Fredric R. Govedich

Social group size, potential sperm competition and reproductive investment in a hermaphroditic leech, Helobdella papillornata (Euhirudinea: Glossiphoniidae)

Social group size may affect the potential for sperm competition, and this in turn may favour ontogenetic adjustments in testicular mass according to the likely requirements for sperm and spermatophore production. In a number of comparative analyses of testis mass among vertebrate species that differ in mating system or social organization, increasing potential for sperm competition is associated with larger testis size. Intraspecific phenotypic plasticity should be able to produce the same pattern if social group size is heterogenous and reflects differing degrees of average sperm competition, but this intraspecific effect is less well studied. We tested the effect of social groups on both male and female investment in the simultaneously hermaphroditic leech, Helobdella papillornata. Leeches were placed in groups of one, two, four or eight. Sexual investment at the onset of reproductive maturity was quantified as the total testisac volume for male function and total egg volume for female function. We found that testisac volume (statistically adjusted for body size) showed a significant increase with increasing group size. Total egg volume (also adjusted for body size) was unaffected by group size. Our findings indicate adaptive developmental plasticity in male gonad investment in response to the potential for sperm competition.

Annelida (Clitellata): Oligochaeta, Branchiobdellida, Hirudinida, and Acanthobdellida

Publisher Summary This chapter focuses on freshwater annelids of North America. Freshwater annelids (oligochaetes, branchiobdellidans, leeches, and acanthobdellids) can be found in both standing and flowing water and are often an important component of the aquatic food web. There are currently over 200 oligochaete species reported from North America that inhabit freshwater and estuarine bodies, including those in the lesser known groundwater and organic mud habitats. Most oligochaetes feed by ingesting sediment, but several North American genera prey on other worms or on a variety of small invertebrates. Branchiobdellidans or crayfish worms are leech-like ectosymbionts living primarily on astacoidean crayfish. 15 genera and 107 species of Branchiobdellidan are reported from North America. Leeches (Hirudinida), an important component of the benthos of most freshwater lakes, ponds, and quieter flowing sections of streams and rivers, can also be found. There are 76 leech species currently known from North America, most of which prey on chironomids, oligochaetes, amphipods, and molluscs. The chapter describes the ecology, life history, anatomy, morphology, ecology, evolution, and physiology of oligochaetes, branchiobdellidans, leeches, and acanthobdellids found in North America.

Resurrection and Redescription of Placobdella rugosa (Verrill, 1874) (Hirudinida: Glossiphoniidae)

ABSTRACT The identification and taxonomy of papillated leeches of the genus Placobdella have been extremely problematic, confounded by vague descriptions, redescriptions of species without reference to type material or type locality, and more than a century of numerous dubious taxonomic acts. Leeches collected on August 5 and 6, 2011, from North Dakota, USA, the type locality of Clepsine ornata rugosa Verrill, 1874, were determined to be conspecific with Placobdella rugosa (Verrill, 1874) Moore, 1901 on the basis of comparison to the syntype series. The acquisition of these specimens from the type locality facilitated resurrection and redescription of P. rugosa. Placobdella rugosa is similar to P. ali but differs in salivary gland morphology and ventral pigmentation. Molecular comparison of CO-I revealed differences of 16.1% between P. rugosa and P. ali.

Sibling competition in a brood-tending leech

Conflict among siblings over parental investment, particularly over parental feeding, is a feature of family life in many kinds of animals. In some bird species, the size of prey items provided to juveniles has been implicated as a cause of aggressive competition among sibling chicks, because prey size determines whether dominance allows monopolization of parental offerings. Our experiment was meant to test the generality of this factor in creating intrafamilial conflict. We investigated sibling competition in relation to prey size using the carnivorous, brood-tending leech Helobdella papillornata. We equalized the total amount of food available to H. papillornata broods, but varied the size of individual prey items. Competition, measured by disparity in body size at independence, was more intense in broods provisioned with small items than in broods receiving large items, but similar between broods receiving large items and broods fed ad libitum. These patterns suggest that the intensity of conflict did not depend only on the total food amount, but was enhanced by small prey size. Our results indicate that conflict over the provision of parental resources to offspring can have a similar basis across very dissimilar organisms.

Helobdella blinni sp. n. (Hirudinida, Glossiphoniidae) a new species inhabiting Montezuma Well, Arizona, USA

Abstract A new leech species Helobdella blinni sp. n., is described from Montezuma Well, an isolated travertine spring mound located in central Arizona, USA. In its native habitat, Helobdella blinni had been previously identified as Helobdella stagnalis (Linnaeus, 1758), which was later reclassified to Helobdella modesta (Verrill, 1872). Similar to the European Helobdella stagnalis and North American Helobdella modesta, Helobdella blinni has six pairs of testisacs, five pairs of smooth crop caecae, one lobed pair of posteriorly-directed crop caecae, one pair of eyes, a nuchal scute, and diffuse salivary glands. However, the pigmentation of this new species ranges from light to dark brown, unlike Helobdella modesta which tends to be light grey in color. Also, Helobdella modesta produces a clutch of 12-–35 pink eggs, whereas Helobdella blinni produces smaller clutches of white eggs (7–14, 0.5 ± 0.15 mm, N = 7) and consequently broods fewer young (1–14, 7 ± 3.3 mm, N = 97). Helobdella blinni are also able to breed year-round due to the constant warm water conditions in Montezuma Well. Their breeding season is not restricted by seasonal temperatures. These species are morphologically similar, however, comparing the COI mtDNA sequences of Helobdella blinni with sequences from nearby populations of Helobdella modesta and other Helobdella species from GenBank indicate that Helobdella blinni is genetically distinct from these other Helobdella populations.

Hands-On Laboratory Simulation of Evolution: An Investigation of Mutation, Natural Selection, & Speciation

Abstract Evolutionary theory is the foundation of the biological sciences, yet conveying it to General Biology students often presents a challenge, especially at larger institutions where student numbers in foundation courses can exceed several hundred per lecture section. We present a pedagogically sound exercise that utilizes a series of simple and inexpensive simulations to convey the concept of evolution through mutation and natural selection. Questions after each simulation expand student comprehension; a class discussion encourages advanced thinking on mutation and speciation. A final paper requires students to synthesize their learning by summarizing selected papers on these topics. A grading rubric for the papers is included.