Tentacularia Bosc, 1797

Palm, Harry W. & Walter, Thorsten, 2000, Tentaculariid cestodes (Trypanorhyncha) from the Muséum national d’Histoire naturelle, Paris, Zoosystema 22 (4), pp. 641-666 : 662-664

Genus Tentacularia Bosc, 1797

TYPE SPECIES.— Tentacularia coryphaenae Bosc, 1797 . SPECIES INCLUDED.— Tentacularia coryphaenae Bosc, 1797 (synonym Nybelinia lamontae Nigrelli, 1938 [Palm et al. 1997], others see Dollfus [1942]).

DEFINITION

Trypanorhynchs with the characters of the Tentaculariidae Poche, 1926 . Scolex elongated, four elongate sessile narrow bothridia lie along the scolex, with hook-like microtriches along the synonyms of H. estigmena (all described in bothridial borders and filamentous microtriches Dollfus 1960). H. punctatissima is considered a on the rest of the bothridia and scolex. Four ten- synonym of N. lingualis (Cuvier, 1817) , while tacles emerging from scolex; metabasal tentacular the specimens described and illustrated as armature homeoacanthous homeomorphous. H. punctatissima in Dollfus (1960) are specimens Characteristic basal armature present. Retractor of H. estigmena (Dollfus, 1960) . H. rougetcampamuscle originates at base of bulbs. Strobila acras- nae (Dollfus, 1960) is considered a synonym of pedote, cirrus unarmed, genital pores lateral, alter- H. nipponica (Yamaguti, 1952) , and N. rhynchonate irregularly, in anterior third of proglottids. batus Yang et al., 1995 a synonym of Kotorella pronosoma (Stossich, 1901) . To date, a total of

38 species can be recognised within the genera

SPECIES NOT CONSIDERED Nybelinia , Heteronybelinia , Mixonybelinia , and Kotorella . The two species N. tenuis and N. bisul-

Nybelinia anantaramanorum Reimer, 1980 . See cata need further examination.

Remarks under N. goreensis ; Palm et al. (1997), Palm (1999) and Palm & N. bisulcata (Linton, 1889) . Linton deposited Walter (1999) discussed the zoogeographical disvoucher specimens of different Nybelinia , tribution of different species of these tentacula- Heteronybelinia and Mixonybelinia species under riid genera. The authors recorded a wide the name N. bisulcata in the National geographical distribution for N. africana, Helminthological Collection, Beltsville, USA. H. robusta , H. yamagutii and M. beveridgei (Palm The identity of the species needs to be clarified; et al. 1997) as well as for N. perideraeus , K. prono- N. congri Guiart, 1935 (Palm et al. 1997); soma (Palm & Walter 1999), N. lingualis , N. sco- N. macrocephala Asmi, 1983 in Bilqees & liodoni, H. estigmena , and H. heteromorphi (Palm Khurshid (1987) (Palm et al. 1997); 1999). The present results add N. riseri , H. nip- N. tenuis (Linton, 1890) . The identity of the spe- ponica, H. minima , and M. edwinlintoni to the cies needs to be clarified; list of widely distributed species. Thus, 14 species N. trisulcata in Reimer (1980) (Palm et al. 1997); have a wide distribution, indicating an trans- Heteronybelinia karachii (Khurshid & Bilqees, oceanic or sometimes interoceanic occurrence. 1988). The incomplete original description of However, other species seem to be regionally dis- H. karachii does not indicate the number of tributed, such as N. surmenicola (mainly recorded bothridia, and Khurshid & Bilqees (1988: from the North Pacific Ocean and only once fig.1a) demonstrate a trypanorhynch specimenfrom the Southern Pacific, Oliva et al. 1996), with two bothridia. Without re-examination of N. thyrsites , and N. queenslandensis (New the type material, H. karachii can not be assigned Zealand, East Australian coast). Whether this difto any tentaculariid genus. Thus, the species ference is real or only a matter of limited inforshould be treated as species inquirenda. mation can not be decided at present. Tentaculariid trypanorhynchs exhibit a low level of host-specificity and a wide host range within a

DISCUSSION single locality (Dollfus 1942, 1960; Palm et al. 1997, present study). The low host specificity not

The present study summarises the state of know- only applies to the teleost intermediate but also ledge within the genera Nybelinia , Heterony- the final elasmobranch hosts. For example, belinia, Mixonybelinia and Kotorella . A further N. africana , N. scoliodoni , and H. robusta infest species ( M. edwinlintoni n.comb.) is transferred four, three, and three elasmobranch species, resto the genus Mixonybelinia Palm, 1999 , and pectively, including sharks with a wide zoogeo- Nybelinia oodes , Heteronybelinia alloiotica , graphical distribution. Marcogliese (1995) stated H. cadenati , and H. senegalensis are considered that marine helminths exhibit very limited host-

specificity in zooplankton intermediate hosts, and similarly in fish as intermediate (Holmes 1990) and birds as final hosts (Bush 1990). This has been interpreted as spreading the risk of failure to complete their life cycles in the marine environment. The same pattern seems to be also true for tentaculariid trypanorhynchs.

The present study demonstrates that four further species, N. erythraea , N. lingualis , N. surmenicola and H. minima , have muscular rings around the tentacle sheaths directly above the bulbs, which have not been described previously for these species. Palm et al. (1997) proposed a possible systematic value of such muscular rings, which have been earlier described from Heteronybelinia species , e.g., H. elongata and H. estigmena . It seems that muscular rings around the tentacle sheaths are a common feature within these trypanorhynchs, however, they are not always visible, most probably due to different fixation and staining methods. This questions the use of this structure as a systematic character within tentaculariid cestodes. N. africana and N. goreensis had smaller hooks in the apical than in the metabasal armature. This has been described also for Nybelinia aequidentata by Pintner (1927), and thus seems to occur in several different Nybelinia species. This also demonstrates the apical armature as an important taxonomic character, which should be considered in future species descriptions.

It is evident that several of the above recorded tentaculariids have a high intraspecific morphological variability (see also Palm et al. 1997; Palm 1999). Interestingly, within the same host species, postlarvae can have a larger scolex size than the adult worms, as with Heteronybelinia nipponica (= H. rougetcampanae ). The postlarvae ranged between 1 220-2 900 (Yamaguti 1952; Dollfus 1960), and the adults between 510-690 (Sao Clemente & Gomes 1992). Similarly, the scolex sizes of postlarvae and adults of Nybelinia africana varied between 1 118-1 568 (Dollfus 1960; Palm et al. 1997) and 440-536 (Palm 1999), and of H. yamagutii between 1 183-3 904 (Dollfus 1960; Palm et al. 1997) and 2 646 (Palm 1999), respectively. Sao Clemente & Gomes (1992) referred a smaller scolex size of adult worms to the shrinkage condition. Palm et al. (1993) found a similar scolex variability within the non-tentaculariid Otobothrium penetrans Linton, 1907 , and referred it to the plerocercoid age and/or type of fixation and storage. Campbell et al. (1999) referred the occurrence of two different morphotypes of adult Paroncomegas araya to different age, development or population density. Additionally we propose that the scolex size within the final host is influenced by the growth rate of the metacestodes within the first and second intermediate hosts. It could be demonstrated that within another fish parasitic helminth, the nematode Hysterothylacium aduncum (Rudolphi, 1802) , the life-cycle depends on the size the larvae reach within the first and second intermediate hosts (KØie 1993). This might be also true for tentaculariid trypanorhynchs.

Summarising the above, tentaculariid trypanorhynchs are characterised by a characteristic scolex morphology, the lack of a blastocyst, and a wide distribution pattern. The low host-specificity might be another character of these trypanorhynchs, facilitating the wide distribution. As the first intermediate hosts of these cestodes are still unknown, it remains unclear whether these trypanorhynchs also have a specific life cycle with characteristic first intermediate hosts, which might be different to intermediate hosts of other trypanorhynchs. Further data on the zoogeographical distribution of the different species, especially their occurrence also in the central parts of the oceans, as well as information on the first intermediate hosts are needed to really establish the possibly oceanic life cycle pattern of these unspecific trypanorhynchs.