Redescription of Mastacembelus ophidium Günther, 1893 (Synbranchiformes: Mastacembelidae) and description of a new spiny eel from Lake Tanganyika

A detailed morphometric study was undertaken of collections of the Lake Tanganyika endemic Mastacembelus ophidium. On each specimen 27 measurements and 12 meristics were taken. Within the specimens previously identified as M. ophidium a new species was discovered. A redescription of M. ophidium and a description of the new species are provided.


Introduction
Mastacembelidae are anguilliform fishes that can attain a maximum length of about 1 m. Very characteristic is the rostral appendage which bears the two tubulated nostrils, one on each side of the central rostral tentacle. The gill opening is reduced due to a connection of the opercular membrane with the lateral wall of the body. Mastacembelidae have a long series of well-separated dorsal spines, hence their name spiny eels. Further, they also have a short series of anal spines. Pelvic girdle and fins are absent. Most species are characterized by a large number of small cycloid scales. In all African members of the family the dorsal, caudal and anal fins are confluent. Travers (1984aTravers ( , 1984b revised the suborder Mastacembeloidei and divided the family Mastacembelidae in two subfamilies: the Mastacembelinae occurring in Asia and the Afromastacembelinae in Africa. Travers (1984b) recognized two genera in the latter subfamily: Caecomastacembelus Poll, 1958(type species C. brichardi Poll, 1958 and Afromastacembelus Travers, 1984b (type species Mastacembelus tanganicae Gü nther, 1893). In 1988, Travers mentioned that the types of M. tanganicae, in fact, display the generic characters of Caecomastacembelus. Thus, Travers (1988) synonymized Afromastacembelus with Caecomastacembelus. For the other species previously allocated to Afromastacembelus, a new genus, Aethiomastacembelus, was described and a new type species, Mastacembelus marchei Sauvage, 1879, was designated. However, the generic position of many of these species subsequently was found to be confused (Seegers 1996;Teugels 1996, 1997;Vreven 2004). Vreven and Teugels (1996) discussed the problems of the type material of both genera. This study revealed several inaccuracies and contradictions in the diagnoses of both genera. At present, there is no phylogenetic evidence supporting their validity (monophyly) and there are no straightforward diagnostic character(s) available for their diagnosis. The present status is harmful to the stability of the generic nomenclature of the African Mastacembelidae. Therefore, Vreven (forthcoming) proposed that the present use of both genera Caecomastacembelus and Aethiomastacembelus should be abandoned and that both genera are placed in synonymy with Mastacembelus.
In 1893 Gü nther described Mastacembelus ophidium as a new mastacembelid species endemic to Lake Tanganyika. Worthington and Ricardo (1936), based on their observations of a large variability in the dorsal spine numbers, were the first to report that more than one species might be included within the type series of M. ophidium.
Later, Poll (1953) described a few specimens of the lake as Mastacembelus sp. He recognized the juvenile character of these specimens and therefore preferred to postpone the formal description of this new species. Matthes (1962) did not share the opinion of Poll (1953) and recognized the specimens of Mastacembelus sp. as juveniles of M. ophidium. In Matthes' (1962) opinion all characters, including the coloration, except the number of dorsal spines, perfectly agreed with those observed in M. ophidium. He pointed to the striking resemblance in head shape, with the very short snout, the eyes protruding on the surface of the skin and the very large mouth. In addition, he had identified a few intermediate specimens which he considered evidence confirming his opinion. Nevertheless, he referred to two specimens already recognizable as females, of 73.0 and 71.3 mm standard length (SL) (Matthes 1962 , Table IX), respectively, as a ''curious'' fact. Matthes (1962) concluded that much more material would be necessary, especially specimens of intermediate size (100-150 mm), to allow a better supported conclusion on this subject and in this way expressed his own doubt about the fact that all specimens belonged to one and the same species.

Material and methods
The Mastacembelus ophidium specimens housed in the collections of the Natural History Museum (BMNH), London (UK), the Institut Royal des Sciences Naturelles de Belgique (IRSNB), Brussels (Belgium), the Harvard University, Museum of Comparative Zoology (MCZ), Cambridge, MA (USA), the Musée Royal de l'Afrique Centrale (MRAC), Tervuren (Belgium), the Royal Ontario Museum (ROM), Ontario (Canada), and the South African Institute for Aquatic Biodiversity (SAIAB) Grahamstown (South Africa), were examined.
For the methods used I refer to Teugels (1996, 1997, forthcoming). Data were explored and analysed using Principal Component Analysis (PCA) on the correlation matrix of the log-transformed measurements and the raw meristics. PCA is used here as a model-free and distribution-free technique for exploring multivariate data sets (Marcus 1990). All fully examined specimens were included in the analyses. This method allows a size-free comparison of the specimens when the first factor, which accounts mainly for size, is discarded (Humphries et al. 1981;Bookstein et al. 1985). This was confirmed by plotting principal component I (PCI) versus SL.
Non-parametric Mann-Whitney U tests were used for univariate comparisons. As far as possible they were only done on samples of similar length classes and calculated on the relative measurements (percentages) and raw meristics.
For the statistical analyses Statistica for Windows, version 5.1 (1997 edition) from StatSoft., Inc. was used. Distribution maps were made with MapInfo Professional, version 4.0. Coordinates preceded by ''¡'' are from country gazetteers or the MRAC locality database. All other coordinates were copied from the museum labels or listings, provided by the collectors.

Analyses
Meristics. A first PCA performed on the correlation matrix, was carried out on nine meristics (see Table I) of all specimens identified as M. ophidium (Figure 1). A clear separation was found on PCI. The highest loadings on PCI are for the total, caudal and abdominal vertebrae, the anal soft fin ray, the dorsal spine and the dorsal soft fin ray numbers (Table I). This separation was confirmed by the bimodal distribution of the total vertebrae numbers (Figure 2a).
A histogram of the total ( Figure 2a) and caudal (not illustrated) vertebrae numbers clearly illustrates that two discrete groups of specimens can be identified: the first one (Group I) with lower total (72-84) and caudal (48-58) vertebrae numbers including only the smallest of the M. ophidium syntypes; and the second one (Group II) with higher total (90-101) and caudal (63-70) vertebrae numbers including the remaining four syntypes of M. ophidium. These bimodal distributions are not the result of geographical variation, as specimens of both groups occur sympatrically in the various regions of the lake (Figure 2b). The distinctive meristics are correlated, as a higher abdominal vertebrae number implies a higher number of neural spines, a higher number of dorsal spine-supporting pterygiophores and therefore also a higher number of dorsal spines. Further, a higher caudal vertebrae number implies a higher total vertebrae number. Finally, a larger caudal vertebrae number also implies a larger number of neural spines, haemal spines and pterygiophores, being a larger number of supporting elements for a larger number of dorsal and anal soft fin rays.
Mann-Whitney U tests (see Table II) were performed to further explore the differences between both groups for all nine meristics included in the PCA.  All specimens identified as members of Group I (5M. polli sp. nov.) have a standard length of 54 up to 140 mm whereas all specimens identified as Group II (M. ophidium) have a standard length between 149 and 406 mm. Although Worthington and Ricardo (1936) stated that the number of dorsal spines increases with age, I have not found any evidence to support this statement in any of the other African Mastacembelidae species studied. A plot of the dorsal spine and total vertebrae numbers, respectively, shows that the difference is not related to size (Figure 3a, b). Unfortunately, the smallest examined M. ophidium specimen (¡129 mm SL), with 27+1 dorsal spines and a total vertebrae number of 95, is a partially dissected cleared and stained specimen (BMNH 1968.12.30:4).
Morphometrics. Two PCAs on the correlation matrix were carried out, one on 24 logtransformed measurements and one on the measurements as percentages. The postpreorbital spine length has not been included as this spine is absent in both species. None resulted in any reasonable discrimination between both species as the cluster of M. ophidium specimens is almost entirely situated within the cluster of M. polli sp. nov. specimens.  Mann-Whitney U tests were not performed as comparison between similar-sized specimens of both species was impossible. If performed, significant differences between examined morphometrics of the available samples might be due to size differences between the specimens of the samples of the two species (i.e. allometry), to real shape differences between both species (see below) or a combination of both.
Despite the size differences between the specimens in the samples of both species, possible diagnostic characters are the distance from anterior border of snout to last externally visible anal spine (% SL), the postanal length (% SL) and the body depth (% SL) (see Figure 4b-d).
Since none of the type specimens has ever been illustrated (see recommendation ICZN 1999) the largest of the syntypes is here designated as the lectotype. Of the remaining four syntypes, three paralectotypes are here considered conspecific with the lectotype while the smallest paralectotype belongs to the new species described below. Worthington and Ricardo (1936) stated that the description of M. ophidium was based only on the larger syntypes. This can certainly be confirmed, for example, by the fact Gü nther (1893) gave a variation of 31 up to 32 dorsal spines for M. ophidium while the smallest syntype possesses only 23+1 dorsal spines. For more details see M. polli sp. nov.

Diagnosis
Within Lake Tanganyika, M. ophidium can be distinguished from all other species, except M. polli sp. nov., by a relatively long postanal length [54.1-60.5 (57.1)% SL versus 53.5% SL or less] increasing with size (Figure 5a), which is longer than the preanal length, itself being relatively short [38.3-45.0 (41.6)% SL versus 46.1% SL or more] and decreasing with size; by a relatively short distance from snout to last, externally visible, anal spine [40.0-46.6 (43.8)% SL versus 50.6% SL or more] (Figure 5b); and by its protruding eyes, protruding lower jaw, pointed caudal fin, posterior angle of lips situated below eye, from about one-third of the eye diameter, or even behind the posterior border of the eye (versus posterior angle of lips situated more anterior

Description
Meristics and morphometrics are given respectively in Tables III and IV. A representative specimen of this species is illustrated in Figure 6a-c.
Mastacembelus ophidium has protruding eyes, a small rostral appendage, a protruding lower jaw, a pointed caudal fin and a relatively elongated pectoral-fin shape (i.e. not so rounded as in many other species). Posterior angle of lips situated below the region from the middle of the eye up to a distance of about one-third of eye diameter behind posterior border of eye. For the majority of the specimens the posterior angle of lips is situated below the posterior edge of the eye. Mastacembelus ophidium together with M. polli sp. nov. are the only African spiny eels in which the posterior angle of lips is situated so far posteriorly ( Figure 6b). Upper corner of gill opening and the dorsal edge of pectoral-fin base approximately at same level, clearly anterior to ventral edge of pectoral-fin base. Dorsal edge of pectoral-fin base situated above upper corner of the gill opening. Upper corner of gill  opening situated between one-quarter and half (exceptionally three-quarters) of the vertical distance between the dorsal and ventral edge of the pectoral-fin base (Figure 6c). Lateral line continuous from posterior border of head up to region of anus; further posteriorly, it becomes more and more discontinuous. Preanal length always shorter than postanal length; distance from anterior border of snout to last externally visible dorsal spine always longer than distance from anterior border of snout to last externally visible anal spine, and consequently origin of soft dorsal fin always posterior compared to origin of soft anal fin.
A high number of dorsal spines, XXVII+I to XXXIII+I, with spines increasing in size from first to last. Usually a very small, almost entirely reduced spine hidden under the skin, and situated anterior to the base of the first dorsal-fin ray. Nevertheless, the dorsal spine formula is standardized as X+I.
One well-developed, externally visible, anal spine. In addition, a very small almost entirely reduced spine, hidden under the skin, and situated anterior to the base of the first anal-fin ray can be present. First anal pterygiophore well developed, supporting only the first anal spine. Second anal pterygiophore very small, sometimes supporting an almost entirely reduced anal ''spine''. Nevertheless, the anal spine formula is standardized as I+I.
In all specimens the neural spine-supporting pterygiophore of the last externally visible dorsal spine and the haemal spine-supporting pterygiophore of the first anal spine are situated on two different vertebrae and are separated by one to three vertebrae (named in-between vertebrae hereafter). The vertebra with the neural spine supporting the pterygiophore of the last externally visible dorsal spine is always situated posterior to the vertebra whose haemal spine supports the first anal spine.
Coloration (see also Figure 6a) Based on MRAC 75-01-P-119-123 unless otherwise stated. Uniformly light brown background colour with generally numerous small, round, dark brown spots on lateral sides and back of head, body and tail. Spots may be far less abundant or even absent on entire tail, or more posterior part of tail. Exceptionally, spots restricted to head region (MRAC 92-081-P-1441). Further, spots mainly limited to three series, one on the dorsal midline and one on each lateral line forming nearly continuous bands, especially on the tail region (MRAC 90973). In another specimen spots found on each side of dorsal midline and on anterior part of dorsal fin base. Remaining spots far less contrasted with the background colour than in other specimens examined (see also MRAC 85-12-P-7). Background colour lighter, more yellowish white on lips, ventral region of head, belly and most ventral part of tail. Pectoral fins whitish transparent without spots or eventually only spotted at their base. Dorsal fin light brown with a series of numerous small, round, dark brown spots at its base, outer margin white. Caudal fin light brown at its base and yellowish white towards its outer margin. Anal fin yellowish white.
Distribution (see Figure 7) Mastacembelus ophidium is endemic to Lake Tanganyika and confirmed locality records indicate a circumlacustrine coastal distribution. However, at present, it has not been found over large parts of the Democratic Republic of Congo coastline, but this part of the lake is poorly sampled. Kawabata and Mihigo (1982) reported M. ophidium from around the Ruzizi River estuaries. The species is reported to be rare (Poll 1953).

Generic status
Gü nther (1893) described M. ophidium as a new member of the genus Mastacembelus. Travers (1984b) placed M. ophidium within the genus Afromastacembelus (see also Travers et al. 1986). Travers (1988) revealed that the type species of the genus Afromastacembelus, A. tanganicae (Gü nther, 1893) in fact belongs to the genus Caecomastacembelus and created a new genus Aethiomastacembelus to allocate most of the species previously in Afromastacembelus. However, Travers (1988) did not mention to which genus M. ophidium was allocated. Subsequently, Coulter (1991) and Abe (1997Abe ( , 1998 placed it in the genus Caecomastacembelus. Vreven and Teugels (1996) revealed several inaccuracies and contradictions between the type material and the diagnosis of both genera. Vreven (forthcoming) placed Caecomastacembelus and Aethiomastacembelus in synonymy with Mastacembelus. Based on the meristic, morphometric and colour pattern evidence M. ophidium seems to be most closely related to M. polli sp. nov. The more distant affinities of both species remain, at present, unresolved and need additional research.

Biology and ecology
Note. The literature data on M. ophidium provided here need to be handled with care as M. ophidium and M. polli sp. nov. have not been distinguished in the past. Therefore, misidentification of specimens mentioned in the literature can certainly be expected (see Synonyms and Citations).
Habitat. Poll (1953) mentioned M. ophidium occurring in coastal regions of the lake up to a depth of 10 m. Matthes (1962) reported two specimens (verified) as M. ophidium from rocky bottoms. However, most of the other specimens identified by himself as M. ophidium from rocky bottoms are M. polli sp. nov. (see below). Also Brichard (1978) reported the species living in rocky habitats. However, Travers et al. (1986) and Eccles (1992) reported that the species inhabits sandy shores. In addition, M. ophidium was reported as a sanddwelling species occasionally found on rocky slopes (sand/rock) by Brichard (1989). Finally, Abe (1997) also reported that M. ophidium occupies sandy bottoms. Hence, M. ophidium is most probably a sand-dwelling species occasionally found on rocky bottoms (see also under Discussion).
It is well known that sand-dwelling fluviatile species of spiny eels bury themselves in the sand to lay in ambush waiting for prey to pass by, or to do so as a protection against predators (Brichard 1989). Brichard (1989) suggested that it would not be surprising to find also that sand-dwelling Lake Tanganyika species bury themselves in the sand (Brichard 1989). Indeed, this burying and ambush behaviour was confirmed and illustrated by Jäger (2002) based on aquarium observations.
Food. Worthington and Ricardo (1936) mentioned that one specimen had been feeding on small prawns. Poll (1953) reported the presence of one Lamprologus sp. of 5 cm in the stomach of one of the specimens studied by himself. Indeed, based on X-ray data of many specimens, the presence of fish(es) in the stomach of some of the examined specimens is confirmed.
Reproduction. Vast numbers of M. ophidium fry have been noted periodically near the shore at the north of the lake (Coulter 1991), indicating mass spawning (Brichard 1978). It is the only species from which concentrations of thousands of young fry a few centimetres long have been observed in quiet bays during some months of the year (Brichard 1989). Following Brichard (1989) it therefore appears that the spiny eels might migrate and have synchronous spawning, but as yet this observation applies only to M. ophidium and not to any other species (see also below under Discussion). Poll (1953) reported an immature male (MRAC 90973, 349 mm TL, 20 December 1946) and a mature female (ISNB 9431, 332 mm SL, 25 January 1947). Other specimens (MRAC 91643, 400 mm TL, 3 November 1949;MRAC 92-081-P-1441, 341 mm TL, 1 June 1992 are here identified as a ''nearly ripe'' females. Based on these reported data it is obvious that additional specimens will be necessary to identify reproduction period(s). Abe (1998) reported that the oocytes of M. ophidium are small when compared to the oocytes of M. albomaculatus, M. micropectus, M. plagiostomus, and M. tanganicae which have an oocyte diameter larger than or equal to 1.5 mm. Nevertheless, for both specimens I examined (MRAC 91643, 400 mm TL; MRAC 92-081-P-1441, 341 mm TL) the egg diameter is around 1.5 mm.

Fisheries
Mastacembelus ophidium is of little value as food (Poll 1953;Eccles 1992). According to Eccles (1992), their shape makes them difficult to net, although they can be taken with a small hook. Eccles (1992) mentioned that M. ophidium might be of some interest to aquarists. Indeed, M. ophidium is presently available in Germany (www.pet2get.dk/ stockliste 2003).

Other specimens examined
All specimens originated from Lake Tanganyika. For samples with more than one specimen and without separate numbering the exact number is provided. All lengths are total lengths.  Mastacembelus polli sp. nov. (Figure 8)

Type material
Only a small sample (i.e. the specimens>95 mm TL) of the examined specimens identified as M. polli sp. nov. has been designated as type material of the new species. All specimens from Lake Tanganyika. Holotype

Etymology
Named in honour of the late Prof. Dr M. Poll (1908Poll ( -1991, a famous Belgian ichthyologist who pioneered ichthyological studies on Lake Tanganyika and who first drew attention to the fact that his Mastacembelus sp. (Poll 1953) might well be a new species.

Diagnosis
Within Lake Tanganyika, M. polli sp. nov. can be distinguished from all other species, except M. ophidium, by a relatively long postanal length [50.6-56.6 (mean 53.7)% SL versus 53.5% SL or less] increasing with size (Figure 5a), which is longer than preanal length, itself being relatively short [42.7-47.6 (44.7)% SL versus 46.1% SL or more] and decreasing with size; by a relatively short distance from anterior border of snout to the last, externally visible, anal spine [45.9-51.3 (48.3)% SL versus 50.6% SL or more] ( Figure  5b); and by protruding eyes, protruding lower jaw, ''pointed'' caudal fin, posterior angle of lips situated below eye, from about one-third of eye diameter, or even behind posterior border of eye (versus posterior angle of lips situated more anterior  (95)].

Description
Meristics and morphometrics are given in Tables V and VI, respectively. The holotype is illustrated in Figure 8a-c.
Mastacembelus polli sp. nov. has protruding eyes, a small rostral appendage, a protruding lower jaw, a pointed caudal fin and a more elongated pectoral-fin shape (i.e. not so rounded as in many other species). Posterior angle of lips situated below the region from the middle of the eye up to a distance of about one-third of the eye diameter behind posterior border of eye. For the majority of the specimens the posterior angle of lips is situated below the posterior edge of the eye. Mastacembelus polli sp. nov. together with M. ophidium are the only African spiny eels in which the posterior angle of lips is situated so far posteriorly ( Figure 8b). Upper corner of gill opening and dorsal edge of pectoral-fin base approximately at same level, clearly anterior to ventral edge of pectoral-fin base. Dorsal edge of pectoral-fin base situated above upper corner of the gill opening. Upper corner of gill opening situated between one-quarter and half (exceptionally three-quarters) of the vertical distance between the dorsal and ventral edge of pectoral-fin base (Figure 8c). Lateral line continuous from posterior border of head up to one-third or half of distance between head and anus, discontinuous more posteriorly. Preanal length always shorter than postanal length; distance from anterior border of snout to last externally visible dorsal spine always longer than distance from anterior border of snout to last externally visible anal spine, and as a result origin of soft dorsal fin always posterior compared to origin of soft anal fin.
A relatively low number of dorsal spines, XXI+I to XXVIII+I, with spines increasing in size from first to last. Usually a very small almost entirely reduced spine hidden under the skin, and situated anterior to the base of the first dorsal-fin ray. Nevertheless, dorsal spine formula standardized as X+I. One well-developed, externally visible anal spine. In addition, a very small almost entirely reduced spine, hidden under the skin, can be present, situated anterior to the base of the first anal-fin ray. First anal pterygiophore well developed, supporting only the first anal spine. Second anal pterygiophore very small, sometimes supporting an almost entirely reduced anal ''spine''. Nevertheless, the anal spine formula is standardized as I+I.
In all specimens the neural spine-supporting pterygiophore of the last externally visible dorsal spine and the haemal spine-supporting pterygiophore of the first anal spine are situated on two different vertebrae and are separated by one to five in-between vertebrae. The vertebra with the neural spine supporting the pterygiophore of the last externally visible dorsal spine is always situated posterior to the vertebrae whose haemal spine supports the first anal spine.

Coloration (Figure 8a)
Based on the holotype unless otherwise stated. Uniformly light brown overall background colour with numerous small, round, dark brown spots on dorsal part (approximately from around the lateral line up to more dorsal) of head, body and tail. Sometimes, spots larger and more irregularly shaped (MRAC 128687; MRAC 84-23-P-638) or less abundant and less contrasted with the overall background colour (MRAC 128688). Spots may be limited to three series, one on the dorsal midline and one on each lateral line (MRAC 128685-686). Some specimens only lack spots on tail region (MRAC 76-09-P-222-230: 107, 96, 92, 85, and 84 mm TL) whereas others entirely lack spots (MRAC 76-09-P-222-230: 104, 101, 75, and 72 mm TL). Background colour lighter, more yellowish white on lips, ventral region of head, belly and most ventral part of tail. Pectoral fins whitish transparent without spots. Dorsal, caudal and anal fins also whitish transparent.
Distribution (see Figure 9) Mastacembelus polli sp. nov. is endemic to Lake Tanganyika and appears to have a circumlacustrine shore distribution. However, it has not been found over large parts of the Tanzanian-Zambian and Democratic Republic of Congo coastline. I suspect this is due to poor sampling of these parts of the lake rather than to the real distribution of the species. Mastacembelus polli sp. nov. was mentioned by Poll (1953) as rare.

Generic status
Similar to M. ophidium, M. polli sp. nov. is placed within the genus Mastacembelus. Mastacembelus polli sp. nov. seems, based on the meristic, morphometric and colour pattern evidence, to be most closely related to M. ophidium. The more distant affinities of both species remain unresolved at present and need additional research.

Biology and ecology
Habitat. Coastal in distribution (Poll 1953). For several specimens listed by Matthes (1962) additional information on the habitat of the material was provided: rocky bottom, flagstone; rocky bottom, rock slides and pebbles; and pebble bottom.
In addition, another sample of specimens was reported from a sandy bottom with snails, depth 20-40 m (Matthes 1962). These specimens are most probably M. polli sp. nov. (23-26 dorsal spines, according to Matthes 1962). Due to the small size of the latter material I was unable to make sharp X-rays, and make accurate counts of all vertebrae. Therefore, I consider the identification of the latter specimens as tentative. These specimens are the smallest ones reported for M. polli sp. nov.
Reproduction. According to Matthes two specimens of respectively 73.0 and 71.3 mm SL (see Matthes 1962, Table IX) were already recognizable as immature females (Matthes 1962) (MRAC 128685-686, confirmed). Poll (1953) mentioned that the specimens he examined were obviously juveniles. Based on my own observations the holotype of M. polli sp. nov. and another specimen (MRAC 76-09-P-222-230, 103 mm SL) are both nearly ripe females illustrating maturation at small size.

Fisheries and aquaculture
The capture method is variable (Poll 1953).  Abe (1997) reported rock and sand or mud habitats for M. ophidium. This literature statement is probably based on the data provided by Matthes (1962). However, most of the specimens identified as M. ophidium by Matthes (1962) and collected on a rock habitat bottom are in fact M. polli sp. nov. (except for MRAC 130379-380). Based on his own observations Abe (1997) stated that M. ophidium occupies the sand bottom. Also Brichard (1989) reported this species as living mainly on sand. Therefore, both species seem to live in a different habitat with M. ophidium mostly on sandy bottoms and M. polli sp. nov. more restricted to the rock, rock/sand habitat types.