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Home , Ephydatia, Sisyridae, Spongilla, Spongilla lacustris, Spongillidae

Ann. Mus. civ. St. nat. Ferrara Vol. 8 2005 [2007] pp. 153-159 ISSN 1127-4476

Overwintering stages of iridipennis A. Costa, 1884 ( )

Laura Loru1, Roberto A. Pantaleoni1,2 & Antonio Sassu1

1) Istituto per lo Studio degli Ecosistemi, Consiglio Nazionale delle Ricerche, c/o 2) Sezione di Entomologia a- graria, Dipartimento di Protezione delle Piante, Università degli Studi, via Enrico De Nicola, I-07100 Sassari SS, Italia, e-mail: [email protected], [email protected], [email protected]

Sisyra iridipennis has a Western Mediterranean distribution throughout the Iberian Peninsula, Maghreb and Sardinia. Little is known about its history. To determine the overwintering stages of this , a series of surveys were carried out at Riu Bunnari (Sassari, NW Sardinia). In the period between November and February, S. iridipennis was found exclusively as a first . This spongillafly in environments characterized by strong summer dryness, in which the host fluviatilis (Linnaeus,1758) (Porifera ) exhibits a summer quiescence. It is possible that the life history strategy utilised by S. iridipennis has evolved to track this com- monly occurring poriferan.

Key words – Sisyra, freshwater , life cycle, Mediterranean.

Introduction well known. They all have a “northern” distribution: Holarctic in S. nigra, East- The Sisyridae is a small of Neu- Nearctic in S. vicaria and Cl. areolaris, roptera containing about fifty species in and European in S. terminalis. four genera among which Sisyra is co- Sisyra iridipennis A. Costa, 1884 has smopolitan (Tauber et al., 2003). The lar- a Western Mediterranean distribution vae are aquatic obligate predators of throughout the Iberian Peninsula (Mon- freshwater sponges (New, 1986). serrat, 1986), Maghreb (McLachlan, Despite being one of the few freshwa- 1898; Aspöck & Hölzel, 1996; Güsten, ter groups uniquely depen- 2003) and Sardinia (Costa, 1884a, b; dent on Porifera as a food source, there Weißmair, 1999). Little is known about has been little research on sisyrid biology. the life history of S. iridipennis. The fact Parfin and Gurney (1956) summarise that it is found in environments characte- most early information; Brown (1952) first rized by strong summer dryness, in which described the complete sisyrid life cycle. the potential host sponge Ephydatia flu- More recent information is supplied by H. viatilis (Linnaeus,1758) (Porifera Spongil- Aspöck et al. (1980, 2001), Evans & Ne- lidae) exhibits a summer quiescence unzig (1984), Pupedis (1985), New (Pronzato & Manconi, 1994), raises the (1986), Elliott (1996), Meinander (1996), interesting question of the nature of the Weißmair (1999), Hölzel & Weißmair life history strategy utilized by the sysirid (2002). to track this commonly occurring porife- (Retzius, 1783) [= fuscata ran. As a start to addressing this ques- (Fabricius, 1793)], S. vicaria (Walker, tion, we first looked at the overwintering 1853) and S. terminalis Curtis, 1854 as strategy of S. iridipennis. well as areolaris (Hagen,1861) During the two winters of 2003 - 2004 are the only species whose life cycles are and 2004 - 2005, we sampled the host

153 Proceedings of the IX International Symposium on Neuropterology

sponge in a short stretch of Riu Bunnari, near Sassari (NW Sardinia) (Fig. 1). Its macro- near Sassari (NW Sardinia), in to zoobenthic communities was studied by Man- confirm the identity of the overwintering coni et al. (1995). Despite the presence of spongillafly and determine the life stage many signs of human impact, benthic inverte- brate populations in the river do not appear to present during the winter months. be greatly affected by pollution (Mascolo & Loru, 2000). Water flow is at its highest in win- Materials and methods ter. In summer a significant portion of the water flow becomes hyporheic but the loss of all sur- Sampling was carried out, at more or less face flowing water is an extremely rare cata- monthly intervals, in a short stretch (about 200 strophic event. m in length) of the Riu Bunnari between No- During the period of our surveys the vember and May in 2003-2004 and 2004-2005 sponge was active exhibiting a “fleshy” body. (see Fig. 2). Because the number of sponge colonies was This river, about 12 km in length, is situated low and the individual colony sizes were small

Fig. 1 – Map of the Riu Bunnari region marked with the location and photograph of the sampling site in winter.

154 L. Loru et alii – Overwintering stages of Sisyra iridipennis A. Costa, 1884 (Neuroptera Sisyridae)

(diameter of the largest reached only 5 cm), period between November and February, only a portion (between ¼ to ½ ) of 3 - 5 colo- S. iridipennis is found exclusively as a first nies were taken during each sampling trip. The instar larva. From the beginning of March, small amount of samples was assumed not to in addition to first , second instar affect sisyrid and sponge populations and larvae are found. From mid May only third hence future sampling. The fragments of sponge were sampled with a spatula and instar larvae are found. placed in a container with habitat water. In the laboratory the habitat water was Discussion withdrawn from the sponge colony causing the sisyrid larvae to leave the colony whereupon Overwintering stages of only few spe- they were collected and recorded. cies of spongillafly are well known: the As only second and third instar larvae are identifiable to the species level, some first in- Holoarctic S. nigra, the Palearctic S. ter- star larvae were reared to the next stadium, minalis and the Nearctic S. vicaria and Cl. using techniques described in Weißmair areolaris. (1999). The identification of larval stadia and Killington (1936) recorded the first data spongillafly species was made according to about the overwintering stage of S. nigra, Weißmair (1999). subsequently confirmed by Elliott (1996) The sponge fragments were prepared for and Hölzel & Weißmair (2002). This spe- identification as in Pronzato & Manconi (1989) cies spends the winter in the prepupal and identified following Pronzato & Manconi stage within the cocoon and pupates in (2001). Voucher specimens of the sisyrid larvae the following spring. In England, a small and the identification slides of the sponge number of individuals may bypass hiber- colonies have been deposited in the collections nation and continue on to pupate into of the Civico Museo di Storia Naturale di adults; these adults will produce a second Ferrara. generation that grows rapidly and in turn overwinters in the prepupal stage. Results The first data about the overwintering of S. terminalis in the larval stage date Figure 2 shows the results of the study. back to Withycombe (1923) but he makes The total number of larvae collected was this observation generically about the ge- 81, 60 as first instars, 18 as second in- nus Sisyra, since he did not manage to di- stars and 3 as third instars. The sponge stinguish between larvae of S. terminalis collected was always E. fluviatilis. In the and S. nigra. The biology of S. terminalis

Fig. 2 – Records of spongillafly larvae in Riu Bunnari (NW Sardinia) during the winters of 2003-2004 and 2004- 2005.

155 Proceedings of the IX International Symposium on Neuropterology

was clarified later by Weißmair (1994) and by Needham (1909) who relayed the fol- Hölzel & Weißmair (2002). Larvae derived lowing original observations from Dr. An- from eggs laid early are able to complete nandale: “this species is common in the their development, overwintering in the pre- canals of carteri [Carter, 1859], pupal stage whereas larvae derived from one of our most abundant freshwater eggs laid later (August), overwinter in the I sponges in India. I have only found the or II larval stadium. In spring the overwinte- larvae between August and March, that is ring larvae continue their development and to say, in the rains and cold weather, but then pupate together with those which the sponge as a rule dies in the hot overwinter as prepupa. Consequently all weather”. adults emerge at the same time. It is apparent from the results of our Prior to Pupedis (1985) the only infor- survey that most if not all individuals of S. mation about the overwintering stages of iridipennis overwinter in the first larval sta- Cl. areolaris dated back to Roback (1968) dium. The first instars do not exhibit any and White (1976) who found larvae during obvious external development during the the winter. Pupedis (1985) confirmed five winter months; second instars are these observations demonstrating that this found only after March. Even if we cannot species spends the winter as diapausing completely exclude that a small portion of larvae in the second stadium. A small the population overwinters in other stages, number of individuals overwinter as first or we think this hypothesis is rather impro- third instars. In spring, rising water tem- bable on the basis of our knowledge about perature induces growth and moulting; the environmental conditions and the life however, migration out onto land for - cycle of E. fluviatilis. tion does not occur until the photoperiod Freshwater sponges are able to get lengthens to a certain value. This syn- through periods of drought or freezing by chronizes individuals of the spring genera- producing resistant bodies known as tion so that they emerge simultaneously. gemmules; the fleshy portion of the colony The number of yearly generations varies is lost or greatly reduced during the pro- for Cl. areolaris with longitude and de- cess of gemmulation. Gemmules repre- pending upon the local environmental sent the quiescent phase of the sponge conditions. life cycle. When favorable environmental Pupedis (1985) also determined the conditions return, the gemmules, either as overwintering stage of S. vicaria. This a group or individually, give rise to a new species spends the winter as a terrestrial, sponge colony. Gemmulation is a sea- pharate first instar within the eggshell. The sonal process that, in temperate regions, eggs are laid on permanent structures usually occurs in late summer or at the overhanging the water. In spring the first beginning of autumn. Gemmules are con- instar larvae hatch, fall into the water, and sequently present during the winter (hi- seek out the new sponge colonies. The bernation). On the other hand, in dry re- larvae develop rapidly and adults start to gions the opposite can happen: gemmula- appear in the middle of June. In Connecti- tion occurs during the spring so that cut the first generation adults lay diapau- gemmules are present in summer (aesti- sing eggs, only a few females may pro- vation). E. fluviatilis populations hibernate duce non diapausing eggs and conse- in sites north of the 40°N parallel and ae- quently a possible second yearly genera- stivate south of it. E. fluviatilis is the only tion. More southerly populations of S. vi- species known, up until now, to exhibit a caria do appear to be multivoltine. life cycle inversion, but it is possible that In regards to the life cycles of Tropical other cosmopolitan species have the sisyrids, the only data available concerns same behaviour (Pronzato & Manconi, S. indica Needham, 1909 and is supplied 1994). On the basis of morphometrical

156 L. Loru et alii – Overwintering stages of Sisyra iridipennis A. Costa, 1884 (Neuroptera Sisyridae)

Fig. 3 – Life cycle in different populations of E. fluviatilis. Coloured sectors represent the presence of active sponges while numbers represent months. In the period represented by empty sectors the sponge is in quie- scence and gemmules are present. The sponge figure is only illustrative and does not represent the aspect of the species in every considered habitat. The active phase of the sponge is preceded by a hatching process and followed by a gemmulation process which both last a few weeks. The border between coloured and empty sec- tors is therefore approximate (data from Pronzato et al., 1988).

157 Proceedings of the IX International Symposium on Neuropterology

Fig. 4 – Adult records of S. iridipennis.

data this species was split, by Ezcurra de (2003) for Maghreb, Costa (1884a, b) for Drago (1975), into two subspecies, E. flu- Sardinia. The first adults emerge at the viatilis fluviatilis (Linnaeus, 1758) living in end of April; subsequent adult emergence northern habitats and E. fluviatilis ramsay appears to be concentrated in May, the (Haswell, 1882) living in southern ones. end of June and the beginning of August. The existence of two morphological taxa is There is a complete lack of information consistent with the data on life cycle in- concerning the fate of Sisyra populations version. in August and in September. In this period The life cycle of E. fluviatilis is well E. fluviatilis is quiescent and present only known in Italy (Figure 3). In Sardinia, E. flu- as gemmules. Many hypotheses about the viatilis starts gemmulation in July; the sub- life history stages employed by sisyrids sequent aestivation period in the gemmule during this period are possible: aestivation stage lasts from August to late September. as eggs, larvae, prepupae or adults or de- The hatching process begins in October and velopment on other sponge species in the active sponge is present from November permanent rivers. (Pronzato & Manconi, 1994). While we have determined a portion of In Sardinia other sponge species with the life history strategy of S. iridipennis, it a non-inverted life cycle are also present: is still necessary to continue our research (Lieberkühn, 1855) and with sampling throughout the year to cla- (Linnaeus, 1759) (Pron- rify many unknown aspects of the life hi- zato & Manconi, 2001). story of Sisyra iridipennis. From the data in our possession, it is possible to hypothesize the following spon- Acknowledgments gillafly life-cycle. First-instar larvae of S. iridipennis establish themselves on E. fluvi- We wish to thank the referees – Prof. Ray- atilis in autumn when the sponges reactiva- mond Pupedis and Werner Weißmair – for te. They spend the whole winter in quie- their valuable comments on the manuscript scence, or possibly diapause, sheltering in and particularly for the linguistic improvement. the sponges and resuming their develop- Cordial thanks to Alessandro Molinu for his ment in March. It may be possible that a help in collecting material. small portion of the population may over- winter in either the third or second stadium. Bibliography In figure 4 the records of adult cap- tures, obtained from published and unpu- Aspöck H., Aspöck U. & Hölzel H., 1980 – Die Neu- blished data, are plotted. Published re- ropteren Europas. Eine zusammenfassende Dar- cords are from Monserrat (1986), Monser- stellung der Systematik, Ökologie und Chorologie der Neuropteroidea (Megaloptera, Raphidioptera, rat & Marin (1995) for the Iberian Penin- Planipennia) Europas. Goecke & Evers, Krefeld, sula, McLachlan (1898) and Güsten Vol. I: 495 pp., Vol. II: 335 pp.

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