Feeding Habits of D. moniloceras W. F. Marshall, Jr. INTRODUCTION Dorvillea moniloceras (Moore, 1909) is a common represen¬ tative of the polychaete family Dorvilleidae in the Monterey Bay area. Originally known as Stauronereis moniloceras, its external morphology was first described by Moore (1909). Cham¬ berlin (1919) noted that gut analyses of another species of Dorvillea, D. cr ssa, yielded sand, diatoms, sponge spicules. and crustacean fragments. According to Hartman (1945) speci- mens can be collected intertidally among coralline algae in Pacific Grove. Two other populations have been found in the area, (1) subtidally in Macrocystis pyrifera holdfasts and (2) on the underside of the boat floats at the Monterey Mar- ina. To expand on gut analysis studies by Chamberlin (1919) and in an attempt to elucidate the diet of D. moniloceras, fecal pellet analyses were performed on specimens from the latter habitat. Also laboratory feeding experiments were conducted on specimens from the same habitat to support fecal pellet data. PERTA MATEHIALS and ME HODS FECAL PELLET ANALYSIS Specimens of D. moniloceras were collected by hand from among the clusters of Phyllochaetopterus prolifica (abbreviated as PCT), a polychaete, and colonies of Ascidia ceratodes, a tunicate, on the underside of the boat floats at the Monterey Marina. Two containers were used to transport each group of Feeding Habits of D. moniloceras W. F. Marshall, Jr. 2 worms from the marina to the laboratory where individuals were immediately isolated into numbered Petri dishes. Specimens were maintained in standing sea water at 12°0 for 1.5-2.0 days, after which time the majority had defecated. Fecal pellets were extracted from individual dishes with a Pasteur pipette, isolated in separate compartments in sea water, and reserved for analysis. Size data of specimens consisted of width, length, and number of segments. Data were obtained by anesthetizing each worm separately in isotonic Mgcl, to impose a uniform body cond¬ ments were taken using a dissecting microscope, ition. Measur Worm width was measured from parapodia tip to parapodia tip in the approximate middle section of the worm. Length was measured from tip of prostomium to tip of pygidium. The prostomium, peristomium, and pygidium were included in the number of seg¬ ments of each worm. Analyses of pellets proceeded as follows. Relative amount of feces was first estimated for each specimen on an arbitrary scale of 0-5. Then individual pellets were placed on glass slides and gently teased apart with needle probes. Finally, a compound microscope (100x) was used in estimating relative percentages in terms of volume of fecal pellet constituents. FD. T FEEDING EXPERIMENTS 1). To determine whether or not D. moniloceras would eat det- ritus present in laboratory sea water, the following steps were taken. Six small fingerbowls were submerged in a plastic tub, 50x30x20 cm, with fresh running sea water. One starved Feeding Habits of D. moniloceras W. F. Marshall, Jr. 3 worm with an empty gut was placed in each bowl with approx- imately 4 mm2 of detritus previously collected from running sea water in the laboratory. Observations of gut appearances were taken approximately every 6 hours. 2). A variety of organic materials was chosen as food: a tunicate, a brown alga (Macrocystis), a sea anemone (Corynactis), tunicate matrix (of A. ceratodes), and phytoplankton. The first four were sliced into small pieces within the range 0.5-1.5 mm2. Approximately 12 particles of each food and 5 drops of phytoplankton were introduced to separate small fin- gerbowls with standing sea water. Nothing was added to the control bowl. Two worms were added to each bowl and observed for 6 hours. 3). To determine whether or not the worm would eat certain organisms under simulated semi-natural conditions, scrubbed Por tubes were added to two large fingerbowls until the bowls were moderately full and the material dense. Then 6-7 spec- imens, enough fresh sea water to cover the tubes, and 8 pieces of food were introduced to each bowl. Bowl 1 contained Bugula, a Bryozoan, with associated hydroids as food, and Bowl 2 con- tained Obelia, a hydroid, as food. The bowls were maintained at 12°0, and the water was replaced once a day. SULTS and DISCUSSION FECAL PELLET ANALYSIS Data on worm size obtained from measuring specimens from the field was used to generate Figures la,b,c. Figure la plots Feeding Habits of D. moniloceras W. F. Marshall, Jr. 4 the number of worms against width range for a sample size of 101. The resulting histogram implies by its symmetry a normal frequency distribution of widths about a mean value of 3.3 mm. Figure ib plots the number of worms as a function of length. The histogram generated suggests the existence of a bimodal distrubution with the depression occurring in the 30-40 mm range. A skewed distribution is depicted in Fig. 1c which plots number of worms against number of segments. The occur- rence of more worms with more segments connotes the possibil- ity that worms add segments until a maximum determinate number is reached. The i ntuitive notion that worm length increases with worm width is borne out by Fig. 2. Figures la,b.c show that worm width serves as the best index of worm size. Figure 3 cor jains information from direct fecal pellet analysis. Percent occurrences of the most common diet constit- uents are illustrated for both the PCT and the tunicate popula- tions in a decreasing order and an increasing order, respect- ively. Although setae are shown to occur 46% of the time in the POT population fecal pellets, an inadvertant sampling error caused this value to be high. Figure 4 compares the average percent composition by volume of 103 pellet samples obtained from PoT and tunicate populations in terms of the most common identifiable constituents. The arrangement of Fig. 4 is the same as that of Fig. 3. In all pellets examined, detritus was present, comprising most of the average pellet in all worm size groups. Rasping surfaces to free detritus appears to be one of the two actions Feeding Habits of D. moniloceras W. F. Marshall, Jr. 5 of the jaw apparatus of D. moniloceras. The second action is that of grasping larger objects and passing them to the esoph- ogeal opening. The laboratory feeding experiment using detri- tus as the food showed that captive D. moniloceras will eat detritus. After 30.5 hrs., four of the six experimental worms had darkened guts, indicating presence of food material. Detrital material is ubiquitous among Por tubes and tunicate clusters, the habitat of the experimental animals. Accompanying detritus in pellets are naviculoid diatoms. Approximately half of the frustules appear devoid of the org anism which susgests that they are being digested by the worm. Diatoms are a rich source of lipid which could supply the worm with high energy fuel. The small volume of diatoms accounts for their small value in average percent composition (see Figs. 5a,b). The high incidence of crustaceans in feces can be accounted for by the following. The identifiable crustaceans are benthic copepods and ostracods, normally found in habitats similar to Por and tunicate clusters. Detritus grazing by the worms could include the consumption of these crustaceans. The fourth most common constituents and third highest in relative % composition are hydroids of several genera including Obelia, Campanularia, Halecium, Sertularella, Bougainvillia, ytia, and Gonothyraea (see Fig. 6). In spite of their large size, they appear in specimens in the smallest size group of Por samples. They occur more commonly in large worns. since larger worms have the appropriate mouth apparatus size Feeding Habits of D. moniloceras W. F. Marshall, Jr. 6 to consume the hydroid (see Fig. 7). The majority of the hydroid exoskeletons were empty, suggesting either that the worms are consuming empty tubes or that they are taking in living hydroid colonies and digesting the animal matter. In the lat- ter case, D. moniloceras must have a high tolerance for nemat- ocysts. Bowerbankia gracilis (Bryozoa) occurs in the fecal pel- lets analyzed (see Fig.8). Because of its large size relative to setae and sponge spicules, Bowerbankia possesses a high value for percent composition of fecal pellet despite pos- sessing the lowest value for percent occurrence. Statistically, the only significant variation in per- cent occurrence between size classes occurs with sponge spic- ules from worms found in POT clusters (p«.005). Other fecal constituents show increasing or decreasing tendencies as a function of size class. For example, both hydroids and Bowerbankia decrease in percent occurrence as width decreases while Por crustaceans and diatoms increase as width decreases. Conceivably, smaller worms may be forced to feed on smaller food choices due to the limited size of their mouths. Two species of a filamentous red alga, Polysiphonia, were found in pellets of 5 worms taken at the same time from tunicate clusters. These worms ingesting algae were larger than 3.0 mm: smaller worms did not have any algae in their pellets. Dietary constituents of worms from both habitats, PGT and tunicates, closely resemble each other in occurrence and percent composition of fecal pellets. Since PoT and A. ceratodes Feeding Habits of D. moniloceras W. F. Marshall, Jr. 7 grow near each other on the floats, the two microhabitats are very similar. Also, it is possible for worms to migrate freely from one habitat to the other. Standard deviations of average percent compositions were large in all cases where the percent composition was substan- tial. This suggests a large variability in diet in a sample of worms. However, as a group, they could be selecting prim¬ arily for the food sources shown in Fig. 4. TET a LABORATORY FEEDING EXPERIMENTS 1). The first laboratory feeding experiments used detritus (above). 2). No specimens performed feeding motions during the first 1.25 hrs. of observation. Then both worms in the bowl with chopped Co ictis began feeding on the anemone surrounded by mucous. Feeding lasted approximately 5 minutes with the worms moving their mouth apparati extensively. Within 5 hrs., one worm developed an open sore on its dorsal anterior. Within 24 hrs., both worms were dead. No other worms were observed performing the feeding behavior during 2 hrs. of observation. Like hydroids, anemones are coelenterates and possess nemato- cysts. However, D. moniloceras can apparently withstand only the nematocysts of hydroids but perhaps not of anemones. 3). Gut analysis of one worm from each bowl after 3.8 days yielded the following. Bugula appeared in the gut of the worm from the bowl where Bugula was introduced as food. Sertularella was present in the intestine of the specimen that was given this genus and other hydroid genera as food. Thus, by placing Feeding Habits of D. moniloceras W. F. Marshall, Jr. 8 D. moniloceras in an environment resembling its natural one. the worm ate food that it normally eats, Sertularella, and also ate food that it apparently does not normally eat, Bugula. SUMMARY The following conclusions can be made concerning the feeding habits of D. moniloceras: 1. A wide variety of food material is ingested including hydroids, Bowerbankia (a Bryozoan), sponge spicules, diatoms. and crustaceans. Detrital material is the most commonly found substance. 2. There is a tendency for larger worms to eat larger pieces of food and smaller worms to eat smaller pieces. 3. D. mor loceras was induced to eat some organisms under laboratory conditions that it apparently does not nor- mally eat in nature, although available to them there. Feeding Habits of D. moniloceras W. F. Marshall, Jr. 9 ACKNOULEDGEMENTS Not to mention the help I received during the course of this investigation would be terribly unappreciative if not blatantly rude. Thus, I hereby express my thanks to Isabella Abbott, Chuck Baxter, Zobin Burnett, Don Abbott, Larry Harris. and the entire student body at Hopkins this Spring for lend- ing a helping hand whenever I needed it. Feeding Habits of D. moniloceras W. F. Marshall, Jr.10 REFERENCES Chamberlin, Ralph V., 1919. The Annelide Polychaeta Vol. 1. The Cosmos Press. 493 pp. Fraser, C. Mekean, 1937. Kydroids of the Pacific Coast of Canada and the United States. The University of Toronto Press. 207 pp. Rartman, O., 1944. Polychaetous Annelids Part V. Eunicea. Alan Hancock Pacific Expeditions 10. 522 pp. Moore, J. P., 1909. Polychaetous Annelids from Monterey Bay and San Diego, California. Proc. Acad. Nat. Sci. aila. 51: 235-299. Smith Ralpa I., and James T. Carlton, (eds.) 1975. Lightis Manual: Intertidal Invert brates of the Central ifor à Coast. The University of California Press. 716 pp. Feeding Habits of D. moniloceras W. F. Marshall, 11 GEND. Figure la: Frequency distribution of width D. moniloceras. Figure 1b: Frequency distribution of length D. moniloceras. Figure ic: Frequency distribution of number of segments per worm for D. moniloceras. Figure 2: Plot of length of worm vs. width for D. moniloceras. Figure 3: Percent occurrences of fecal pellet constituents. Figure 4: Average percent conposition of fecal pellets with standard deviations. Figure 5a: Percent occurrence in feces. gure 5b: Percent volume of feces. Figure 6: ydroid exoskeletons collected from fecal pellets of D. moniloceras. Figure 7: Percent occurrence in feces. Figure 8: Bryozoans found in gut and fecal pellet analysis of D. moniloceras. O 11 O Feeding Habits of D. moniloceras W. F. Marshall, Jr. 12 O IHHHHHEE ttt ++++++++ +++ tt ++++ +++ F +++++ +- ++ + ttit- P + ++++++ + +— ot ++++ + + + + ++++++ +++++ +++ +++ + —44— ++ ++++++ ++++ + — + t ++ +++ +++++ t — —— O 15 0 2102 404 5o ++ + E EIGURE + + + ++ ++ —5 ++ + L + + 20 ++ +++++ 1 — + ++ +++ . t + + + 0 —+++ ++++ 16 ++ + 8 + + ++ + 1020 30405 607080 +++ - + FIGURE 45 + + ++ + i L + + ++ + i p + + +++ ++ — + + —47 — ++ + ++ ++++ + 7 — ++ — + ——:— 16 + — I —— + +1 4 — ++ 3 + + — ++ ++ + —1— +++ ++ ++ — —— O20 ++ + + +++ h FGUF + c Feeding Habits of D. moniloceras W. F. Marshall, Jr. 13 tt E tt tttttt + ttt +++++ tt ptt t ++ mttt + +++ + +++ ++++ p +++++ +++++++++ + +++ ptttt +++++ ++++ tptttttttt +++ ttt t ++++ ++ + + ++ ++++ + ++ + + ++ ++++ +++++ + ++ +++ + + + t + +++ +++ + — +++ + +++ + ++ + — ++ ++ ++ t ++ +++ o ++ ++ ++ + t — +++ — +++ + t + ++ + +++ t + +++++ + + I ++ —+ ++ + ++ ++ + + ewt +L + me ++++ + +++ +++ p t + + + + ++ + 0 + 1 + + —+ ++ + + + + P + + + ++ + 9+ + + + 0 + + t tttt ++ ON ++ + +++ tt ++ +++ ++ + ++ + P + + +++ ++++ — + + + + tt + + + - + + + + P Feeding Habits of D. moniloceras PC — O 70 60 O 43 - 55 50 40 N-7 0 11 0 33 -42 N-15 0 11 23 3. U 0 111 0 N-11 O -55 N -48 W. F. Marshall, Jr. 14 TUNICATE 50 43-55 30 N=6 50 33-42 30 N -22 50-23-32 30 N =22 50 0-22 B0 N-4 O- 5.5 - N= 53 IFIGURE3 Feeding Habits of D. moniloceras W. F. Marshall, Jr. 15 + — ——— U + — 2 8 — 2 — uito o — — — —— ——— 8 8 2 35 + 2 8 3010 + 1 —+ 5.52 — — 120 2 + 1s HE a + — —— E 8 — X 2 S o S —130 + 3.4 21 S 2 — — e ++ 8 — 30 —136 0 221 —20 20 15 —1 0 0 0 5 0 oooo o 0 —| — N=55 548 — — EGURE + — W. F. Marshall, Jr. 16 Feeding Habits of D. moniloceras — — — — o —0)— N — — — — D —11 —— — —— — — — — - — — — — — + - — — ++ ——— — +— — + S —10— 1 — 8 1 — —o — + S 2 — — — — — O 0 — + —— — —+ 8 — +— — — — — ++ Feeding Habits of D. moniloceras 255 189a ACTUAL SIZE S. TANNERI 1595 SRTULARSLA TANN BRODUCTIVE POLYP CAMPANULARIA 53c 535 AMPA W. F. Marshall, Jr. 17 1245 1905 HALECIUM S. TENELLA 895 OBELIA FIGURE 6 855 — Feeding Habits of D. moniloceras — - — — —— — — — — — + + 1 —— — S + — + — — -— — — + + — — — S + + — — — + — — —0 —0 — + — —0 — — — — S —+ — — X S — —— —— W. F. Marshall, Jr. 18 — — — — — — — + — — ++ 8 O — 01 1 o1 S — — -0 X V 0 — — 6 + — S —u — — —— — —1 O+ — 1 E — 1 — — 0 — — — — 0 — 10 + + — t — — — + — — — —-— Feeding Habits of D. moniloceras W. F. Marshall, Jr 19 T Eowerbonkio grocils 54. Bugulo perisisn