Ranitomeya vanzolinii ( Myers, 1982 )

Klein, Benjamin, Regnet, Ruth Anastasia, Krings, Markus & Rödder, Dennis, 2020, Larval development and morphology of six Neotropical poison-dart frogs of the genus Ranitomeya (Anura: Dendrobatidae) based on captive-raised specimens, Bonn zoological Bulletin 69 (2), pp. 191-223 : 216-218

Ranitomeya vanzolinii ( Myers, 1982)

Breeding behavior in captivity. Successful reproductions were observed in two different terraria, each inhabited by four specimens. While the breeding pairs of the first tank deposited the clutches of two to three whitish to beige eggs in a horizontally orientated and dry film con- tainer, the breeding pairs of the second tank placed their clutches of similar size in the bromeliad phytotelm. In rare cases, tadpoles at different development stages were found within the bromeliad phytotelm. Reproduction occurred occasionally.

Larval morphology. The description is based on a single specimen at stage 41 ( ZFMK 97361 ). Further voucher specimens are ZFMK 97369 and 97379. According to McDiarmid & Altig (1999), the tadpole belongs to the exotrophic, lentic, benthic and arboreal larval type. All measurements that were used to calculate the following proportions and its comparison with the other species of this study, can be found in Appendix III .

Dorsal view: Body shape is oval and elongated (MBW/ BL = 0.76). The snout is short and moderately pointed (RED/BL= 0.23, BWN/BWE = 0.65). The shape of the nares is not visible in dorsal view. A skin fold connects the nares with the anterior margin of the eyes. Eyes are large (ED/BL= 0.10), located dorsally and orientated laterally. Internarial distance is smaller than interorbital distance (IND/IOD = 0.48). The single sinistral spiracle is not visible in dorsal view.

Lateral view: Body is depressed (MBH/MBW = 0.71), snout is round. Nares are shaped elliptically, located laterally and orientated ventrolaterally. The single, sinistral spiracle is situated below the longitudinal axis, at the second half of the body (RSD/BL = 0.61), and is oriented laterally. The inner wall is free from the body and the opening is round. The maximum body height is situated posterior to the eye. The tail is long and broadly round- ed (TAL/BL= 1.87, TAL/TL = 0.65). The musculature is well developed (TMH/MTH = 0.54, TMW/MBW = 0.33). “V”-shaped myosepta are visible along the whole length of the tail, particularly in the second half. At the maximum tail height, the upper fin is nearly double as high as the lower fin. Both fins originate at the tail-body junction. Ventral tube is slightly reduced, dextral, emergence sagittal from abdomen. Hindlimb development is completed. Upper and lower labia are visible in lateral view.

Oral apparatus: The oral disc is elliptical, emarginated, positioned ventrally and covers nearly one third of the maximum body width (ODW/MBW = 0.27). Marginal, transparent and rounded papillae are present at the posterior labium and except of six to seven papillae at the most lateral part, absent at the anterior labium. Submarginal papillae are absent. The anterior labium contains two tooth rows of the same width (A1, A2) with a large medial gap in the second row (A2-GAP). The posterior labium contains three tooth rows (P1, P2, P3) of which the first row has a moderate medial gap (P1-GAP). P2 is slightly shorter than P1, P3 is slightly shorter than P2. Both jaw sheaths are black and serrated, lateral processes of the upper jaw sheath are present and extend barely past the lower jaw sheath. The tooth row formula is 2(2)/3(1) ( Fig. 13D ).

Coloration of a living tadpole of R. vanzolinii (ZFMK 97361). The basic color of the dorsum is dark gray to black and lacks any pattern of another color ( Fig. 13A 1 , A 2 ). Hindlimbs are equally colored. The tail is brighter than the dorsum, with a color gradient between the first and the second half of the tail, whereas the color becomes brighter till the tip. The transparent fins are spotted with dark dots.

Coloration of a preserved tadpole of R. vanzolinii (ZFMK 97361). The basic color of the dorsum is anthracite, with some beige spotted areas at the forelimb pouches and the muscle attachment of the tail as well as a light gray area which originates at the tip of the snout and extends to the posterior margin of the eyes. The hindlimbs are of the same color as the dorsum, slightly spotted with beige dots. The tail is beige; the anterior half is darker than the posterior one. Fins are transparent and spotted with gray dots. The ventral side is as anthracite as the dorsal side, slightly spotted with beige dots.

Larval staging. At stage 25, right after hatching, the tadpoles had a surface area of 0.19 ± 0.05 cm ². During the transition from stage 25 to 27, when the hindlimb bud was just slightly visible in some rare cases, the tadpoles had a surface area of 0.32 ± 0.11 cm ² ( Table 12). After 32 to 52 days, 50% of the larvae had reached stage 28. At this time, while the hindlimb bud was as long as wide and therefore clearly discernible, the tadpoles had a mean surface area of 0.53 ± 0.15 cm ². In between the stages 29 to 40, the development of the hindlimbs was completed and the larvae had a mean surface area of 0.76 ± 0.13 cm ². All toes became separated and the hindlimbs pigmented. After 51 to 73 days (mean = 60 days), half of all tadpoles had reached stage 41 ( Fig. 6 ). The forelimb buds were clearly discernible and the larvae had a mean surface area of 0.98 ± 0.09 cm ². While the forelimbs grew inside the body, the larval growth rate decreased. After 64 to 94 days (median = 73 days), half of the tadpoles reached stage 42 and the forelimbs emerged. At this time the tadpoles reached their peak of growth with a surface area of 1.03 ± 0.11 cm ². Afterwards, as a part of the ongoing metamorphosis during the stages 43 to 46, the tail was reduced and the mean surface area decreased to a value of 0.86 ± 0.13 cm ² ( Fig. 6 , Table 12). Altogeth- er, the transition from a free living larva to a metamorph which initiated the resorption of the tail lasted 61 to 107 days, while half of all tadpoles reached that development period after 66 to 91 days (median = 77 days).

The development was observed under constant conditions with a temperature of 24 °C, while the annual mean temperature within the natural distribution area of R. vanzolinii is slightly higher (T Mean = 24.6 °C, T Max = 28.9 °C, T Min = 19.6 °C: Karger et al. 2017; Fig. 7 ).

Figures

Fig. 13. Illustrations of the tadpole of Ranitomeya vanzolinii, stage 41 of Gosner (1960). A1. Dorsal view, photograph. A2. Dorsal view, drawing. B1. Ventral view, photograph. B2. Ventral view, drawing. C1. Lateral view, photograph. C1. Lateral view, drawing. D. Drawing of the oral disc. LTRF = 2(2)/3(1).

Fig. 1. Known distribution of Ranitomeya amazonica (green), R. benedicta (light blue), R. imitator (red), R. reticulata (yellow), R. sirensis (blue) and R. vanzolinii (orange). Darker shades of gray indicate higher elevations. The inset map displays the distribution of all six compared species, which are shown in the upper right corner of that figure with the corresponding color code.

Fig. 2. Landmarks andmeasurements of a tadpole body and definitions of the oral apparatus.A. Lateral view.B. Dorsal view.C. Oral apparatus. Abbreviations A–B: BL=body length; TAL=tail length; TL=total length; TMH =tail muscle height; MTH=maximum tail height; IND=internarial distance; IOD=interorbital distance; TMW=tail muscle width. The dotted line indicates the accurate progression of the measurement which represents the body length. Abbreviations C: A1=first anterior tooth row;A2=second ante- rior tooth row;A2-GAP=medial gap in second anterior tooth row; AL=anterior (upper) labium; LJ=lower jaw sheath; LP=lateral process of upper jaw sheath; M=mouth; MP=marginal papillae; OD=oral disc; PL=posterior (lower) labium; P1=first posterior tooth row; P2=second posterior tooth row; P3=third posterior tooth row; SM=submarginal papillae; UJ=upper jaw sheath.

Fig. 6. Developmental series of six Ranitomeya species during the transition from a hatchling to a froglet. The upper panel illustrates the increase of surface area over time, whereby the surface area [cm²] is highly correlated with the body mass. Warmer colors indicate a higher sample density; each circle represents one data point. Loess function represented by the red lines, whereby the outer lines display the 95% confidence interval. The lower panel illustrates the temporal occurrence of the following traits: 1=no limb bud discernible; 2=hindlimb bud discernible; 3=forelimb pouches discernible; 4=forelimbs emerged; 5=initiation of tail resorption.

Fig. 7. Climatic characteristics within the geographic ranges of six Ranitomeya species in terms of annual mean temperature, minimum and maximum temperature of the coldest / warmest month. Boxplots show the 95% range, lower and upper hinge enclosing 50% of the samples and the median based on a random sample per 10 km2.