INTRODUCTION

Terrestrial leeches have been recorded on all continents except Antarctica (Borda et al., 2008; Sawyer, 1986), with only one trignathous species with teeth described from Africa: Mesobella lineata Sciacchitano, 1959. Mesobdella lineata was placed in the genus Mesobdella, and in the family Haemadipsidae, with consideration of its terrestrial habit and Sciacchitano's (1959) observation of triannulate midbody somites. Leech taxonomists active at the time and since have repudiated much of Sciacchitano's work (Moore, 1938, 1958; Oosthuizen, 1978, 1979, 1982, 1989; Sawyer, 1986), in which he described numerous species and genera without sufficient diagnostic characters (Sciacchitano, 1935, 1936, 1941, 1952, 1960). Many of Sciacchitano's available names, particularly of the family Hirudinidae, have subsequently been synonomized with other taxa or are considered species inquirendae (Soós, 1969; Sawyer, 1986). Sciacchitanos' (1959) description of M. lineata (1959) was based upon mostly external morphological characters observed in specimens of the Museum of Zoology at the University of Lund, Sweden, that were collected during a university sponsored expedition in 1950–1951. Aside from a trivial diagram of the external characters (fig. 1; shown here for clarification), very little was known about the morphology and natural history of this leech when described.

Since its description, M. lineata has been passively carried along through taxonomic recategorizations of the genus, yet without morphological examination (Ringuelet, 1972; Sawyer, 1986; Borda et al., 2008). Even though it was an exception in geographic distribution and several morphological characters, Blanchard (1849) placed Mesobdella within the family Haemadipsidae. Moore (1946) found Mesobdella gemmata (Blanchard, 1849) to be morphologically similar to Xerobdella lecomtei (Frauenfeld, 1868) and Diestecostoma species, but the report of haemadipsine reproductive structures by Ringuelet (1943) caused Moore to hesitate in suggesting the subfamily Xerobdellinae should include Xerobdella and Diestecostoma, but not Mesobdella. Ringuelet (1972) placed Mesobdella into its own family, Mesobdellidae. Disregarding previous taxonomy, Sawyer (1986) returned all blood-feeding terrestrial leeches to Haemadipsidae and separated the taxa into duognathous and trignathous series, the latter of which included Mesobdella.

The systematics of both haemadipsoid and hirudinoid leeches has been substantially altered in consideration of molecular phylogenetic work and the recognition of various morphological synapomorphies (Apakupakul et al., 1999; Borda and Siddall, 2004; Phillips and Siddall, 2005; Borda et al., 2008). With the addition of molecular data, Trontelj et al. (1999) and Borda and Siddall (2004) found Xerobdella lecomtei and Mesobdella gemmata not to be sisters to the blood-feeding terrestrial leeches of the IndoPacific (i.e., Haemadipsidae). Mesobdella was returned to the subfamily Xerobdellinae, which was at the same time elevated to family Xerobdellidae, with additional morphological and molecular examinations of more taxa by Borda et al. (2008).

Until now, morphological and molecular investigations of Mesobdella have focused primarily on M. gemmata while M. lineata has received little attention. Mesobdella lineata stands apart as the sole African species in Xerobdellidae, yet inhabiting similar temperate latitudes as its South American counterpart. Reexaminations of internal and external morphological characters of the holotype as well as additional specimens of M. lineata were performed. Phylogenetic methods were used to analyze morphological characters and taxonomic reassignment is made.

MATERIALS AND METHODS

Specimens examined include the holotype (Museum of Zoology, University of Lund, Sweden; catalog number L951/4421) and a paratype specimen (Museum of Zoology, University of Lund; catalog number L951/3643). On 7 March 1975 three specimens of Mesobdella lineata were collected from moist vegetation near streams at Dap Naude Dam (23°48′30.84″S 29°58′12.18″E), Limpopo Province, South Africa, 6.7 km west of the type locality, and an additional five specimens were collected between 27 December and 31 December 1975 from the same locality (all deposited in the collections of the American Museum of Natural History, catalog numbers 4502, 4503, 4726, 4728, 4729, 4730, 4731, 4733). Leeches were either relaxed in 30% ethanol and fixed and preserved in 70% ethanol or fixed in 10% formalin and preserved in 5% formalin. Examination of external and internal morphology was accomplished with a Nikon® SMZ645 stereomicroscope on whole and dissected specimens. Roman numerals in all cases indicate body somites (e.g., prostomium and peristomium are I and II) and annuli receive alphanumeric designations as per Sawyer (1986). Photographs were taken with a Nikon Coolpix® 5000 digital camera and drawings were made by hand. Illustrations were digitized using Adobe Illustrator* 10.

Table 1:

Taxa included in the phylogenetic analyses.

FIGURE 1.

Sciacchitano's (1959) illustration of Mesobdella lineata from the original description.

FIGURE 2.

Wholebody photograph including the color pattern in a preserved specimen.

FIGURE 3

(below). Parapraobdella lineata, n. gen. A. Dorsal surface of body with somites indicated by Roman numerals. B. Dorsal view of the head showing five pairs of eyespots, position of the first nine pairs of nephridia on the ventral side, sensillae around the oral opening, and location of male and female gonopores on the ventral side. Intersegmental furrows indicated with small black arrows. C. Internal gastric system. D. Jaws with eight small teeth and pharynx. E. Internal male and female reproductive organs relative to somatic ganglia XI through XII.

FIGURE 4.

Strict consensus of 12 equally parsimonious trees obtained from 32 morphological characters with implied weighting.

Representative taxa (table 1) of the families Haemadipsidae, Xerobdellidae, Semiscolecidae, Macrobdellidae, Hirudinidae, and Praobdellidae were included with M. lineata in a morphological matrix of 32 characters (appendix 1) adapted from Borda and Siddall (2004). Parsimony analyses of the morphological matrix employed PAUP* 4.0b10 (Swofford, 2002). Heuristic searches used 500 replicates of the data set with random taxon addition and tree bisection-reconnection branch swapping. Parsimony jackknife (jac) values were obtained using random taxon addition and tree bisection-reconnection branch swapping with 36% deletion and 100 pseudoreplicates. All characters initially were weighted equally and were nonadditive. Additional searches were performed with implied weighting (Goloboff, 1993) varying values of k from 1 to 20.

RESULTS

The morphological dataset analyzed under implied weighting yielded 12 equally parsimonious trees with a best score of -23.59329. The strict consensus tree (fig. 4) remained unchanged for values of k ranging from 1 to 20. Parapraobdella lineata was in a clade with Tyrannobdella rex and Myxobdella annandalei (Oka, 1917) among a paraphyletic Praobdellidae.

SUBORDER ARHYNCHOBDELLIDA BLANCHARD, 1894 FAMILY PRAOBDELLIDAE (SAWYER, 1986)

DISCUSSION

This redescription based on morphological characters indicates that the species formerly known as Mesobdella lineata requires a new genus, Parapraobdella. Sciacchitano (1959) placed this species in the genus Mesobdella on the basis of its terrestrial habitat and apparent possession of three annuli per midbody somite. Examination of Sciacchitanos' (1959) types and the Dap Naude Dam material revealed five annuli per midbody somite, not three. In complete somites, b1 and b6 annuli are smaller than annuli b2, a2, and b5 leading to a trian nulate appearance.

Praobdellidae is the best family to accommodate this genus and species when considering the wide caudal sucker, eight teeth per jaw, internal reproductive morphology, and lack of postanal annuli of Parapraobdella lineata. When first proposed by Sawyer (1986) as a subfamily within the distichodont series, Praobdellinae was distinguished as having a velar mouth, mesomorphic reproductive structures, most species with a large caudal sucker, typically parasitic in nasal passages in mammals, and distributed in Africa and southeast Asia. The subfamily was elevated to family Praobdellidae and expanded by Phillips et al. (2010) to include Praobdella, Myxobdella, and Dinobdella (sensu Sawyer, 1986), with the addition of Limnobdella, Limnatis, Pintobdella, and Tyrannobdella strongly supported by molecular data. This expansion was supported by morphological and behavioral observations: 0–12 teeth per jaw in most members of the group but 30–40 teeth per jaw in Limnatis and Limnobdella, the caudal sucker being wider than the four most posterior somites of the body, a lack of postanal annuli, and primarily feeding from mammalian mucous membranes (Phillips et al., 2010). This unique combination of morphological and behavioral characters encompasses the diversity of morphologies seen across these eight genera as well as defines the family.

Phylogenetic analyses of the morphological data while inconclusive when left unweighted, are shown to carry more information in favor of P. lineata's place among the Praobdellidae than against it. While the family is not supported as monophyletic here, the clade is well supported with DNA sequence data (Phillips et al., 2010). The feeding preference of P. lineata has not yet been observed, yet the crop is cecate and several specimens were filled with what appears to be blood. The teeth and jaws are also equipped to allow blood feeding although host preference cannot be determined from these structures. It is more similar in teeth morphology, lacking a velar mouth, the number of annuli between gonopores, and micromorphic reproductive structures to the Neotropical members of Praobdellidae (Pintobdella and Tyrannobdella) than those with geographic distributions in the Old World.