dcsimg

Comprehensive Description

provided by Smithsonian Contributions to Zoology
Coniophanes fissidens

NATURAL HISTORY

Coniophanes fissidens is a small (snout-vent length to 550 mm, but adults usually less than 400 mm), predominantly diurnal snake of the forest floor. It is most common in the leaf litter of well-drained mesic forest below 1000 m (Myers, 1969), although it has been found up to 1600 m (Landy, et al., 1966) and in secondary growth forests (Duellman, 1963; Minton and Smith, 1960). Hidden beneath the leaf litter with only its head and neck exposed and elevated, the snake surveys the surrounding area for prey or prowls and searches for prey (Myers, 1969). Small, terrestrial amphibians and reptiles appear to be the major prey, e.g., Leptodactylus (Landy, et al., 1966; Minton and Smith, 1960), Colostethus, and Lepidoblepharis (Myers, 1969).

BODY SIZE

HATCHLINGS.—The largest snake with a yolk-sac scar had a snout-vent length of 123 mm. Our total Coniophanes sample contained 10 individuals this length or less, three (114, 120, and 123 mm long) of which had yolk-sac scars. The mean snout-vent length of hatchlings is 117.7 mm (standard deviation, ± 3.6 mm; range, 111–123 mm). Perhaps owing to the small sample size, the hatchlings from southern Mexico (N = 7) average somewhat larger (118.6 mm) than those from Costa Rica and Panama (115.7 mm; N = 3); however, geographic variation in hatchling size is a possibility.

GROWTH AND SEXUAL MATURITY.—In the absence of long-term mark and recapture data on individual snakes, it is impossible to provide precise information on growth and sexual maturity. Nonetheless, we believe that we can provide estimates of these two life history parameters. Females with class V follicles or oviducal ova are considered sexually mature. Such females are assumed to be, at most, a month or two away from egg deposition.

Combining the sexually mature females (N = 27) from all localities yields an average snout-vent length of 298.8 ± a standard deviation of 51.5 mm and a range of 230–425 mm. The mean snout-vent length of females (13) with only oviducal eggs is slightly higher, 307.8 ± 44.9 mm (244–425 mm). The sexually mature females from Chiapas (10) have a mean length of 306.6 ± 28.8 mm (276–374 mm), from Guatemala (13) 267.6 ± 30.1 mm (230–330), from Costa Rica (3) 361.0 ± 55.6 mm (325–425), and from Panama (1) 439.0. Thus, we estimate that, on the average, most females with a snout-vent length greater than 250 mm are sexually mature even if they do not possess mature follicles or oviducal eggs. Our data do not permit us to estimate the size at which males reach sexual maturity; however, based on results of most snake species studied (Shine, 1978), we speculate that it is reached at a smaller size.

Hatchling size and the size at sexual maturity provide the two end points for the period of fastest and greatest postembryonic growth. They further provide a means of estimating the history of growth in terms of months and years when the distribution of body size classes is analyzed in a size-month matrix (Figure 4).

Although the adequacy of our sample sizes has forced the combination of sample localities, thereby possibly obscuring discrete size classes or age cohorts, a general trend is indicated in the body size/month matrix (Figure 4). Using this matrix, we speculate that most hatchlings appear in June to September. By nine months, the juveniles have grown to approximately 150–180 mm and to 170–210 mm by first year. At the end of their second year, they range in size between 210–250 mm. A few larger ones have attained a body length indicating sexual maturity; however, the entire cohort probably does not reach sexual maturity until the end of three years of growth. These speculative data suggest an approximate growth rate of 1 mm/week for the first two years. Neither the rate of growth nor the timing of sexual maturity is greatly different from the small terrestrial snake Carphophis vermis (Figure 5). Carphophis vermis is, however, a temperate-zone species and has little or no growth during the winter months, yet it still averages a growth rate of about 1.2 mm/week for the first two years of life (Clark, 1970). There is no reason to assume that growth rate is continuous in tropical snakes, for most live in seasonal environments where parameters other than temperature, e.g., rainfall and prey abundance, fluctuate throughout the year.

SEXUAL DIMORPHISM

BODY AND TAIL LENGTH.—Myers (1969) noted that the ranges in relative tail lengths of females (26–38 percent of total length) and males (33–41 percent) were not greatly different in Panamanian C. fissidens. Our samples also demonstrate little difference in male and female tail lengths (Figure 6). However, most overlaps in tail length occur in the immature individuals, i.e., those less than 250 mm snout-vent length. Thus, in C. fissidens sexually mature males average longer tails than females, but only slightly longer.

GONAD POSITION.—Since the difference in tail length of males and females has been hypothesized as caudad displacement of the cloaca-vent region in females or the craniad displacement in males, the position of the gonads relative to the vent might also be sexually dimorphic. The relative position of the posterior edge of the left gonad was determined by dividing gonad displacement by snout-vent length. Sexual dimorphism of this displacement does not exist in any regional samples, e.g., Chiapas sample F = 0.1, df 1/54. The mean displacement falls between 0.15 and 0.16 for adults of both sexes in the entire Coniophanes sample.

TAIL BREAKAGE.—Coniophanes fissidens shows a high frequency of broken tails (approximately 30 percent of our sample). The frequency of broken or regenerated tails has been used in lizards to indicate the intensity of predation (Vitt and Ohmart, 1977). It is an oft-stated assumption that female snakes are more secretive than males and are presumably exposed less to predation. The frequency of broken tails is a potential indicator of differential predation.

Considering snakes of all sizes, only three localities show a Chi-square probability of less than 25 percent, which suggests a differential predation on the sexes. In the Guatemalan Olas de Moca sample, females have more broken tails (8 broken: 11 entire, females; 1:8, males; x2 = 2.69). The Guatemalan Porvenir sample also suggests higher predation on females, whereas the adjacent Costa Rican Río Frío samples suggests higher predation on males; however, their sample sizes (8 and 11, respectively) are too small to be more than indicative. At all other localities, males and females share the same proportion of broken and entire tails and presumably the same level of predation.

Considering only the sexually mature snakes (viz., snout-vent length greater than 250 mm), the trends are the same as observed above. The local samples were combined into regional samples (Figure 7) to the Chiapas and Guatemalan samples show no difincrease sample sizes. Of the three larger samples, ferential predation (x2 = 0.001 and 0.341, respectively), whereas the Costa Rican sample indicates a higher frequency of predation on males (x2 =2.778). In respect to all the samples, it appears that females and males are usually subjected to equal predation pressure.

SEX RATIO

Males did not strongly outnumber females even in the smaller samples. A 1:1 ratio or close approximation thereof (Chi-square less than 0.800) occurs in 11 of the 13 local samples when considering only sexually mature snakes—in contrast to five local samples when snakes of all sizes are included. The majority (5) of the remaining eight samples show a preponderance of males, with females strongly dominant in only the Escuintla and Olas de Moca samples. The regional samples (Figure 7) show the mixed pattern of the local samples, whereas the combination of all the samples clearly demonstrates a 1:1 ratio (x2 = 0.021, all sizes; 0.256, mature). In spite of our small sample size and the nonrandomness of museum specimen samples, the evidence suggests an equality of sexes in Coniophanes fissidens.

REPRODUCTION

CLUTCH SIZE.—The modal clutch size for oviducal eggs in C.fissidens is three. Classes IV and V follicles show the same modal clutch size (Table 2). The range in the entire Coniophanes sample is one to seven. The seven eggs occurred in the largest gravid female (snout-vent length 425 mm; Costa Rica) and suggest a correlation between body size and clutch size. A positive correlation does exist (Figure 8), although a larger sample size is required to confirm this correlation. Factors other than body size also appear to affect clutch size, since four females between 275–330 mm snout-vent length possess only one or two eggs. Furthermore the largest female (439 mm) has only a single class V follicle, but five class IV follicles. Presumably these numbers reflect the next two clutches; however, a single clutch of six eggs might occur next.

We assume that each follicle class represents a discrete clutch. The ranges and modes of follicle classes IV and V (Table 2) support this assumption. The number of class III follicles usually equals those of the older follicle classes. A few females do have more III follicles than those of either IV or V so retrogression of III follicles may occur. Retrogression or atrophy of a portion of the class II follicles seems certain, because the number of II follicles is seldom less than double the number of the follicles in classes IV or V and often more. The number of class I follicles usually does not exceed four, probably owing to our failure to see and record the tiny follicles.

Livezey and Peckham (1953) reported a female (240 mm snout-vent length) from San Marcos, Guatemala, with two oviducal eggs in May. This body length suggests that this was her first clutch. The eggs were 25.1 and 33.2 mm long. Our sample of oviducal eggs ranged from 14.8 to 31.0 mm long with a mean of 22.4 and standard deviation of 3.66.

REPRODUCTIVE CYCLE.—Our data (Table 3) are too sparse to provide an unequivocal answer to the existence of cyclic or acyclic reproduction in C. fissidens populations. All large monthly samples contain both gravid and nongravid individuals, but no locality has adequate representation for all months. Thus, our data can be used to argue for either a cyclic or acyclic pattern. We interpret the data (Table 3) to suggest that Chiapas snakes have an extended reproductive period from May through September (because of hatchlings present in July and gravid females in August); Guatemalan snakes, March through June; and Costa Rican snakes, April through July. Panamanian snakes may lay their eggs at the beginning of the dry season, December through February.
license
cc-by-nc-sa-3.0
bibliographic citation
Zug, George R., Hedges, S. Blair, and Sunkel, Sara. 1979. "Variation in reproductive parameters of three neotropical snakes, Coniophanes fissidens, Dipsas catesbyi, and Imantodes cenchoa." Smithsonian Contributions to Zoology. 1-20. https://doi.org/10.5479/si.00810282.300

Coniophanes fissidens

provided by wikipedia EN

Coniophanes fissidens, the yellowbelly snake, is a species of snake in the family Colubridae. The species is native to Mexico, Guatemala, Honduras, Belize, Nicaragua, El Salvador, Costa Rica, Panama, Ecuador, Peru, and Colombia.[2]

References

  1. ^ Flores-Villela, O.; Nicholson, K.; Wilson, L.D.; Caicedo, J. (2019). "Coniophanes fissidens". IUCN Red List of Threatened Species. 2019: e.T197471A217775409. Retrieved 19 November 2021.
  2. ^ Species Coniophanes fissidens at The Reptile Database
license
cc-by-sa-3.0
copyright
Wikipedia authors and editors
original
visit source
partner site
wikipedia EN

Coniophanes fissidens: Brief Summary

provided by wikipedia EN

Coniophanes fissidens, the yellowbelly snake, is a species of snake in the family Colubridae. The species is native to Mexico, Guatemala, Honduras, Belize, Nicaragua, El Salvador, Costa Rica, Panama, Ecuador, Peru, and Colombia.

license
cc-by-sa-3.0
copyright
Wikipedia authors and editors
original
visit source
partner site
wikipedia EN