Snake Head Research Articles

Body condition and head size in snakes

AbstractOn several occasions during my many years of working with various snake species, I observed a significant positive relationship between body condition and head size (the former calculated from residual scores from a general linear regression of ln-transformed mass on ln-transformed snout-vent length). Based on results from my long-term study of water pythons (Liasis fuscus) this relationship is, however, most likely caused by a condition-dependent bias when recording snake snout-vent length (SVL). Water pythons in good condition were recorded as being "shorter" and hence having relatively larger head size, whereas snakes in poor condition were recorded as being "longer" with concomitant smaller head relative head size. Such a systematic bias may lead to spurious conclusions concerning the adaptive significance of the relationship between snake body condition and head size.

An iron belt-buckle from the Late Iron Age discovered in Arad – Aurel Vlaicu Boulevard

The accidental discovery in the year 2001 of an iron bracelet, with snake head ornaments in Arad (Aurel Vlaicu Boulevard, near Betel Pentecostal Church) has signalled the existence of an archaeological site in the area. In the year 2011, from this very site, we have saved a piece used in clothing, a belt buckle with iron plates, covered with bronze sheeting (partially conserved). It belongs to the Babes II type (Rustoiu 6b). Similar pieces can be found in the “ Geto-Dacian” group, having been made in 1 century BC. Across the territory of the modern city Arad, traces of numerous archaeological sites have been found dating from the 2nd century BC to 1st century AD some of the more important being Arad – Gai I, Arad -Sala Polivalentă, Arad – Strada Caisului, Micălaca – Deluţ and Micălaca – Old Cemetery.

Born Knowing: Tentacled Snakes Innately Predict Future Prey Behavior

BackgroundAquatic tentacled snakes (Erpeton tentaculatus) can take advantage of their prey's escape response by startling fish with their body before striking. The feint usually startles fish toward the snake's approaching jaws. But when fish are oriented at a right angle to the jaws, the C-start escape response translates fish parallel to the snake's head. To exploit this latter response, snakes must predict the future location of the fish. Adult snakes can make this prediction. Is it learned, or are tentacled snakes born able to predict future fish behavior?Methods and FindingsLaboratory-born, naïve snakes were investigated as they struck at fish. Trials were recorded at 250 or 500 frames per second. To prevent learning, snakes were placed in a water container with a clear transparency sheet or glass bottom. The chamber was placed over a channel in a separate aquarium with fish below. Thus snakes could see and strike at fish, without contact. The snake's body feint elicited C-starts in the fish below the transparency sheet, allowing strike accuracy to be quantified in relationship to the C-starts. When fish were oriented at a right angle to the jaws, naïve snakes biased their strikes to the future location of the escaping fish's head, such that the snake's jaws and the fish's translating head usually converged. Several different types of predictive strikes were observed.ConclusionsThe results show that some predators have adapted their nervous systems to directly compensate for the future behavior of prey in a sensory realm that usually requires learning. Instead of behavior selected during their lifetime, newborn tentacled snakes exhibit behavior that has been selected on a different scale—over many generations. Counter adaptations in fish are not expected, as tentacled snakes are rare predators exploiting fish responses that are usually adaptive.

Feeding ecology of Liophis reginae semilineatus (Serpentes: Colubridae: Xenodontinae) in eastern Amazon, Brazil

We studied the diet of Liophis reginae semilineatus (Wagler, 1824) from eastern Amazon, Brazil, based on the analysis of 182 preserved specimens. Thirty-six individuals had prey in their stomachs; 34 (95%) contained exclusively anurans and 2 (5%) contained both anurans and lizards. The most common prey items were small Leptodactylus sp. (33.3%), followed by Physalaemus ephippifer (Steindachner, 1864) (10.3%). Prey ingested head-first (78%; n = 25) were significantly larger than prey ingested tail-first (22%; n = 7). Females of L. reginae semilineatus have longer and wider heads than conspecific males with the same body length, which correspond to sexual divergences in the diet (size of the prey). No correlation was found between snake head length vs. prey size (SVL, width and mass). Liophis reginae semilineatus is an anurophagous snake that probably forages actively on the ground.

Superoxide dismutase activity and isoenzyme profiles in bulbs of snake's head fritillary in response to cold treatment

The activities and isoenzyme profiles of superoxide dismutase (SOD) in in vitro Fritillaria meleagris bulbs in response to cold treatment (4?C) were investigated. Differences in SOD activity and isoenzyme profiles in bulbs under standard growth conditions, six weeks chilling, as well as seven days after the completion of cold treatment are presented. SOD activity initially decreased but then rapidly increased seven days after cold treatment. Four isoforms of SOD are active under standard and chilling conditions, while three isoforms are presented 7 days after cold treatment. Native gel electrophoresis indicated the presence of mitochondrial and chloroplast localized SODs. .

Optimisation and validation of a real-time reverse transcriptase-polymerase chain reaction assay for detection of betanodavirus

A RT-qPCR assay that was developed and optimised for detection of betanodaviruses was validated for use as a diagnostic test for viral nervous necrosis disease of fish. Four betanodavirus genotypes were detected but the sensitivity was greatest for redspotted grouper nervous necrosis virus (RGNNV). The analytical sensitivity was 10–1000-fold greater than that of a nested RT-PCR assay and the limit of detection was <0.4 TCID 50 units per reaction. The assay was highly repeatable (standard deviation of estimated log 10 (viral copies) 0.10 ± 0.08) and reproducible (standard deviation of estimated log 10 (viral copies) 0.08 ± 0.06). Diagnostic accuracy was assessed in 2193 samples comprising tissue homogenates from Australian bass ( Macquaria novemaculeata) and barramundi ( Lates calcarifer), and also in SSN-1 tissue culture supernatants, using virus isolation in striped snake head (SSN-1) cell culture as the gold standard. Diagnostic sensitivity and specificity were 100% when the assay was applied to Australian bass tissue and SSN-1 tissue culture supernatants, but for barramundi tissue were 99.1% and 92.8%, respectively. The apparent imperfect specificity was shown by specific amplification of alternate regions of the betanodavirus genome to be due to the lower sensitivity of virus isolation. This is the first study to report the diagnostic performance of a RT-qPCR assay for detection of betanodavirus.

Tentacled snakes turn C-starts to their advantage and predict future prey behavior

Fish are elusive prey with a short-latency escape behavior--the C-start--initiated to either the left or right by a "race" between 2 giant Mauthner neurons in the fish brainstem. Water disturbances usually excite the ipsilateral neuron, which massively excites contralateral motor neurons, resulting in a rapid turn away from striking predators. Here, it is reported that tentacled snakes (Erpeton tentaculatus) exploit this normally adaptive circuitry by feinting with their body, triggering the Mauthner cell that is furthest from their head milliseconds before a ballistic strike is initiated. As a result, fish that were oriented parallel to the long axis of the snake's head most often turned toward the approaching jaws, sometimes swimming directly into the snake's mouth. When strikes were instead directed at fish oriented at a right angle to the snake's head, snakes anticipated future fish behavior by striking to where fish would later be if they escaped from the snake's body feint, which fish usually did. The results provide an example of a rare predator taking advantage of a prey's normally adaptive escape circuitry and suggest that the snake's sensory-motor system is adapted to predict future behavior.

Snakeheads and Smuggling

Snakeheads and Smuggling

Determinants of feeding performance in free-ranging pit-vipers (Viperidae: Ovophis okinavensis): key roles for head size and body temperature

Feeding performance (handling time, capture success) in numerous animal species is well known to be influenced by a variety of ecological, functional, and physiological factors. Nonetheless, few studies have tested which factors are the strongest determinants of animal feeding performance in the wild. Using a field-based experiment, we examined the relationships among a number of functionally important variables and the predatory behaviour of free-ranging pit-vipers (Ovophis okinavensis) from Okinawa Island, Japan. Our main findings were: (1) strike latency was negatively related to snake body temperature and, hence, hotter snakes struck at frogs more readily than colder snakes; (2) initial bite position was correlated with ingestion direction (headfirst versus hindfirst) but ingestion direction was not correlated with ingestion duration; and (3) both snake head length and body temperature were negatively related with ingestion duration and, thus, snakes with longer heads and higher body temperatures had shorter ingestion durations. In O. okinavensis, head size and body temperature are therefore likely to have direct ecological consequences in terms of its feeding rate on explosively breeding frogs. More generally, however, this field-based study adds to the growing body of literature demonstrating that temperature has a pervasive influence on the feeding performance of ectotherms in general. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 93, 53–62.

Larval Rearing of the Spotted Snake head Channa punctatus Fed with Different Feeding Regimes

Larval Rearing of the Spotted Snake head Channa punctatus Fed with Different Feeding Regimes

Studies on Fecundity of Captive Reared Spotted Snake head Channa punctatus (Channidae)

Studies on Fecundity of Captive Reared Spotted Snake head Channa punctatus (Channidae)

Allometry and selection in a novel predator–prey system: Australian snakes and the invading cane toad

Because many organismal traits vary with body size, interactions between species can be affected by the respective body sizes of the participants. We focus on a novel predator–prey system involving an introduced, highly toxic anuran (the cane toad, Bufo marinus) and native Australian snakes. The chance of a snake dying after ingesting a toad depends on the size of the snake and the size of the toad, and ultimately reflects the effect of four allometries: (1) physiological tolerance (the rate that physiological tolerance to toad toxin changes with snake size); (2) swallowing ability (the rate that maximal ingestible toad size (i.e. snake head size) increases with snake body size); (3) prey size (the rate that prey size taken by snakes increases with snake head size) and (4) toad toxicity (the rate that toxicity increases with toad size). We measured these allometries, and combined them to estimate the rate at which a snake's resistance changes with toad toxicity. The parotoid glands (and thus, toxicity) of toads increased disproportionately with toad size (i.e. relative to body size, larger toads were more toxic) but simultaneously, head size relative to body size (and thus, maximal ingestible prey size relative to predator size) declined with increasing body size in snakes. Thus, these two allometries tended to cancel each other out. Physiological tolerance to toxins did not vary with snake body size. The end result was that across snake species, mean adult body size did not affect vulnerability. Within species, however, smaller predators were more vulnerable, because the intraspecific rate of decrease in relative head size of snakes was steeper than the rate of increase in toxicity of toads. Thus, toad invasion may cause disproportionate mortality of juvenile snakes, and adults of the sex with smaller mean adult body sizes.

Development of intermediate foodstuff derived from freshwater fish in China

According to the three-dimensional contour maps showing the gel-forming properties of surimi derived from freshwater fish, 8 species of surimi were classified into two types. The V-valley type surimi (silver carp, big-head carp, Chinese snake head and blunt snout bream) shows easy setting, low resistance to gel collapse, high enhancement ability with two-step heating, and narrow optimum heating temperature and time area, which are of the same characteristics as the wall-eye pollack surimi. In contrast, the Plateau type surimi (tilapia, grass carp, mud carp and common carp) exhibits difficult setting, high resistance to gel collapse, no enhancement ability with two-step heating, and wide optimum heating temperature and time area. There are seasonal changes of gelling properties of silver carp surimi, and the setting ability of surimi gel is higher in winter and lower in summer. The marine fish meat gels and the freshwater fish meat gels have the same acceptability for inland Chinese according to the sensory evaluation results. A slight increase in sensory scorings of kamaboko gels occurred when the extract from walleye pollack muscle was added, especially in the odor scoring of silver carp kamaboko gels.

Expression of 20β-hydroxysteroid dehydrogenase and P450 17α-hydroxylase/c17–20 lyase during hCG-induced in vitro oocyte maturation in snake head murrel Channa striatus

Partial cDNAs encoding carbonyl reductase like 20beta-hydroxysteroid dehydrogenase (20beta-HSD) and P450 17alpha-hydroxylase/c17-20 lyase (CYP17) were isolated from the ovary of snake head murrel and they exhibited high sequence identity to the Nile tilapia and rainbow trout, respectively. A low transcript level of both 20beta-HSD and CYP17 were detected in pre-vitellogenic follicles, while the transcript level was high in full-grown immature follicles. In hCG-induced in vitro oocyte maturation, we found a significant increase in 20beta-HSD transcript level after 2 h. The CYP17 transcripts also showed a considerable increase following hCG-induction compared to saline-treated controls. On the other hand, Western blot analysis demonstrated no significant change in the CYP17 protein level during hCG-induced in vitro oocyte maturation. Taken together, we suggest that in addition to 20beta-HSD, the CYP17 might have a role in the shift in steroidogenesis during meiotic maturation of snake head murrel.

Seabream GnRH: partial cDNA cloning, localization and stage-dependent expression in the ovary of snake head murrel, Channa striatus

Vertebrate reproduction is under the neuroendocrine control of the hypothalamic decapeptide GnRH which synchronizes various reproductive events and influences other reproduction related aspects like spawning behavior and pheromonal action in fish. Multiple forms of GnRH peptides have been reported across diverse vertebrate and invertebrate classes. Here we report the partial seabream GnRH (sbGnRH) cDNA sequence cloned from the brain of Channa striatus (snake head murrel) a fresh water perciform with immense economic and medicinal value across Asiatic countries. sbGnRH mRNA was found in brain, gill and ovary of mature murrel with possible implications to the effect of GnRH on pheromonal phenomena and on reinitiation of oocyte meiosis. In keeping with the earlier reported role of GnRH in initiation of oocyte meiosis we here present evidence from RT-PCR, ICC demonstrating an increase in the level of sbGnRH mRNA in ovary from pre-vitellogenic to post-vitellogenic follicles.

한국산 어류 8종 추출물의 생리활성

A search for contraction and relaxation responses on the smooth muscles, antimicrobial and antioxidant activity in different body parts of 4 freshwater fish and 4 marine fish were conducted. The four freshwater fish studied were Sarotherodon niloticus (tilapia), Channa arus (snake head), Cyprinus carpio (Israel carp) and Siluru osotus (catfish), and the four marine fish were Scyliorhinus torazame (tiger shark), Ateiepus japonicus (tadpole fish), Mugil cephalus (gray mullet) and Thamnaconus modestus (file fish). Frozen samples were extracted with distilled water containing <TEX>$1{\%}$</TEX> acetic acid. Antimicrobial activity against Bacillus subtilis and Eschrrichia coli was detected in extracts from several tissues in all species tested. Relatively high antimicrobial activity could also be detected in the bile extracts from C. carpio, M. cephalus, and T. modestus. Contraction and relaxation responses on smooth muscles could be detected in all species tested, especially in the intestine extracts. Antioxidant activity was also detected in extracts from several tissues in all species tested, while in the extracts from S. osotus, excluding livers and spleens, no antioxidant activity was detected. Results from this study suggest that fish are a potential source for the discovery of novel bioactive materials.

Return of the snakehead

Return of the snakehead

Bacterial and helminth bioload of cultured &lt;i&gt;Channa obscura&lt;/i&gt; fish

An investigation of the bacterial and helminth fuana of organs of diseased and healthy African snake head fish (Channa obscura) from Nigeria Agip Green River project, River State, Nigeria was undertaken. The intestine, skin, fin, gill, tissue and liver of the fish were examined for both bacterial and helminth load. The results indicated that the bacterial load of the diseased fish samples were higher than those of the apparently healthy fish. Identification tests of the probable isolates revealed the isolation of the following genera: Aeromonas, Citrobacter, Enterobacter, Klebsiella, Lactobacillus, Pseudomonas, Campylobacter, Proteus, Serratia, Staphyloccocus, Yersinia and Vibro sp. Whereas helminth fauna isolated were Camallanus sp., Capillaria sp., Acetodoxtra sp., Chimostomum sp, Diphostomum sp. and Polyonchobethium sp. Percentage helminth infestation was found to be higher in adults than sub-adults and juveniles, while the percentage prevalence of the helminth infections amongst the fishes examined was found to be 41%. Helminth infection therefore varies amongst age groups. This study reveals the bacteria and load of cultured Channa obscura Key words: Bioload, helminths, Bacteria, Cultured fish Journal of Aquatic Sciences Vol.18(2) 2003: 93-100

Semantic Eliminativism and the Theory-Theory of Linguistic Understanding

Suppose, familiarly, that you and a friend have landed in an alien territory, amidst people who speak a language you do not know. Upon seeing you, one of them starts yelling, seemingly alarmed. You say to your friend, “She thinks we want to hurt her. She's scared. We must seem very strange to her.” Your friend, who is facing you, says, “No, I think she's actually trying to warn you: there's a snake right above your head, on that tree. You see the sling in her hand? I think she's going to try to shoot it down.“On a prevalent view, much discussed in recent years, you and your friend have engaged in a mini-theoretical enterprise. Using certain observations of the alien's behaviour as your data, and deploying certain generalizations and principles concerning human behaviour, you advance hypotheses regarding the internal psychological states which issued in her observed behaviour.

The Cantilever Abilities of Snakes

The Cantilever Abilities of Snakes