Helobdella octatestisaca Lai & Chang, 2009

Helobdella octatestisaca Lai & Chang, 2009

= Helobdella octatestisaca Lai et al. (2009): 30 View Cited Treatment , figs 1-2 [original description; holotype NTNUB L00077 ; type locality: Guandu Plain , Taipei, Taiwan, China].

Figures 1 View Figure 1 E-F, 2, 3, 7, Table 1

Native range: Central America: Mexico and Panama ( Salas-Montiel et al. 2014; Tessler et al. 2018; Gerardo 2019; Jiménez-Armenta and Oceguera-Figueroa 2019; Iwama et al. 2019) ( Figures 2 View Figure 2 , 3 View Figure 3 , 7 View Figure 7 ).

Non-native range: Argentina, China: Taiwan, India: Manipur (first country-level record), Portugal, South Africa, Spain, Tunisia, and the USA ( Shankland et al. 1992; Lai et al. 2009; Oceguera-Figueroa et al. 2010; Richardson et al. 2017a; Gerardo 2019; Iyer et al. 2019; Perera et al. 2019; Ben Ahmed et al. 2024; also see Supplementary information online, Table S1 for GenBank sequences; Figures 2-3 View Figure 2 View Figure 3 for genetic data; and Figure 7 View Figure 7 for map).

Ecological notes: On Taiwan Island, this species was collected from the surface of shell and operculum of the invasive Golden Apple Snail Pomacea canaliculata (Lamarck, 1822) ( Gastropoda: Ampullariidae ) ( Lai and Chen 2010). Additionally, it was recorded on the body surface of other leech species, that is, Whitmania laevis (Baird, 1869) on Taiwan ( Lai and Chen 2010), Placobdella parasitica in Texas ( Richardson et al. 2017a), and Helobdella europaea in Portugal ( Perera et al. 2019). These field observations indicate that Hel. octatestisaca may act as a hyperparasite, sucking body fluids of other leeches, although this hypothesis is yet to be confirmed experimentally ( Richardson et al. 2017a). Here, we show that it should be considered a facultative snail-associated leech, as it was found dwelling in the mantle cavity of viviparid gastropods ( Table 1). Additionally, H. octatestisaca was repeatedly recorded in a phoretic association with freshwater turtles in various regions, including Europe ( Perera et al. 2019) and North America ( Richardson et al. 2017a).

Taxonomic comments: Several authors thought that Hel. octatestisaca may be conspecific with Hel . adiastola Ringuelet, 1972 based on available DNA sequences from Mexico ( Gerardo 2019; Ben Ahmed et al. 2024). Conversely, Iwawa and Arrudo (2016: 415) stated that: “ Previous reports in Mexico of H. adiastola ( Ringuelet 1972) must be a misidentification of a North American species that integrates the stagnalis complex since no reports of this species are available on recent literature ”. In the brief original description of this species, Ringuelet (1972: 101) did not mention the type locality of Hel . adiastola but stated that its holotype is an “ejemplar en las colecciones Del Museo de La Plata”. The range of this nominal species in its original understanding covers Mexico, Brazil, Paraguay, Uruguay, and Argentina but there is no information for the geographic origin of the holotype ( Ringuelet 1972). Earlier, Ringuelet (1948) published a more detailed description of this species (as Hel . scutifera Blanchard, 1900) based on samples from Paraguay. However, it is unknown whether Ringuelet (1972) selected the holotype from Paraguayan specimens or not. Thus, the status of the nominal species Hel . adiastola can be clarified in the future based on examination of the holotype in the La Plata Museum (La Plata, Argentina). Hel. octatestisaca seems to be native to Central America ( Mexico and Panama), whereas its samples from Argentina share a single invasive COI haplotype, indicating a non-native origin of the population in South America (see Figures 2-3 View Figure 2 View Figure 3 ).

Helobdella nilae Negm-Eldin, Govedich & Davies, 2000 [holotype NMV F83620 View Materials ; type locality: “tributaries of Bahr Mois and Ryah El-Tawfiki in the Nile Delta, Egypt ”] morphologically aligns with Hel. octatestisaca , except for five pairs of testisacs ( Negm-Eldin et al. 2000). If the latter feature has some levels of intraspecific variability (i.e., changes from five to four pairs of testisacs), Hel. nilae shall be considered a senior synonym of Hel. octatestisaca .