Castrada infernalis Papi, 1951

Steenkiste, Niels Van, Tessens, Bart, Krznaric, Kathleen & Artois, Tom, 2011, Dalytyphloplanida (Platyhelminthes: Rhabdocoela) from Andalusia, Spain, with the description of four new species, Zootaxa 2791, pp. 1-29 : 13-14

Castrada infernalis Papi, 1951

New locality. Doñana National Park, Provincia de Huelva, Spain (36°49’27”N, 6°21’40”W). Llanos del Taraje near Ecomuseo Robledo de la Plancha: muddy temporal pond with Ranunculus aquatilis and sedges (25/03/2008).

Other localities in Spain. Central areas (Sierra de Guadarrama and river Tajo basin, see Gamo & Noreña- Janssen 1998); Congostrina (Provincia de Guadalajara, Castilla-La Mancha) ( Gamo 1987b), Beleña lagoons (Provincia de Guadalajara, Castilla-La Mancha) ( Gamo & Schwank 1987), Alburquerque (Provincia de Badajoz, Extremadura) and Cáceres (Provincia de Cáceres, Extremadura) ( Noreña et al. 1999).

Known distribution. Palearctic: Southern Europe ( Italy) ( Papi 1951, 1954).

Material. Observations on a live animal.

Remarks. The animal is transparent and colourless. Rostrally, the typical darkly-stained pigment spots are visible in transmitted light. The pharynx is situated between 40 and 50%.

The male system consists of an atrium copulatorium receiving the oviform copulatory bulb, a large blind sac with small proximal spines and large, slender distal spines, and a copulatory bursa without bursal stalk and armed with small spines. The ejaculatory duct is a thick-walled funnel, proximally curled inwards. Of the female system, only the ovary could be observed, flanking the male system at one side.

Although an accessory bursa has not been observed, all other features, including the lack of zoochlorellae, the pigmented spots in the front, the organization of the male system and the armature of the blind sac in particular, are diagnostic for C. infernalis Papi, 1951 . Papi (1954) also describes the subspecies C. infernalis breviorispina Papi, 1954 , from the same region in Italy as C. infernalis . It only differs from C. infernalis by shorter spines in the blind sac of the atrium copulatorium, smaller spines in the copulatory bursa, a double sphincter separating the atrium copulatorium and the common genital atrium, and less pigment in the front end of the body. This subspecies has also been found in central Spain (see Gamo 1987b). Since the spines of the specimen from Andalusia have not been measured and the sphincter around the atrium copulatorium has not been observed, its infraspecific taxonomic position could not be established.

Discussion of Castrada . Based on the position of the nephridiopores, Nasonov (1926) has split the taxon Castrada into Castrada and Castradella ( Nasonov, 1926) Luther, 1963 , whereas Luther (1963) lumped them back together as subgenera of the genus Castrada . Awaiting a thorough cladistical analysis, we adopt Luther’s (1963) classification.

The position of the taxon Castrada and the closely related taxa Mesocastrada Volz, 1898 , Tetracelis Ehrenberg, 1831 , Papiella Mack-Fira, 1970a and Rhynchomesostoma Luther, 1904 , has been controversial (for a discussion see Papi 1959; Mack-Fira 1970a; and more recently Willems et al. 2005 and Noreña et al. 2008). Formerly placed within the Typhloplaninae ( Castrada , Castradella , Mesocastrada ), Olisthanellinae Luther, 1904 ( Papiella ) and even the Protoplanellinae (Castradella) , these taxa are now considered representatives of the Rhynchomesostominae Bresslau, 1933 because of the construction of the genital system, and in particular the presence of an atrium copulatorium ( Papi 1959; Mack-Fira 1970a). The position of Tetracelis remains unclear. Most authors (including Luther 1963; Tyler et al. 2006–2010, web reference [2]; Noreña et al. 2008) put Tetracelis within the Typhloplaninae , but Papi (1959) and Mack-Fira (1970a) conjecture a close relationship with the above-mentioned taxa because of the presence of an atrium copulatorium.

With nephridiopores opening in the buccal tube, C. purgatorialis n. sp. and C. paradisea n. sp. clearly belong to the nominal subtaxon Castrada . Main differences between these two new species include the armature of the atrium copulatorium and its blind sac, the appearance of the ejaculatory duct and the presence of spermatophores in the copulatory bursa. Few species of Castrada have the combination of an accessory bursa and one spiny blind sac in the atrium copulatorium. Only C. infernalis and C. viridis Volz, 1898 share these characters. C. viridis differs from C. purgatorialis n. sp. in the fact that it has uniform, small spines in the blind sac and a less-developed accessory bursa, and from C. paradisea n. sp. by the presence of zoochlorellae in C. viridis .

C. purgatorialis n. sp. strongly resembles C. infernalis (and its subspecies C. infernalis subsp. breviorispina Papi, 1954), because of the combination of large and small spines in the blind sac of the atrium copulatorium, and the presence of a well-developed accessory bursa. It differs from C. infernalis by lacking the dark, pigmented spots in the front end of the body typical for this latter species. Moreover, C. purgatorialis has zoochlorellae and bursal vesicles, which are absent in C. infernalis . The two species also have a different granular secretion of the accessory bursa (eosinophilic in C. infernalis , while basophilic in C. purgatorialis n. sp.; see Papi 1951, 1954).

Other species within the subtaxon Castrada having large spines or teeth in the atrium copulatorium all lack an accessory bursa ( C. chlorea Braun, 1885 , C. cristatispina Papi, 1951 , C. multispina Noreña et al., 2008 , C. neocomensis Volz, 1898 , C. sphagnetorum Luther, 1904 and C. trispina Willems et al., 2005 ). C. quadridentata Hofsten, 1907 could also be included in this list, but it is not clear whether this species belongs to Castrada or Castradella . Moreover, whether this species has an accessory bursa or not, is not known ( Hofsten 1907; Luther 1963). The seminal receptacle of C. purgatorialis n. sp., consisting of large nucleated cells, strongly resembles that of C. montana Papi, 1959 (see Papi 1959). However, the latter species differs in many other features including the lack of zoochlorellae and the general organization of the genital system (e.g. sphincter partitioning the common genital atrium, atrium copulatorium with two small blind sacs provided with small “allineated pseudocuticular bodies”, no accessory bursa; see Papi 1959).

A number of mostly poorly described taxa of Castrada share some common features of the male genital system with C. paradisea n. sp. (one blind sac, uniform spines and a simple ejaculatory duct). C. spinulosa Hofsten, 1907 is similar to C. paradisea n. sp., but has a stalked seminal receptacle in the female system. C. horrida Schmidt, 1861 is also poorly known, but lacks spermatophores and an accessory bursa. C. subsalsa Luther, 1946 is only known from brackish habitats and also lacks an accessory bursa and has no spines in the copulatory bursa.

As many species of Castrada lack a detailed description, identification and morphological comparison of specimens is often difficult. Many species may possibly consist of species complexes or could be lumped in one large species pool. A thorough molecular analysis would probably help to unravel the complex evolutionary history of this taxon, and help species delimitation and identification.