Bennice, Chelsea

Cryptic species remain poorly studied in octopuses. Following the reinstatement of the cryptic species, Octopus americanus, suggestions that it should supplant two taxa, Octopus vulgaris types I & II, in the western central and southwestern Atlantic Ocean, respectively, had yet been investigated in southeast Florida. To delineate this species, an integrative approach including morphological assessments and phylogenetic analyses of mitochondrial (16S & COI) and nuclear (rhodopsin) genes was employed. The utility of swabbing as a minimally invasive alternative DNA sampling method to tissue was also investigated. This taxon displays similar morphological traits to O. americanus. Maximum Likelihood phylogenetic inference placed this taxon in a highly supported monophyletic group with O. americanus. Both sampling methods delineated this taxon, though tissue was more successful. These results indicate that southeast Florida’s O. vulgaris-like species represents O. americanus. Thorough species delineation approaches advance our understanding of biodiversity, evolution, and ecology, and inform management practices.

Theoretically, sympatric species must partition resources or space to allow for coexistence. Determining empirically the specific resources each species exploits and species’ interactions (e.g., intra- and interspecific competition) can sometimes be challenging, thus the data are relatively sparse for certain taxa. This paucity of data exists for octopuses. Therefore, I chose to study niches of two sympatric octopuses (Octopus vulgaris and Macrotritopus defilippi) in an intracoastal habitat. Specifically, I assessed (1) spatial distribution of octopus home or “den” space, (2) habitat association, (3) octopus abundance, (4) foraging activity periods, (5) diet, and (6) associated substrates and behaviors used during foraging events. Octopus den locations were marked by GPS to quantify spatial patterns of both species and their spatial relationship to each other. Habitat associations were measured by quantifying photoquadrats of den and surrounding habitats. For foraging activity periods, a video camera was placed near an octopus den for 24-h observation to determine when each octopus species leaves/returns from foraging. Underwater video recording was used to determine associated foraging substrates and behaviors for both species. Prey remains from octopus’ dens and video recordings indicating prey consumption were used to determine diets of the two octopus species. Video recordings from the 24-h camera and foraging behavior events also provided observations of intra- and interspecific interactions. Results revealed that the two species are interspersed throughout the shallow Florida lagoon and are both abundant during the spring months (March, April, May). Although both species are interspersed throughout the lagoon, their den and surrounding habitat association differed. O. vulgaris was associated with hard bottom and M. defilippi was associated with soft bottom, thus they may not compete strongly for habitats. Each species used different foraging strategies and different primary prey, which may also lessen competition and facilitate coexistence. O. vulgaris had peak foraging activity during night hours, foraged mostly on hard bottom and mainly consumed bivalves while M. defilippi had peak foraging activity during day hours, foraged mostly on soft bottom and mainly consumed crustaceans. Octopuses also had species-specific foraging behaviors, with O. vulgaris using parachute attack and M. defilippi using flounder swimming and tripod stance. Additional intra- and interspecific interactions were video recorded and included: fishes following octopuses, predation attempts, agonistic encounters, cannibalism, and tactile communication. This study identified ecological and behavioral components that may facilitate coexistence of these sympatric species, provided insight into cephalopod niches and ecology, and provided baseline conservation requirements for sand-dwelling cephalopods, both of which may be using this site as a mating and nursery habitat.

Ecological components such as availability of resources, physical make-up of the
environment, and biotic interactions amongst and between species are factors that determine
habitat selection and coexistence of organisms within a community. A stable coexistence of
species within a community is possible if the limited resources are partitioned to be speciesspecific.
However, sympatric species are expected to exploit similar resources. Two species of
octopus Octopus vulargis and Macrotritopus defilippi with similar ecological requirements
coexist at an intra-coastal habitat. The ecological phenomena of coexistence of species can be
quantified by measuring the ecological components of the niche. The objective of this study is to
identify the components that facilitate coexistence. The ecological components being examined
include: general habitat location, habitat heterogeneity, foraging and feeding times and locations,
and biotic interactions. Global Positioning System will be used to determine the general location
of the octopus species den. The importance of habitat heterogeneity will be addressed by looking
at substrate make-up of the different species dens. Foraging and feeding times and locations will
be recorded to determine any temporal or spatial influence on species coexistence. Field
observations and laboratory habitat selection experiments will be conducted to determine what
habitat each species selects in the presence and absence of the other species. Our studies will
allow identifying ecological components that facilitate coexistence of sympatric species, provide
insight to cephalopod ecology, and conservation at a heterogeneous environment, which is of
importance to maintain marine biodiversity and ecotourism in south Florida.

Niche partitioning mechanisms may be used by
closely related, sympatric species to reduce competition.
We examine two dimensions of niche partitioning
(diet and temporal) amongst the common
octopus (Octopus vulgaris) and the Atlantic longarm
octopus (Macrotritopus defilippi), which spatially
overlap in a South Florida intracoastal habitat. SCUBA
is used to collect octopus prey remains and gather
supplemental feeding images to determine diets
of each species. A 24h octopus monitoring camera
records foraging activity times for each species. The
common octopus consumes bivalves (49%), gastropods
(32%) and crustaceans (19%), and forages
at dawn, dusk, and nocturnal hours. The Atlantic
longarm octopus consumes crustaceans (89%) and
bivalves (11%), and forages during diurnal hours. Results
suggest there is diet overlap between species
and octopuses use temporal partitioning. This study
provides additional findings to cephalopod niche
partitioning literature, novel information on the ecology
of the Atlantic longarm octopus, and conservation
requirements for sand-dwelling species.

Pelagic Sargassum was used to determine the effects of habitat architecture for one species of shrimp (Leander tenuicornis) and two species of fish (Stephanolepis hispidus and Histrio histrio). Inter-thallus spacing (low, medium, and high) and depth (shallow versus deep) were manipulated independently to test whether the spatial components of habitat architecture. Two differing habitats (Sargassum versus seagrass species) were tested for the structural component of habitat architecture. There were no significant results for inter-thallus spacing experiments for L. tenuicornis and S. hispidus. H histrio selected habitats with medium inter-thallus spacing in two treatments. Large individual H. histrio contributed mostly to the significant effects. All three species selected habitats with a greater depth aspect. Finally, L. tenuicornis and H. histrio selected habitats with greater structural complexity (i.e., Sargassum). These results demonstrate clearly that habitat architecture of Sargassum influences habitat selection by these shrimp and fishes.