The Evolution of the Sponge Feeding Habit in the Caddisfly Genus Ceraclea ( Trichoptera: Leptoceridae )* VINCENT H. RESH 2 Water Resources Laboratory, University of Louisville, Louisville, KY JOHN C. MORSE 3 Department of Entomology, University of Georgia, Athens, GA IAN D. WALLACE* Department of Zoology, University of Newcastle Upon Tyne, Newcastle, Great Britain ABSTRACT A phylogeny is proposed for 11 species of Ceraclea caddisflies which feed on freshwater sponge during the larval stage of their life cycle. Based on this evolutionary scheme, further probable sponge feeders are postulated. Some morphological differences of the sponge feeders are described. The obligate sponge feeders are morphologi- cally and ecologically different from other species of the genus which may feed on sponge when it is available or when other food sources are scarce, and from the other species of Ceraclea which appear never to eat sponge. Systematic studies of caddisflies have been based primarily on adult morphological characteristics. Potential evolutionary evidence that could be ob- tained from interspecific comparisons of larval mor- phology and ecology has been neglected because the immature and adult stages of most species have not been associated. This study attempts to draw to- gether taxonomic, ecological, and morphological in- formation obtained from detailed studies of the im- mature and adult stages of sponge feeding caddisflies in order to develop a phylogenetic history of this unusual feeding habit. Studies of caddisfly feeding habits have indicated a wide range of potential food sources (Slack 1930, Cummins 1973). Of particular interest have been several European and North American references to aquatic insects ingesting particles of freshwater sponges (Porifera: Spongillidae). Most observations of sponge feeding by aquatic insects have been made on caddisflies of the family Leptoceridae; but larvae of spongilla flies (Neuroptera: Sisyridae) (Brown 1952, Parfin and Gurney 1956), and larval chirono- mids Xenochironomus xenolabris (Keiffer) (Roback 1963, 1968, Wundsch 1943, 1952), and Demeijerea rufipes (L.) (Maitland 1967, Wundsch 1943, 1952), also utilize this food source. The presence of sharp, indigestible spicules may be a deterrent to most potential predators of fresh- water sponge. Spongilla fly larvae avoid these ob- stacles by piercing the sponge and sucking its fluids. The gut contents of the caddisflies and midges in- clude spicules, which indicates that these larvae do ingest the sponge; but how these sharp particles are kept from damaging the digestive tract, is unknown. The evolution of the morphological structures of Ceraclea larvae, upon which this paper is based, seems to have occurred independently of their food 1 Contribution from the Dept. of Biology, Univ. of Louisville. Received for publication Aug. IS, 1975. 8 Present Address: Div. of Entomol. and Parasitol., Univ. of Calif., Berkeley, CA 94720. 8 Present Address: Dept. of Entomol. and Eco. Zool., Clemson Univ., Clemson, SC 29631. * Present Address: Merseyside Co., Museum, William Brown St., Liverpool 1, Great Britain. habits and makes no apparent contribution to the ability of these species to ingest the spicules. Leptoceridae systematics have been recently re- vised by the separation of the large genus Athrip- sodes into 2 genera, Athripsodes Billberg and Cera- clea Stephens (Morse and Wallace 1976). Although, most references to leptocerid sponge feeding mention the genus Athripsodes, the sponge feeding caddisflies actually belong to the genus Ceraclea. European and Japanese workers have been able to identify and discuss sponge feeding at the specific level, e.g., Ceraclea fulva (Rambur) by Siltala (1907) (as Leptocerus fulvus) and Lepneva (1966) (as Athrip- sodes fulvus) ; C. senilis (Burmeister) by Lepneva (1966) (as A. senilis) and Siltala (1907) and Niel- sen (1948) (as L. senilis) ; C. nigronervosa (Retzius) by Nielsen (1948) (as L. nigronervosus) and Mait- land (1966, 1967) (as A. nigronervosus) ; C. albi- macula (Rambur) by Satija (1964) (as A. albogut- tatus) ; and C. biwaensis by Tsuda and Kuwayama (1954) (as L. biwaensis). However, most references to sponge feeding by North American caddisflies have been at the generic or family level. The earliest description of sponge feeding by a North American species was by Krecker (1920), who described a caddisfly larva he assigned to the family Rhyacophilidae feeding on Spongilla fragilis Leidy in Lake Erie. From the description of the larval case, this species is in the leptocerid genus Ceraclea, and is probably C. resurgens (Walker). In addition, Ross (1944) and Roback (1968) re- ported that larvae described as Athripsodes sp. a were found in association with freshwater sponge. Through rearing, sp. a has been associated with the adult of C. transversa (Hagen) (—A. angusta (Banks)). Other references to Ceraclea sponge feeding in North America incude Lehmkuhl's (1970) reference to an Athripsodes sp. (which has been identified as C. resurgens), and Roback's (1968) report on Athripsodes nr transversa, which is prob- ably C. spongillovorax (Resh). In addition to feeding on freshwater sponge as evidenced by the presence of sponge spicules in the 937 Downloaded from https://academic.oup.com/aesa/article/69/5/937/33616 by guest on 14 June 2022