Pleurodeles nebulosus
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Taxonomy notes:
Revalidated by: Carranza, S., and Wade, E. (2004). Taxonomic revision of Algero- Tunisian Pleurodeles (Caudata: Salamandridae) using molecular and morphological data. Revalidation of the taxon Pleurodeles nebulosus (Guichenot, 1950). Zootaxa, 488, 1-24.
At the moment there are no recognised subspecies.
Description:
Similar species:
According to the latest update in 2023, three species belonging to the genus Pleurodeles are currently recognized: P. waltl, present in the Iberian Peninsula and Morocco, P. nebulosus and P. poireti, both present in North Africa (Ben Hassine and Escoriza 2014).
Pleurodeles nebulosus is similar to P. poireti in coloration (Schleich et al. 1996), but can be distinguished on the basis of larger size, wider interorbital distance and longer forelimbs. The species under consideration also has a more U-shaped row of palatine teeth, rather than V-shaped as in P. poireti, P. nebulosus also has shorter teeth and slightly curved skin tubercles, which appear less prominent and closer together than those of P. poireti (Carranza and Wade 2004). The males of P. nebulosus also have a longer tail, broader, more depressed head, and longer forearms than males of P. poireti. Pleurodeles nebulosus hybridizes with P. poireti in different locations. Most hybrids have mitochondrial DNA from P. nebulosus, indicating that this species is the maternal source. The two species share habitat types and niches, so it is hypothesized that they mutually exclude the other species from their ranges with their population density (Escoriza et al. 2016).
From P. waltl, P. nebulosus can be differentiated by the fact that the latter is smaller and lacks reddish-yellow spots on the ribs, sharp protruding rib tips, and glandular rows of swelling on the flanks (Schleich et al. 1996, Carranza and Wade 2004). Furthermore, compared to the Iberian ribbed newt, the dorsal spots appear more concentrated and marked, and the chromatic separation between dorsum and belly is clearer.
Before 2004, all Pleurodeles nebulosus were marketed under the name of Pleurodeles poireti, which actually corresponds to an endemic entity restricted to the Edough Peninsula. It is widely believed that this last species has therefore never actually entered the market.
Distribution and Habitat:
This is an endemic species with a restricted range limited to the coast of Algeria and Tunisia, with the exception of the Edough peninsula and its surroundings (Carranza and Wade 2004). In particular, it can be found from central-northern Algeria to the Cape Bon peninsula in Tunisia (Amor et al. 2013) and from the Mascara wilaya in the west to Tunisia in the east (Merabet et al. 2016). Its current range and populations are very fragmented. Pleurodeles nebulosus occupies and inhabits humid environments near rivers, streams and ponds, but can also colonize semi-arid areas (Joger 2003). During the terrestrial phase they are found in mesothermal deciduous forests or in the Mediterranean scrub, in cavities in the ground or under trunks or stones. They also have a certain degree of tolerance towards altered landscapes, such as agricultural fields (Ben Hassine and Escoriza 2017, IUCN 2021). The species has been found from sea level up to 1185 m above sea level. (Merabet et al. 2016).
Care in captivity
The species is highly aquatic during the breeding season and highly terrestrial during the non-breeding season (which corresponds to aestivation) (Ben Hassine and Escoriza 2017, IUCN 2021), they can therefore be kept in a completely aquatic setup for most of the year with an aquarium or aquaterrarium proving to be an adequate structure for correct housing. This species is known to aestivate in the soil among plant roots during hot, dry periods between June – September/October and can be found in groups of more than ten but can also be solitary (Amor et al. 2013, IUCN 2021).
The aestivation in captivity, which will take place approximately between the months of June and August (depending on the temperatures), will consist of a short terrestrial phase, in which the animals will leave the water to take refuge under stones or bark , they will eat less and appear relatively static. An aquarium between 100-120 litres is sufficient to accommodate a small group between 5 and 9 individuals, while smaller tanks, such as 70 or 80 litres, will be sufficient for a couple or a trio. Housing in the terrestrial phase can be carried out in separate containers of relatively small dimensions (containers developed horizontally from 15 to 30 litres, or 40x30cm or 40x40cm terrariums), or within the same aquarium in which the animals will be kept during the rest of the year, building a more or less elaborate emerged area, which can be represented by a simple floating cork bark or stacked rocks, or by an actual planted and well-arranged emerged areas (terraquarium model). Regardless, it will be very important to maintain an average level of humidity both at the level of the substrate (which must always be humid but never soaked) and at the air level and provide many shelters, such as bark, moss, trunks and stones. For the substratum of the emerged area, a layer of expanded clay can be used as a draining material, to be covered with coconut fibre, peat or topsoil free of chemical substances and which can be mixed with sand.
As regards the aquatic area, the bottom of the tank can be covered with fine granulated sand, large pebbles or kept bare, to facilitate cleaning operations; gravel or other intermediate-sized substrates must be strictly avoided, as they could easily be ingested and cause dangerous intestinal obstructions. The water column can be maintained between 10 and 20 cm, with fluctuations based on seasonality (lower water column in winter and summer, and higher during the courtship period, to simulate the rainy season). For the aquatic phase, a slightly acidic water pH is recommended (we recommend the use of osmosis water at least in part), although these are animals with little sensitivity regarding the water values, as long as there are not high concentrations of chlorine or heavy metals. The tank must also have various shelters and furnishings, which may consist of rocks, logs, aquatic plants such as Najas sp. , Ceratophyllum sp. , Egeria dense, Rotala sp. , Vallisneria (also useful for egg laying), floating plants such as Salvinia natans, Pistia or Lemna, aquatic mosses, dry broad-leaved leaves and catappa, to best simulate the stagnant pools in which they normally reproduce. An aquarium filter may not be added if large volumes are used and water changes are carried out regularly; if you opt to insert a filter this will have to generate little or minimal current. The lighting of the aquarium or terraquarium is not strictly necessary but is recommended for the correct development of the plants, and to maintain a correct circadian cycle for the animals (between 5 and 8 hours of light are recommended, depending on the season).
Optimal temperatures should never exceed 25-27 C°, although Pleurodeles nebulosus is extremely resistant to high temperatures, compared to the average tolerance of most urodele species. In winter, to encourage reproduction and allow correct maturation of the gonads, temperatures will need to drop below 20°C; for example, effective brumation was achieved with temperatures between 15°C and 10°C. It will be necessary to equip the tank with an escape-proof lid, which also guarantees optimal air exchange, such as a mesh or mosquito net lid or lid with abundant ventilation grills.
Diet:
This species, if kept in suitable conditions, proves to be extremely voracious, reaching the point of readily accepting any prey of suitable size that is offered to it. The diet is mainly composed of annelids and arthropods, in captivity earthworms and frozen Chironomus larvae can therefore be offered as basic foods, and then the diet can be varied with Daphnia, < i>Cyclops, Lombriculus sp. (California black worms), frozen Artemia or Krill (to be rinsed well before administration). Useful for the terrestrial phase but not always accepted are small crickets, cockroaches and isopods. As always, a varied diet will be reflected in the health of the animals. The prey must be fed 2 to 3 times a week, with a lower frequency in the winter period and a greater frequency in the reproductive period, in reference to adult/subadult animals, while the young will be fed more frequently.
Reproduction:
Mating usually begins between the end of February and the beginning of March, and can continue until late spring, depending on the temperatures. Unusually warm winters can stimulate a second breeding season.
Once the males enter the water, they develop skin thickening, called nuptial calluses, on the front legs, which become reddish-brown during the reproductive period (Sparreboom 2014, IUCN 2021) and a more marked and prominent cloaca. Fertilization is internal. During mating, the male surrounds the female with his front legs from behind and from below, attaching himself to the latter’s front legs. During this intercourse, which can last from hours to days, numerous spermatophores are deposited and then transferred to the female, with the male detaching himself from the intercourse and “incentivising” his partner to perform a circular movement until positioning her perfectly above the spermatophore, which it can thus be taken from the female’s cloaca to fertilize the eggs inside her body. Generally, the passage of the spermatophore from the cloaca of the male to that of the female occurs without trauma or particular aggression on the part of the males towards the females.
Oviposition is aquatic (Donaire-Barroso et al. 2006, IUCN 2021). The eggs are adhered to the leaves of aquatic plants, stones or trunks and are laid over several weeks. From the eggs, which are relatively small and wrapped in very large gelatinous shells (on average more substantial and voluminous than those of Pleurodeles waltl (Personal observation)), the larvae are born after about 8-12 days.
Just as they tolerate coexistence between conspecifics of the same size well, the animals do not show a particular tendency to feed on their own eggs. However, it is still recommended to remove the eggs from the tank or laying place, to avoid phenomena of cannibalism on the part of the parents towards the future larvae and for the purposes of better monitoring hatching. The eggs should be removed if possible without cutting the gelatinous membrane, completely or partially remove the leaves or parts of the log to which they are attached, and placed inside containers of between 5 and 20+ litres. To combat the onset of mould, it is recommended to use slightly acidic water (you can proceed with an equal percentage of water from the deposition tank and new osmosis water) or to add catappa or oak leaves. However, the onset of mold is usually low for this species and the hatching percentage is relatively high (but still on average lower than for P. waltl). We recommend inserting an aerator or air filter for aquariums, to maintain a minimum of movement on the surface and not let the water stagnate.
Growth and development of the Larvae:
Upon hatching the larvae have three gill arches and elongated barbells on each side of the head. Barbells are lost within a few days. Cone-shaped buds on the forelimbs are already visible after a few days. At the subsequent larval stage, in which the hind limbs already have well-formed fingers, but the external gills are still fully developed, the larvae have an average length between 39.3 and 73.7 mm (Ben Hassine and Escoriza 2014). The larvae of P. nebulosus are significantly smaller than the larvae of P. waltl (Ben Hassine and Escoriza 2014).
Once out of the egg, the larvae will be fed with aquatic microorganisms, such as small crustaceans like Daphnia, Cyclops and nauplii of Artemia salina (well rinsed before being administered) and other small freshwater invertebrates. Starting from 2-3 cm in length they can also be fed with frozen food, such as red Chironomus, and annelids of the right size, such as Enchytraeus and Lombriculus. It will gradually be necessary to separate the different larvae into different containers in relation to their size (growth will progress at the same rhythms for all of them), to avoid cannibalism. The larvae take on average between 2.5 – 4 months to metamorphose, and in the wild, they generally leave waterways between March and June (IUCN 2021).
When the larvae are close to metamorphosis (they will have all 4 well-formed limbs and will begin to reabsorb the gills) it will be necessary to lower the water level and position emerging platforms, stones, trunks and floating bark to facilitate their exit from the waterfall. The newly metamorphosed can be kept in an aquatic environment, similar to that described for adult individuals, but maintaining a high number of emerged areas and floating bark, until they reach sexual maturity, which can occur in extraordinary cases within the year, usually after two. The young will be fed with Chironomus, Daphnia, small earthworms and Enchytraeus in water (provided with tweezers if in the terrestrial phase).
In Pleurodeles nebulosus larval sex is influenced by external temperature (Schleich et al. 1996), making them excellent models for sex determination studies.
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On the Author...
Jacopo Martino, born in Rome in 1997, graduating in biological sciences at “La Sapienza”University of Rome.
He worked for two years as a laboratory assistant for the zoology department of his university, then, he assisted and participated in various projects for the monitoring and study of herpetofauna, entomofauna and chiroptera. In 2022, is co-author of the paper “Sexual dichromatism and throat display in spectacled salamanders: a role in visual communication?”, later on, he participates in the publication of new works and scientific notes, in the herpetofaunistic, entomological, arachnological and ichthyological fields. Member of the Italian Gekko association (IGA), and administrator for projects and activities related to the world of amphibians for it. Member and social media manager for the Societas Herpetologica Italica (SHI). Member of the Italian Arachnology association (AIA) and special collaborator for the Arthropoda live Museum association. Founder and head of the research group of the ProgettoSeeds cultural association, which deals with naturalistic and environmental issues, within the Lazio region.
He has been keeping and breeding amphibians since 2014, with particular interest in the Ambystomatidae and Hynobidae families, and the Gymnophiona order.
References
Citazione: Carranza, S., & Wade, E. D. W. A. R. D. (2004). Taxonomic revision of Algero-Tunisian Pleurodeles (Caudata: Salamandridae) using molecular and morphological data. Revalidation of the taxon Pleurodeles nebulosus (Guichenot, 1850). Zootaxa, 488(1), 1-24.
Citazione: Salvador, A. (1996). Amphibians of northwest Africa.
Citazione: Schleich, H. H., Kästle, W., & Kabisch, K. (1996). Amphibians and reptiles of North Africa (Vol. 63). Germany: Koeltz scientific books, Koenigstein.
Citazione: Sparreboom, M. (2014). Salamanders of the Old World: the salamanders of Europe, Asia and northern Africa. Brill.
Citazione: Hassine, J. B., & ESCORIZA, D. (2014). New ecological data on the family Salamandridae in the Maghreb. Herpetological Review, 45(2), 1-5.
Citazione: Escoriza, D., Gutiérrez-Rodríguez, J., Ben Hassine, J., & Martínez-Solano, I. (2016). Genetic assessment of the threatened microendemic Pleurodeles poireti (Caudata, Salamandridae), with molecular evidence for hybridization with Pleurodeles nebulosus. Conservation genetics, 17, 1445-1458.
Citazione: Amor, N., Kalboussi, M., & Said, K. (2013). Conservation status of amphibians in Tunisia. Basic and Applied Herpetology, 27, 85-100.
Citazione: Merabet, K., Dahmana, A., Karar, M., & Moali, A. (2016). New occurrence record of the Algerian ribbed newt Pleurodeles nebulosus (Guichenot, 1850) in Algeria. Herpetological Bulletin, 137, 43.
Citazione: Escoriza, D., & Hassine, J. B. (2017). Niche separation among north-west African semi-aquatic reptiles. Hydrobiologia, 797(1), 47-56.
Citazione: IUCN SSC Amphibian Specialist Group. 2021. Pleurodeles nebulosus. The IUCN Red List of Threatened Species 2021: e.T61919A179948304. https://dx.doi.org/10.2305/IUCN.UK.2021-3.RLTS.T61919A179948304.en. Accessed on 22 April 2024.
Citazione: Hassine, J. B., & Nouira, S. (2012). The amphibians of Tunisia: biodiversity, distribution, status and major threats. FrogLog, 101, 32-34.