Biology of Ilythea caniceps, I. spilota, and Zeros flavipes (Diptera: Ephydridae), case-making consumers of diatoms on shorelines

2007·3.1 MB·

by  B A Foote

PROC. ENTOMOL. SOC. WASH.
109(1), 2006, pp. 125-130
BIOLOGY OF ILYTHEA CANICEPS, SPILOTA,
I.
AND ZEROS FLA VIPES (DIPTERA: EPHYDRIDAE),
CASE-MAKING CONSUMERS OF DIATOMS ON SHORELINES
B. A. FooTE
Department of Biological Sciences, Kent State University, Kent, Ohio 44242 (e-
mail: [email protected])
—
Abstract. Life history information is presented for Ilythea caniceps Cresson, /.
spilota (Curtis), and Zerosflavipes (Wilhston) (Diptera: Ephydridae). Adults of all
three species were commonly encountered along shorelines of small streams that
possessed moist to wet substrates, where adults deposited eggs. The incubation
period lasted two to three days. Larvae consumed a mix ofpinnate diatoms. Newly
hatched larvae formed a protective case by affixing a mix ofsand grains and detrital
particles to their dorsal surfaces. The larval period lasted 8-10 days. Puparia were
formed in the same habitat occupied by the larvae. The dorsal cases formed by the
larvae remained in place on the upper surface ofthe puparia. The pupal period lasted
6-10 days. All three species were multivoltine.
Key Words: Diptera, Ephydridae, Ilythea, Zeros, life histories, larval feeding habits
Shore flies of the family Ephydridae the tribe Ephydrini that are found in
occur in nearly all of the world's biotic alkaline or saline lakes and ponds and in
regions and consist of nearly 1800 de- thermal springs are fairly numerous, but
scribed species, as well as a host of relatively few studies have focused on the
undescribed taxa (Mathis and Zatwar- numerous species of the family that
nicki 1995). It is the second largest family occur in less exotic habitats (Foote
of acalyptrate Diptera in the Nearctic 1995). Overall, probably no more than
Region, consisting of over 460 species in 25% of the Nearctic species of Ephydri-
71 genera. Phylogenetically, the family is dae have been investigated with respect
considered to be particularly close to the to their life cycles and larval feeding
Risidae, and both families are currently habits. Knowledge ofthe morphology of
placed in the superfamily Ephydroidea the immature stages is even less exten-
along with the Camillidae, Diastatidae, sive, and probably less than 10% of the
Campichoetidae, Drosophilidae, and larvae of the North American species
Curtonotidae (Grimaldi 1990). have been described. In agreement with
Knowledge ofthe biology and ecology those of the Drosophilidae, most ephy-
of the Nearctic species of Ephydridae is drid larvae are basically microphagous in
weak but improving (Deonier 1979, feeding habits, with microorganisms and
Foote 1995). Information is particularly finely divided particulate matter serving
extensive for those species that occur as the nutrient base. However, in con-
in more unusual aquatic habitats. For trast to the yeast-feeding habits of the
example, life history studies ofspecies of drosophilids, larvae of some ephydrid
126 PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON
taxa commonly ingest algal cells (see illustrated by Scheiring and Council
references in Foote 1995, Keiper et al. (1979) who reported that eggs are
2002). Another biological difference in inserted into moist soil. They suggested
the two families is the occurrence of that the slender filament arising from the
Drosophilidae in shaded forested habi- dorsal surface of the egg serves as an
tats, whereas species of Ephydridae are aeropyle (Hinton 1968). Foote (1995)
most commonly encountered in open reported that larvae ofIlythea and Zeros
wetland sites where autotrophic micro- consume diatoms.
organisms are abundant. This paper presents information on
Ilythea, Zeros, and Donaceus are the habitat occurrence, larval feeding habits,
only genera belonging to the tribe case-building behavior, and general life
Ilytheini (Ilytheinae) (Mathis and Zat- history ofIlythea caniceps, I spilota, and
warnicki 1995). The genus Donaceus, Zeros flavipes whose larvae consume
consisting of two species, is Oriental diatoms in shoreline habitats. The bi-
and Afrotropical in distribution and ology of the three species is contrasted
unknown biologically. Ilythea, with 12 and compared with that of other species
species, has a Holarctic, Neotropical, ofEphydridae having larvae that feed on
and Afrotropical distribution, whereas diatoms, and resource partitioning with-
Zeros, with 11 species, occurs in the in this guild of diatom-feeders is dis-
Holarctic, Neotropical, Afrotropical, cussed.
and Oriental regions. The Nearctic Re-
gion contains three species of Ilythea. Materials and Methods
Ilythea caniceps Cresson has been rec- Field work for this study was carried
orded from California, Oregon, and out in northeastern Ohio near Kent in
Washington south into Mexico and Portage County between 1982 and 1996,
Costa Rica, /.flaviceps Cresson is known and in southern Arizona in 1970-1971.
only from Arizona and California, and /. Habitats studied included riffle rocks in
spilota (Curtis) has a transcontinental small woodland streams, gravely, sandy
distribution in North America and also desert streams, and muddy shorelines.
occurs in the Palearctic Region. The Pairs ofadults obtained by sweep netting
genus Zeros has five species in North
in nature were established in small
America. Zeros calverti (Cresson) and Z. breeding jars (5.5 X 7.0 cm) containing
fenestralis (Cresson) are known only
substrate taken from the habitat. Eggs
from Florida in the Nearctic Region
obtained from these pairs were either
but also occur in the Neotropical Re-
allowed to hatch on the field-collected
gion, Z.flavipes (Williston) is widespread substrate or were transferred to large
in the eastern states and Canadian
Petri dishes containing a monoculture of
provinces and also occurs in the Neo-
diatoms (Navicula pelliculosa (Breb.)
tropical and Afrotropical Regions, Z.
Hilse) growing on nutrient agar (Zack
obscurus (Cresson) has been recorded
only from Arizona and New Mexico and and Foote 1978).
from the Neotropical Region, and Z. Results and Discussion
vicinus Cresson occurs only in Florida in
North America but also has been rec- Life History of Ilythea Caniceps
orded from the Afrotropical Region. Rearings of this species were initiated
Little has been published on the bi- on 12-V-1971 from a gravid female
ology of any species of the tribe Ilythei- collected along a small, intermittent
nae, and no larvae or puparia have been stream in Upper Sabino Canyon near
described. The egg of Z. flavipes was Tucson, AZ (32"19T9"N, 110° 48' 35"W).
VOLUME NUMBER
109, 1 127
Additional rearings were initiated with the dorsal case from one of the larvae
larvae collected in a sandy substrate and noted that it immediately gathered
along the same shallow stream on 20-V- up small particles from the substrate and
1971. Other ephydrid adults collected at reformed the case within a few minutes.
the same site included Lytogaster ex- Larvae moved about on the surface of
cavata (Sturtevant and Wheeler), Pelina the moist sand but did not burrow down
sp., Athyroglossa sp., Discocerina obscur- into it. The gut on one examined larva
ella (Fallen), Parydra appendiculata was filled with a mix of pinnate diatoms
Loew, Scatella laxa Cresson, S. mari- belonging to the genera Navicula, Staur-
nensis (Cresson), and S. paludum (Mei- oneis, and Synedra. No non-diatom algal
gen). The sand shore was moist to wet taxa were noted in the gut, suggesting
and had a distinct yellow-green cast due that this species is a specialist on
to an abundance ofalgae, including large diatoms.
numbers ofdiatoms. Examination ofthe On V-24, numerous eggs, and at least
gut of one adult showed that it had 16 second- and third-instar larvae were
ingested diatoms. found in a Petri dish-sized sample (area
Four eggs were noticed on V-15 in the of 64 cm2) taken near the center of the
sand substrate in the breeding jar. They sampling site that was about 3600 cm2.
were placed horizontally in the moist The larval period varied from 5 to
sand and had a distinct elongate stalk at 10 days (5 larvae).
midlength that extended into the over- Puparia were formed in the same area
lying air. Hatching began that evening where larvae occurred and all retained
when one larva was discovered moving the dorsal case. The pupal period lasted
slowly over the sand substrate. It had 9-10 days (4 puparia).
a distinct hump-backed shape and con-
tinuously moved its mouthparts in Life History of Ilythea Spilota
a flickering motion. Within an hour of Adults of this species were most
hatching, I noticed that the larva had commonly encountered in shoreline hab-
formed a case composed of sand grains itats that contained large populations
and small detritus particles that covered of pinnate diatoms. Numerous speci-
its dorsal surface. The case retained its mens were also collected from various-
shape when removed from the larva, sized rocks that projected above the
and the particles appeared to be glued water line in riffles of small woodland
together by a secretion released by the streams. Interestingly, habitats that were
larva. open to sunlight did not contain larger
On V-20, six third-instar larvae of / populations of Ilythea than sites that
caniceps, 12 larvae of a species of were partially or mostly shaded. In fact,
Lamproscatella, 6 larvae of at least 2 populations frequently were compara-
species ofScatella, and numerous eggs of tively larger in shaded habitats than in
Parydra appendiculata were collected at the more open areas of the shoreline or
the same site. All of the Ilythea were riffle. Deonier (1965), in a study of
distinctly hump-backed and possessed ephydrid habitats in Iowa, reported that
dorsal cases composed of sand grains /. spilota was most commonly encoun-
and detritus. The integument appeared tered in the stream-rock habitat, al-
to be distinctly thinner in the area though it was found also in the limnic-
covered by the dorsal case. The larvae wrack, sedge- meadow, and muddy-
moved about on the moist sand rather shore habitats. In contrast, Scheiring
swiftly while exhibiting the flickering and Foote (1973) collected adults most
movement ofthe mouthparts. I removed commonly on muddy shores, with fewer
128 PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON
recorded from limnic-wrack, grass-shore, Navicula culture. Adults emerged from
rain-pool, and marsh-reed habitats. Re- the 5 puparia on IX-08 and IX-09, giving
sults similar to the latter paper were a pupal period of 6-7 days. Three of the
obtained in Scandinavia by Dahl (1959) emerged adults (2 males, 1 female) that
who reported that the center of ecolog- were transferred to a fresh plate of
ical distribution for adults ofthis species Navicula on IX-13 began laying eggs on
was the mud-shore biotope, although IX-23, giving a pre-oviposition period of
he also regularly encountered them in some 10 days.
moist meadows and over wrack deposit- Several larvae were collected from
ed on high beaches bordering freshwater a muddy, diatom-laced shoreline ofCave
lakes. Creek in the Chiracahua Mountains of
This is a multivoltine species, and southeastern Arizona on X-23-1976. All
adults are repeatedly collected through- larvae bore dorsal cases composed of
out the warm season in northeastern diatoms and detrital particles, although
Ohio. The first specimens were obtained one larva had attached an empty Ilythea
on April 15, and the last on October 2. egg shell, and another had affixed
Populations were particularly large in a small, dead larva to the case. Gut
mid and late summer once stream flows examinations of two third-instar larvae
stabihzed and diatom populations disclosed a nearly pure culture ofpinnate
surged. As reported by Deonier (1972), diatoms belonging to several undeter-
adults fed on pinnate diatoms. Guts of mined genera.
field-collected adults of both sexes con- Numerous collections of adults and
tained nearly pure cultures of diatoms immature stages between late May and
with only occasional cells of other algal early October in northeastern Ohio in-
taxa. There was no obvious trophic dicate that this is a multivoltine species.
separation between adults and larvae, With an incubation period of 2-3 days,
as similar diatom taxa were found in a larval period of 10-13 days, and
both life stages. a pupal period of 6-10 days, there could
A male and female collected in a stand be as many as 7-8 generations produced
of skunk cabbage {Syniploricarposfoeti- during a warm season of some 180 days
dus (L.) Nuttall) along the Cuyahoga in this latitude and longitude.
River in Kent, Ohio, was placed in a Petri
dish supporting a pure culture of Navi- Life History of Zeros Flavipes
ciila diatoms on 20-VIII-1976. Adults fed The single rearing of this species was
on the lawn of diatoms, as numerous initiated from a gravid female collected
areas cleaned of cells were noted. Six on Vin-13-1976, from the sandy/muddy
eggs were laid on August 23. All were shores of the Cuyahoga River in Kent.
placed horizontally in the layer of She was placed in a large Petri dish that
diatoms and all supported an upright contained a monoculture of the diatom
stalk at mid-length. Hatching began on Naviculapelliculosa. By VIII-15, she had
VIII-24, giving an incubation period of scattered eight eggs over the diatom
1-2 days. The larvae fed steadily on the culture, with each egg being buried
monoculture of Navicula and all formed horizontally in the agar except for the
dorsal cases of diatoms. Larval feeding upward-directed projection arising at
ended on IX-02, giving a larval period of mid-length on the dorsal side of the
8-10 days (n = 5). The dorsal cases egg. The incubation period of the eight
remained in place on the upper surface of eggs was two days. The female died on
the puparia. The female died on IX-06, VIII-16, although numerous eggs were
having lived for 17-18 days in the still visible within her abdomen.
VOLUME NUMBER
109, 1 129
The six newly hatched larvae moved tacting predators such as larvae of
slowly over the surface of the diatom Hydrophilidae (Coleoptera) that are
culture and quickly began ingesting common in such habitats. Therefore, it
diatoms, as shown by the yellowish is possible that the case serves a pro-
material that appeared in the gut. All tective role in that it serves to camou-
larvae constructed a dorsal case of flage the feeding larva. The integument
diatoms and egg shells within one day of larva appears to be quite thin under
of hatching. Larvae continued to feed the case, and it is possible that the case
on the diatom culture, with the first shields the larva from ultra-violet radia-
stadium lasting three days (n = 6); the tion, prevents overheating or retards
second, two days (n = 2); and the third desiccation.
stadium, five days (n = 1). The total One interesting puzzle is how the co-
larval period from hatching to puparia- occurring larvae of two or more spe-
tion in the single larva that formed cies manage to avoid competition, as-
a puparium was nine days. The dorsal suming that there is a limiting resource.
case was-reconstructed after each of the This was not explored in this study, but
first two molts and remained in place it quite possible that there is some
A
over the puparium. male emerged on microspatial segregation of the feeding
VIII-31, giving a pupal period of 6 days larvae. For example, larvae of one spe-
(n = 1). cies could occur on somewhat drier sur-
Another gravid female was collected faces, whereas the second species occurs
on IX-01-1982 near the original collect- more commonly on wetter surfaces. Of
ing site. She was associated with the course, there is also the possibility that
shore flies /. spilota, Athyroglossa gran- there is no limiting resource (diatoms)
ulosa, and Scatella picea, but deposited because larval populations are relatively
no eggs during the 14 days she was held low.
in a Petri dish containing a monoculture The utilization ofdiatoms by ephydrid
of Navicula. This collection was interest- larvae is particularly well developed in
ing in that it showed that both /. spilota these two genera and in species of
and Z. flavipes can co-occur in the same Parydra, and all commonly co-occur in
habitat. diatom-rich habitats. One interesting
Undoubtedly the most interesting and difference in the feeding of Parydra
distinctive behavior ofthe larvae ofthese larvae (Deonier 1978) versus that of the
two genera was the repeated construc- larvae ofIlythea and Zeros is their mode
tion of a case that covered their dorsal of segregating diatoms from the sub-
surfaces. Case building began almost as strate. There is no indication of pharyn-
soon as larvae hatched, was maintained geal ridges in the mouthparts ofParydra,
through all three larval instars, and but they are present in larvae ofthe other
remained in place on the dorsal side of two genera. It has been shown that
the puparium. When I removed the case, pharyngeal ridges serve as a filtering
the larva quickly began the construction device in particle-feeding larvae of aca-
of a replacement. Because the construc- lyptrate larvae (Ferrar 1987), but the
tion of a dorsal case requires an energy mode of filter-feeding in Parydra larvae
expenditure, it appears that there is remains unknown.
selective value in its construction, and
Acknowledgments
at least two possible roles ofthe case can
be suggested. Because the larvae crawl I am indebted to Joe B. Keiper,
about on exposed surfaces (mud, sand, Cleveland Museum of Natural History,
rock), there is high likelihood of con- and Eric. G. Chapman, Department of
PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON
130
Biological Sciences, Kent State Univer- Foote, B. A. 1995. Biology of shore flies. Annual
sity, for making numerous suggestions GrimaRledvii,ewDo.fEA.nto1m9o90l.ogAy 40p:hy4l1og7e^n4e2ti.c, revised
for the improvement of this manuscript.
classification of genera in the Drosophilidae
(Diptera). Bulletin of the American Museum
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