Phonorhynchoides gondwanae Willems & Artois, n. sp

Autor: Willems, Wim R., Reygel, Patrick, Steenkiste, Niels Van, Tessens, Bart, Artois, Tom J.
Rok vydání: 2017
Předmět:
ISSN: 0394-6975
DOI: 10.5281/zenodo.5689678
Popis: Phonorhynchoides gondwanae Willems & Artois n. sp. (Fig. 6 D���G) Phonorhynchoides n.sp. 2 in Tessens et al. (2014) Localities in South Africa. Mseleni, crossing of stream with main road (R22), slightly brackish, intermittent stream connected to Lake Sibaya (27��21���48.67������S, 32��31���36.73������E), peaty shore with Leersia hexandra and sedges, 06/12/2009 (collected by Dr R. Taylor) (type locality). iSimangaliso Wetland Park, Kosi Bay estuary, water plants from the eastern shore of main lake, salinity 3���4���, December 15, 2009 (collected by Xander Combrink). Localities in India. Goa, Siolim (15��37���01.3���N, 73��46���22.4���E), brackish irrigation ditches with grasses and water lilies, November 25, 2008. Goa, north of Nadora (15��41���18.8���N, 73��52���38.1���E), plant material including grasses and roots from freshwater swamp in small valley, November 29, 2008. Goa, Parcem (15��39���40.5���N, 73��46���33.2���E), waterweed-like vegetation and water lilies from freshwater stream, November 29, 2008. Material. Several animals studied alive. One whole mount from South Africa, designated holotype (SMNH, type-8856) and three from India (HU, nos VII.4.1���VII.4.3). Three serially-sectioned individuals from India (in poor condition) (HU, nos VII.4.4���VII.4.6). Etymology. Species name refers to the supercontinent Gondwana, which included, among others, modern day India and Africa, where this species occurs. Diagnosis. Species of Phonorhynchoides with a prostate stylet type IV between 199 and 262 ��m long, slightly spiralled, but not corkscrew-shaped, with distal end cut-off straight. Needle-shaped accessory stylet type IV between 83 and 112 ��m long. Accessory stylet to prostate stylet ratio between 42���46 %. Bursa not bipartite, lacking a muscular part. Description. Live animals are long and slender, colourless, with two eyes. They are 0.7���0.9 mm long (measured on whole mounts). A protonephridial duct can be seen running along both sides of the animals, from the level of the eyes to the level of the bursa. Size and position of proboscis and pharynx are similar to that of other species of Phonorhynchoides Beklemischev, 1927, as is the general organisation of the genital system (see Beklemischev 1927; Schockaert 1971; Artois & Schockaert 2001; Artois & Tessens 2008). The spindle-shaped prostate vesicle type IV (Fig. 6 E: pv4) receives partly-extracapsular prostate glands and is connected to a very long and slender prostate stylet type IV (Fig. 6 E: pst4, 6G). This stylet is slightly spiralled, but in none of the specimens studied alive does it form a regular, corkscrew-shaped spiral. It is 262 ��m long in the South African specimen and 199���222 ��m (��� = 210 ��m; n = 3) in the Indian specimens. The accessory vesicle type IV (Fig. 6 E: acg4) is rather large, almost globular in shape and its glands have an extracapsular part. It is connected to a straight-to-slightly-bent, needle-shaped accessory stylet type IV (Fig. 6 E: ast4, 6F), which is clearly shorter than the prostate stylet, i.e. 112 ��m in the South African specimen and 83���97 ��m (��� = 92 ��m; n = 3) in the Indian specimens. Both hard parts have a pointed distal tip. The ratio ast4 / pst4 is 43 % in the South African specimen and 42���46 % in the Indian specimens. The bursa lacks a separate muscular part and therefore is not bipartite. Two narrow, but clearly muscular ducts are present and even visible on live specimens: a female duct type I (Fig. 6 E: fdI), connecting the bursa with the common genital atrium, and a common oviduct, in between the bursa and the junction of both oviducts. The female duct type II is barely visible in live animals (Fig. 6 E: fdII). Discussion. Based on its morphology, the new species can easily be placed in the taxon Phonorhynchoides Beklemischev, 1927, as it shows all of the diagnostic features of this taxon (see Schockaert 1971 and emendation by Artois & Tessens 2008). However, the molecular phylogenetic analysis of Tessens et al. (2014) shows that the genus Phonorhynchoides is not monophyletic and falls apart into two separate monophyletic clades: one clade consisting of P. linguatus Artois & Tessens, 2008 and an undescribed species from Australia, the other clade only represented in the analysis by P. gondwanae n. sp. No other species of Phonorhynchoides was included in the analysis. Based on morphological features Artois & Tessens (2008) distinguish two species groups within the genus. The first group consists of P. haegheni Artois & Schockaert, 2001 and P. linguatus. Its representatives are characterised by a prostate stylet type IV that is considerably shorter than the accessory stylet type IV. Moreover, both species have a rather broad tubular prostate stylet and a bipartite bursa, consisting of a muscular and a spermresorbing part (Artois & Tessens, 2008). The prostate stylet of the new species from Australia included in the analysis of Tessens et al. (2014) is also broad and tubular and shorter than the accessory stylet (own unpublished data). Unfortunately, the female system in the specimens from Australia was not entirely developed, so it is unknown whether the bursa in this species is also bipartite. The data available, therefore, at least suggest that this morphological group corresponds to one of the two monophyletic clades in the analysis of Tessens et al. (2014). The second morphological group consists of P. carinostylis Ax & Armonies, 1987, P. flagellatus Beklemischev, 1927, P. japonicus Ax, 2008 and P. somaliensis Schockaert, 1971. In all these species the prostate stylet is clearly longer than the accessory stylet, as in P. gondwanae n. sp. In addition, the hard parts are similar in shape, although there are some clear differences in size and detailed structure and in the ast4 / pst4 ratio (see Table 1). Of the abovementioned group of species, at least P. somaliensis, P. gondwanae n. sp. and, most probably, also P. flagellatus. (see Beklemischev 1927; Schockaert 1971) do not have a bipartite bursa. For P. carinostylis and P. japonicus, the situation remains unclear, although drawings of live specimens (Ax & Armonies 1987; Ax 2008) suggest a bipartite bursa is absent. Apart from P. gondwanae n. sp., no other species of this morphological group was part of the datamatrix of Tessens et al. (2014), hence it is unknown whether this group indeed represents a monophyletic clade. Following these considerations, we propose to formally split the genus Phonorhynchoides and erect the new genus Phonorhynchopsis Willems & Artois n. gen. for P. haegheni (type species) and P. linguatus. The diagnoses can be found at the end this discussion. There is a considerable variation in length of both hard parts between different specimens of P. gondwanae n. sp., with the South African specimen clearly standing out against the Indian population. However, the proportions of their lengths are the same. Furthermore, there are no structural differences in the stylets between the two populations. Considerable intraspecific variation in stylet length is demonstrated for all species of Phonorhynchoides for which measurements for more than a few specimens are available, i.e. P. somaliensis, P. haegheni and P. linguatus (Schockaert 1971; Artois & Schockaert 2001; Artois & Tessens 2008). P. gondwanae n. sp. is the third species of Phonorhynchoides, recorded from the African continent. P. linguatus is the most widespread species, being recorded from the Kenyan and Tanzanian coast and the Seychelles, whereas P. somaliensis (Somali coast) and P. gondwanae n. sp. have a more limited distribution (see Schockaert 1971; Artois & Tessens 2008). Apart from P. somaliensis, which is found in a hyper-saline environment, and P. linguatus, which is found in a purely marine habitat, all other species of Phonorhynchoides, including P. gondwanae n. sp., occur in brackish water. P. haegheni is also found in marine habitats (Beklemischev 1927; Schockaert 1971; Mack-Fira 1974; Ax & Armonies 1987; Artois & Schockaert 2001; Ax 2008; Artois & Tessens 2008). P. gondwanae n. sp. is the only species of the genus that also occurs in freshwater habitats, both in South Africa and India. Within Polycystididae, occurrence in freshwater is (very) uncommon, only recorded for several populations of the Gyratrix hermaphroditus species complex (for an overview see Tessens 2012) and for all species in the genus Opisthocystis Sekera, 1911. The latter taxon contains one freshwater species, which is very widespread in Europe and North America [O. goettei (Bresslau, 1906) Sekera, 1911], but shows an enormous radiation in Lake Baikal (see Timoshkin et al. 2010; 2014 and references therein). P. gondwanae, therefore, seems to represent a third, independent case of invasion of the freshwater habitat within Polycystididae. Diagnoses. Phonorhynchoides (emended from Schockaert 1971). Phonorhynchoidinae with two stylets in the male atrial organs: a prostate stylet type IV and an accessory stylet type IV. Prostate stylet long and slender, (much) longer than the accessory stylet. The bursa consisting of one compartment only, not bipartite. Type species: P. flagellatus. Other species: P. carinostylis, P. gondwanae n. sp., P. somaliensis. Phonorhynchopsis Willems & Artois n. gen. Phonorhynchoidinae with two stylets in the male atrial organs: a prostate stylet type IV and an accessory stylet type IV. Prostate stylet type IV rather broad and tubular, shorter than the accessory stylet type IV. Bursa bipartite, consisting of a muscular and a sperm-resorbing part. Type species: P. haegheni (Artois & Schockaert, 2001) n. comb. Other species: P. linguatus (Artois & Tessens, 2008) n. comb.
Published as part of Willems, Wim R., Reygel, Patrick, Steenkiste, Niels Van, Tessens, Bart & Artois, Tom J., 2017, Kalyptorhynchia (Platyhelminthes: Rhabdocoela) from KwaZulu-Natal (South Africa), with the description of six new species, pp. 441-466 in Zootaxa 4242 (3) on pages 456-458, DOI: 10.11646/zootaxa.4242.3.2, http://zenodo.org/record/376905
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