The Natural History of Santo

Fijian mastiff bat about the genus Emballonura: Emballonurid bats Chaerephon bregullae use the second harmonic as main call, the first (kHz) harmonic being masked. The ME could corre­ spond to the Polynesian sheath-tailed bat, but it is a modulated to quasi-constant frequency, low and spaced. 100 ME: 28 kHz CD: 12 (8-15) kHz BW: 14 (9-21) kHz TBC: 270 ms

50 ••• Frequency-modulated calls \ Myotis/Nyctophilus sp. ->to '.. (kHz) o 200 400 (rns)

80 Only a few sequences have been recorded from caught animals. The call is a quasi-constant fre­ quency, much deeper and more spaced than that of any other bat from Santo as size would suggest. ME : 14-17 kHz. 40 Emballonura sp. ? (kHz)

150

Abrupt frequency modulated calls, with a some­ 100 what "explosive" beginning and a high terminal frequency, were recorded in forest habitat. This type of call is characteristic of Myotis species. They were tentatively attributed to the Large footed 50 mouse-cared bat Myotis adversus. Type 1: TF: 38 kHz (37,9-38,9) CD: 4,5 ms (3-6) BW: 13 kHz 02-14) o 50 100 (ms) TBC: 136 ms 017-179) Some unidentified calls have been recorded in the Type 2: Similar to type 1, wild. Their characteristics cope with what is known but TF higher, up to 42 kHz (N = 15).

FISH AND SHRIMPS OF SANTO KARSTIC SYSTEMS Marc Pouilly & Philippe Keith

The eastern part of Espiritu San to Island is con­ enough to have led to local speciation (appear­ stituted by a coral karst, which nowadays presents ance of new species through a specialisation from an important subterranean system with freshwater an ancestor) adapted to subterranean conditions. habitats such as sinks, lakes and rivers. These spe­ cific habitats increase the local diversity of ecolog­ Crustacean decapods (crabs and shrimps) are ical conditions and may be colonized by species regularly found in subterranean freshwater or with ecological and behaviour predispositions to brackish habitats. Due to their ecological predis­ living in lightless environment. Espiritu San to is positions, they can survive in such habitat with around 22 millions of years old, making it one of or without genetic adaptation. More than 90 the oldest islands of the Vanuatu Archipelago, old subterranean fish species are now described from Caves andSoils around the world. Directly related to the recent For fish, Keith and collaborators have inven toried increase in karst system explora tion, this number 67 species on th e archipelago , th e majority of has rise n continuo us ly from 1970. Th e maj ority of which are amphidromous. Most of these species are known species co mes from the Asian (especially restricted to the lower parts of the river (altitude China) and South American continents. However, below 50 m ) and in the estuarine area. some species have been described from differen t regions of the Indo-pacific: Madagascar (three Espiritu Santa Island is the largest of the 80 islands spe cie s) , Australia (two sp ecies), Papcuasia, of the Vanuatu republic archipelago. The western Malaysia, Sulawesi and Galap agos (one species in part of the island is volcanic and the eastern part eac h area). Two of th e princip al fish families that is covered by calcareous coral that culmin ate at an colonized freshwater habitats of Vanuatu Islands alti tude of c. 600 m. In this landscape rivers are show spec ies ada pted to subterra nea n co nd itio ns short and steep . Only the bigger ones (Sarakata, elsewhe re: Gobiidae (Glossogobius anharanensis jourdain) present a lower part with a small alluvia l from Madagascar ) and Eleotridae (Typhleotris floodplain . pauliani , T madagascariensis, Oxy eleotris caeca). Many species of th e family Anguillidae (ee ls), During the Santa 2006 expedition we sampled wh ich is also common in the Vanuatu Islands, different karst freshwater aquatic habitats (rivers, are able to survive in subterranean habitats with­ sinks and blue hol es) to identify crab , sh rimp and ou t any adaptation.It is th erefore possible that fish species that colonize these habitats, and to local spe cies of Espiritu San ta Island ma y have look for evidence of subte rra nea n adap tations. \"le co lonized sub terranea n rivers, sinks or lak es and carried out a comparative sampling of the aqua tic developed adaptations to maintain su ch popula­ fauna (fish and decapods) of superficial (EXT) tions. However, two important factors may limit and subterran ean (lN T) freshwater aquatic habitats this colonization and, mo reover, prevent ada pta ­ belonging to four systems : tion of the species to sub terranean condition s. • Fapon system (Bu tmas region): river upstream Firstly, the local sp ecies have a predominantly of Fapon Cave (EXT) and in the Fapon doline herbivorous diet. In order to survive in sub­ (lNT); terran ean habitats, su ch sp ecies would hav e to • Amarur system (Nambel region); Amarur shift th eir diet toward reso urces that are not River in the cave (l NT), at the resurgence (EXT) light-dependant, su ch as detritus or small prey. and downstream near Nambel village (EXT) ; Second, most of these sp ecies present a priori a •Patunar sys tem (Funafus region): river in diadromou s migration cycle (they sp end part of Kafae Cave (lN T), upstream (EXT) and down­ th eir biolo gical cycle in freshwater hab itats and stream (lNT) of the Patunar doline, resurgence th e rest in marine habitats ) . For example, eels (EXT) and downstream reaches at altitudes of are generally catadromous. They carry out their 90 m and 15 m; reproduction in the ocean, th e larvae migrate to • Fioha system (Funafus region): Fioha River in rive rs and, once adult, th e eels return to the ocean the cave (l NT) and at the resurgence (EXT). for reproduction. On th e contrary, Gobiidae and Eleotridae are gene rally amphidromo us. In this case, the sp ecies spawn in freshwater and the free embryos drift downstream to the sea, wh ere they undergo a plan ktonic phase before returning to th e rivers to gro w and reproduce. A complete shift to subterranean live would required a tot al ch ange of the reproduction strategy and bi o­ logical cycle of these sp ecies , with a shift from a mig ration to a sedentary cycle, because subter­ ran ean life requires pro fou nd morphological and ph ysiological adaptations (regress ion of ocular system , pigmentat ion loss , etc.) that are in com­ patible wi th an oceanic existenc e.

• •• Study sites, material and method Th ere are only a few records of freshwater fish and decapods crustaceans (cra b and shrimp) available for Vanuatu Island. Sampling carried ou t since 200 0 by the Nati onal Mus eum of Natural Hist ory, Paris (MNHN) and th e Sant a 2006 ex pedition are under evalua tion and should rapidly improve this situa tion. Curren tly, 29 sp ecies are known from Figure 398: Electrofisfing in the subterranean river of the Van uatu and 26 from San ta . Amarur Cave in Santa, during the Santa 2006 expedition . The Natural History of Sa nto

Most of the sampling si tes were situated at altitu de • •• Results abo ve 50 m and correspon d to small streams, less The kar stic rivers of Espi ritu San to Island are colo­ th an 10 m wide and 1 m deep, with gra vel or roc k n ized by 20 fish species, belonging to 10 differen t substrate. All presen t an alka line pH (8.0 to 8.2) in families (Table 36). The mos t dive rse famil y (that th e upper reach es and neutra l pH (7.0 to 7.4) in showing th e hi ghest number ofspecies) is Go biidae the lower reaches. Co nduct ivity in creased with the (Fig. 399), represented by ni ne ge nera and 14 spe­ downstream gradient from (13 0 pS .cm -l ) to salted cies . Eleo tridae is th e seco nd most di verse fam­ water. Most of the sampli ng sites had a co nduc tiv­ ily, with four genera and six species. The fam ily ity between 200 an d 350 pS.cm 1 Other occas ional Poecilidae is only represen ted by Gambusia affinis, observations were mad e in sink parts of the same whi ch is a no n -native species introduced for m os­ syst ems by d ivers of the Santo 2006 karst tea m quito co ntrol. and in four blue holes (Sarabo , ClRAD, Nanda and Porpor sp ring) situ ated near the ocean . Most o f the native species colon ize on ly th e lower parts of the rivers « 50 m) , or only the es tuary and Du e to these charact eristics and difficu lti es of river mo u th : Ambassidae, Krae m eriidae, Ku h liidae, access, electrofishing is lik ely to be an efficien t Ophich thidae and Syn gn athidae. Only th ree fami­ sampling m eth od (Fig. 398). It was th e m ost used lies (An gui llidae, Eleotrid ae an d Gobiidae) colonize and was so me times, when possible, co mplemen ted the rivers at high er altitude and in clu de species by dipne ts and traps. typi cal of th ese rivers. Species richness decrease dras tica lly wi th altitude, fall ing from Table 36: List of freshwater fish, shrimp and crab genera captured in karst systems of 30 sp ecies in river reaches below Santa during the Santa 2006 expedition. 50 m in altitude to eight species in Family Genus Species >SOm Subterranean upper rea ches. Fish Decapods are represented b y two Ambassidae Ambossis 1 0 0 s h rim p fam ilies, Pal a emonidae - f- Anguillidae Anguil/a 2 I 1 (ge nus Macrobrachium) and Atyidae, - f-- and one crab fam ily, Grapsidae. Eleotridae Bu/is 1 " 0 0 .; Macrobrachium shrimps are wi dely Efeotris ,- 1 0 0 distrib ut ed in the Pacific region and Hyp-eleotris 2 0 0 eight species are present on San to - Island. As for fish, species richness I Ophieleotris 2 0 0 I ~ decreased wi th altitu de and th ere Gobiidae I Awaous 1 0 0 are on ly two or th ree species th at -- - -- colonize the rivers above an altitude Lentipes 1 1 0 1..- of 50 m . PsammogoblU 1 0 0 - - - Redigobiu 2 0 0 Glob ally,at hi gher alti tu des (» 50 m) -r - rivers present a high abundance of ISChlsmatogoblUs 1 0 0 sh rimps and only a few fishes « 10 ISicyopterus 2 1 0 individuals/lOO m-). This tendency , -, is reversed in rivers at low alti tudes SiCyop1l5 1 1 0 -i - - and in hab itats near th e estuaries Smilosicyopus 1 1 (blue h oles an d river m ouths) . --L'- StenogoblLJS 1 0 0 No fish or decapods species cap­ Stiphodon ---3 2 0 1-- -- tured or observed s howed clear Krae meriida e GobitnchlllolUs 1 0 0 evidence of s trong adap tatio n to ~ subterr anean con d itions (dep ig­ Kuhli idae - Kuhlia 3 0 0 -- f- - - : - -- mentatio n , oc u lar system reg res­ Ophichthidae lanmostotna 2 0 0 sion). Sh rimps, especiall y of the ~ Syngnathidae Microphis 3 0 0 famil y Atyidae, sometim es showed pi gm en tation differ en ces be tween Shrimp - -- individuals cap tured in superficial Palaemonidae MacrobrochilllTl 8 7 3 and in sub terranean riv ers . However -- - f- theses differences fade wi th the co n­ Atyidae Carldina 3 3 2 ~ servation of the specimens, so that Atyoida -" 1 1 1 it is likely that they correspon d Crab m ore to a res ponse to light st imu lus -- f--- - than to a genetic differen ce. On ly Grapsidae Utica 11 1 1 1 few individua ls of Atyidae captured Caves and Soils

Figure 399: Sicyopterus logocepholus. (Gobiid ae). A common fish species in Santo freshwater rivers (male is coloured and female drab). present ed a strong depigmentation accompanied by a slight microphthalmy (reduction of the size of ext ernal ocular system) (Fig. 400).

All the aqua tic subterranea n habitats (sinks, riv­ ers and small lak es) are colonized by decapods (crabs and shrimps) . The same spe cies colonize both superficial and subterranean rivers (five of the eight Macrobrachium species are present in both conditions) . Habitats with low veloci ties (small lakes, sinks) appeared to be more favourable for Paleomonidae shrimps, although lot ic habitats are more suitable for Atyida e shrimps. Some fam­ ily density variations exist be tween the different systems. For example, the Ama ru r sys tem has a Figure 401: Eels (here A. marmorata) are the only fish that high density of Paleomonidae, whereas the Fioh a colonize the subterranean rivers of Santa. Due to their nocturnal system has high density of Atyid ae. These varia­ behaviour and carnivorous diet, they can coloni ze indifferently tions rema in unexplained and require a more detail both superficial and subterranean rivers without any kind of adaptation. However, their biological cycle requires a migration study to understand the environmental factors that to the ocean for reproducti on, thus limiting the probability of determine the quality of an habitat for each type of an adaptation to a strictly subterranean way of live. The eel is organisms. one of the few freshwater fish appreciated by local peopl e.

Fish are absent in the subterra nean habitats, with exception of eels (Anguilla marmorata and A. obscura) (Fig. 401) tha t were observed in almost all the explored sinks and in many sampled rivers at different altitudes .

The presence of eels can be explained by their car­ nivoro us diet and nocturnal activity. This is in con­ trast to most of the other sp ecies of other groups , which are limited in their coloniza tion of subterra­ nea n habitats by their herbivorou s die ts, as well as by local ph ysical conditions, such as the openness and connectivity of the subterranean systems (river or sink vs grou ndwater), altitude, high inclinations and waterfalls that cha racterize the uppe r river reaches. However, even if these fish species have not colonized the sub terranean habitats , it should be noted that most of them use it at least to pass through and attain the river upper reaches. Ind eed , Figure 400 : Specimens of Atyoido pilipes (decapods shrimps). because most of these species are amphicl romous, The first (A) was captured in a superficial river reach and the second (B) from a subterranean reach. The pigmentat ion they somet imes need to pass through long su bter­ difference is obvious, but in almost all the case itdid not appear ranea n sec tions (e.g. the Pat unar system , which is to correspond to an adaptation to subterranean life. more than 1 km long) to get to the upper reaches. Pouilly Marc, Keith P. Fish and shrimps of Santo karstic systems. In : Bouchet P. (ed.), Le Guyader H. (ed.), Pascal O. (ed.). The natural history of Santo. Paris (FRA), Marseille (FRA), Paris : MNHN, IRD, Pro-Natura International, 2011, p. 323- 326. (Patrimoines Naturels). ISSN 1281-6213