A check-list of the pentastomid parasites of crocodilians and freshwater chelonians

JUNKER, K. & BOOMKER, J. 2006. A check-list of the pentastomid parasites of crocodilians and freshwater chelonians. Onderstepoort Journal of Veterinary Research, 73:27–36 Based on published records and own data a summary is given of the geographical distribution of the currently known species of pentastomid parasites infecting crocodiles and alligators, as well as freshwater chelonians. A brief generic diagnosis is provided for each genus. Fourteen out of the currently 23 living crocodilian species have been recorded as being host to one or more pentastomes. Out of the 32 pentastome species six are considered species inquirendae. Presently, six genera of crocodilian pentastomes, Agema, Alofia, Leiperia, Sebekia, Selfia and Subtriquetra are recognized. African crocodiles harbour eight pentastome species, six of which have been recorded from the Nile crocodile, Crocodylus niloticus. Three species belong to the genus Sebekia, Alofia being represented by two and Leiperia by only one species. Two species, Alofia parva and Agema silvaepalustris, occur in the dwarf crocodile, Osteolaemus tetraspis, and the slender-snouted crocodile, Crocodylus cataphractus, exclusively, but a single Sebekia species is shared with the Nile crocodile. The genus Agema is endemic to the African region. Infective stages of the pentastome Sub triquetra rileyi, thought to utilize Nile crocodiles as final hosts, have been recovered only from fishes. The largest number of pentastome species is found in the Australasian region. Of these, the Indo-Pacific croc odile, Crocodylus porosus, harbours seven, representing the genera Alofia, Sebekia, Lei peria and Selfia. Selfia is exclusive to the latter host. The genus Subtriquetra has been reported from “Indian crocodiles”, a term possibly referring to either Crocodylus palustris, Crocodylus porosus or Gavi alis gangeticus. Ten species of pentastomes parasitizing the crocodilian genera Alligator, Caiman, Crocodylus and Melanosuchus have been recorded from the Neotropical region including the southern states of the North American continent. The two most wide-spread pentastome genera, Alofia and Sebekia, have been recorded together with representatives of the genus Sub triquetra and immature and larval forms of Leiperia. To date the two monospecific genera, Pelonia, from two terrapin species, Pelusios sinuatus and Pelomedusa subrufa, in South Africa, and Diesingia from Hydraspis geoffroyana and Hydromedusa tectifera in South America, are the only chelonian pentastomes recovered world-wide. A possible exception is the crocodilian pentastome Sebekia mississippiensis which can reach maturity in exper imentally infected terrapins.

A single member of Sebekia, Sebekia mississippiensis, might be able to reach maturity in chelonians, too, but as yet no mature specimens have been collected from naturally infected hosts (Dukes, Shealy & Rogers 1971).Members of the monogeneric family Sub triquetridae inhabit the nasopharynx of their crocodilian final hosts, but Subtriquetra rileyi, of which currently only infective larvae have been recovered, needs verification (Winch & Riley 1986a;Junker, Boomker & Booyse 1998).
During the past 10 years renewed progress has been made as regards the taxonomy of crocodilian pentastomes.The older genera, Alofia, Sebekia and Leiperia, have been revised, and examination of new material has led to the description of several new genera and species (Riley 1994;Riley et al. 1990Riley et al. , 1997;;Riley & Huchzermeyer 1996;Junker et al. 1998).However, there is a dearth of data concerning the chelonian pentastomids.
In order to provide a quick reference tool, this checklist consists of two parts, following the example of Sambon (1922).The first part lists the parasites under their scientific names, their synonyms and their authorities.A short generic diagnosis precedes each genus and the parasites are grouped according to the geographic distribution of their respective hosts.The list starts with Africa, followed by Australasia.South and North America are listed last.
The second part of the check-list alphabetically lists the hosts and their synonyms, and, also in alphabetical order, their respective parasites.The nomenclature and synonyms of the crocodilian and chelonian hosts are according to Getz (2002).
Only references dealing with mature pentastomes are included in the check-list, but for completeness' sake the intermediate hosts of pentastome species of which only larval forms are known are listed.

FAMILY SEBEKIDAE SAMBON, 1922
Genus Agema Riley, Hill & Huchzermeyer, 1997 GENERIC DIAGNOSIS: Overall shape typical of smaller members of the Sebekidae; males claviform, females with more uniform diameter and conical posterior terminating in a small blunt point; adult hooks smooth; blades smoothly curved without abrupt right-angled bend near to base; blade on anterior hook pair larger than that of posterior pair; fulcrum without cowl; mouth ovoid and sides of cadre united anteriorly and posteriorly by segments of chitin which appear as two crescents; copulatory spicules delicate and elongate; basal section without a hooked collar (Riley et al. 1997).AFRICA 1. Agema silvaepalustris Riley, Hill & Huchzermeyer, 1997 Crocodylus cataphractus Riley, Hill & Huchzermeyer (1997), Republic of the Congo Osteolaemus tetraspis Riley, Hill & Huchzermeyer (1997), Republic of the Congo

Genus Alofia Giglioli, 1922
GENERIC DIAGNOSIS: Size small; body banana-shaped; hooks large with long, narrow, slightly curved blade and a slender base; absence of chitinous formation at the base of the anterior hook; chitinous buccal cadre large and U-shaped; intestine as in Sebekia; found in crocodiles (Fain 1961in Riley 1994); caudal extremity of female bluntly rounded, often swollen into a bulb (Riley 1994); hooks usually smooth (rarely with patches of minute spines [see Alofia nilotici and Alofia parva (Riley & Huchzermeyer 1995a, b)], blades finely canaliculated, bent through almost a right angle at the base; peg-like extension of oral cadre projects into oesophagus; copulatory spicules with double-hooked collar on the shorter of the two anterior extensions (Riley & Huchzermeyer 1995a, b;Junker, Boomker & Bolton 1999).
Crocodylus porosus (?) Riley (1994), Philippines The collector did not specify the host, but Riley (1994) concludes it to be C. porosus, as the only other Philippinian crocodile, Crocodylus mindorensis, does not occur in the region from which the parasites were recovered.

Alofia merki Giglioli, 1922
Sebekia merki Heymons, 1941 Unknown crocodilian Sambon (1922), Samoa Most probably Crocodylus porosus, as it is the only crocodilian whose range extends as far as Fiji in the Pacific Ocean and it is known to have colonized many small islands as far as nearly 1 000 km from land (Ross 1989).