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Copyright by Louis Burrell Carrick COPYRIGHT BY LOUIS BURRELL CARRICK 1957 A STUDY OP HYDRAS IN LAKE ERIE Contribution toward a Natural History of the Great Lakes Hydridae DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of philosophy in the Graduate School of The Ohio State University By LOUIS BURRELL CARRICK, B. A., M. S. •SKHHKHS- The Ohio State University 19 £6 Approved by: Advisor / Department of Zoology and Entomology TABLE OP CONTENTS INTRODUCTION .......................................... 1 I. PROBLEMS OP TAXONOMY ................. 7 1. CRITERIA FOR THE GE N E R A ............... 7 2. METHODS USED FOR SPECIES DETERMINATION .... 11 3. IDENTIFICATION OP THE. LAKE ERIE SPECIES . 16 (a) Hydra ollgactis Pallas, 1776 ............ 17 (b) Hydra pseudollgaotis (Hyman, 1931) .... 20 (c) Hydra amerlcana Hyman, 1929 21 (d) Hydra littoralls Hyman, 1931 . .. 23 (e) Hydra came a L. Agassiz, l8jp0 .... 2I4. II. HABITATS AND DISTRIBUTION IN THE GREAT LAKES . 27 1. ABIOTIC HABITAT FACTORS AFFECTING DISTRIBUTION ................................ 29 2. DISCUSSION OF HABITATS AND DISTRIBUTION- RECORDS .............................. 32 (a) Aggregations on N e t s ..................... 34 (b) occurrence in the Plankton ............... 47 (c) Deep-Water Communities................... 49 (d) Vegetation Zones ......................... 54 (e) Lake Erie Island Ponds ................... 60 (f) Wave-swept S h o r e s ....................... 65 - ii - III. COMMUNITY INTERACTIONS WITH SPECIAL REFERENCE TO H. LITTORALIS............................. 67 1. METHODS USED IN THE STUDY A R E A ........ 69 2. SEASONAL ABUNDANCE ..................... 8l (a) The Annual C y c l e .................. 86 (b) Reproductive Potential under Culture C o n d i t i o n s ........................... 95 (c) Survival under Adverse Conditions .... 108 3. CHANGING AGGREGATIONS IN THE MICROHABITATS. 114). (a) The Swift-Water Community of the Block Rubble ......................... .. 11+6 (b) The MyriophyHum-Leaf Community..... 153 (c) Hydras as Epizoites of Molluscs..... 156 i+. FOOD-CHAIN RELATIONS ................... 161+ (a) Predators of H y d r a ........................ 165 (b) Feeding Reactions and Availability of P r e y ........................... 171 (c) Hydra’s Niche in the Microcommunity . 180 5. PARASITES AND COMMENSALS ................... 185 (a) Amoebic Infestations ................... 186 (b) Ciliate Commensals ..................... 192 (c) Host Relationship with the Cladoceran Anchistropus m i n o r ................... 197 6 . THE HYDRA N U I S A N C E ......................... 212 (a) Destruction of Fish F r y ................. 215 (b) Injury of Fishermen’s S k i n ............. 22k - iii - IV. SEXUAL REPRODUCTION . ............................ 227 1. SEXUAL PERIODS, GONAD DEVELOPMENT, AND SEX R A T I O S .................................. 228 (a) Sexuality in H. littoralis................ 229 (b) Hermaphroditism in H. am e r i c a n a .......... 2I4.O (c) H. oligactis and H. pseudoligactis Compared .............................. 250 2. INFLUENCE OF EXTERNAL FACTORS ON GONAD FORMATION .................................. 257 3. SURVIVAL, DISPERSAL, AND HATCHING OF THE EGGS . .............................. 27k k» SPECIATION PROBLEMS ......................... 289 LITERATURE CITED ...................................... 295 APPENDIX: TABLES I- I X ................................ 308 AUTOBIOGRAPHY ......................... 318 - iv - LIST OP PIGORES 1. The four types of hydra neraatocysts drawn to scale from Lake Erie sexual specimens.......... 15 2 . Hap showing location of collecting stations in Fishery B a y ................................ 71 3. Photograph showing slide-rack and stone-anchor collecting rig exposed on bottom at Oak Point bar, station 1|., during seiche of December 10, 1953 . .................................. 75 Ij.. Photograph of station 1 location between the two large dolomite rocks (at left) split off from Gibraltar Island cliff face ............ 75 5. Diagram of the annual hydra cycle in western Lake E r i e ...................................... 93 6 . Photographs of the cladoceran Anchistropus minor parasitic on h y d r a s ........................... 203 7. Photograph of hydras attacking fry of the Erie whitefish Coregonus clupeaformis latus .... 218 8 . photograph of hydras attached to eggs of the yellow pikeperch Stizostedion vitreum vitreum and stinging newly hatched fry ............... 221 - V - LIST OP TABLES (APPENDIX) I. Mean sizes in microns of the species of Hydra from Lake E r i e ..................... 309 II. Nematocyst measurements in microns from L. H. Hyman’s descriptions of species of H y d r a .................................... 310 III. Mean numbers of hydras per square meter of rubble bottom, Gibraltar Island shore, Fishery Bay, 1951-1952, as determined by Britt’s concrete block-chemical bath sampling m e t h o d ........................... 311 IV. Summary of 1952 seasonal data from stone- anchor collections: numbers of hydras (H. littoralls) colonizing'stone anchor at rubble-bottom stations (la, lb, lc, 2 , 3 , Ij., 6 ), Fishery B a y ......................... 312 V. Summary of 1952 seasonal data from slide-rack collections: numbers of hydras (H. littor- alis) colonizing 18 slides at rubble-hottom stations (la, lb, lc, 2, 3, Ij., 6 ), Fishery B a y ..................................... 313 VI. Summary of 1953 seasonal data from slide-rack collections: numbers of hydras (H. littor- alis) colonizing 18 slides at rubble-bottom' stations (1, 2, 3, I4.), Fishery B a y ........ 31I4. VII. Summary of 195^ seasonal data from slide-rack collections: numbers of hydras (H. littoralis) colonizing 18 slides at rubble-bottom stations (1, 2, 3, It-, 6 ), Fishery B a y ............... 3l£ VIII. Number of buds per hydra during spring pulse as determined by counts from samples of 50 specimens from mixed H. oligactis-H. pseudo- ligaotis population at station 5 .......... 316 IX. Occurrence of gonadal individuals of H. littor­ alis in collections from slide-rack and stone- anchor rigs made during sexual period, 1952, Fishery B a y ............................... 317 - vi - INTRODUCTION That huge aggregations of hydras occur in Lake Erie has been known for over a quarter of a century. Attention of biologists was directed, to this phenomenon by Wilbert A. Clemens (1922), who reported the observations he made during the summer of 1920 while staying at a pound-net fishery located on the north shore of Lake Erie midway between Pelee Point and Rondeau Harbor. A conception of the extent of the hydra settlement on the twenty pound nets, which were operated in strings of five spaced for about nine miles along the shore, is best gained from Clemens' own words: All of the nets when lifted, in late July and early August were loaded with a; very conspicuous brownish-orange growth in addition to the bright green algal growths. At first sight diatomaceous ooze or a bacterial production was suggested but microscopic examination showed it to be composed of innumerable living Hydras* The nets were lifted into the characteristic flat-bottomed pound-net boats and brought to the dock. The boats were anchored 100 to l£0 yards from the dock and the nets dragged through the water to oars on the dock in order to wash off some of the loose material, especially mud. In addi­ tion to the mud many Hydras were washed off and these gave to the water a brownish-orange color quite dis­ tinct from the lighter color of the mud. The bottoms, seats, etc., of the boats were covered with Hydras to the depth of from l/8 to l/lf inches and a quart jar was quickly filled simply by running a hand along the seats. A fisherman eight miles to the west and another seven miles to the east reported Hydra in apparently equal abundance. This means a distribution of at least fifteen miles along this part of the shore. The beach is sandy to gravelly with some large stones. Very - 1 - little life was found on the bottom out as far as one could wade. However, out beyond the region of strong wave action there must be places of attachment for the Hydras other than the nets In order to account for the existence of the species from one fishing season to another, since in 1920 they had not reached sexual maturity by the first week in December when the nets were removed for the season. The immense population manifesting Itself on the nets appears to have been composed primarily of individuals belonging to the species Hydra ollgactis Pallas. In the absence of gonads, however, no absolute determination could be made by Professor Prank Smith to whom Clemens submitted specimens. Smith at the time, had provided the first synop­ sis of American hydras in Ward and Whipple's "Fresh-Water Biology" (Smith, 1918). Even without benefit of Paul Schulze's monograph on the genus Hydra (1917), he was un­ doubtedly able to recognize the species so often misidenti- fied by other American workers. Consequently, I am accept­ ing Clemens' report of the occurrence of H. ollgactis as the only reliable species record for Lake Erie published when the present investigation was undertaken in 1951. A primary objective of the study has been to establish the identity of the hydras inhabiting western Lake Erie, the "key area" (Langlois, 191*8) in this most productive of the Great Lakes. Working year,-round from the summer of 1951 through the summer of 1951* at Ohio State university's Franz Theodore Stone Laboratory at South Bass Island, I have been able to observe the life histories of the local hydras and obtain specimens
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