Temnocephala ivandarioi, Lenis & Ruiz & Muskus & Marcilla & Vélez, 2020

Lenis, Carolina, Ruiz, Freddy, Muskus, Carlos, Marcilla, Antonio & Velez, Imelda, 2020, A new flatworm species of Temnocephala (Rhabdocoela, Temnocephalidae) ectosymbiont on the freshwater crab Valdivia serrata (Decapoda, Trichodactylidae) from Amazonas, Colombia, ZooKeys 918, pp. 1-14 : 3-9

publication ID	https://dx.doi.org/10.3897/zookeys.918.38201
publication LSID	lsid:zoobank.org:pub:712C2648-7255-4391-8DEC-DC875E8EA237
persistent identifier	https://treatment.plazi.org/id/E7284E9B-D311-46C3-B5CF-26CA544B15EF
taxon LSID	lsid:zoobank.org:act:E7284E9B-D311-46C3-B5CF-26CA544B15EF
treatment provided by	ZooKeys by Pensoft
scientific name	Temnocephala ivandarioi
status	sp. nov.

Treatment

Temnocephala ivandarioi sp. nov. Figs 1A -C View Figure 1 , 2A -C View Figure 2

Type host.

Valdivia serrata White, 1847 (Fig. 1D-F View Figure 1 ).

Site of infection.

Branchial chambers.

Prevalence.

36% of the eleven hosts were infected.

Type locality.

Kilómetro 11, Reserva Natural Tanimboca, Leticia, Amazonas (4°07'39.8"S, 69°57'13.0"W), Colombia.

Type specimens.

Holotype: CCH.116 (159); Paratypes: CCH.116 (160).

Examined material.

10 whole mounted specimens; 5 stained in Meyer’s paracarmine; 5 stained in Borax carmine; 6 dissected cirrus; 2 samples observed by SEM, 5 unhatched eggs observed by SEM.

Description.

External characteristics. Body (without tentacles) 1.36-2.26 mm (1.75 ± 0.25) long by 1.18-1.56 mm (1.36 ± 0.11) wide; adhesive disk ventral, subterminal 280-520 (370 ± 82) long by 320-520 (400 ± 40) wide (Figs 1A-C View Figure 1 , 2A View Figure 2 ); eyespots with red pigmentation (observations made on live specimens; Fig. 3E View Figure 3 ). DLSPs small, elliptical-shaped (Fig. 3A, B View Figure 3 ), 167 long by 141 wide (N = 2); excretory pore “subcentral” in the DSLP, displaced towards the internal limit (Fig. 3A View Figure 3 ); length ratio of DLSPs:total body length, without tentacles, 1.0:10.7.

Alimentary system. Mouth surrounded by a large muscular sphincter 200-280 (220 ± 26) long by 210-310 (248 ± 32) wide; pharynx 330-620 (417 ± 56) long by 450-620 (511 ± 52) wide; intestine saccular, without septations (Fig. 2A View Figure 2 ).

Glands. Rhabditogenic glands forming bunches in the lateral fields of the body extending from the pharynx to the middle level of the adhesive disk. Haswell cells in front of the eyespots and the brain. Disk glands between the adhesive disk and the genital complex (Fig. 2A View Figure 2 ).

Female. Ovary ventral to the resorbens vesicle 57-100 (83 ± 13; N = 7), long by 60-145 (105 ± 26; N = 7) wide. Vagina elongated with strong muscular wall, connects to the genital atrium dorsally, 75-180 (125 ± 37; N = 4) long by 16-30 (23 ± 4; N = 6) wide with a widening of the distal portion; proximal vaginal sphincter symmetrical 16-34 (23 ± 6; N = 6) and distal vaginal sphincter symmetrical (16-20; N = 2) (Figs 2B View Figure 2 , 4A, B View Figure 4 ). Resorbens vesicle ovoid 110-180 (134 ± 24, N = 9) long by 172-212 (194 ± 16; N = 9) wide. Vitellarium arborescent and thin (Fig. 2A View Figure 2 ). Eggs 557-638 (585 ± 37; N = 4) long by 302-331 (312 ± 13; N = 4) wide; filament small, subapical or apical (Fig. 3C, D, F View Figure 3 ); peduncles 146-243 (341 ± 97); the plane of fracture is oblique with respect to the longitudinal axis of the egg (Fig. 3C, D View Figure 3 ). Eggs deposited on branchial chambers of host (Fig. 3G, H View Figure 3 ).

Male. Two pairs of testes, medium-sized, usually rounded, slightly oblique, anterior testes 180-310 (231 ± 34) long by 120-320 (220 ± 48) wide; posterior testes 200-400 (260 ± 60) long by 110-360 (254 ± 65) wide (Fig. 2A View Figure 2 ). Seminal vesicle dorsal and anterolateral to the prostatic bulb (Figs 2B View Figure 2 , 4D View Figure 4 ), 52-137 (92 ± 27) long by 82-237 (168 ± 47) wide, wall 8.6 thick. Prostatic bulb 70-107 (91 ± 14) long by 155-240 (191 ± 30) wide (Figs 2B View Figure 2 , 4C View Figure 4 ). Cirrus small-sized, 120-147 (129 ± 8) long; shaft cone-shaped, slightly curved up, with maximum width at base 40-47 (44 ± 2); introvert cone-shaped, not oblique, not curved, with a circle of sclerites (range 18-20) in the distal portion followed by a smooth portion without spines or ridges, 7.5-15 (10 ± 3; N = 8) long, with maximum width 15-22 (18 ± 3; N = 10) at level of the distal portion (Figs 2C View Figure 2 , 4C, E, F View Figure 4 , 6A View Figure 6 ). Ratio between total body length, without tentacles:total length of cirrus 14:1; ratio between total length of cirrus:width of shaft´s base 3:1; ratio between total length of cirrus:total length of introvert 13:1.

Etymology.

The new species is dedicated to Dr. Iván Darío Vélez Bernal for his outstanding contributions to the study of helminthology and the understanding of tropical diseases in Colombia.

Discussion.

Temnocephalida is a monophyletic group within the Platyhelminthes included in Lymnotyphloplanida, which is part of the Dalytyphloplanida clade, a major group of Rhabdocoela ( Van Steenkiste et al. 2013). Temnocephalidae Monticelli, 1899 is the most diverse family of the Temnocephalida . Its members are distributed around Australia and the Neotropics ( Martínez-Aquino et al. 2014); the type genus of Temnocephalidae , Temnocephala Blanchard, 1849, is exclusive to the Neotropics. Autapomorphies of the Temnocephala include red-pigmented eyespots, four epidermal syncytial plates, and excretory pores enclosed within the boundaries of the DLSPs ( Damborenea and Cannon 2001). Major hosts to the members of the Temnocephala are chelonians, molluscs, insects, and crustaceans, each hosting a particular assemblage of Temnocephala species. Particular host families are also specific for particular Temnocephala species ( Martínez-Aquino et al. 2014).

Taxonomy of temnocephalans is based on morphology of adult specimens with emphasis on the reproductive system. The structure of the cirrus is the trait of greatest taxonomic value ( Damborenea 1991, Damborenea and Cannon 2001, Sewell et al. 2007, Garcés et al. 2013). Other traits important for species differentiation include composition of the female reproductive complex, eggs deposit areas in the host, and the shape of the DLSPs ( Damborenea and Brusa 2008, Amato et al. 2010, Volonterio 2010, Seixas et al. 2011, 2015, 2018).

Nine species of Temnocephala are known for their association with crabs of the Trichodactylidae family. Of these, T. ivandarioi sp. nov., T. longivaginata Seixas, Amato & Amato, 2011, and T. lutzi Monticelli, 1913 ( Amato et al. 2005) present a similar-sized cirri and have the Amazon River basin as a biogeographical connection. Temnocephala longivaginata and T. ivandarioi sp. nov. are most similar to each other in the length of the vagina and the presence of sclerites in the distal portion of the cirrus.

Temnocephala ivandarioi sp. nov. can be distinguished by the combination of the following features: cirrus with a circle of small sclerites (range 18-20) in the distal portion of the introvert, without spines or ridges in the inner wall of the introvert (Fig. 2C View Figure 2 ). The ovary lies ventral to vesicle resorbens followed by an elongated vagina with two vaginal sphincters similar in size, one symmetric and proximal, and one symmetric and distal; the vagina connects to the genital atrium dorsally. The seminal vesicle is located anterolateral to the prostatic bulb. The DLSPs are small and ‘elliptical-shape’, with a partially sinuous contour.

On an ecological-level T. ivandarioi sp. nov., T. longivaginata , and T. lutzi inhabit the branchial chambers of trichodactylid crabs from the middle basin and lower basin of the Amazon River (Leticia, Amazonas, Colombia; Peixe-Boi, Pará State; Rio Amapá, Amapá State, northern Brazil, respectively). Temnocephala ivandarioi sp. nov. is the third species described from Colombia, and therefore V. serrata is registered as a new trichodactylid host for neotropical temnocephalans. Valdivia serrata is widely distributed throughout the Orinoco and Amazon River basins in Venezuela, the islands of Trinidad and Tobago, the Guianas, Colombia, Brazil, Peru and Bolivia ( Cumberlidge 2008). In Colombia this species is found in the eastern region of the country (Amazonas, Arauca, Caqueta, Meta, Putumayo, and Vichada Departments) in the Putumayo and Maqueta rivers that drain into the Amazon River, and the Guaviare, Meta, and Arauca rivers that drain into the Orinoco River ( Campos 2005, 2014). It is likely that T. ivandarioi sp. nov., T. longivaginata , and T. lutzi are closely related due to their morphological similarities and geographical proximity. The implementation of molecular studies will reveal the phylogenetic relationships between the different species of Temnocephala in the Neotropics.

In Colombia more than 132 species of decapod crustaceans have been recorded ( Campos 2014), while only two associated species of temnocephalans have been reported to date: T. icononcensis ( Arias-Pineda et al. 2015) and T. ivandarioi sp. nov. The great diversity of these potential hosts ( Campos 2014) suggests that most temnocephalans remain undescribed.

Comparative notes.

The cirrus is the only rigid structure and therefore of constant general morphology in juveniles and adults (except for small intraspecific variations) for each species. The morphology of the cirrus constitutes one of the few characters used and is the most valuable taxonomic character for species identification ( Seixas et al. 2015b). In the present study, terminology describing the temnocephalan cirrus is updated for neotropical species (Fig. 5 View Figure 5 ), according to Sewell et al. (2007), Seixas et al. (2011), Garcés et al. (2013) and Ponce de León et al. (2015). The cirrus of the species of Temnocephala described from trichodactylid crabs (Fig. 6 View Figure 6 ) are compared based on this terminology.

The cirrus is defined as the entire sclerotised male copulatory organ comprised of a ‘shaft’ (rigid, tubular region tapering distally; Fig. 5A View Figure 5 ) and an ‘introvert’ (flexible distal eversible region armed with grooves, spines, sclerites or ridges, Fig. 5B View Figure 5 ) (modified from Sewell et al. 2007). Furthermore, the degree of shaft curvature is a reliable taxonomic characteristic of neotropical temnocephalans ( Garcés et al. 2013).

The shape of the shaft may be described as a ‘funnel’, ‘goblet’, or ‘cone’. Funnel- or goblet-shaped shafts have a wide proximal region which tapers rapidly into a narrow tubular distal region ( Sewell et al. 2007). The cirrus may be more or less curved, and it may be described as 'curved up’, ‘straight’, or 'curved down’. Similarly, the position of the cirrus with respect to the body may be described as 'towards the forebody’, ‘horizontal’, or 'towards the hindbody’ (modified from Garcés et al. 2013). The position of the cirrus can or may not depend on the cirrus curvature i.e. cirrus 'curved up’ directed 'towards the forebody’, but cirrus ‘straight’ are directed towards the ‘forebody’, ‘horizontal’ or 'towards the hindbody’. The cirrus position can be examined only from a complete diagram of the temnocephalan.

The introvert shape can be described as ‘cylindrical’, ‘cone’; ‘scoop’, or ‘goblet’. Scoop- or goblet-shaped introvert have a wide middle region, which tapers into a narrow distal region. In addition, the introvert may be ‘unarmed’, armed with ‘grooves’ in the proximal limit of the introvert, or armed with ‘spines’, ‘sclerites’, and ‘ridges’ in the inner wall of the introvert. The distal opening of the introvert may be at right angles with respect to the proximal limit of the introvert i.e. 'not oblique’, ‘oblique’, or 'very oblique’ (modified from Sewell et al. 2007). Additionally, the distal region of the introvert may be curved (with or without spines, sclerites, or ridges), and described as 'forward curved’, ‘straight’ or 'backward curved’ (described as with non-spined region or without non-spined region by Sewell et al. 2007).

The morphology of the cirrus is necessary for species identification and should be clearly described based on the terminology proposed in the present study. This new terminology can be applied to species of neotropical temnocephalans described to date.