidal lymphoid sheath were separated by a discontinuous layer of reticular cell processes. In the inner zone, surface Ig-positive lymphoid cells predominated as well as dendritic cells, resembling ultrastructurally the mammalian follicular dendritic cells, although no germinal centres were found in the turtle spleen. Macrophages, some cytoplasmic Ig-positive cells, and Ig-negative lymphoid cells appeared in the outer zone of the periellipsoidal lymphoid sheath. These results allow us to speculate on a phylogenetic relationship between the periarteriolar lymphoid sheath and the inner and the outer zones of the periellipsoidal lymphoid sheath of the spleen of M. caspica and the periarteriolar lymphoid tissue, the lymphoid follicles and the marginal zone, respectively, of the mammalian splenic white pulp.     

Creatine kinase and mitochondrial respiration in hearts of trout,cod and freshwater turtle

The importance of the creatine kinase system in the cardiac muscle of ectothermic vertebrates is unclear. Mammalian cardiac muscle seems to be structurally organized in a manner that compartmentalizes the intracellular environment as evidenced by the substantially higher mitochondrial apparent K_m for ADP in skinned fibres compared to isolated mitochondria. A mitochondrial fraction of creatine kinase is functionally coupled to the mitochondrial respiration, and the transport of phosphocreatine and creatine as energy equivalents of ATP and ADP, respectively, increases the mitochondrial apparent ADP affinity, i.e. lowers the K_m. This function of creatine kinase seems to be absent in hearts of frog species. To find out whether this applies to hearts of ectothermic vertebrate species in general, we investigated the effect of creatine on the mitochondrial respiration of saponin-skinned fibres from the ventricle of rainbow trout, Atlantic cod and freshwater turtle. For all three species, the apparent K_m for ADP appeared to be substantially higher than for isolated mitochondria. Creatine lowered this K_m in trout and turtle, thus indicating a functional coupling between mitochondrial creatine kinase and respiration. However, creatine had no effect on K_m in cod ventricle. In conclusion, the creatine kinase-system in trout and turtle hearts seems to fulfil the same functions as in the mammalian heart, i.e. facilitating energy transport and communication between cellular compartments. In cod heart, however, this does not seem to be the case.Abbreviations ACR acceptor control ratio - CK creatine kinase - PCr creatine phosphate - V_ADP ADP-stimulated respiration rate - V_max maximal respiration rate - V₀ respiration rate in the absence of ADPCommunicated by: G. Heidmaier     

Characterization of microsatellite DNA markers for the alligator snapping turtle,Macrochelys temminckii

Two trinucleotide and seven tetranucleotide microsatellite loci were isolated from an alligator snapping turtle Macrochelys temminckii. To assess the degree of variability in these nine microsatellite loci, we genotyped 174 individuals collected from eight river drainage basins in the southeastern USA. These markers revealed a moderate degree of allelic diversity (six to 16 alleles per locus) and observed heterozygosity (0.166–0.686). These polymorphic microsatellite loci provide powerful tools for population genetic studies for a species that is afforded some level of conservation protection in every state in which it occurs.     

Incidental nest predation in freshwater turtles: inter- and intraspecific differences in vulnerability are explained by relative crypsis

There has long been interest in the influence of predators on prey populations, although most predator–prey studies have focused on prey species that are targets of directed predator searching. Conversely, few have addressed depredation that occurs after incidental encounters with predators. We tested two predictions stemming from the hypothesis that nest predation on two sympatric freshwater turtle species whose nests are differentially prone to opportunistic detection—painted turtles (Chrysemys picta) and snapping turtles (Chelydra serpentina)—is incidental: (1) predation rates should be density independent, and (2) individual predators should not alter their foraging behavior after encountering nests. After monitoring nest survival and predator behavior following nest depredation over 2 years, we confirmed that predation by raccoons (Procyon lotor), the primary nest predators in our study area, matched both predictions. Furthermore, cryptic C. picta nests were victimized with lower frequency than more detectable C. serpentina nests, and nests of both species were more vulnerable in human-modified areas where opportunistic nest discovery is facilitated. Despite apparently being incidental, predation on nests of both species was intensive (57% for painted turtles, 84% for snapping turtles), and most depredations occurred within 1 day of nest establishment. By implication, predation need not be directed to affect prey demography, and factors influencing prey crypsis are drivers of the impact of incidental predation on prey. Our results also imply that efforts to conserve imperiled turtle populations in human-modified landscapes should include restoration of undisturbed conditions that are less likely to expose nests to incidental predators.     

大鳄龟感染蛙病毒的PCR检测及组织病理分析

2013年3月成都市某海洋馆送检2只发病大鳄龟(Macrochelys temminckii),临床特征表现为:精神状态萎靡,爬行无力,对外界刺激反应迟钝;颈部和四肢局部红肿,腹甲溃烂,严重部位甚至穿孔,最后死亡。为明确患病大鳄龟的病因,进行了细菌学、组织病理学和PCR检查。细菌学检查阴性;病理组织学观察发现,大鳄龟多组织、器官均发生严重病变,尤其是肾、肝、肺和心的损伤最为严重,表现为明显的变性、坏死和炎症细胞浸润,并在一些病变组织细胞浆内见嗜酸性或嗜碱性包涵体。针对蛙病毒(Ranavirus)病毒的特异性PCR检测扩增出蛙病毒主要衣壳蛋白(MCP)基因500 bp目的片段,测序后的DNA序列与Gen Bank中已知核酸序列进行Blast比对,发现其与Gen Bank中的蛙病毒主要衣壳蛋白基因同源性达95%~99%。根据组织病理特点及PCR检测结果推测大鳄龟的死亡是感染蛙病毒所致。     

Post-autotomy claw regrowth and functional recovery in the snapping shrimp Alpheus angulosus

The ability to regenerate lost tissues, organs or whole body parts is widespread across animal taxa; in some animals, regeneration includes transforming a remaining structure to replace the one that was lost. The transformation of one limb into another involves considerable plasticity in morphology, physiology and behavior, and snapping shrimp offer excellent opportunities for studying this process. We examined the changes required for the transformation of the small pincer to a mature snapping claw in Alpheus angulosus. First molt claws differ from mature claws in overall shape as well as in morphology related to snapping function; nonetheless, shrimp with first molt claws do produce snaps. While most shape variables of second molt claws do not differ significantly from mature claws, the plunger (structure required for snap production) does not reach mature size until the third molt for females, or later for males. Thus, the pincer claw can be transformed into a functional snapping claw in one molt, although both the underlying morphology and superficial shape are not fully regenerated at this stage. The rapid production of a functional snapping claw that we observe in this study suggests that this particular function is of significant importance to snapping shrimp behavior and survival.     

Conversion of cholesterol to progesterone by turtle corpus luteum

Homogenates of corpora lutea from the snapping turtle, $\text{Chelydra}$$\text{serpentina serpentina}$ were capable of converting small (< 1%) amounts of cholesterol-³H to progesterone-³H. There was about twice as much steroidogenic activity in corpora lutea taken from animals still carrying oviducal eggs as in those from animals that had laid their eggs. However, the latter showed up to an 80% increase in conversion of cholesterol to progesterone when turtle pituitary homogenate was incubated along with the luteal homogenate. Approximately 4 and 9 mg/g of free and esterified sterol, respectively, were found in the turtle corpus luteum. These results suggest that the corpus luteum of the oviparous turtle functions as a steroidogenic organ.     

Problem of reptile play: Environmental enrichment and play behavior in a captive Nile soft-shelled turtle,Trionyx triunguis

Giving captive animals the opportunity to interact with objects in a “playful” manner is often considered a method of environmental enrichment. However, the occurrence of play in nonavian reptiles is controversial and poorly documented. Similarly, the role of environmental enrichment in fostering psychological well-being in reptiles has been little studied. For several years, an adult, long-term captive, Nile soft-shelled turtle, Trionyx triunguis, at the National Zoo (Washington, D.C.), was provided objects such as balls, sticks, and hoses in an attempt to reduce self-mutilation behavior. The turtle spent considerable time with the objects, and the level of self-mutilation behavior decreased greatly over many months. Video recordings made in various contexts were analyzed in detail, and an ethogram of this turtle's behavior was developed. The turtle interacted with the objects (e.g., basketball, hose, stick) for 20.7% of the time it was observed and was active for 67.7% of the time. Both figures are unusually high for any animal, especially a turtle. The relative lack of play in ectothermic reptiles is supported by the surplus resource theory of play, which considers the joint effects of parental care, metabolism, endothermy, and arousal in providing the context in which playfulness could be manifested and promoted in vertebrate evolution. The existence of vigorous playlike behavior in a member of an ancient reptilian lineage indicates that, in the right circumstances, object play can be performed by reptiles and that having the opportunity to do so may be beneficial in captivity. © 1996 Wiley-Liss, Inc.